LTC3300-2 [Linear]
Addressable High Efficiency Bidirectional Multicell Battery Balancer;型号: | LTC3300-2 |
厂家: | Linear |
描述: | Addressable High Efficiency Bidirectional Multicell Battery Balancer 电池 |
文件: | 总42页 (文件大小:473K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC3300-2
Addressable High Efficiency
Bidirectional Multicell
Battery Balancer
FEATURES
DESCRIPTION
The LTC®3300-2 is a fault-protected controller IC for
transformer-based bidirectional active balancing of multi-
cell battery stacks. All associated gate drive circuitry,
precision current sensing, fault detection circuitry and a
robust serial interface with built-in watchdog timer are
integrated.
n
Bidirectional Synchronous Flyback Balancing
of Up to 6 Li-Ion or LiFePO Cells in Series
4
n
Up to 10A Balancing Current (Set by Externals)
n
Integrates Seamlessly with the LTC680x Family of
Multicell Battery Stack Monitors
n
Bidirectional Architecture Minimizes Balancing
Time and Power Dissipation
Up to 92% Charge Transfer Efficiency
Each LTC3300-2 can balance up to 6 series-connected
battery cells with an input common mode voltage up to
36V. Charge from any selected cell can be transferred at
high efficiency to or from 12 or more adjacent cells. Each
LTC3300-2hasanindividuallyaddressableserialinterface,
allowing up to 32 LTC3300-2 devices to interface to one
control processor.
n
n
Stackable Architecture Enables >800V Systems
n
Uses Simple 2-Winding Transformers
n
1MHz Serial Interface with 4-Bit
CRC Packet Error Checking
n
Individually Addressable with 5-Bit Address
n
Numerous Fault Protection Features
n
Fault protection features include readback capability, cy-
clic redundancy check (CRC) error detection, maximum
on-time volt-second clamps, and overvoltage shutoffs.
48-Lead Exposed Pad QFN and LQFP Packages
APPLICATIONS
n
Electric Vehicles/Plug-in HEVs
The related LTC3300-1 offers a serial interface that allows
theserialportsofmultipleLTC3300-1devicestobedaisy-
chained without opto-couplers or isolators.
n
High Power UPS/Grid Energy Storage Systems
n
General Purpose Multicell Battery Stacks
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and isoSPI
is a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
TYPICAL APPLICATION
High Efficiency Bidirectional Balancing
NEXT CELL ABOVE
CHARGE
Balancer Efficiency
+
SUPPLY
CHARGE
RETURN
DISCHARGE
CELL 12
LTC3300-2
100
(I
1-6)
CHARGE
4
5
DC2064A DEMO BOARD
(I
1-6)
ISOLATOR
I
V
= I
= 2.5A
CHARGE DISCHARGE
= 3.6V
CELL
+
+
ADDRESS n + 1
CELL 7
CELL 6
95
90
85
80
•
CHARGE
DISCHARGE
CHARGE
RETURN
I
DISCHARGE
4
•
4
SERIAL I/O
LTC3300-2
•
6
8
10
12
+
CHARGE
SUPPLY
I
4
CHARGE
CELL 1
NUMBER OF CELLS (SECONDARY SIDE)
33001 TA01b
•
4
5
ISOLATOR
ADDRESS n
33002 TA01a
NEXT CELL BELOW
33002f
1
For more information www.linear.com/LTC3300-2
LTC3300-2
ABSOLUTE MAXIMUM RATINGS (Note 1)
–
Total Supply Voltage (C6 to V ).................................36V
Voltage Between Pins
–
Input Voltage (Relative to V )
Cn to Cn-1* .............................................. –0.3V to 6V
InP to Cn-1* .......................................... –0.3V to 0.3V
C1 ........................................................... –0.3V to 6V
I1P ....................................................... –0.3V to 0.3V
I1S, I2S, I3S, I4S, I5S, I6S.................... –0.3V to 0.3V
CSBI, SCKI, SDI ....................................... –0.3V to 6V
+
BOOST to C6 .......................................... –0.3V to 6V
SDO Current...........................................................10mA
–
G1P, GnP, G1S, GnS, BOOST Current............... ± 200mA
V
, SDO ............................................... –0.3V to 6V
Operating Junction Temperature Range (Notes 2, 7)
LTC3300I-2........................................ –40°C to 125°C
LTC3300H-2 ...................................... –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
*n = 2 to 6
REG
RTONP, RTONS...........–0.3V to Min[V
CTRL, BOOST, WDT....–0.3V to Min[V
A4, A3, A2, A1, A0.......–0.3V to Min[V
+ 0.3V, 6V]
+ 0.3V, 6V]
+ 0.3V, 6V]
REG
REG
REG
PIN CONFIGURATION
TOP VIEW
TOP VIEW
G6S
I6S
G5S
I5S
G4S
I4S
G3S
I3S
1
2
3
4
5
6
7
8
9
36 C5
G6S
I6S
G5S
I5S
G4S
I4S
G3S
I3S
G2S
I2S 10
G1S 11
I1S 12
1
2
3
4
5
6
7
8
9
36 C5
35 G5P
34 I5P
33 C4
32 G4P
31 I4P
30 C3
29 G3P
28 I3P
27 C2
26 G2P
25 I2P
35 G5P
34 I5P
33 C4
32 G4P
31 I4P
30 C3
29 G3P
28 I3P
27 C2
49
49
–
–
V
V
G2S
I2S 10
G1S 11
I1S 12
26 G2P
25 I2P
UK PACKAGE
LXE PACKAGE
48-LEAD (7mm × 7mm) PLASTIC QFN
48-LEAD (7mm × 7mm) PLASTIC LQFP
T
= 150°C, θ = 34°C/W, θ = 3°C/W
JA JC
JMAX
–
T
= 150°C, θ = 20.46°C/W, θ = 3.68°C/W
JMAX JA JC
EXPOSED PAD (PIN 49) IS V , MUST BE SOLDERED TO PCB
–
EXPOSED PAD (PIN 49) IS V , MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3300IUK-2#PBF
LTC3300HUK-2#PBF
LEAD FREE FINISH
LTC3300ILXE-2#PBF
LTC3300HLXE-2#PBF
TAPE AND REEL
PART MARKING*
LTC3300UK-2
PACKAGE DESCRIPTION
48-Lead (7mm × 7mm) Plastic QFN
48-Lead (7mm × 7mm) Plastic QFN
PACKAGE DESCRIPTION
TEMPERATURE RANGE
–40°C to 125°C
LTC3300IUK-2#TRPBF
LTC3300HUK-2#TRPBF
TRAY
LTC3300UK-2
–40°C to 150°C
PART MARKING*
LTC3300LXE-2
LTC3300LXE-2
TEMPERATURE RANGE
–40°C to 125°C
LTC3300ILXE-2#PBF
LTC3300HLXE-2#PBF
48-Lead (7mm × 7mm) Plastic eLQFP
48-Lead (7mm × 7mm) Plastic eLQFP
–40°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
33002f
2
For more information www.linear.com/LTC3300-2
LTC3300-2
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C. (Note 2) BOOST+ = 25.2V, C6 = 21.6V, C5 = 18V, C4 = 14.4V,
C3 = 10.8V, C2 = 7.2V, C1 = 3.6V, V– = 0V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC Specifications
I
Supply Current When Not
Balancing (Post Suspend or Pre
First Execute)
Measured at C1, C2, C3, C4, C5
Measured at C6
0
14
0
1
µA
µA
µA
Q_SD
6
22
10
+
Measured at BOOST
–
I
Supply Current When Balancing
(Note 3)
Balancing C1 Only (Note 4 for V , C2, C6)
Measured at C1
Q_ACTIVE
250
70
560
0
375
105
840
10
µA
µA
µA
µA
Measured at C2, C3, C4, C5
Measured at C6
+
Measured at BOOST
Balancing C2 Only (Note 4 for C1, C3, C6)
Measured at C1
–105
–70
250
70
560
0
µA
µA
µA
µA
µA
Measured at C2
375
105
840
10
Measured at C3, C4, C5
Measured at C6
+
Measured at BOOST
Balancing C3 Only (Note 4 for C2, C4, C6)
Measured at C1, C4, C5
Measured at C2
70
–70
250
560
0
105
µA
µA
µA
µA
µA
–105
–105
–105
–105
Measured at C3
375
840
10
Measured at C6
Measured at BOOST
+
Balancing C4 Only (Note 4 for C3, C5, C6)
Measured at C1, C2, C5
Measured at C3
70
–70
250
560
0
105
µA
µA
µA
µA
µA
Measured at C4
375
840
10
Measured at C6
Measured at BOOST
+
Balancing C5 Only (Note 4 for C4, C6)
Measured at C1, C2, C3
Measured at C4
70
–70
250
560
0
105
µA
µA
µA
µA
µA
Measured at C5
375
840
10
Measured at C6
Measured at BOOST
+
+
Balancing C6 Only (Note 4 for C5, C6, BOOST )
Measured at C1, C2, C3, C4
Measured at C5
70
–70
740
60
105
µA
µA
µA
µA
µA
Measured at C6
1110
90
10
+
+
–
Measured at BOOST (BOOST = V )
Measured at BOOST (BOOST = V
)
0
REG
l
l
l
l
V
Minimum Cell Voltage (Rising)
Required for Primary Gate Drive
Cn to Cn – 1 Voltage to Balance Cn, n = 2 to 6
C1 Voltage to Balance C1
1.8
1.8
1.8
1.8
2
2
2
2
2.2
2.2
2.2
2.2
V
V
V
V
CELL|MIN
Cn + 1 to Cn Voltage to Balance Cn, n = 1 to 5
+
–
BOOST to C6 Voltage to Balance C6, BOOST = V
V
V
V
Comparator Hysteresis
CELL|MIN
70
5
mV
V
CELL|MIN(HYST)
l
Maximum Cell Voltage (Rising)
Before Disabling Balancing
C1, Cn to Cn – 1 Voltage to Balance Any Cell,
n = 2 to 6
4.7
5.3
CELL|MAX
V
V
V
Comparator Hysteresis
CELL|MAX
0.5
V
V
CELL|MAX(HYST)
l
l
Maximum Cell Voltage (Falling) to
Re-Enable Balancing
4.25
4.4
CELL|RECONNECT
V
V
Regulator Pin Voltage
9V ≤ C6 ≤ 36V, 0mA ≤ I
≤ 20mA
4.8
4.0
5.2
V
V
REG
LOAD
V
Voltage (Rising) for
REG
REG|POR
Power-On Reset
Minimum V Voltage (Falling)
l
V
V Voltage to Balance Cn, n = 1 to 6
REG
3.8
V
REG|MIN
REG
for Secondary Gate Drive
33002f
3
For more information www.linear.com/LTC3300-2
LTC3300-2
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C. (Note 2) BOOST+ = 25.2V, C6 = 21.6V, C5 = 18V, C4 = 14.4V,
C3 = 10.8V, C2 = 7.2V, C1 = 3.6V, V– = 0V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
= 0V
MIN
TYP
MAX
UNITS
I
Regulator Pin Short Circuit Current
Limit
V
55
mA
REG_SC
REG
l
l
l
l
V
V
RTONP Servo Voltage
R
R
R
R
= 20kΩ
1.158
1.158
72
1.2
1.2
1.242
1.242
88
V
V
RTONP
RTONP
RTONS Servo Voltage
= 15kΩ
RTONS
RTONS
I
I
WDT Pin Current, Balancing
WDT Pin Current as a Percentage
= 15kΩ, WDT = 0.5V
= 15kΩ, WDT = 2V
80
µA
%
WDT_RISING
WDT_FALLING
TONS
TONS
85
87.5
90
of I
, Secondary OV
WDT_RISING
l
l
V
V
V
Primary Winding Peak Current
Sense Voltage
I1P
45
45
50
50
55
55
mV
mV
PEAK_P
PEAK_S
ZERO_P
InP to Cn – 1, n = 2 to 6
l
V
Matching (All 6)
± [(Max – Min)/(Max + Min)] ꢀ 100%
± 1.7
± 5
%
PEAK_P
l
l
Secondary Winding Peak Current
Sense Voltage
I1S
45
45
50
50
55
55
mV
mV
InS to Cn – 1, n = 2 to 6, CTRL = 0 Only
l
V
Matching (All 6)
± [(Max – Min)/(Max + Min)] ꢀ 100%
± 0.5
± 3
%
PEAK_S
l
l
Primary Winding Zero Current
Sense Voltage (Note 5)
I1P
–7
–7
–2
–2
3
3
mV
mV
InP to Cn – 1, n = 2 to 6
l
V
Matching (All 6)
± ±[(Max – Min)/2]/(V
)} ꢀ 100%
PEAK_P|MIDRANGE
± 1.7
± 5
%
ZERO_P
Normalized to Mid-Range V
(Note 6)
PEAK_P
l
l
V
Secondary Winding Zero Current
Sense Voltage (Note 5)
I1S
–12
–12
–7
–7
–2
–2
mV
mV
ZERO_S
InS to Cn – 1, n = 2 to 6, CTRL = 0 Only
l
V
Matching (All 6)
± ±[(Max – Min)/2]/(V
)} ꢀ 100%
PEAK_S|MIDRANGE
± 0.5
± 3
%
ZERO_S
Normalized to Mid-Range V
(Note 6)
PEAK_S
–
R
R
BOOST Pin Pull-Down R
Measured at 100mA Into Pin, BOOST = V
REG
2.5
4
Ω
Ω
BOOST_L
BOOST_H
SD
ON
–
BOOST Pin Pull-Up R
Measured at 100mA Out of Pin, BOOST = V
Rising Temperature
ON
REG
T
T
Thermal Shutdown Threshold
(Note 7)
155
°C
Thermal Shutdown Hysteresis
10
°C
HYS
Timing Specifications
t
t
t
t
t
Primary Winding Gate Drive Rise
Time (10% to 90%)
G1P Through G6P, C
G1P Through G6P, C
= 2500pF
= 2500pF
35
20
70
40
ns
ns
r_P
GATE
Primary Winding Gate Drive Fall
Time (90% to 10%)
f_P
GATE
Secondary Winding Gate Drive
Rise Time (10% to 90%)
G1S, C
= 2500pF
30
30
60
60
ns
ns
r_S
GATE
G2S Through G6S, CTRL = 0 Only, C
= 2500pF
= 2500pF
GATE
GATE
Secondary Winding Gate Drive Fall G1S, C
Time (90% to 10%)
= 2500pF
20
20
40
40
ns
ns
f_S
GATE
G2S Through G6S, CTRL = 0 Only, C
l
Primary Winding Switch Maximum
On-Time
R
RTONP
= 20kΩ (Measured at G1P-G6P)
6
1
7.2
8.4
µs
ONP|MAX
l
l
t
Matching (All 6)
± [(Max – Min)/(Max + Min)] ꢀ 100%
= 15kΩ (Measured at G1S-G6S)
± 1
± 4
%
ONP|MAX
t
t
Secondary Winding Switch
Maximum On-Time
R
RTONS
1.2
1.4
µs
ONS|MAX
l
t
Matching (All 6)
± [(Max – Min)/(Max + Min)] ꢀ 100%
± 1
2
± 4
%
ONS|MAX
Delayed Start Time After New/
Different Balance Command or
Recovery from Voltage/Temp Fault
ms
DLY_START
SPI Port Timing Specifications
l
l
l
l
t
1
t
2
t
3
t
4
SDI Valid to SCKI Rising Setup
SDI Valid from SCKI Rising Hold
SCKI Low
Write Operation
Write Operation
10
ns
ns
ns
250
400
400
SCKI High
ns
33002f
4
For more information www.linear.com/LTC3300-2
LTC3300-2
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C. (Note 2) BOOST+ = 25.2V, C6 = 21.6V, C5 = 18V, C4 = 14.4V,
C3 = 10.8V, C2 = 7.2V, C1 = 3.6V, V– = 0V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
400
100
100
TYP
MAX
UNITS
ns
l
l
l
l
l
l
t
t
t
t
f
t
CSBI Pulse Width
5
SCKI Rising to CSBI Rising
CSBI Falling to SCKI Rising
SCKI Falling to SDO Valid
Clock Frequency
ns
6
ns
7
Read Operation
250
1
ns
8
MHz
second
CLK
WD1
Watchdog Timer Timeout Period
WDT Assertion Measured from Last Valid
Command Byte
0.75
1.5
1.5
2.25
l
t
Watchdog Timer Reset Time
WDT Negation Measured from Last Valid
Command Byte
5
µs
WD2
Digital I/O Specifications
l
l
l
l
V
Digital Input Voltage High
Digital Input Voltage Low
Digital Input Current High
Digital Input Current Low
Pins CSBI, SCKI, SDI
Pins CTRL, BOOST
Pins A4, A3, A2, A1, A0
Pin WDT
V
V
V
– 0.5
V
V
V
V
IH
REG
REG
REG
– 0.5
– 0.5
2
l
l
l
l
V
IL
Pins CSBI, SCKI, SDI
Pins CTRL, BOOST
Pins A4, A3, A2, A1, A0
Pin WDT
0.5
0.5
0.5
0.8
V
V
V
V
I
I
Pins CSBI, SCKI, SDI
Pins CTRL, BOOST
Pins A4, A3, A2, A1, A0
Pin WDT, Timed Out
–1
–1
–1
–1
0
0
0
0
1
1
1
1
µA
µA
µA
µA
IH
Pins CSBI, SCKI, SDI
Pins CTRL, BOOST
Pins A4, A3, A2, A1, A0
Pin WDT, Not Balancing
–1
–1
–1
–1
0
0
0
0
1
1
1
1
µA
µA
µA
µA
IL
l
l
V
Digital Output Voltage Low
Digital Output Current High
Pin SDO, Sinking 500µA; Read
Pin SDO at 6V
0.3
V
OL
I
OH
100
nA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
that are on. Second, for each additional balancer that is on, subtract 70µA
from the resultant sums for C1, C2, C3, C4, and C5, and 450µA from the
resultant sum for C6. For example, if all six balancers are on, the resultant
current for C1 is [250 – 70 + 70 + 70 + 70 + 70 – 5(70)]µA = 110µA and
for C6 is [560 + 560 + 560 + 560 + 560 + 740 – 5(450)]µA = 1290µA.
Note 2: The LTC3300-2 is tested under pulsed load conditions such
that T ≈ T . The LTC3300I-2 is guaranteed over the –40°C to 125°C
Note 4: Dynamic supply current is higher due to gate charge being
delivered at the switching frequency during active balancing. See Gate
Drivers/Gate Drive Comparators and Voltage Regulator in the Operation
section for more information on estimating these currents.
Note 5: The zero current sense voltages given in the table are DC
thresholds. The actual zero current sense voltage seen in application will
be closer to zero due to the slew rate of the winding current and the finite
delay of the current sense comparator.
Note 6: The mid-range value is the average of the minimum and maximum
readings within the group of six.
Note 7: This IC includes overtemperature protection intended to protect
the device during momentary overload conditions. The maximum junction
temperature may be exceeded when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may result in device degradation or failure.
J
A
operating junction temperature range and the LTC3300H-2 is guaranteed
over the –40°C to 150°C operating junction temperature. High junction
temperatures degrade operating lifetimes; operating lifetime is derated
for junction temperatures greater than 125°C. Note that the maximum
ambient temperature consistent with these specifications is determined by
specific operating conditions in conjunction with board layout, the rated
package thermal impedance and other environmental factors. The junction
temperature (T , in °C) is calculated from the ambient temperature
J
(T , in °C) and power dissipation (P , in Watts) according to the formula:
A
D
T = T + (P ꢀ θ )
JA
J
A
D
where θ (in °C/W) is the package thermal impedance.
JA
Note 3: When balancing more than one cell at a time, the individual cell
supply currents can be calculated from the values given in the table as
follows: First add the appropriate table entries cell by cell for the balancers
33002f
5
For more information www.linear.com/LTC3300-2
LTC3300-2
TA = 25°C unless otherwise specified.
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Cell Voltage Required
for Primary Gate Drive vs
Temperature
C6 Supply Current When Not
Balancing vs Temperature
Supply Current When Balancing
vs Temperature Normalized to 25°C
20
18
16
14
12
10
2.10
2.05
2.00
1.95
1.90
1.85
1.80
1.06
1.04
1.02
1.00
0.98
0.96
0.94
C6 = 21.6V
3.6V PER CELL
MATCH CURVE WITH TABLE ENTRY
CELL VOLTAGE RISING
CELL VOLTAGE FALLING
TYP = 740µA
TYP = 560µA
TYP = 250µA
TYP = 70µA
TYP = 60µA
TYP = –70µA
75 100
50
TEMPERATURE (°C)
–50 –25
0
25 50
125 150
–50 –25
0
25
75 100 125 150
75 100
–50 –25
0
25 50
125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
33002 G01
33002 G03
33002 G02
Maximum Cell Voltage to Allow
Balancing vs Temperature
VREG Load Regulation
VREG Voltage vs Temperature
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5
4.4
4.3
4.2
4.70
4.69
4.68
4.67
4.66
4.65
4.64
4.63
4.62
4.61
4.60
5.0
4.9
4.8
I
= 10mA
T
A
= 25°C
VREG
CELL VOLTAGE RISING
C6 = 36V
C6 = 9V
4.7
4.6
4.5
CELL VOLTAGE FALLING
C6 = 36V
C6 = 9V
–50
50
100 125
0
5
10 15
30 35 40 45 50
–50
50
100 125
150
–25
0
25
75
150
20 25
–25
0
25
75
TEMPERATURE (°C)
TEMPERATURE (°C)
I
(mA)
VREG
LT33002 G04
33002 G05
33002 G06
VREG POR Voltage and Minimum
Secondary Gate Drive vs
Temperature
V
REG Short-Circuit Current Limit
vs Temperature
VRTONP, VRTONS vs Temperature
60
59
58
57
56
55
54
53
52
51
50
4.100
4.075
4.050
4.025
4.000
3.975
3.950
3.925
3.900
1.236
1.224
1.212
1.200
1.188
1.176
1.164
C6 = 21.6V
C6 = 21.6V
V
RISING (POR)
REG
V
RTONP
V
RTONS
V
FALLING
REG
(MIN SEC. GATE DRIVE)
75 100
50 75
TEMPERATURE (°C)
–50
125
150
–50 –25
0
25 50
125 150
–50 –25
0
25
100 125 150
–25
0
25 50 75 100
TEMPERATURE (°C)
TEMPERATURE (°C)
33002 G07
33002 G08
33002 G09
33002f
6
For more information www.linear.com/LTC3300-2
LTC3300-2
TA = 25°C unless otherwise specified.
TYPICAL PERFORMANCE CHARACTERISTICS
VRTONP, VRTONS
vs External Resistance
WDT Pin Current vs Temperature
WDT Pin Current vs RTONS
1.236
1.224
1.212
1.200
1.188
1.176
1.164
85
80
75
70
240
200
160
120
80
T
= 25°C
R
= 15k
T
= 25°C
A
TONS
A
BALANCING
WDT = 0.5V
BALANCING
WDT = 0.5V
SECONDARY OV
WDT = 2V
V
V
RTONP
RTONS
40
SECONDARY OV
WDT = 2V
65
0
30 35
(kΩ)
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
5
10 15 20 25
40 45
1
10
100
R
TONS
R
, R
RESISTANCE (kΩ)
TONP TONS
33002 G10
33002 G11
33002 G12
Peak Current Sense Threshold
vs Temperature
Zero Current Sense Threshold
vs Temperature
Primary Winding Switch Maximum
On-Time vs Temperature
5.0
2.5
8.4
8.0
7.6
7.2
6.8
6.4
6.0
55
53
51
V
= 3.6V
R
= 20k
= 3.6V
CELL
TONP
CELL
V
= 3.6V
CELL
RANDOM CELL SELECTED
V
RANDOM CELL SELECTED
PRIMARY
PRIMARY
0
–2.5
–5.0
–7.5
–10.0
SECONDARY
SECONDARY
49
47
45
75 100
75 100
125 150
–50 –25
0
25 50
125 150
–50 –25
0
25 50
50
–50 –25
0
25
75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
33002 G14
33002 G15
33002 G13
Secondary Winding Switch
Maximum On-Time vs Temperature
Maximum On-Time
vs RTONP, RTONS
Watchdog Timer Timeout Period
vs Temperature
20
18
16
14
12
10
8
1.4
1.3
1.2
1.1
1.65
1.60
1.55
1.50
1.45
1.40
1.35
T
= 25°C
R
TONS
= 15k
A
PRIMARY
6
4
SECONDARY
2
1.0
0
75 100
TEMPERATURE (°C)
5
40
–50 –25
0
25 50
125 150
33002 G18
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
10 15 20 25 30 35
, R (kΩ)
45
R
TONP TONS
33002 G16
33002 G17
33002f
7
For more information www.linear.com/LTC3300-2
LTC3300-2
TA = 25°C unless otherwise specified.
TYPICAL PERFORMANCE CHARACTERISTICS
Balancer Efficiency
vs Cell Voltage
Balance Current vs Cell Voltage
2.7
2.6
2.5
2.4
93
92
91
90
DC2064A DEMO BOARD
= I = 2.5A
CHARGE, 12-CELL STACK
I
CHARGE DISCHARGE
FOR 12-CELL STACK ONLY
DISCHARGE, 12-CELL STACK
DISCHARGE, 6-CELL STACK
DC2064A DEMO BOARD
2.3
2.2
2.1
I
= I
= 2.5A
CHARGE DISCHARGE
DISCHARGE, 12-CELL STACK
FOR 12-CELL STACK ONLY
DISCHARGE, 6-CELL STACK
CHARGE, 6-CELL STACK
CHARGE, 12-CELL STACK
CHARGE, 6-CELL STACK
89
2.8 3.0
3.2 3.4 3.6 3.8 4.0 4.2
VOLTAGE PER CELL (V)
3.6
VOLTAGE PER CELL (V)
4.0
4.2
2.8 3.0
3.2 3.4
3.8
33002 G19
33002 G20
Typical Charge Waveforms
Typical Discharge Waveforms
I1S
50mV/DIV
I1P
50mV/DIV
I1P
50mV/DIV
I1S
50mV/DIV
PRIMARY
DRAIN
SECONDARY
DRAIN
50V/DIV
50V/DIV
SECONDARY
PRIMARY
DRAIN
50V/DIV
DRAIN
50V/DIV
33002 G21
33002 G22
2µs/DIV
2µs/DIV
DC2064A DEMO BOARD
DC2064A DEMO BOARD
I
= 2.5A
I
= 2.5A
CHARGE
DISCHARGE
T = 2
T = 2
S = 12
S = 12
Protection for Broken Connection
to Secondary Stack While
Discharging
Protection for Broken Connection
to Cell While Charging
Changing Balancer Direction
“On the Fly”
SCKI
2ms
~5.2V
~66V
5V/DIV
C1 PIN
CHARGING
SECONDARY
STACK VOLTAGE
10V/DIV
1V/DIV 3.6V
I1P
50mV/DIV
DISCHARGING
CONNECTION TO
STACK BROKEN
CONNECTION TO
C1 BROKEN
43.2V
BALANCING
SHUTS OFF
G1P
2V/DIV
G1P
2V/DIV
G1P
2V/DIV
BALANCING
SHUTS OFF
33002 G24
33002 G25
33002 G23
500µs/DIV
20µs/DIV
50µs/DIV
33002f
8
For more information www.linear.com/LTC3300-2
LTC3300-2
PIN FUNCTIONS
Note: The convention adopted in this data sheet is to refer
tothetransformerwindingparallelinganindividualbattery
cellastheprimaryandthetransformerwindingparalleling
multiple series-stacked cells as the secondary, regardless
of the direction of energy transfer.
CSBI (Pin 16): Chip Select (Active Low) Input. The CSBI
pin interfaces to a rail-to-rail output logic gate. See Serial
Port in the Operation section.
SCKI (Pin 17): Serial Clock Input. The SCKI pin interfaces
to a rail-to-rail output logic gate. See Serial Port in the
Operation section.
G6S, G5S, G4S, G3S, G2S, G1S (Pins 1, 3, 5, 7, 9,
11): G1S through G6S are gate driver outputs for driving
external NMOS transistors connected in series with the
secondary windings of transformers whose primaries are
connected in parallel with battery cells 1 through 6. For
the minimum part count balancing application employing
SDI (Pin 18): Serial Data Input. When writing data to the
LTC3300-2, the SDI pin interfaces to a rail-to-rail output
logic gate. See Serial Port in the Operation section.
SDO (Pin 19): Serial Data Output. When reading data
from the LTC3300-2, the SDO pin is an NMOS open-drain
output. See Serial Port in the Operation section.
a single transformer (CTRL = V ), G2S through G6S
are no connects.
REG
WDT (Pin 20): Watchdog Timer Output (Active High). At
initialpower-upandwhennotattemptingtoexecuteavalid
balancecommand,theWDTpinishighimpedanceandwill
be pulled high (internally clamped to ~5.6V) if an external
pull-up resistor is present. While balancing (or attempt-
ing to balance but not able to due to voltage/temperature
faults)andduringnormalcommunicationactivity,theWDT
pin is pulled low by a precision current source slaved to
I6S, I5S, I4S, I3S, I2S, I1S (Pins 2, 4, 6, 8, 10, 12): I1S
through I6S are current sense inputs for measuring sec-
ondary winding current in transformers whose primaries
are connected in parallel with battery cells 1 through 6.
Fortheminimumpartcountbalancingapplicationemploy-
ing a single transformer (CTRL = V ), I2S through I6S
REG
–
should be tied to V .
RTONS (Pin 13): Secondary Winding Max t Setting
ON
the R
resistor. However, if no valid command byte is
TONS
Resistor. The RTONS pin servos to 1.2V. A resistor to
written for 1.5 seconds (typical), the WDT output will go
back high. When WDT is high, all balancers are off. The
watchdog timer function can be disabled by connecting
–
V programs the maximum on-time for all external NMOS
transistors connected in series with secondary windings.
This protects against a short-circuited current sense re-
sistor in any secondary winding. To defeat this function,
–
WDT to V . The secondary winding OVP function can also
be implemented using this pin (See Operation section).
connect RTONS to V . The secondary winding OVP
REG
–
–
V (Pin 21, Exposed Pad Pin 49): Connect V to the most
negative potential in the series of cells. The exposed pad
shouldbeconnectedtoacontinuous(ground)planebiased
threshold (see WDT pin) is also slaved to the value of the
R
TONS
resistor.
RTONP (Pin 14): Primary Winding Max tON Setting
Resistor. The RTONP pin servos to 1.2V. A resistor to
V–programs the maximum on-time for all external NMOS
transistorsconnectedinserieswithprimarywindings.This
protects against a short-circuited current sense resistor
in any primary winding. To defeat this function, connect
–
at V on the second layer of the printed circuit board by
several vias directly under the LTC3300-2.
I1P, I2P, I3P, I4P, I5P, I6P (Pins 22, 25, 28, 31, 34, 37):
I1P through I6P are current sense inputs for measuring
primary winding current in transformers connected in
parallel with battery cells 1 through 6.
RTONP to VREG
.
G1P, G2P, G3P, G4P, G5P, G6P (Pins 23, 26, 29, 32, 35,
38): G1P through G6P are gate driver outputs for driving
external NMOS transistors connected in series with the
primary windings of transformers connected in parallel
with battery cells 1 through 6.
CTRL: (Pin 15): Control Input. The CTRL pin configures
the LTC3300-2 for the minimum part count application
employing a single transformer if CTRL is tied to V
or
REG
for the multiple transformer application if CTRL is tied to
–
–
V . This pin must be tied to either V
or V .
REG
33002f
9
For more information www.linear.com/LTC3300-2
LTC3300-2
PIN FUNCTIONS
C1, C2, C3, C4, C5, C6 (Pins 24, 27, 30, 33, 36, 39):
C1 through C6 connect to the positive terminals of bat-
tery cells 1 through 6. Connect the negative terminal of
BOOST(Pin42):EnableBoostPin.ConnectBOOSTtoV
REG
to enable the boosted gate drive needed for balancing the
+
top cellin a given LTC3300-2 sub-stack. If the BOOST pin
–
battery cell 1 to V .
can be connected to the next cell up in the stack (i.e., C1
of the next LTC3300-2 in the stack), then BOOST should
+
+
BOOST (Pin 40): Boost Pin. Connects to the anode of
the external flying capacitor used for generating sufficient
gatedrivenecessaryforbalancingthetopmostbatterycell
in a given LTC3300-2 sub-stack. A Schottky diode from
–
–
be tied to V and BOOST no connected. This pin must
–
be tied to either V
or V .
REG
A0, A1, A2, A3, A4 (Pins 43, 44, 45, 46, 47): Address
+
+
–
C6 to BOOST is needed as well. Alternately, the BOOST
Inputs. The state of the address pins (V
= 1, V = 0)
REG
pin can connect to one cell up in the above sub-stack (if
present).ThispiniseffectivelyC7.(Note:“Sub-stack”refers
to the 3-6 battery cells connected locally to an individual
LTC3300-2 as part of a larger stack.)
determines the LTC3300-2 address. These pins must be
–
tied to either V
section.
or V . See Serial Port in the Operation
REG
V
(Pin 48): Linear Voltage Regulator Output. This 4.8V
REG
–
–
BOOST (Pin 41): Boost Pin. Connects to the cathode of
the external flying capacitor used for generating sufficient
gate drive necessary for balancing the topmost battery
cell in a given LTC3300-2 sub-stack. Alternately, if the
output should be bypassed with a 1µF or larger capacitor
–
to V . The V
to internal and external loads. The V
current.
pin is capable of supplying up to 40mA
REG
pin does not sink
REG
+
BOOST pin connects to the next higher cell in the above
sub-stack (if present), this pin is a no connect.
33002f
10
For more information www.linear.com/LTC3300-2
LTC3300-2
BLOCK DIAGRAM
48
41
BOOST
40
BOOST
–
+
V
REG
C6
C6
40mA
MAX
V
REG
BOOST
GATE DRIVE
GENERATOR
BOOST
C6
VOLTAGE
REGULATOR
THERMAL
SHUTDOWN
SD
42
39
4.8V
POR
–
V
+
BOOST
G6P
I6P
38
37
C5
47
46
45
44
43
A4
A3
A2
A1
A0
C5
+
–
–
+
2
50mV/0
0/50mV
5
ADDRESS
I6S
2
1
V
REG
LEVEL-SHIFTING
SERIAL
INTERFACE
G6S
–
V
PINS 3 TO 10,
25 TO 36
DATA
12
6-CELL
SYNCHRONOUS
FLYBACK
CONTROLLER
BALANCER
16
STATUS
12
C1
G1P
I1P
24
23
22
SDO
C2
19
18
SDI
–
V
+
–
–
+
ACTIVE
2
SCKI
WATCHDOG
TIMER
50mV/0
0/50mV
17
16
20
CSBI
WDT
I1S
12
11
V
REG
RESET
G1S
5.6V
–
–
V
V
–
V
MAX ON-TIME
VOLT-SEC
CLAMPS
1.2V
TONS
R
EXPOSED
PAD
–
–
V
CTRL
RTONS
RTONP
14
V
21
49
15
13
33002 BD
33002f
11
For more information www.linear.com/LTC3300-2
LTC3300-2
TIMING DIAGRAM
Timing Diagram of the Serial Interface
t
t
4
1
t
6
t
t
3
t
7
2
SCKI
SDI
t
5
CSBI
SDO
t
8
33002 TD
33002f
12
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
Battery Management System (BMS)
In the process of bringing the cells into balance, the over-
all stack is slightly discharged. The charger component
provides a means for net charging of the entire stack from
an alternate power source.
The LTC3300-2 multicell battery cell balancer is a key
component in a high performance battery management
system (BMS) for series-connected Li-Ion cells. It is de-
signedtooperateinconjunctionwithamonitor, acharger,
and a microprocessor or microcontroller (see Figure 1).
The last component in the BMS is a microprocessor/
microcontroller which communicates directly with the
balancer, monitor, and charger to receive voltage, cur-
rent, and temperature information and to implement a
balancing algorithm.
Thefunctionofthebalanceristoefficientlytransfercharge
to/from a given out-of-balance cell in the stack from/to
a larger group of neighboring cells (which includes that
individual cell) in order to bring that cell into voltage or
capacity balance with its neighboring cells. Ideally, this
charge would always be transferred directly from/to the
entire stack, but this is impractical for voltage reasons
when the number of cells in the overall stack is large. The
LTC3300-2 is designed to interface to a group of up to 6
series cells, so the number of LTC3300-2 ICs required to
balance a series stack of N cells is N/6 rounded up to the
nearest integer. Since the LTC3300-2 address is 5 bits,
the maximum N can be is 192 cells. For connecting an
individual LTC3300-2 in the stack to fewer than 6 cells,
refer to the Applications Information section.
There is no single balancing algorithm optimal for all
situations. For example, during net charging of the overall
stack, it may be desirable to discharge the highest voltage
cells first to avoid reaching terminal charge on any cell
before the entire stack is fully charged. Similarly, during
net discharging of the overall stack, it may be desirable
to charge the lowest voltage cells first to keep them from
reaching a critically low level. Other algorithms may
prioritize fastest time to overall balance. The LTC3300-2
implementsnoalgorithmforbalancingthestack.Insteadit
providesmaximumflexibilitybyimposingnolimitationon
the algorithm implemented as all individual cell balancers
can operate simultaneously and bidirectionally.
Because the balancing function entails switching large
(multiampere) currents between cells, precision voltage
monitoring in the BMS is better served by a dedicated
monitor component such as the LTC6803-2 or one of its
familyofparts.TheLTC6803-2providesforhighprecision
A/D monitoring of up to 12 series cells. The only voltage
monitoring provided by the LTC3300-2 is a coarse “out-
of-range” overvoltage and undervoltage cell balancing
disqualification, which provides a safety shutoff in the
event Kelvin sensing to the monitor component is lost.
Unidirectional Versus Bidirectional Balancing
Most balancers in use today employ a unidirectional (dis-
charge only) approach. The simplest of these operate by
switching in a resistor across the highest voltage cell(s)
in the stack (passive balancing). No charge is recovered
in this approach -instead it is dissipated as heat in the
resistive element. This can be improved by employing an
energystorageelement(inductiveorcapacitive)totransfer
33002f
13
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
TOP OF STACK
+
CELL N
I
CHARGE
I
LOAD
C6
C12
C5
C4
C3
C2
C1
C11
C10
C9
+
+
+
+
+
+
+
+
+
+
+
CELL N – 1
CELL N – 2
CELL N – 3
CELL N – 4
CELL N – 5
LTC3300-2
BALANCER
C8
DIGITAL
ISOLATOR
–
C7
V
LTC6803-2
MONITOR
C6
C5
C4
C3
C2
C1
CELL N – 6
CELL N – 7
CELL N – 8
C6
C5
C4
C3
C2
C1
LTC3300-2
BALANCER
CELL N – 9
CELL N – 10
CELL N – 11
DIGITAL
ISOLATOR
DIGITAL
ISOLATOR
–
–
V
V
CN
•
•
•
CHARGER
+
+
+
+
+
+
+
+
+
+
+
+
CELL 12
CELL 11
CELL 10
CELL 9
–
V
C6
C12
C5
C4
C3
C2
C1
C11
C10
C9
LTC3300-2
BALANCER
C8
DIGITAL
ISOLATOR
CELL 8
–
C7
V
LTC6803-2
MONITOR
CELL 7
CELL 6
C6
C5
C4
C3
C6
C5
C4
C3
CELL 5
CELL 4
CELL 3
CELL 2
CELL 1
LTC3300-2
BALANCER
C2
C1
C2
C1
–
–
V
V
V
CC
µP/µC
33002 F01
SERIAL COMMUNICATION BUS
V
EE
Figure 1. LTC3300-2/LTC6803-2 Typical Battery Management System (BMS)
33002f
14
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
chargefromthehighestvoltagecell(s)inthestacktoother
lower voltage cells in the stack (active balancing). This
can be very efficient (in terms of charge recovery) for the
case where only a few cells in the overall stack are high,
but will be very inefficient (and time consuming) for the
case where only a few cells in the overall stack are low. A
bidirectionalactivebalancingapproach,suchasemployed
by the LTC3300-2, is needed to achieve minimum balanc-
ing time and maximum charge recovery for all common
cell capacity errors.
Synchronous Flyback Balancer
ThebalancingarchitectureimplementedbytheLTC3300-2
is bidirectional synchronous flyback. Each LTC3300-2
containssixindependentsynchronousflybackcontrollers
that are capable of directly charging or discharging an
individual cell. Balance current is scalable with external
components. Each balancer operates independently of
the others and provides a means for bidirectional charge
transfer between an individual cell and a larger group of
adjacent cells. Refer to Figure 2.
Single-Cell Discharge Cycle for Cell 1
Single-Cell Charge Cycle for Cell 1
I
= 2A
I
= 2A
PEAK_SEC
PEAK_PRI
(I1P = 50mV)
(I1S = 50mV)
V
CC
I
I
PRIMARY
SECONDARY
I
CHARGE
V
TOP_OF_STACK
t
t
5µs
+
~417ns
I
CELL N
LOAD
2A
2A
+
+
–I
–I
PRIMARY
I
SECONDARY
CELL 13
(48V)
SECONDARY
t
5µs
t
CELL 12
~417ns
50mV
52.05V
52V
52V
48V
48V
+
+
CELL 2
(4V)
I
PRIMARY
V
V
SECONDARY
PRIMARY
T:1
•
L
CELL 1
PRI
50mV
4V
4V
50mV
10µH
t
t
•
V
V
PRIMARY
SECONDARY
G1S
52V
52V
50mV
51.95V
G1P
48V
48V
I1P
I1S
R
R
SNS_PRI
25mΩ
V
SNS_SEC
25mΩ
V
PRIMARY
SECONDARY
4V
4V
50mV
t
t
50mV
33002 F02
Figure 2. Synchronous Flyback Balancing Example with T = 1, S = 12
33002f
15
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
Cell Discharging (Synchronous)
at the InS pin), the secondary switch is turned off and
current then flows in the primary side thus charging the
selected cell from the entire stack of secondary cells. As
with the discharging case, the primary-side synchronous
switch is turned on to minimize power loss during the cell
charging phase. Once the primary current drops to zero,
the primary switch is turned off and the secondary-side
switch is turned back on thus repeating the cycle.
When discharging is enabled for a given cell, the primary
side switch is turned on and current ramps in the primary
winding of the transformer until the programmed peak
current (I ) is detected at the InP pin. The primary
PEAK_PRI
side switch is then turned off, and the stored energy in
the transformer is transferred to the secondary-side cells
causing current to flow in the secondary winding of the
transformer. The secondary-side synchronous switch
is turned on to minimize power loss during the transfer
period until the secondary current drops to zero (detected
at InS). Once the secondary current reaches zero, the
secondary switch turns off and the primary-side switch is
turned back on thus repeating the cycle. In this manner,
charge is transferred from the cell being discharged to
all of the cells connected between the top and bottom of
the secondary side—thereby charging the adjacent cells.
In the example of Figure 2, the secondary-side connects
across 12 cells including the cell being discharged.
I
is programmed using the following equation:
PEAK_SEC
50mV
RSNS_SEC
IPEAK_SEC
=
Cell charge current and corresponding secondary-side
discharge current are determined to first order by the
following equations:
IPEAK_SEC
ST
S+T
⎛
⎜
⎝
⎞
⎟
⎠
ICHARGE
=
ηCHARGE
2
IPEAK_SEC
T
S+T
⎛
⎞
⎟
I
is programmed using the following equation:
ISECONDARY
=
PEAK_PRI
⎜
⎝
⎠
2
50mV
RSNS_PRI
IPEAK_PRI
=
where S is the number of secondary cells in the stack, 1:T
is the transformer turns ratio from primary to secondary,
andη
isthetransferefficiencyfromsecondary-side
Cell discharge current (primary side) and secondary-side
charge recovery current are determined to first order by
the following equations:
CHARGE
stack discharge to the primary-side cell.
Each balancer’s charge transfer “frequency” and duty
factor depend on a number of factors including I ,
IPEAK_PRI
S
S+T
⎛
⎜
⎝
⎞
⎟
⎠
PEAK_PRI
IDISCHARGE
=
I
, transformer winding inductances, turns ratio,
cell voltage and the number of secondary-side cells.
PEAK_SEC
2
IPEAK_PRI
1
S+T
⎛
⎞
⎠
The frequency of switching seen at the gate driver outputs
is given by:
ISECONDARY
=
ηDISCHARGE
⎟
⎜
⎝
2
S
VCELL
where S is the number of secondary-side cells, 1:T is the
transformer turns ratio from primary to secondary, and
DISCHARGE
fDISCHARGE
=
•
S+T LPRI •IPEAK_PRI
η
is the transfer efficiency from primary cell
S
VCELL
discharge to the secondary side stack.
fCHARGE
=
•
S+T LPRI •IPEAK_SEC •T
Cell Charging
where L is the primary winding inductance.
PRI
When charging is enabled for a given cell, the secondary-
sideswitchfortheenabledcellisturnedonandcurrentflows
from the secondary-side cells through the transformer.
OnceIPEAK_SEC isreachedinthesecondaryside(detected
Figure 3 shows a fully populated LTC3300-2 application
employing all six balancers.
33002f
16
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
6.8Ω
0.1µF
UP TO
CELL 12
•
•
•
–
+
BOOST BOOST
C6
1:1
•
10µF
10µH
10µH
•
G6P
I6P
+
CELL 6
25mΩ
G6S
I6S
25mΩ
1:1
C5
•
10µF
10µH
10µH
•
G5P
I5P
+
CELL 5
25mΩ
G5S
I5S
25mΩ
C4
C3
•
•
•
•
•
•
LTC3300-2
C2
1:1
•
10µF
10µH
10µH
•
G2P
I2P
A4
A3
A2
A1
A0
+
CELL 2
25mΩ
SERIAL
COMMUNICATION
RELATED
G2S
I2S
CSBI
SCKI
SDI
PINS
25mΩ
1:1
SDO
C1
WDT
•
10µF
10µH
10µH
•
G1P
I1P
+
CELL 1
25mΩ
V
G1S
I1S
REG
BOOST
25mΩ
–
V
CTRL
RTONP RTONS
22.6k
•
•
•
10µF
6.98k
33002 F03
Figure 3. LTC3300-2 6-Cell Active Balancer Module Showing Power Connections for the Multi-Transformer Application (CTRL = V–)
33002f
17
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
Balancing High Voltage Battery Stacks
TOP
LTC3300-2
Balancing series connected batteries which contain >>12
cellsinseriesrequiresinterleavingofthetransformersec-
ondaryconnectionsinordertoachievefullstackbalancing
while limiting the breakdown voltage requirements of the
primary- and secondary-side power FETs. Figure 4 shows
typical interleaved transformer connections for a multicell
battery stack in the generic sense, and Figure 5 for the
specific case of an 18-cell stack. In these examples, the
secondary side of each transformer is connected to the
top of the cell that is 12 positions higher in the stack than
the bottom of the lowest voltage cell in each LTC3300-2
sub-stack. For the top most LTC3300-2 in the stack, it is
not possible to connect the secondary side of the trans-
former across 12 cells. Instead, it is connected to the top
of the stack, or effectively across only 6 cells. Interleaving
in this fashion allows charge to transfer between 6-cell
sub-stacks throughout the entire battery stack.
PRI
SEC
POWER STAGES
•
+
+
CELL N
•
•
•
•
•
•
FROM CELL N-12
SECONDARY
CELL N-6
TO CELL 24
•
•
•
LTC3300-2
SEC POWER STAGES PRI
•
+
CELL 18
•
•
•
•
•
+
CELL 13
PRI
•
LTC3300-2
POWER STAGES
SEC
•
+
CELL 12
Max On-Time Volt-Sec Clamps
•
•
•
The LTC3300-2 contains programmable fault protection
clamps which limit the amount of time that current is
allowed to ramp in either the primary or secondary wind-
ings in the event of a shorted sense resistor. Maximum
on time for all primary connections (active during cell
discharging)andallsecondaryconnections(activeduring
•
•
•
+
CELL 7
PRI
LTC3300-2
SEC
POWER STAGES
•
+
+
+
+
+
+
CELL 6
cellcharging)isindividuallyprogrammablebyconnecting
•
•
•
•
•
•
•
•
•
•
•
–
resistors from the R
and R
pins to V according
TONP
TONS
CELL 5
CELL 4
CELL 3
CELL 2
CELL 1
to the following equations:
RTONP
20kΩ
t
t
ON(MAX)|PRIMARY = 7.2µs
RTONS
15kΩ
ON(MAX)|SECONDARY =1.2µs
For more information on selecting the appropriate
maximum on-times, refer to the Applications Information
section.
33002 F04
To defeat this function, short the appropriate R
pin(s)
TON
to V
.
REG
Figure 4. Diagram of Power Transfer Interleaving Through the
Stack, Transformer Connections for High Voltage Stacks
33002f
18
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
0.1µF
6.8Ω
–
+
BOOST BOOST
C6
C1
+
+
TO TRANSFORMER
SECONDARIES OF
CELL 18
BALANCERS 14 TO 18
1:1
•
10µH
10µH
10µF
10µF
10µF
•
LTC3300-2
G1P
I1P
CELL 13
25mΩ
G1S
I1S
V
25mΩ
REG
–
V
BOOST
+
BOOST
C6
C1
+
+
TO TRANSFORMER
SECONDARIES OF
BALANCERS 8 TO 12
CELL 12
1:1
•
10µH
10µH
•
LTC3300-2
G1P
I1P
CELL 7
25mΩ
G1S
I1S
25mΩ
–
V
BOOST
+
BOOST
C6
C1
+
+
TO TRANSFORMER
SECONDARIES OF
BALANCERS 2 TO 6
CELL 6
1:1
•
10µH
10µH
•
LTC3300-2
G1P
I1P
CELL 1
25mΩ
G1S
I1S
25mΩ
–
V
BOOST
33002 F05
Figure 5. 18-Cell Active Balancer Showing Power Connections, Interleaved
Transformer Secondaries and BOOST+ Rail Generation Up the Stack
33002f
19
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
Gate Drivers/Gate Drive Comparators
balancer(s) and only the affected balancer(s) will shut off.
The balance command remains stored in memory, and
active balancing will resume where it left off if sufficient
gate drive is subsequently restored. This can happen if,
for example, the stack is being charged.
All secondary-side gate drivers (G1S through G6S) are
powered from the V
output, pulling up to 4.8V when
REG
–
on and pulling down to V when off. All primary-side
gate drivers (G1P through G6P) are powered from their
respective cell voltage and the next cell voltage higher in
the stack (see Table 1). An individual cell balancer will only
be enabled if its corresponding cell voltage is greater than
2V and the cell voltage of the next higher cell in the stack
is also greater than 2V. For the G6P gate driver output,
the next higher cell in the stack is C1 of the next higher
LTC3300-2 in the stack (if present) and is only used if the
boosted gate drive is disabled (by connecting BOOST =
Cell Overvoltage Comparators
In addition to sufficient gate drive being required to en-
able balancing, there are additional comparators which
disable all active balancing if any of the six individual cell
voltages is greater than 5V. These comparators have a
DC hysteresis of 500mV. For improved noise immunity,
the inputs are internally low pass filtered and the outputs
are filtered so as to not transition unless the internal
comparator state is unchanged for 3µs to 6µs (typical).
If any cell voltage goes overvoltage while active balanc-
ing is in progress, all active balancers will shut off. The
balance command remains stored in memory, and active
balancing will resume where if left off if the cell voltage
subsequently comes back in range. These comparators
will protect the LTC3300-2 if a connection to a battery is
lost while balancing and the cell voltage is still increasing
as a result of that balancing.
–
V ). If the boosted gate drive is enabled (by connecting
BOOST = V ), only the C6 cell voltage is looked at to
REG
enable balancing of Cell 6. In the case of the topmost
LTC3300-2 in the stack, the boosted gate drive must be
enabled. Theboostedgatedriverequiresanexternaldiode
+
+
from C6 to BOOST and a boost capacitor from BOOST to
–
BOOST . For information on selecting these components,
refer to the Applications Information section. Also note
that the dynamic supply current referred to in Note 4 of
the Electrical Characteristics table adds to the terminal
currents of the pins indicated in the Voltage When Off and
Voltage When On columns of Table 1.
Voltage Regulator
A linear voltage regulator powered from C6 creates a
ThegatedrivecomparatorshaveaDChysteresisof70mV.
For improved noise immunity, the inputs are internally
low pass filtered and the outputs are filtered so as to
not transition unless the internal comparator state is
unchangedfor3µsto6µs(typical).Ifinsufficientgatedrive
is detected while active balancing is in progress (perhaps,
for example, if the stack is under heavy load), the affected
4.8V rail at the V
pin which is used for powering
REG
certain internal circuitry of the LTC3300-2 including all 6
secondary gate drivers. The V output can also be used
REG
for powering external loads, provided that the total DC
loading of the regulator does not exceed 40mA at which
point current limit is imposed to limit on-chip power dis-
Table 1
DRIVER OUTPUT
VOLTAGE WHEN OFF
VOLTAGE WHEN ON
GATE DRIVE REQUIRED TO ENABLE BALANCING
–
G1P
G2P
G3P
G4P
G5P
G6P
V-
C1
C2
C3
C4
C5
C2
C3
C4
C5
C6
(C2 – C1) ≥ 2V and (C1 – V ) ≥2V
(C3 – C2) ≥ 2V and (C2 – C1) ≥2V
(C4 – C3) ≥ 2V and (C3 – C2) ≥2V
(C5 – C4) ≥ 2V and (C4 – C3) ≥2V
(C6 – C5) ≥ 2V and (C5 – C4) ≥2V
(C6 – C5) ≥ 2V
If BOOST = V : BOOST+ (Generated)
REG
–
+
If BOOST = V : BOOST = C7*
(C7* – C6) ≥ 2V and (C6 – C5) ≥ 2V
*C7 is equal to C1 of the next higher LTC3300-2 in the stack if this connection is used.
33002f
20
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
sipation. The internal component of the DC load current
is dominated by the average gate driver current(s) (G1S
through G6S), each approximated by C ꢀ V ꢀ f, where C
is the gate capacitance of the external NMOS transistor,
Watchdog Timer Circuit
The watchdog timer circuit provides a means of shutting
down all active balancing in the event that communication
to the LTC3300-2 is lost. The watchdog timer initiates
when a balance command begins executing and is reset
to zero every time a valid 8-bit command byte (see Serial
Port Operation) is written. The valid command byte can
be an execute, a write, or a read (command or status).
“Partial” reads and writes are considered valid, i.e., it is
only necessary that the first 8 bits have to be written and
contain the correct address.
V = V
= 4.8V, and f is the frequency that the gate
REG
driver output is running at. FET manufacturers usually
specify the C ꢀ V product as Q (gate charge) measured
g
in coulombs at a given gate drive voltage. The frequency,
f, is dependent on many terms, primarily the voltage of
each individual cell, the number of cells in the secondary
stack, the programmed peak balancing current, and the
transformer primary and secondary winding inductances.
In a typical application, the C ꢀ V ꢀ f current loading the
Referring to Figure 6a, at initial power-up and when not
balancing, the WDT pin is high impedance and will be
pulled high (internally clamped to ~5.6V) if an external
pull-up resistor is present. While balancing and during
normal communication activity, the WDT pin is pulled
V
outputisexpectedtobelowsingle-digitmilliamperes
REG
per driver. Note that the V
loading current is ultimately
REG
delivered from the C6 pin. For applications involving very
large balance currents and/or employing external NMOS
low by a precision current source equal to 1.2V/R
.
transistors with very large gate capacitance, the V
TONS
REG
(Note: if the secondary volt-second clamp is defeated
by connecting R to V , the watchdog function is
output may need to source more than 40mA average. For
information on how to design for these situations, refer
to the Applications Information section.
TONS
REG
also defeated.) If no valid command byte is written for
1.5 seconds (typical), the WDT output will go back high.
When WDT is high, all balancers will be shut down but
the previously executing balance command still remains
in memory. From this timed-out state, a subsequent valid
command byte will reset the timer, but the balancers will
only restart if an execute command is written. To defeat
One additional function slaved to the V
the power-on reset (POR). During initial power-up and
subsequently if the V pin voltage ever falls below ap-
proximately 4V (e.g., due to overloading), the serial port
is cleared to the default power-up state with no balancers
active.Thisfeaturethusguaranteesthattheminimumgate
drive provided to the external secondary side FETs is also
4V.Fora10µFcapacitorloadingtheoutputatinitialpower-
up, the output reaches regulation in approximately 1ms.
output is
REG
REG
–
the watchdog function, simply connect the WDT pin to V .
Pause/Resume Balancing (via WDT Pin)
The WDT output pin doubles as a logic input (TTL levels)
which can be driven by an external logic gate as shown in
Figure 6b (no watchdog), or by a PMOS/three-state logic
gate as shown in Figure 6c (with watchdog) to pause and
resume balancing in progress. The external pull-up must
havesufficientdrivecapabilitytooverridethecurrentsource
Thermal Shutdown
The LTC3300-2 has an overtemperature protection circuit
whichshutsdownallactivebalancingiftheinternalsilicon
die temperature rises to approximately 155°C. When in
thermalshutdown,allserialcommunicationremainsactive
and the cell balancer status (which contains temperature
information) can be read back. The balance command
whichhadbeenbeingexecutedremainsstoredinmemory.
This function has 10°C of hysteresis so that when the die
temperature subsequently falls to approximately 145°C,
active balancing will resume with the previously execut-
ing command.
to ground at the WDT pin (= 1.2V/R
). Provided that
TONS
the internal watchdog timer has not independently timed
out, externally pulling the WDT pin high will immediately
pause balancing, and it will resume where it left off when
the pin is released.
33002f
21
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
Secondary Winding OVP Function (via WDT pin)
balance command remains stored in memory, and active
balancing will resume where it left off if the stack voltage
subsequently falls to a safer level.
The precision current source pull-down on the WDT pin
during balancing can be used to construct an accurate
secondary winding OVP protection circuit as shown in
Single Transformer Application (CTRL = V
)
REG
Figure 6c. A second external resistor, scaled to R
TONS
Figure 7 shows a fully populated LTC3300-2 application
employing all six balancers with a single shared custom
transformer. In this application, the transformer has six
primary windings coupled to a single secondary winding.
Only one balancer can be active at a given time as all six
sharethesecondarygatedriverG1Sandsecondarycurrent
sense input I1S. The unused gate driver outputs G2S-G6S
must be left floating and the unused current sense inputs
and connected to the transformer secondary winding, is
used to set the comparator threshold. An NMOS cascode
device (with gate tied to V ) is also needed to protect
REG
the WDT pin from high voltage. The secondary winding
OVP thresholds are given by:
V
V
= 1.4V + 1.2V ꢀ (R
/R
)
SEC|OVP(RISING)
SEC_OVP TONS
= 1.4V + 1.05V ꢀ (R
/R
)
SEC|OVP(FALLING)
SEC_OVP TONS
–
I2S-I6SshouldbeconnectedtoV .Anybalancecommand
This comparator will protect the LTC3300-2 application
circuit if the secondary winding connection to the battery
stack is lost while balancing and the secondary winding
voltage is still increasing as a result of that balancing. The
whichattemptstooperatemorethanonebalanceratatime
will be ignored. This application represents the minimum
component count active balancer achievable.
V
REG
V
REG
V
= 1.4V
LTC3300-2
WDT
TH
LTC3300-2
R
WDT
PAUSE/
RESUME
WDT
5.6V
1.2V
ACTIVE
5.6V
1.2V
ACTIVE
RTONS
RTONS
R
TONS
R
TONS
R
TONS
R
TONS
–
V
33002 F06b
33002 F06a
(6a) Watchdog Timer Only (WDT = V– to Defeat)
(6b) Pause/Resume Balancing Only
TO TRANSFORMER
SECONDARY WINDINGS
V
REG
R
SEC_OVP
LTC3300-2
PAUSE/
RESUME
V
REG
WDT
EITHER/OR
5.6V
1.2V
V
V
REG
ACTIVE
REG
RTONS
PAUSE/
RESUME
R
TONS
R
TONS
33002 F06c
(6c) Watchdog Timer with Pause/Resume Balancing and Secondary Winding OVP Protection
Figure 6. WDT Pin Connection Options
33002f
22
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
0.1µF
6.8Ω
C6
•
•
•
–
+
BOOST BOOST
UP TO CELL 12
EACH
1:1
•
10µH
10µF
•
•
•
•
•
•
G6P
I6P
25mΩ
CELL 6
+
C5
10µH
10µF
G5P
I5P
25mΩ
CELL 5
+
C4
10µH
10µF
G4P
I4P
25mΩ
CELL 4
+
C3
LTC3300-2
10µH
10µH
10µH
10µF
G3P
I3P
25mΩ
CELL 3
+
C2
10µF
G2P
I2P
A4
A3
A2
A1
A0
25mΩ
CELL 2
+
SERIAL
COMMUNICATION
RELATED
C1
CSBI
SCKI
SDI
PINS
10µF
SDO
G1P
I1P
WDT
25mΩ
G1S
V
REG
I1S
G2S-G6S
I2S-I6S
BOOST
+
NC
25mΩ
CELL 1
–
CTRL
V
33002 F07
RTONP RTONS
22.6k
10µF
6.98k
Figure 7. LTC3300-2 6-Cell Active Balancer Module Showing Power Connections for the Single Transformer Application (CTRL = VREG
)
33002f
23
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
SERIAL PORT OPERATION
Data Link Layer
Clock Phase and Polarity: The LTC3300-2 SPI-compatible
interface is configured to operate in a system using
CPHA = 1 and CPOL = 1. Consequently, data on SDI must
be stable during the rising edge of SCKI.
Overview
The LTC3300-2 has an SPI bus compatible serial port.
Devicescanbeconnectedinparallel,usingdigitalisolators.
Multiple devices are uniquely identified by a part address
determined by the A0 to A4 pins.
Data Transfers: Every byte consists of 8 bits. Bytes are
transferred with the most significant bit (MSB) first. On a
write, the data value on SDI is latched into the device on
the rising edge of SCKI (Figure 8a). Similarly, on a read,
the data value on SDO is valid during the rising edge of
SCKIandtransitionsonthefallingedgeofSCKI(Figure8b).
Physical Layer
On theLTC3300-2, fourpinscomprise theserialinterface:
CSBI, SCKI, SDI and SDO. The SDO and SDI pins may
be tied together, if desired, to form a single bidirectional
port. Five address pins (A0 to A4) set the part address.
All serial communication related pins are voltage mode
withvoltagelevelsreferencedtotheV
CSBI must remain low for the entire duration of a com-
mand sequence, including between a command byte and
subsequent data. On a write command, data is latched in
on the rising edge of CSBI.
–
andV supplies.
REG
CSBI
SCKI
LSB (DATA)
MSB (CMD)
LSB (CMD)
MSB (DATA)
SDI
(8a) Transmission Format (Write)
CSBI
SCKI
SDI
MSB (CMD)
LSB (CMD)
LSB (DATA)
SDO
MSB (DATA)
33002 F08
(8b) Transmission Format (Read)
Figure 8.
33002f
24
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
Command Byte
Write Balance Command
AllcommunicationtotheLTC3300-2takesplacewithCSBI
logic low. The first 8 clocked in data bits after a high-to-
low transition on CSBI represent the command byte. The
8-bit command byte is written MSB first per Table 2. The
first 5 bits must match the fixed pin-strapped address
[A4 A3 A2 A1 A0] for the individual device, or all sub-
sequent data will be ignored until CSBI transitions high
and then low again. The 6th and 7th bits program one of
four commands as shown in Table 3. The 8th bit in the
command byte must be set such that the entire 8-bit com-
mand byte has even parity. If the parity is incorrect, the
current balance command being executed (from the last
previouslysuccessfulwrite)isterminatedimmediatelyand
all subsequent (write) data is ignored until CSBI transi-
tions high and then low again. Incorrect parity takes this
action whether or not the address matches. This thereby
providesafastmeanstoimmediatelyterminatebalancing-
in-progress by intentionally writing a command byte with
incorrect parity.
If the command bits program Write Balance Command,
all subsequent write data must be exactly 16 bits (before
CSBI transitions high) or it will be ignored. The internal
command holding register will be cleared which can be
verifiedonreadback. Thecurrentbalancecommandbeing
executed (from the last previously successful write) will
continue, but all active balancing will be turned off if an
Execute Balance Command is subsequently written. Only
the individual LTC3300-2 in the stack with the matching
addresswillloadinthewritedata. The16-bitwritebalance
command is written MSB first per Table 4.
The first 12 bits of the 16-bit balance command are used
to indicate which balancer (or balancers) is active and in
which direction (charge or discharge). Each of the 6 cell
balancers is controlled by 2 bits of this data per Table 5.
The balancing algorithm for a given cell is:
Charge Cell n: Ramp up to I
in secondary winding,
PEAK
ramp down to I
in primary winding. Repeat.
ZERO
Discharge Cell n (Synchronous): Ramp up to Ipeak in
Table 2. Command Byte Bit Mapping
(Defaults to 0x00 in Reset State)
primary winding, ramp down to I
winding. Repeat.
in secondary
ZERO
A4
A3
A2
A1
A0
CMDA CMDB Parity Bit
(LSB)
(MSB)
Table 5. Cell Balancer Control Bits
Table 3. Command Bits
DnA
DnB
BALANCING ACTION (n = 1 to 6)
None
CMDA
CMDB
COMMUNICATION ACTION
0
0
1
1
0
1
0
1
0
0
1
1
0
1
0
1
Write Balance Command (without Executing)
Readback Balance Command
Read Balance Status
Discharge Cell n (Nonsynchronous)
Discharge Cell n (Synchronous)
Charge Cell n
Execute Balance Command
Table 4. Write Balance Command Data Bit Mapping (Defaults to 0x000F in Reset State)
D1A
(MSB)
D1B
D2A
D2B
D3A
D3B
D4A
D4B
D5A
D5B
D6A
D6B
CRC[3] CRC[2] CRC[1] CRC[0]
(LSB)
33002f
25
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
For nonsynchronous discharging of cell n, both the sec-
ondary winding gate drive and (zero) current sense amp
are disabled. The secondary current will conduct either
through the body diode of the secondary switch (if pres-
ent) or through a substitute Schottky diode. The primary
will only turn on again after the secondary winding Volt-
sec clamp times out. In a bidirectional application with a
secondary switch, it may be possible to achieve slightly
higherdischargeefficiencybyoptingfornonsynchronous
discharge mode (if the gate charge savings exceed the
added diode drop losses) but the balancing current will be
less predictable because the secondary winding Volt-sec
clamp must be set longer than the expected time for the
current to hit zero in order to guarantee no current rever-
sal. In the case where a Schottky diode replaces the sec-
ondary switch, it is possible to build a undirectional
discharge-only balancing application charging an isolated
auxiliary cell as shown in Figure 16 in the Typical Applica-
tions section.
Commandareinverted.Thiswasdonesothatan“allzeros”
command is invalid. The LTC3300-2 will ignore the write
data if the remainder is not zero and the internal command
holding register will be cleared which can be verified on
readback. The current balance command being executed
(from the last previously successful write) will continue,
but all active balancing will be turned off if an Execute Bal-
ance Command is subsequently written. For information
on how to calculate the CRC including an example, refer
to the Applications Information section.
Readback Balance Command
ThebitmappingforReadbackBalanceCommandisidenti-
cal to that for Write Balance Command. If the command
bits program Readback Balance Command, the 16 bits of
previously written data (latched in 12-bit message plus
newly calculated 4-bit CRC) are shifted out in the same
order bitwise (MSB first) per Table 4. Only the individ-
ual LTC3300-2 in the stack with the matching address
will send out the read data. This command allows for
microprocessor verification of written commands before
executing. Note that the CRC bits in the Readback Balance
Command are also inverted. This was done so that an “all
zeros” readback is invalid.
In the CTRL = 1 application of Figure 7 employing a single
transformer which can only balance one cell at a time,
anycommandrequestingsimultaneousbalancingofmore
than one cell will be ignored. All active balancing will be
turned off if an Execute Balance Command is subse-
quently written.
Read Balance Status
The last 4 bits of the 16-bit balance command are used
for packet error checking (PEC). The 16 bits of write data
(12-bit message plus 4-bit CRC) are input to a cyclic re-
dundancy check (CRC) block employing the International
Telecommunication Union CRC-4 standard characteristic
polynomial:
IfthecommandbitsprogramReadBalanceStatus, 16bits
of status data (12 bits of data plus associated 4-bit CRC)
areshiftedoutMSBfirstperTable6. SimilartoaReadback
Balance Command, the last 4 bits in each 16-bit balance
status are used for error detection. The first 12 bits of
the status are input to a cyclic redundancy check (CRC)
block employing the same characteristic polynomial used
for write commands. The LTC3300-2 will calculate and
append the appropriate 4-bit CRC to the outgoing 12-bit
message which can then be used for microprocessor er-
4
x + x + 1
In the write data, the 4-bit CRC appended to the message
must be selected such that the remainder of the CRC divi-
sion is zero. Note that the CRC bits in the Write Balance
Table 6. Read Balance Status Data Bit Mapping (defaults to 0x000F in Reset State)
Gate
Gate
Gate
Gate
Gate
Gate
Cells
Sec
Temp
OK
0
0
0
CRC[3] CRC[2] CRC[1] CRC[0]
(LSB)
Drive 1 Drive 2 Drive 3 Drive 4 Drive 5 Drive 6 Not OV Not OV
OK
(MSB)
OK
OK
OK
OK
OK
33002f
26
For more information www.linear.com/LTC3300-2
LTC3300-2
OPERATION
Execute Balance Command
ror checking. Only the individual LTC3300-2 in the stack
with the matching address will send out the status data.
Note that the CRC bits in the Read Balance Status are
inverted. This was done so that an “all zeros” readback
is invalid.
If the command bits program Execute Balance Command,
the last successfully written and latched in balance com-
mandwillbeexecutedimmediately.Allsubsequent(write)
data will be ignored until CSBI transitions high and then
low again.
The first 6 bits of the read balance status indicate if there
is sufficient gate drive for each of the 6 balancers. These
bits correspond to the right-most column in Table 1, but
can only be logic high for a given balancer following an
execute command involving that same balancer. If a bal-
ancer is not active, its Gate Drive OK bit will be logic low.
The7th,8th,and9thbitsinthereadbalancestatusindicate
that all 6 cells are not overvoltage, that the transformer
secondary is not overvoltage, and that the LTC3300-2 die
isnotovertemperature, respectively. These3bitscanonly
be logic high following an execute command involving at
least one balancer. The 10th, 11th, and 12th bits in the
read balance status are currently not used and will always
be logic zero. As an example, if balancers 1 and 4 are both
active with no voltage or temperature faults, the 12-bit
read balance status should be 100100111000.
Pause/Resume Balancing (via SPI Port)
The LTC3300-2 provides a simple means to interrupt bal-
ancing in progress (stack wide) and then restart without
having to rewrite the previous balance command to all
LTC3300-2 ICs in the stack. To pause balancing, simply
write an 8-bit Execute Balance Command with incorrect
parity. To resume balancing, simply write an Execute Bal-
ance Command with the correct parity to each different
address. This feature is useful if precision cell voltage
measurements want to be performed during balancing
with the stack “quiet.” Immediate pausing of balancing
in progress will occur for any 8-bit Command Byte with
incorrect parity.
The restart time is typically 2ms which is the same as the
delayedstarttimeafteranewordifferentbalancecommand
(t
). It is measured from the 8th rising SCKI edge
DLY_START
until the balancer turns on and is illustrated in G25 in the
Typical Performance Characteristics section.
33002f
27
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
External Sense Resistor Selection
LTC3300-2 compared to the true sense resistor voltage.
ThiserrorcanbecompensatedforbyselectingtheRvalue
to add back this same drop using the typical current value
of 20µA out of the LTC3300-2 current sense pins at the
comparator trip point.
The external current sense resistors for both primary
and secondary windings set the peak balancing current
according to the following formulas:
50mV
IPEAK_PRI
RSENSE|PRIMARY
=
Setting Appropriate Max On-Times
The primary and secondary winding volt-second clamps
are intended to be used as a current runaway protection
feature and not as a substitute means of current control
replacing the sense resistors. In order to not interfere with
50mV
=
RSENSE|SECONDARY
IPEAK_SEC
Balancer Synchronization
normalI
/I
operation,themaximumontimesmust
PEAK ZERO
be set longer than the time required to ramp to I
(or
PEAK
Duetothestackedconfigurationoftheindividualsynchro-
nous flyback power circuits and the interleaved nature of
the gate drivers, it is possible at higher balance currents
for adjacent and/or penadjacent balancers within a group
of six to sync up. The synchronization will typically be to
thehighestfrequencyofanyactiveindividualbalancerand
can result in a slightly lower balance current in the other
affected balancer(s). This error will typically be very small
provided that the individual cells are not significantly out
I
)fortheminimumcellvoltageseenintheapplication:
ZERO
t
> L ꢀ I
/V
ON(MAX)|PRIMARY
PRI PEAK_PRI CELL(MIN)
t
>L ꢀI
ꢀT/(SꢀV
)
ON(MAX)|SECONDARY PRI PEAK_SEC
CELL(MIN)
These can be further increased by 20% to account for
manufacturing tolerance in the transformer winding
inductance and by 10% to account for I
variation.
PEAK
External FET Selection
of balance voltage-wise and due to the matched I
/
PEAK
I
’s and matched power circuits. Balancer synchro-
In addition to being rated to handle the peak balancing
current, external NMOS transistors for both primary and
secondary windings must be rated with a drain-to-source
breakdown such that for the primary MOSFET:
ZERO
nization can be reduced by lowpass filtering the primary
and/or secondary current sense signals with a simple RC
network as shown in Figure 9. A good starting point for
the RC time constant is one-tenth of the on-time of the
associated switch (primary or secondary). In the case
V
STACK + VDIODE
VDS(BREAKDOWN)|MIN > VCELL
+
T
of I
sensing, phase lag associated with the lowpass
PEAK
S
T
VDIODE
⎛
⎝
⎞
⎟
⎠
filter will result in a slightly lower voltage seen by the
= VCELL 1+
+
⎜
T
and for the secondary MOSFET:
DS(BREAKDOWN)|MIN > VSTACK +T VCELL + VDIODE
LTC3300-2
G1P/GnP/G1S/GnS
V
(
)
20µA
R
I1P/InP/I1S/InS
= VCELL S+T +TV
(
)
C
DIODE
R
SNS
–
–
–
V /Cn – 1/V /V
n = 2 TO 6
where S is the number of cells in the secondary winding
stack and 1:T is the transformer turns ratio from primary
to secondary. For example, if there are 12 Li-Ion cells in
the secondary stack and using a turns ratio of 1:2, the
primary FETs would have to be rated for greater than 4.2V
(1 + 6) + 0.5 = 29.9V and the secondary FETs would have
to be rated for greater than 4.2V (12 + 2) + 2V = 60.8V.
33002 F09
Figure 9. Using an RC Network to Filter
Current Sense Inputs to the LTC3300-2
33002f
28
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
Gooddesignpracticerecommendsincreasingthisvoltage
ratingbyatleast20%toaccountforhighervoltagespresent
due to leakage inductance ringing. See Table 7 for a list of
FETs that are recommended for use with the LTC3300-2.
Snubber Design
Careful attention must be paid to any transient ringing
seen at the drain voltages of the primary and secondary
windingFETsinapplication.Thepeakoftheringingshould
not approach and must not exceed the breakdown voltage
rating of the FETs chosen. Minimizing leakage inductance
present in the application and utilizing good board layout
techniques can help mitigate the amount of ringing. In
some applications, it may be necessary to place a series
resistor + capacitor snubber network in parallel with each
winding of the transformer. This network will typically
lower efficiency by a few percent, but will keep the FETs
in a safer operating region. Determining values for R and
C usually requires some trial-and-error optimization in the
application. For the transformers shown in Table 8, good
starting point values for the snubber network are 330Ω
in series with 100pF.
Table 7
PART NUMBER
SiR882DP
MANUFACTURER
Vishay
I
V
DS(MAX)
DS(MAX)
60A
100V
SiS892DN
Vishay
25A
70A
35A
60A
92A
100V
100V
100V
100V
100V
IPD70N10S3-12
IPB35N10S3L-26
RJK1051DPB
RJK1054DPB
Infineon
Infineon
Renesas
Renesas
Transformer Selection
The LTC3300-2 is optimized to work with simple 2-wind-
ing transformers with a primary winding inductance of
between 1 and 20 microhenries, a 1:2 turns ratio (primary
to secondary), and the secondary winding paralleling up
to 12 cells. If a larger number of cells in the secondary
stackisdesiredformoreefficientbalancing,atransformer
with a higher turns ratio can be selected. For example, a
1:10 transformer would be optimized for up to 60 cells in
the secondary stack. In this case the external FETs would
need to be rated for a higher voltage (see above). In all
cases the saturation current of the transformer must be
selected to be higher than the peak currents seen in the
application.
Boosted Gate Drive Component Selection
(BOOST = V
)
REG
+
The external boost capacitor connected from BOOST to
–
BOOST suppliesthegatedrivevoltagerequiredforturning
on the external NMOS connected to G6P. This capacitor
is charged through the external Schottky diode from C6
+
–
–
to BOOST when the NMOS is off (G6P = BOOST = C5).
When the NMOS is to be turned on, the BOOST driver
switches the lower plate of the capacitor from C5 to C6,
+
and the BOOST voltage common modes up to one cell
SeeTable8foralistoftransformersthatarerecommended
for use with the LTC3300-2.
voltage higher than C6. When the NMOS turns off again,
–
the BOOST driver switches the lower plate of the capaci-
tor back to C5 so that the boost capacitor is refreshed.
Table 8
TURNS
PRIMARY
A good rule of thumb is to make the value of the boost
capacitor 100 times that of the input capacitance of the
NMOSatG6P.Formostapplications,a0.1µF/10Vcapacitor
will suffice. The reverse breakdown of the Schottky diode
must only be greater than 6V. To prevent an excessive and
potentially damaging surge current from flowing in the
boostedgatedrivecomponentsduringinitialconnectionof
the battery voltages to the LTC3300-2, it is recommended
to place a 6.8Ω resistor in series with the Schottky diode
as shown in Figure 3. The surge current must be limited
to 1A to avoid potential damage.
PART NUMBER
MANUFACTURER RATIO* INDUCTANCE
I
SAT
750312504 (SMT) Würth Electronics
750312677 (THT) Würth Electronics
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
3.5µH
3.5µH
3.4µH
3.4µH
3µH
10A
10A
10A
10A
10A
10A
10A
10A
10A
MA5421-AL
CTX02-18892-R
XF0036-EP13S
LOO-3218
Coilcraft
Coiltronics
XFMRS Inc
BH Electronics
TOKO
3.4µH
3.4µH
3.4µH
3.4µH
DHCP-X79-1001
C128057LF
GCI
T10857-1
Inter Tech
*All transformers listed in the table are 8-pin components and can be
configured with turns ratios of 1:1, 1:2, 2:1, or 2:2.
33002f
29
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
Sizing the Cell Bypass Caps for Broken Connection
Protection
Protection from a broken connection to a cluster of sec-
ondary windings is provided local to each LTC3300-2 in
the stack by the secondary winding OVP function (via
WDT pin) described in the Operation section. However,
because of the interleaving of the transformer windings
up the stack, it is possible for a remote LTC3300-2 to still
act on the cell voltage seen locally by another LTC3300-2
at the point of the break which has shut itself off. For this
reason, each cluster of secondary windings must have
a dedicated connection to the stack separate from the
individual cell connection that it connects to.
If a single connection to the battery stack is lost while bal-
ancing,thedifferentialcellvoltagesseenbytheLTC3300-2
power circuit on each side of the break can increase or
decrease depending on whether charging or discharging
and where the actual break occurred. The worst-case
scenario is when the balancers on each side of the break
are both active and balancing in opposite directions. In
this scenario, the differential cell voltage will increase
rapidly on one side of the break and decrease rapidly
on the other. The cell overvoltage comparators working
in conjunction with appropriately-sized differential cell
bypass capacitors protect the LTC3300-2 and its asso-
ciated power components by shutting off all balancing
before any local differential cell voltage reaches its abso-
lute maximum rating. The comparator threshold (rising)
is 5V, and it takes 3µs to 6μs for the balancing to stop,
during which the bypass capacitor must prevent the dif-
ferential cell voltage from increasing past 6V. Therefore,
the minimum differential bypass capacitor value for full
broken connection protection is:
Using the LTC3300-2 with Fewer Than 6 Cells
To balance a series stack of N cells, the required number
ofLTC3300-2ICsisN/6roundeduptothenearestinteger.
SincetheLTC3300-2addressis5bits,themaximumNcan
be is 192 cells. Additionally, each LTC3300-2 in the stack
must interface to a minimum of 3 cells (must include C4,
C5, and C6). Thus, any stack of between 3 and 192 cells
can be balanced using an appropriate stack of LTC3300-2
ICs. Unused cell inputs (C1, C1 + C2, or C1 + C2 + C3) in a
–
given LTC3300-2 sub-stack should be shorted to V (see
Figure 10). However, in all configurations, the write data
remains at 16 bits. The LTC3300-2 will not act on the cell
balancing bits for the unused cell(s) but these bits are still
included in the CRC calculation.
I
CHARGE +IDISCHARGE •6µs
(
)
CBYPASS(MIN)
=
6V –5V
are set nominally equal, then
DISCHARGE
If I
and I
CHARGE
approximately12µFofrealcapacitanceperampofbalance
current is required.
•
•
•
•
•
•
•
•
•
+
+
+
+
+
+
+
+
CELL n + 3
CELL n + 2
CELL n + 1
CELL n
CELL n + 2
CELL n + 1
CELL n
C6
CELL n + 4
CELL n + 3
CELL n + 2
CELL n + 1
CELL n
C6
C6
C5
C4
C5
C4
C5
C4
+
+
+
+
LTC3300-2
C3
LTC3300-2
C3
LTC3300-2
C3
C2
C1
C2
C1
C2
C1
–
–
–
V
V
V
•
•
•
•
•
•
•
•
•
33002 F10
(10a) Sub-Stack Using Only 5 Cells (10b) Sub-Stack Using Only 4 Cells (10c) Sub-Stack Using Only 3 Cells
Figure 10. Battery Stack Connections for 5, 4 or 3 Cells
33002f
30
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
Supplementary Voltage Regulator Drive (>40mA)
The4.8VlinearvoltageregulatorinternaltotheLTC3300-2
powered from C6 as shown in Figure 11. The internal
regulator of the LTC3300-2 has very limited sink current
capability and will not fight the higher forced voltage.
is capable of providing 40mA at the V
pin. If additional
REG
current capability is required, the V
pin can be back-
REG
Fault Protection
driven by an external low cost 5V buck DC/DC regulator
Care should always be taken when using high energy
sources such as batteries. There are numerous ways
that systems can be misconfigured when considering
the assembly and service procedures that might affect a
battery system during its useful lifespan. Table 9 shows
the various situations that should be considered when
planning protection circuitry. The first four scenarios
are to be anticipated during production and appropriate
protection is included within the LTC3300-2 device itself.
C6
LTC3300-2
I
> 40mA
OUT
4.8V
LINEAR
VOLTAGE
REGULATOR
L
5V
V
V
IN
REG
SW
BUCK
DC/DC
R
FB2
C
IN
C
–
OUT
FB
V
GND
33002 F11
R
FB1
Figure 11. Adding External Buck DC/DC for >40mA VREG Drive
Table 9. LTC3300-2 Failure Mechanism Effect Analysis
SCENARIO
EFFECT
DESIGN MITIGATION
–
Top cell (C6) input connection loss to LTC3300-2.
Power will come from highest connected cell
input or via data port fault current.
Clamp diodes at each pin to C6 and V (within IC)
provide alternate power path. Diode conduction at
data ports will impair communication with higher
potential units.
–
–
Bottom cell (V ) input connection loss to
LTC3300-2.
Power will come from lowest connected cell
input or via data port fault current.
Clamp diodes at each pin to C6 and V (within IC)
provide alternate power path. Diode conduction at
data ports will impair communication with higher
potential units.
–
Random cell (C1-C5) input connection loss to
LTC3300-2.
Power-up sequence at IC inputs/differential
input voltage overstress.
Clamp diodes at each pin to C6 and V (within IC)
provide alternate power path. Zener diodes across
each cell voltage input pair (within IC) limit stress.
–
Disconnection of a harness between a sub-stack
of battery cells and the LTC3300-2 (in a system of
stacked groups).
Loss of all supply connections to the IC.
Clamp diodes at each pin to C6 and V (within
IC) provide alternate power path if there are other
devices (which can supply power) connected to
the LTC3300-2.
Secondary winding connection loss to battery
stack.
Secondary winding power FET could be
subjected to a higher voltage as bypass
capacitor charges up.
WDT pin implements a secondary winding OVP
circuit which will detect overvoltage and terminate
balancing.
Shorted primary winding sense resistor.
Shorted secondary winding sense resistor.
Primary winding peak current cannot be
detected to shut off primary switch.
Maximum ON-time set by R
resistor will shut
TONP
off primary switch if peak current detect doesn’t
occur.
Secondary winding peak current cannot be
detected to shut off secondary switch.
Maximum ON-time set by R
shut off secondary switch if peak current detect
doesn’t occur.
resistor will
TONS
Data error (noise margin induced or otherwise)
occurs during a write command.
Incoming checksum will not agree with the
incoming message when read in by any
individual LTC3300-2 in the stack.
Since the CRC remainder will not be zero, the
LTC3300-2 will not execute the write command,
even if an execute command is given. All
balancers with nonzero remainders will be off.
Data error (noise margin induced or otherwise)
occurs during a read command.
Outgoing checksum (calculated by the
LTC3300-2) will not agree with the
outgoing message when read in by the host
microprocessor.
Since the CRC remainder (calculated by the
host) will not be zero, the data cannot be trusted.
All balancers will remain in the state of the last
previously successful write.
33002f
31
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
Internal Protection Diodes
–
14μA shows up at the V pin of the LTC3300-2. To the
extentthatthe14μAcurrentsmatchperfectlychip-to-chip
in a long series stack, the resultant stack terminal currents
in shutdown are as follows: 14μA out of the top of stack
node and 14μA into the bottom of stack node. All other
intermediate node currents are zero.
Each pin of the LTC3300-2 has protection diodes to help
prevent damage to the internal device structures caused
by external application of voltages beyond the supply rails
asshowninFigure12. Thediodesshownareconventional
silicon diodes with a forward breakdown voltage of 0.5V.
The unlabeled Zener diode structures have a reverse-
breakdown characteristic which initially breaks down at
9V then snaps back to a 7V clamping potential. The Zener
Differences Between LTC3300-2 and LTC3300-1
TheLTC3300-1employsanSPI-compatibleserialinterface
inwhicheachICinthestackcommunicatesbidirectionally
to the ICs of the same type above and below it via currents.
There is no limit to the stack height. Large common mode
voltage differences are handled by each LTC3300-1. The
microprocessor in the BMS system communicates ONLY
with the bottom IC in the stack and subsequently all of
the ICs use the same fixed internal address.
diodes labeled Z
are higher voltage devices with an
CLAMP
initial reverse breakdown of 25V snapping back to 22V.
The forward voltage drop of all Zeners is 0.5V.
The internal protection diodes shown in Figure 12 are
power devices which are intended to protect against
limited-power transient voltage excursions. Given that
these voltages exceed the absolute maximum ratings of
the LTC3300-2, any sustained operation at these voltage
levels will damage the IC.
TheLTC3300-2employsanSPI-compatibleserialinterface
in which each IC has a unique 5-bit pin-strapped address.
The microprocessor in the BMS system communicates
directly with every IC in the stack with common mode
voltage differences handled by digital isolators or opto-
couplers. Because of the 5-bit address, the stack height is
limited to 32 LTC3300-2 ICs or 192 cells (~800V).
Initial Battery Connection to LTC3300-2
In addition to the above-mentioned internal protection
diodes, there are additional lower voltage/lower current
diodes across each of the six differential cell inputs (not
shown in Figure 12) which protect the LTC3300-2 during
initial installation of the battery voltages in the application.
Thesediodeshaveabreakdownvoltageof5.3Vwith20kΩ
of series resistance and keep the differential cell voltages
below their absolute maximum rating during power-up
when the cell terminal currents are zero to tens of mi-
croamps. This allows the six batteries to be connected in
any random sequence without fear of an unconnected cell
input pin overvoltaging due to leakage currents acting on
its high impedance input. Differential cell-to-cell bypass
capacitors used in the application must be of the same
nominal value for full random sequence protection.
There are 5 pins which have a different assignment, all of
them serial interface related.
See Table 10 for a summary of differences between
LTC3300-1 and LTC3300-2
Table 10. LTC3300-1 vs LTC3300-2 Differences
LTC3300-1
LTC3300-2
High Side Current Mode SPI Pins
CSBO, SCKO,
SDOI
None
“Where Am I in The Stack?” Pins
SPI Address
V
, TOS
None*
MODE
10101 (Fixed)
A A A A A
4 3 2 1 0
(Pin Strapped)
32 × 6 = 192 Cells
14µA
Maximum Height of Battery Stack
Unlimited
23.5µA
–
GND (V ) Pin Current in
Analysis of Stack Terminal Currents in Shutdown
Shutdown/Suspend
AsgivenintheElectricalCharacteristicstable,thequiescent
current of the LTC3300-2 when not balancing is 14μA at
the C6 pin and zero at the C1 through C5 pins. All of this
*LTC3300-2 has V
= TOS = 1 fixed internally. Each IC in the stack
MODE
thinks it is both top-of-stack and bottom-of-stack. Consequently, opto-
couplers or digital isolators are needed to communicate between the µP
and each IC.
33002f
32
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
V
REG
48
LTC3300-2
WDT
SDO
20
19
18
17
16
42
A4
47
A3
46
SDI
A2
45
SCKI
CSBI
BOOST
A1
44
A0
43
+
BOOST
CTRL
RTONP
RTONS
40
15
14
13
–
BOOST
41
C6
39
G6P
38
G6S
I6S
1
2
I6P
37
C5
36
G5P
35
G5S
I5S
3
4
I5P
34
C4
33
Z
CLAMP
G4P
32
G4S
I4S
5
6
I4P
31
C3
30
G3P
29
G3S
I3S
7
8
I3P
28
C2
27
Z
CLAMP
G2P
26
G2S
I2S
9
I2P
25
10
C1
24
G1S
I1S
G1P
23
11
12
I1P
22
4Ω
–
EXPOSED PAD
49
V
33002 F12
21
Figure 12. Internal Protection Diodes
33002f
33
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
How to Calculate the CRC
desiredbalancecommandcallsforsimultaneouscharging
ofCell1andsynchronousdischargingofCell4. The12-bit
message (MSB first) will be 110000010000. Appending
4 zeros results in 1100000100000000 for the dividend.
The long division is shown in Figure 13a with a resultant
CRC of 1101. Note that the CRC bits in the write balance
command are inverted. Thus the correct 16-bit balance
command is 1100000100000010. Figure 13b shows the
same long division procedure being used to check the
CRC of data (command or status) read back from the
LTC3300-2. In this scenario, the remainder after the long
division must be zero (0000) for the data to be valid. Note
thatthereadbackCRCbitsmustbeinvertedinthedividend
before performing the division.
Onesimplemethodofcomputingann-bitCRCistoperform
arithmetic modulo-2 division of the n+1 bit characteristic
polynomial into the m bit message appended with n ze-
ros (m+n bits). Arithmetic modulo-2 division resembles
normal long division absent borrows and carries. At each
intermediate step of the long division, if the leading bit
of the dividend is a 1, a 1 is entered in the quotient and
the dividend is exclusive-ORed bitwise with the divisor.
If the leading bit of the dividend is a 0, a 0 is entered in
the quotient and the dividend is exclusive-ORed bitwise
with n zeros. This process is repeated m times. At the end
of the long division, the quotient is disregarded and the
n-bit remainder is the CRC. This will be more clear in the
example to follow.
An alternate method to calculate the CRC is shown in
Figure 14 in which the balance command bits are input to
a combinational logic circuit comprised solely of 2-input
exclusive-OR gates. This “brute force” implementation is
easily replicated in a few lines of C code.
For the CRC implementation in the LTC3300-2, n = 4 and
4
m = 12. The characteristic polynomial employed is x + x
4
3
2
1
0
+ 1, which is shorthand for 1x + 0x + 0x + 1x + 1x ,
resulting in 10011 for the divisor. The message is the first
12 bits of the balance command. Suppose for example the
READBACK = 1100000100000010
DIVIDEND = 1100000100001101
1 1 0 1 0 1 1 0 1 0 1 1
1 1 0 1 0 1 1 0 1 0 1 1
1 0 0 1 1 1 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0
1 0 0 1 1 1 1 0 0 0 0 0 1 0 0 0 0 1 1 0 1
1 0 0 1 1
(a)
(b)
1 0 0 1 1
1 0 1 1 0
1 0 0 1 1
0 1 0 1 0
0 0 0 0 0
1 0 1 0 1
1 0 0 1 1
0 1 1 0 0
0 0 0 0 0
1 1 0 0 0
1 0 0 1 1
1 0 1 1 0
1 0 0 1 1
0 1 0 1 0
0 0 0 0 0
1 0 1 0 0
1 0 0 1 1
0 1 1 1 0
0 0 0 0 0
1 1 1 0 0
1 0 0 1 1
1 1 1 1 0
1 0 0 1 1
1 0 1 1 0
1 0 0 1 1
0 1 0 1 0
0 0 0 0 0
1 0 1 0 1
1 0 0 1 1
0 1 1 0 0
0 0 0 0 0
1 1 0 0 0
1 0 0 1 1
1 0 1 1 0
1 0 0 1 1
0 1 0 1 0
0 0 0 0 0
1 0 1 0 1
1 0 0 1 1
0 1 1 0 1
0 0 0 0 0
1 1 0 1 0
1 0 0 1 1
1 0 0 1 1
1 0 0 1 1
REMAINDER = 1 1 0 1 = 4-BIT CRC
REMAINDER = 0
33002 F13
0 0 1 0 = 4-BIT CRC INVERTED
Figure 13. (a) Long Division Example to Calculate CRC for Writes.
(b) Long Division Example to Check CRC for Reads
33002f
34
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
“Ø”
“Ø”
D6B
D5B
CRC [3]
CRC [3]
D3B
D1B
D2A
D5A
CRC [2]
CRC [2]
D3A
D1A
D4B
D2B
CRC [1]
CRC [1]
D4A
D6A
“Ø”
“Ø”
CRC [0]
CRC [0]
33002 F14
Figure 14. Combinational Logic Circuit Implementation of the CRC Calculator
Serial Communication Using the LTC6803 and LTC6804
The Typical Application shown on the back page of this
data sheet shows the serial communication connections
for a joint LTC3300-2/LTC6804-2 BMS. Each stacked
12-cell module contains two LTC3300-2 ICs and a single
LTC6804-2 monitor IC. . The LTC6804-2 in the module
is configured to provide an effective SPI port output at its
GPIO3, GPIO4, and GPIO5 pins which connect directly to
the low side communication pins (CSBI, SDI=SDO, SCKI)
of the lower LTC3300-2. The upper LTC3300-2 in each
module receives its serial communication via a digital
isolator from the lower LTC3300-2. Communication to
the lowermost LTC6804-2 and between monitor chips is
done via the LTC6820 and the isoSPI™ interface. In this
application, unused battery cells can be shorted from
the bottom of any module (i.e., outside the module, not
on the module board) as shown without any decrease in
monitor accuracy.
The LTC3300-2 is compatible with and convenient to
use with all LTC monitor chips, such as the LTC6803 and
LTC6804. Figure 17 in the Typical Applications section
shows the serial communications connections for a joint
LTC3300-2/LTC6803-2 BMS using a common micropro-
cessor SPI port. The SCKI, SDI, and SDO lines of the low-
ermost LTC3300-2 and LTC6803-2 are tied together. The
CSBI lines, however, must be separated to prevent talking
to both ICs at the same time. This is easily accomplished
by using one of the GPIO outputs from the LTC6803-2
to gate and invert the CSBI line to the LTC3300-2. In this
setup, communicating to the LTC6803-2 is no different
than without the LTC3300-2, as the GPIO1 output bit is
normallyhigh.To talktotheLTC3300-2,writtencommands
must be “bookended” with a GPIO1 negation write to the
LTC6803-2 prior to talking to the LTC3300-2 and with
a GPIO1 assertion write after talking to the LTC3300-2.
Communicationtoallnon-groundreferredLTC3300-2and
LTC6803-2 ICs is done through digital isolators.
33002f
35
For more information www.linear.com/LTC3300-2
LTC3300-2
APPLICATIONS INFORMATION
PCB Layout Considerations
2. The differential cell inputs (C6 to C5, C5 to C4, …, C1 to
exposed pad) should be bypassed with a 1µF or larger
capacitor as close to the LTC3300-2 as possible. This
is in addition to bulk capacitance present in the power
stages.
The LTC3300-2 is capable of operation with as much as
+
–
40V between BOOST and V . Care should be taken on
the PCB layout to maintain physical separation of traces
at different potentials. The pinout of the LTC3300-2 was
chosen to facilitate this physical separation. There is no
more than 8.4V between any two adjacent pins with the
–
3. Pin 21 (V ) is the ground sense for current sense resis-
tors connected to I1S-I6S and I1P (seven resistors).
Pin 21 should be Kelvined as well as possible with low
impedance traces to the ground side of these resistors
before connecting to the LTC3300-2 exposed pad.
–
exception of one instance (BOOST to BOOST ). In this
instance, the BOOST pin is pin-strapped in the applica-
–
tion to V or V
and does not need to route far from
REG
the LTC3300-2. The package body is used to separate
the highest voltage (e.g., 25.2V) from the lowest voltage
(0V). As an example, Figure 15 shows the DC voltage on
4. Cell inputs C1 to C5 are the ground sense for current
sense resistors connected to I2P-I6P (five resistors).
These pins should be Kelvined as well as possible
with low impedance traces to the ground side of these
resistors.
–
each pin with respect to V when six 4.2V battery cells
are connected to the LTC3300-2.
Additional “good practice” layout considerations are as
follows:
5. Thegroundsideofthemaximumon-timesettingresis-
tors connected to the RTONS and RTONP pins should
–
1. The V
pin should be bypassed to the exposed pad
be Kelvined to Pin 21 (V ) before connecting to the
REG
–
and to V , each with 1µF or larger capacitors as close
to the LTC3300-2 as possible.
LTC3300-2 exposed pad.
6. Trace lengths from the LTC3300-2 gate drive outputs
(G1S-G6S and G1P-G6P) and current sense inputs
(I1S-I6S and I1P-I6P) should be as short as possible.
7. The boosted gate drive components (diode and ca-
pacitor), if used, should form a tight loop close to the
+
–
LTC3300-2 C6, BOOST , and BOOST pins.
0V TO 4.8V G6S—PIN 1
0V I6S
0V TO 4.8V G5S
0V I5S
0V TO 4.8V G4S
0V I4S
0V TO 4.8V G3S
0V I3S
0V TO 4.8V G2S
0V I2S
0V TO 4.8V G1S
0V I1S
C5 21V
G5P 16.8V TO 25.2V
I5P 16.8V
C4 16.8V
G4P 12.6V TO 21V
I4P 12.6V
C3 12.6V
G3P 8.4V TO 16.8V
I3P 8.4V
C2 8.4V
G2P 4.2V TO 12.6V
I2P 4.2V
8. For the external power components (transformer, FETs
and current sense resistors), it is important to keep the
area encircled by the two high speed current switching
loops (primary and secondary) as tight as possible.
This is greatly aided by having two additional bypass
capacitors local to the power circuit: one differential
cell to cell and one from the transformer secondary to
LTC3300-2
(EXPOSED PAD = 0V)
–
local V .
A representative layout incorporating all of these recom-
mendations is implemented on the DC2064A demo board
for the LTC3300-1 companion product (with further ex-
planation in its accompanying demo board manual). To
accommodate the LTC3300-2, only minor modifications
to Pins 43 to 47 connections need to be made. PCB layout
files (.GRB) are also available from the factory.
33002 F15
Figure 15. Typical Pin Voltages for Six 4.2V Cells
33002f
36
For more information www.linear.com/LTC3300-2
LTC3300-2
TYPICAL APPLICATIONS
6.8Ω
0.1µF
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
–
+
BOOST BOOST
1:1
C6
•
+
CELL 6
10µH
10µH
10µF
•
G6P
I6P
25mΩ
•
1:1
C5
+
CELL 5
10µH
10µH
10µF
•
G5P
I5P
25mΩ
C4
C3
C2
•
•
•
•
•
•
•
•
•
1:1
LTC3300-2
•
+
CELL 2
10µH
10µH
A4
A3
A2
A1
10µF
•
G2P
I2P
A0
SERIAL
COMMUNICATION
RELATED
CSBI
SCKI
SDI
PINS
25mΩ
•
1:1
C1
SDO
+
CELL 1
10µH
10µH
WDT
ISOLATED
+
12V LEAD ACID
AUXILIARY
CELL
10µF
•
G1P
I1P
25mΩ
G1S-G6S
I1S-I6S
NC
V
REG
–
BOOST
V
ISOLATION
BOUNDARY
CTRL
RTONP RTONS
33002 F16
10µF
28k
41.2k
Figure 16. LTC3300-2 Unidirectional Discharge-Only Balancing Application to Charge an Isolated Auxiliary Cell
33002f
37
For more information www.linear.com/LTC3300-2
LTC3300-2
TYPICAL APPLICATIONS
TOP OF BATTERY STACK
+
C6
C5
C4
C3
C2
C1
CELL 24
C12
C11
C10
C9
C8
C7
+
CELL 23
LTC3300-2
DIGITAL
ISOLATOR
ADDRESS =
+
CELL 22
00011
CSBI
SCKI
SDI
+
V
REG
CELL 21
C
–
VREG4
SDO
V
+
CELL 20
LTC6803-2
ADDRESS = 0001
+
CELL 19
C6
+
CELL 18
C6
C5
C4
C3
C2
C1
GPIO2
GPIO1
C5
C4
C3
C2
C1
NC
NC
+
CELL 17
DIGITAL
ISOLATOR
LTC3300-2
ADDRESS =
00010
DIGITAL
ISOLATOR
+
CELL 16
CSBI
SCKI
SDI
CSBI
SCKI
SDI
V
REG
+
V
REG
CELL 15
C
SDO
VREG6
C
VREG3
–
–
+
SDO
V
V
CELL 14
+
CELL 13
+
CELL 12
C6
C5
C4
C3
C2
C1
C12
C11
C10
C9
C8
C7
+
CELL 11
LTC3300-2
ADDRESS =
00001
DIGITAL
ISOLATOR
+
CELL 10
CSBI
SCKI
SDI
+
V
REG
CELL 9
C
–
VREG2
SDO
V
+
CELL 8
LTC6803-2
ADDRESS = 0000
+
CELL 7
C6
+
CELL 6
C6
C5
C4
C3
C2
C1
GPIO2
GPIO1
NC
C5
C4
C3
C2
C1
V
+
DIGITAL
ISOLATOR
CELL 5
3V
LTC3300-2
ADDRESS =
00000
V
REG1
V
REG5
OR
+
+
V1
V2
+
CELL 4
CSBI
SCKI
SDI
CS
MPU
CLK
CSBI
SCKI
SDI
V
V
V
REG5
REG1
REG
REG
+
CELL 3
C
C
VREG5
SDO
VREG1
–
–
+
SDO
V
V
CELL 2
MOSI
+
MOSO
CELL 1
–
V1
–
V2
33002 F17
Figure 17. LTC3300-2/LTC6803-2 Battery and Serial Communication Connections for a 24-Cell Stack
33002f
38
For more information www.linear.com/LTC3300-2
LTC3300-2
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
UK Package
48-Lead Plastic QFN (7mm × 7mm)
(Reference LTC DWG # 05-08-ꢀ704 Rev C)
0.70 0.05
5.ꢀ5 0.05
5.50 REF
6.ꢀ0 0.05 7.50 0.05
(4 SIDES)
5.ꢀ5 0.05
PACKAGE OUTLINE
0.25 0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
0.75 0.05
R = 0.ꢀꢀ5
TYP
7.00 0.ꢀ0
(4 SIDES)
R = 0.ꢀ0
TYP
47 48
0.40 0.ꢀ0
PIN ꢀ TOP MARK
(SEE NOTE 6)
ꢀ
2
PIN ꢀ
CHAMFER
C = 0.35
5.ꢀ5 0.ꢀ0
5.50 REF
(4-SIDES)
5.ꢀ5 0.ꢀ0
(UK48) QFN 0406 REV C
0.200 REF
0.25 0.05
0.50 BSC
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
NOTE:
ꢀ. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WKKD-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE, IF PRESENT
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN ꢀ LOCATION ON THE TOP AND BOTTOM OF PACKAGE
33002f
39
For more information www.linear.com/LTC3300-2
LTC3300-2
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
LXE Package
48-Lead Plastic Exposed Pad LQFP (7mm × 7mm)
(Reference LTC DWG #05-08-1832 Rev C)
7.15 – 7.25
5.50 REF
48
37
36
1
0.50 BSC
C0.30
5.50 REF
7.15 – 7.25
0.20 – 0.30
3.60 0.05
3.60 0.05
e 3
12
13
25
PACKAGE OUTLINE
24
COMPONENT
PIN “A1”
1.30 MIN
TRAY PIN 1
BEVEL
RECOMMENDED SOLDER PAD LAYOUT
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
PACKAGE IN TRAY LOADING ORIENTATION
9.00 BSC
7.00 BSC
3.60 0.10
48
37
37
48
SEE NOTE: 3
1
36
36
1
C0.30
9.00 BSC
7.00 BSC
3.60 0.10
A
A
25
12
12
25
C0.30 – 0.50
24
13
13
24
BOTTOM OF PACKAGE—EXPOSED PAD (SHADED AREA)
1.60
11° – 13°
1.35 – 1.45 MAX
R0.08 – 0.20
GAUGE PLANE
0.25
0° – 7°
LXE48 LQFP 0113 REV C
11° – 13°
1.00 REF
0.50
BSC
0.09 – 0.20
0.17 – 0.27
SIDE VIEW
0.05 – 0.15
0.45 – 0.75
SECTION A – A
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
3. PIN-1 INDENTIFIER IS A MOLDED INDENTATION, 0.50mm DIAMETER
4. DRAWING IS NOT TO SCALE
2. DIMENSIONS OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.25mm ON ANY SIDE, IF PRESENT
33002f
40
For more information www.linear.com/LTC3300-2
LTC3300-2
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
12/13 Add new bullet Integrates Seamlessly with the LTC680x Family of Multicell Battery Stack Monitors
Change part number XF0036-EP135 to XF0036-EP13S
1
29
33002f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
41
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LTC3300-2
TYPICAL APPLICATION
LTC3300-2/LTC6804-2 Serial Communication Connections
DATA
12-CELL
MODULE 2
LTC3300-2
ADDRESS =
00011
4
DIGITAL
ISOLATOR
LTC6804-2
9 CELLS
LTC3300-2
ADDRESS =
0001
ADDRESS =
00010
SCKI
GPIO5
SDI
GPIO4
ISO IN
SDO
CSBI
GPIO3
12-CELL
MODULE 1
LTC3300-2
ADDRESS =
00001
4
DIGITAL
ISOLATOR
LTC6804-2
12 CELLS
LTC3300-2
ADDRESS =
00000
SCKI
ADDRESS =
0000
LTC6820
isoSPI
GPIO5
GPIO4
4
SDI
ISO SPI
ISO IN
SDO
CSBI
GPIO3
33002 TA02
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC3300-1
High Efficiency Bidirectional Mulitcell Battery Balancer Allows Serial Ports of Multiple Devices to Be Daisy-Chained without
Opto-Couplers or Isolators
LTC6801
Independent Multicell Battery Stack Monitor
Monitors Up to 12 Series-Connected Battery Cells for Undervoltage or
Overvoltage, Companion to LTC6802, LTC6803 and LTC6804
LTC6802-1/LTC6802-2 Multicell Battery Stack Monitors
Measures Up to 12 Series-Connected Battery Cells, 1st Generation:
Superseded by the LTC6803 and LTC6804 for New Designs
LTC6803-1/LTC6803-3 Multicell Battery Stack Monitors
LTC6803-2/LTC6803-4
Measures Up to 12 Series-Connected Battery Cells, 2nd Generation:
Functionally Enhanced and Pin Compatible to the LTC6802
LTC6804-1/LTC6804-2 Multicell Battery Monitors
Measures Up to 12 Series-Connected Battery Cells, 3rd Generation:
Higher Precision Than LTC6803 and Built-In isoSPI Interface
LTC6820
isoSPI Isolated Communications Interface
Provides an Isolated Interface for SPI Communication Up to 100m
Using a Twisted Pair, Companion to the LTC6804
33002f
LT 0813 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
42
●
●
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC3300-2
LINEAR TECHNOLOGY CORPORATION 2013
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