LT3650IMSE-4.1PBF [Linear]
High Voltage 2 Amp Monolithic Li-Ion Battery Charger; 高电压2安培单片锂离子电池充电器
| 型号： | LT3650IMSE-4.1PBF |
| 厂家： | 
Linear |
| 描述： | High Voltage 2 Amp Monolithic Li-Ion Battery Charger |
| 文件： | 总20页 (文件大小：209K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3650-4.1/LT3650-4.2
High Voltage 2 Amp
Monolithic Li-Ion Battery Charger
FEATURES
DESCRIPTION
The LT®3650 is a complete monolithic single-cell Li-Ion/
Polymer battery charger that operates over a 4.75V to
32V input voltage range (7.5V minimum start-up voltage).
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Wide Input Voltage Range: 4.75V to 32V
(40V Absolute Maximum)
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Programmable Charge Current Up to 2A
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User-Selectable Termination: C/10 or Onboard
Termination Timer
The LT3650 provides a constant-current/constant-volt-
age charge characteristic, with maximum charge current
externally programmable up to 2A, set using an external
current sense resistor. A precondition feature trickle-
charges a low voltage battery, and bad-battery detection
provides a signal and suspends charging if a battery does
not respond to preconditioning.
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n
n
n
n
n
n
n
n
n
n
n
n
n
Dynamic Charge Rate Programming/Soft-Start Pin
Programmable Input Current Limit
No V Blocking Diode Required
IN
1MHz Fixed Frequency
Average Current Mode Control
0.5% Float Voltage Accuracy
TheLT3650canbeconfiguredtoterminatechargingwhen
chargecurrentfallstoC/10, orone-tenththeprogrammed
maximumcurrent.Oncechargingisterminated,theLT3650
entersalowcurrent(85μA)standbymode.Anauto-restart
feature starts a new charging cycle if the battery voltage
drops 2.5% from the float voltage, or if a new battery is
inserted into a charging system.
5% Charge Current Accuracy
2.5% C/10 Detection Accuracy
NTC Resistor Temperature Monitor
Auto-Recharge at 97.5% Float Voltage
Auto-Precondition at <70% Float Voltage
Bad-Battery Detection with Auto-Reset
Binary Coded Open-Collector Status Pins
3mm × 3mm DFN-12 or MSOP-12 Package
The LT3650 contains a user-programmable internal safety
timer (typically set to a three hour full cycle time). The IC
can be configured to use this internal timer if a time-based
termination scheme is desired in which charging can con-
tinue below C/10 until a desired time is reached.
APPLICATIONS
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Industrial Handheld Instruments
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12V to 24V Automotive and Heavy Equipment
The LT3650 is available in a low profile (0.75mm) 3mm ×
3mm 12-pin DFN and 12-pin MSOP packages.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
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Desktop Cradle Chargers
Notebook Computers
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VBAT and Efficiency vs IBAT
TYPICAL APPLICATION
100
7.5V to 32V Single-Cell Li-Ion 2A Charger
V
BAT
4.20
4.15
4.10
4.05
CMSH3-40MA
V
IN
7.5V to 32V
90
80
70
60
SW
V
IN
V
= 12V
IN
1μF
10μF
CLP
BOOST
6.8μH
V
= 20V
IN
LT3650-4.2
CMPSH1-4
SHDN
CHRG
SENSE
0.05Ω
BAT
NTC
FAULT
+
Li-ION
BATTERY
10μF
TIMER
RNG/SS
0
0.5
1
1.5
2
I
(A)
3650 TA01a
BAT
365042 TA01b
36504142fb
1
LT3650-4.1/LT3650-4.2
ABSOLUTE MAXIMUM RATINGS (Note 1)
SENSE-BAT............................................... –0.5V to 0.5V
TIMER, RNG/SS, NTC ..............................................2.5V
Operating Junction Temperature Range
(Note 2)..................................................–40°C to 125°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
V ............................................................................40V
IN
SHDN, CHRG, FAULT............................... V + 0.5V, 40V
IN
IN
CLP......................................................... V
0.5V, 40V
SW............................................................................40V
SW-V .....................................................................4.5V
IN
BOOST .....................................................SW + 10V, 50V
MSE.................................................................. 300°C
SENSE, BAT ..............................................................10V
PIN CONFIGURATION
TOP VIEW
TOP VIEW
1
2
3
4
5
6
12 SW
V
IN
1
2
3
4
5
6
V
12 SW
11 BOOST
10 SENSE
IN
CLP
SHDN
CHRG
FAULT
TIMER
11 BOOST
CLP
SHDN
CHRG
FAULT
TIMER
SENSE
BAT
10
9
13
13
9
8
7
BAT
NTC
RNG/SS
NTC
8
7
RNG/SS
MSE PACKAGE
DD PACKAGE
12-LEAD PLASTIC MSOP
12-LEAD (3mm s 3mm) PLASTIC DFN
T
= 125°C, θ = 43°C/W, θ = 3°C/W
JA JC
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
JMAX
T
= 125°C, θ = 43°C/W, θ = 3°C/W
JA JC
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
JMAX
ORDER INFORMATION
LEAD FREE FINISH
LT3650EDD-4.1#PBF
LT3650IDD-4.1#PBF
LT3650EDD-4.2#PBF
LT3650IDD-4.2#PBF
LT3650EMSE-4.1#PBF
LT3650IMSE-4.1#PBF
LT3650EMSE-4.2#PBF
LT3650IMSE-4.2#PBF
TAPE AND REEL
PART MARKING*
LFGQ
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3650EDD-4.1#TRPBF
LT3650IDD-4.1#TRPBF
LT3650EDD-4.2#TRPBF
LT3650IDD-4.2#TRPBF
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
12-Lead Plastic DFN (3mm × 3mm)
12-Lead Plastic DFN (3mm × 3mm)
12-Lead Plastic DFN (3mm × 3mm)
12-Lead Plastic DFN (3mm × 3mm)
12-Lead Plastic MSOP
LFGQ
LDDS
LDDS
LT3650EMSE-4.1#TRPBF 365041
LT3650IMSE-4.1#TRPBF 365041
LT3650EMSE-4.2#TRPBF 365042
LT3650IMSE-4.2#TRPBF 365042
12-Lead Plastic MSOP
12-Lead Plastic MSOP
12-Lead Plastic MSOP
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 non-standard 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/
36504142fb
2
LT3650-4.1/LT3650-4.2
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at VIN = 20V, BOOST-SW = 4V, SHDN = 2V, SENSE = BAT = VBAT(FLT), CTIMER = 0.68μF.
SYMBOL
LT3650
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
V
V
V
V
V
V
Operating Range
Start Voltage
(Note 3)
4.75
32
32
V
V
IN
IN
IN
7.5
l
OVLO Threshold
OVLO Hysteresis
V
V
Rising
Rising
35
1
40
V
V
IN(OVLO)
IN(UVLO)
BAT(FLT)
IN
IN
l
UVLO Threshold
UVLO Hysteresis
4.6
0.2
4.75
V
V
Battery Float Voltage
LT3650-4.1
4.08
4.06
4.1
4.12
4.14
V
V
l
l
LT3650-4.2
4.18
4.16
4.2
4.22
4.24
V
V
Recharge Battery Threshold
Threshold Voltage Relative to V
–100
2.9
mV
V
ΔV
BAT(FLT)
RECHRG
V
Battery Precondition Threshold Voltage
V
BAT
Rising
BAT(PRE)
V
Battery Precondition Threshold
Hysteresis
90
mV
BAT(PREHYST)
l
I
Operating Input Supply Current
CC/CV Mode, I = 0
2.5
85
15
3.5
mA
μA
μA
VIN
SW
Standby Mode
Shutdown (SHDN = 0)
I
I
BOOST Supply Current
Switch-On, I = 0
BOOST
SW
(BOOST – SW)
2.5V < V
< 4.5V
20
30
mA
mA/A
mV
/I
BOOST Switch Drive
I
SW
= 2A
BOOST SW
V
Switch-On Voltage Drop
Switch Current Limit
V
IN
– V , I = 2A
350
SW(ON)
SW SW
l
l
I
2.5
A
SW(MAX)
V
Precondition Current Sense Voltage
V
V
– V
BAT
15
mV
SENSE(PRE)
SENSE
BAT
= 2.5
V
CLP Threshold Voltage
V
CLP
– V ; V
– V = 50mV
37.5
50
200
100
10
62.5
mV
nA
CLP(DC)
CLP
IN SENSE
BAT
I
CLP Input Bias Current
l
l
l
l
V
V
Maximum Current Sense Voltage
C/10 Trigger Sense Voltage
BAT Input Bias Current
V
SENSE
– V ; V = 3.5V, V = 1.2V
RNG/SS
95
105
12.5
1
mV
mV
μA
SENSE(DC)
SENSE(C/10)
BAT
BAT BAT
7.5
I
I
I
Charging Terminated
Charging Terminated
0.1
0.1
1
SENSE Input Bias Current
Charger Reverse Current:
1
μA
SENSE
V
= 0V; BAT = SENSE = SW = V
BAT(FLT)
μA
REVERSE
IN
I
+ I
+ I
SENSE SW
BAT
l
l
V
V
V
NTC Range Limit (High)
NTC Range Limit (Low)
NTC Threshold Hysteresis
NTC Disable Impedance
NTC Bias Current
V
V
Rising
Falling
1.25
0.27
1.36
0.29
20
1.45
V
V
NTC(H)
NTC
0.315
NTC(L)
NTC
% of Threshold
Minimum External Impedance to GND
%
NTC(HYST)
l
l
l
l
R
250
47.5
45
500
50
kΩ
μA
μA
V/V
NTC(DIS)
NTC
I
I
V
NTC
= 0.8V
52.5
55
I
Bias Current
RNG/SS
50
RNG/SS
V
/V
Current Limit Programming:
/V
V = 0.5
RNG/SS
8.5
10
11.5
RNG/SS SENSE
V
RNG/SS SENSE(MAX)
l
V
V
Shutdown Threshold
Shutdown Hysteresis
SHDN Input Bias Current
Rising
1.17
1.20
120
–10
1.23
V
mV
SHDN
SHDN(HYST)
SHDN
I
nA
36504142fb
3
LT3650-4.1/LT3650-4.2
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at VIN = 20V, BOOST-SW = 4V, SHDN = 2V, SENSE = BAT = VBAT(FLT), CTIMER = 0.68μF.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
l
l
V
, V
Status Low Voltage
Charge/Discharge Current
Timer Disable Threshold
Full Charge Cycle Timeout
Precondition Timeout
Timer Accuracy
10mA Load
0.4
CHRG FAULT
I
25
0.25
3
μA
TIMER
V
0.1
V
TIMER(DIS)
t
hr
TIMER
22.5
min
%
l
l
l
–10
0.9
15
10
1.1
90
f
O
Operating Frequency
Duty Cycle Range
1
MHz
%
DC
Continuous Operation
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.
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT3650I specifications are
guaranteed over the full –40°C to 85°C temperature range. High junction
temperatures degrade operating lifetimes.
Note 2: The LT3650E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
Note 3: V voltages below the start threshold are only supported if
IN
(V
– V ) > 2V.
BOOST SW
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Maximum Charge Current vs IRNG/SS
Voltage, ICHG(MAX) as a Percentage
of Programmed IMAX
Battery Float Voltage
vs Temperature
VIN Standby Mode Current
vs Temperature
100
95
90
85
80
75
70
65
100
80
60
40
20
0
0.1
0.05
0
–0.05
–0.1
–50
0
25
50
75 100 125
–25
50
–50
0
25
75
100
–25
0
0.4
0.6
0.8
1.0
1.2
0.2
TEMPERATURE (°C)
TEMPERATURE (°C)
V
RNG/SS
3650 G01
365042 G02
365042 G03
36504142fb
4
LT3650-4.1/LT3650-4.2
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
CC/CV Charging; SENSE Pin Bias
Current vs VSENSE
Switch Drive (ISW/IBOOST
)
Switch Forward Drop (VIN – VSW
)
vs ISW
vs Temperature
480
460
440
420
400
380
360
340
320
100
50
36
33
30
27
24
21
18
15
12
9
LT3650-4.2
I
= 2A
SW
0
–50
–100
–150
–200
–250
–300
–350
6
3
0
3.5
4
4.5
–50
0
25
50
75 100 125
0
0.5
1
1.5
2
2.5
(V)
3
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
(A)
–25
TEMPERATURE (°C)
V
I
SENSE
SW
365042 G06
365042 G04
365042 G05
CLP Input Limit Threshold
(VCLP – VIN) vs Temperature,
ICHG at 50%
C/10 Threshold (VSENSE – VBAT
)
IMAX Current Limit (VSENSE – VBAT
)
vs Temperature
vs Temperature
12
11
10
9
51.0
50.8
50.6
50.4
50.2
50.0
49.8
49.6
49.4
49.2
49.0
101.0
100.8
100.6
100.4
100.2
100.0
99.8
V
= 3.5V
BAT
99.6
99.4
99.2
8
99.0
–50
0
25
50
75 100 125
–50
0
25
50
75 100 125
–50
0
25
50
75 100 125
–25
–25
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
365042 G07
365042 G08
365042 G09
Thermal Foldback – IMAX
Current Limit (VSENSE – VBAT
)
CC/CV Charging; BAT Pin Bias
Current vs VBAT
vs Temperature
2.2
120
100
80
60
40
20
0
LT3650-4.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
–0.2
–0.4
0
0.5
1
1.5
2
V
BAT
2.5
(V)
3
3.5
4
4.5
25 35 45 55 65 75 85 95 105 115 125 135
TEMPERATURE (°C)
365042 G11
365042 G10
36504142fb
5
LT3650-4.1/LT3650-4.2
PIN FUNCTIONS
V (Pin1):ChargerInputSupply.V pinoperatingrangeis
be pulled low. If no fault conditions exist, the FAULT pin
remains high impedance (see the Applications Informa-
tion section).
IN
IN
4.75Vto32V. V ≥7.5Vor(V
–V )>2Visrequired
IN
BOOST
SW
for start-up. I = 85μA after charge termination.
VIN
CLP (Pin 2): System Current Limit Input. System current
levels can be monitored by connecting the input power
supply to the CLP pin and connecting a sense resistor
TIMER (Pin 6): End-Of-Cycle Timer Programming Pin.
If a timer-based charge termination is desired, connect
a capacitor from this pin to ground. Full charge end-of-
cycle time (in hours) is programmed with this capacitor
following the equation:
from the CLP pin to the V pin. Additional system load is
IN
drawn from the V pin connection, and maximum system
IN
load is achieved when V
– V = 50mV. The LT3650
6
CLP
VIN
t
= C
• 4.4 • 10
EOC
TIMER
servos the maximum charge current required to maintain
A bad-battery fault is generated if the battery does not
reachthepreconditionthresholdvoltagewithinone-eighth
programmed maximum system current. If this function is
not desired, connect the CLP pin to the V pin (see the
IN
of t , or:
Applications Information section).
EOC
5
t
= C
• 5.5 • 10
SHDN (Pin 3): Precision Threshold Shutdown Pin. The
enable threshold is 1.225V (rising), with 120mV of input
hysteresis.Wheninshutdownmode,allchargingfunctions
are disabled. The precision threshold allows use of the
SHDN pin to incorporate UVLO functions. If the SHDN pin
is pulled below 0.4V, the IC enters a low current shutdown
PRE
TIMER
A 0.68μF capacitor is typically used, which generates a
timer EOC at three hours, and a precondition limit time of
22.5 minutes. If a timer-based termination is not desired,
the timer function is disabled by connecting the TIMER
pin to ground. With the timer function disabled, charging
terminates when the charge current drops below a C/10
mode where the V pin current is reduced to 15μA. Typi-
IN
cal SHDN pin input bias current is 10nA. If the shutdown
rate, or I /10.
CHG(MAX)
function is not desired, connect the pin to the V pin.
IN
RNG/SS (Pin 7): Charge Current Programming Pin. This
pin allows a dynamic adjustment of the maximum charge
current, and can be used to employ a soft-start function.
Maximum charge current is adjusted by setting the volt-
age on this pin, such that the maximum desired voltage
CHRG (Pin 4): Open-Collector Charger Status Output;
typically pulled up through a resistor to a reference volt-
age. This status pin can be pulled up to voltages as high
as V when disabled, and can sink currents up to 10mA
IN
when enabled. During a battery charging cycle, CHRG is
pulledlow. Whenthechargecycleisterminated, theCHRG
pin becomes high impedance. If the internal timer is used
for termination, the pin stays low during the charging
cycle until the charge current drops below a C/10 rate, or
across theinductor current sense resistor (V
– V ) is
SENSE
BAT
0.1 • V
, so the maximum charge current reduces to:
RNG/SS
V
• I
RNG/SS CHG(MAX)
This pin has an effective range from 0V to 1V. 50μA is
sourced from this pin, so the maximum charge current
I
/10.Atemperaturefaultalsocausesthispintobe
CHG(MAX)
pulled low (see the Applications Information section).
can be programmed by connecting a resistor (R
)
RNG/SS
from RNG/SS to ground, such that the voltage dropped
across the resistor is equivalent to the desired program-
ming voltage, or:
FAULT (Pin 5): Open-Collector Fault Status Output; typi-
cally pulled up through a resistor to a reference voltage.
This status pin can be pulled up to voltages as high as V
IN
when disabled, and can sink currents up to 10mA when
enabled. This pin indicates charge cycle fault conditions
duringabatterychargingcycle.Atemperaturefaultcauses
this pin to be pulled low. If the internal timer is used for
termination, a bad-battery fault also causes this pin to
V
= 50μA • R
RNG/SS
RNG/SS
Soft-start functionality can be implemented by con-
necting a capacitor (C
) from RNG/SS to ground,
RNG/SS
such that the time required to charge the capacitor to 1V
36504142fb
6
LT3650-4.1/LT3650-4.2
PIN FUNCTIONS
(full charge current) is the desired soft-start interval (t ).
the BAT pin falls 2.5% below this float voltage. Once the
charge cycle is terminated, the input bias current of the
BATpinisreducedto<0.1μA,tominimizebatterydischarge
while the charger remains connected.
SS
For no R , this capacitor value follows the relation:
RNG/SS
CRNG/SS = 50μA • tSS
The RNG/SS pin is pulled low during fault conditions,
allowing graceful recovery from faults should soft-start
functionality be implemented. Both the soft-start capaci-
tor and the programming resistor can be implemented in
parallel. All C/10 monitoring functions are disabled while
SENSE (Pin 10): Charge Current Sense Pin. Connect the
more positive voltage end of the inductor sense resistor
(R
) to the SENSE pin and the other end to the BAT
SENSE
pin. The voltage across this resistor sets the average
charge current. The maximum average charge current
V
is below 0.1V to accommodate long soft-start
RNG/SS
intervals.
(I
MAX
) corresponds to 100mV across the sense resistor.
This resistor can be set to program maximum charge
currents as high as 2A. The sense resistor value follows
the relation:
RNG/SS voltage can also be manipulated using an active
device,employingapull-downtransistortodisablecharge
current or to dynamically servo maximum charge current.
Manipulation of the RNG/SS pin with active devices that
have low impedance pull-up capability is not allowed (see
the Applications Information section).
0.1V
IMAX
RSENSE
=
Once the charge cycle is terminated, the input bias current
oftheSENSEpinisreducedto<0.1μA, tominimizebattery
discharge while the charger remains connected.
NTC (Pin 8): Battery Temperature Monitor Pin. This pin
is the input to the NTC (negative temperature coefficient)
thermistortemperaturemonitoringcircuit.Thisfunctionis
enabled by connecting a 10kΩ, B = 3380 NTC thermistor
from the NTC pin to ground. The pin sources 50μA, and
monitors the voltage across the 10kΩ thermistor. When
the voltage on this pin is above 1.36V (T < 0°C) or below
0.29V (T > 40°C), charging is disabled and the CHRG and
FAULT pins are both pulled low. If internal timer termina-
tion is being used, the timer is paused, suspending the
chargingcycle.ChargingresumeswhenthevoltageonNTC
returns to within the 0.29V to 1.36V active region. There
isapproximately5°Coftemperaturehysteresisassociated
with each of the temperature thresholds. The temperature
monitoring function remains enabled while thermistor
resistancetogroundislessthan250kΩ, soifthisfunction
is not desired, leave the NTC pin unconnected.
BOOST (Pin 11): Bootstrapped Supply Rail for Switch
Drive.Thispinfacilitatessaturationoftheswitchtransistor.
Connect a 1μF or greater capacitor from the BOOST pin
to the SW pin. Operating range of this pin is 0V to 4.5V,
referenced to the SW pin. The voltage on the decoupling
capacitor is refreshed through a rectifying diode, with
the anode connected to either the battery output voltage
or an external source, and the cathode connected to the
BOOST pin.
SW (Pin 12): Switch Output Pin. This pin is the output
of the charger switch, and corresponds to the emitter of
the switch transistor. When enabled, the switch shorts
the SW pin to the V supply. The drive circuitry for this
IN
switch is bootstrapped above the V supply using the
IN
BOOST supply pin, allowing saturation of the switch for
maximum efficiency. The effective on-resistance of the
boosted switch is 0.175Ω.
BAT (Pin 9): Battery Voltage Monitor Pin. Connect 10μF
decoupling capacitance (C ) from this pin to ground.
BAT
Depending on application requirements, larger value
decoupling capacitors may be required (see the Applica-
tion Information section). The charge function operates to
achieve the final float voltage at this pin. The auto-restart
feature initiates a new charging cycle when the voltage at
SGND (Pin 13): Ground Reference and Backside Exposed
Lead Frame Thermal Connection. Solder the exposed lead
frame to the PCB ground plane.
36504142fb
7
LT3650-4.1/LT3650-4.2
BLOCK DIAGRAM
CLP
125°C
+
–
–
+
STANDBY
UVLO
+
–
T
DIE
4.6V
BOOST
50mV
+
–
OVLO
V
IN
35V
10mΩ
+
–
R
0.2V
TIMER
LATCH
S
Q
30mV
–
+
OSC
1MHz
+
–
TIMER
OSC.
SW
SENSE
BAT
V
C
R
S
S
–
C-EA
STANDBY
R
+
RIPPLE
COUNTER
OFFSET
COUNT
+
–
RESET
–
COUNT
0.3V
V-EA
+
COUNT
MODE
RESET
ENABLE
I
TH
10 s R
S
RNG/SS
(TIMER OR C/10)
CHRG
FAULT
CONTROL LOGIC
TERMINATE
SS
RESET
SS
RESET
50μA
STATUS
–
+
C/10
0.1V
–
+
1V
0.15V
PRECONDITION
2.9V
NTC
–
+
SHDN
V
2.7V
INT
x2.25
+
–
–
+
1.2V
STANDBY
1.2V 4.2V*
4.1V**
1.36V
–
+
TERMINATE
50μA
0.29V
NTC
+
–
1.3V
* V
** V
: 4.2V FOR LT3650-4.2, 4.1V FOR LT3650-4.1
BAT(FLT)
BAT(FLT)
– ΔV
: 4.1V FOR LT3650-4.2, 4.0 FOR LT3650-4.1
RECHRG
0.7V
46μA
365042 BD
36504142fb
8
LT3650-4.1/LT3650-4.2
OPERATION
OVERVIEW
timer-based scheme is used, the IC also supports bad-
battery detection, which triggers a system fault if a battery
stays in precondition mode for more than one-eighth of
the total programmed charge cycle time.
LT3650isacompletemonolithic,mid-power,Li-Ionbattery
charger, addressing high input voltage applications with
solutions that use a minimum of external components.
The IC uses a 1MHz constant-frequency, average current
mode step-down architecture. Internal reverse-voltage
protection allows direct connection to the input supply
without a blocking diode.
Once charging is terminated and the LT3650 is not
actively charging, the IC automatically enters a low
current standby mode in which supply bias currents
are reduced to 85μA. If the battery voltage drops 2.5%
from the full charge float voltage, the LT3650 engages
an automatic charge cycle restart. The IC also automati-
cally restarts a new charge cycle after a bad-battery fault
once the failed battery is removed and replaced with
another battery.
The LT3650 incorporates a 2A switch that is driven by
a bootstrapped supply to maximize efficiency during
charging cycles. A wide input range allows the operation
to full charge from 5V 5% to 32V. A precision threshold
shutdown pin allows incorporation of UVLO functionality
using a simple resistor divider. The IC can also be put into
a low current shutdown mode, in which the input supply
bias is reduced to only 15μA.
The LT3650 contains provisions for a battery temperature
monitoringcircuit. Thisfeaturemonitorsbatterytempera-
ture by using a thermistor during the charging cycle, sus-
pends charging, and signals a fault condition if the battery
temperature moves outside a safe charging range.
TheLT3650incorporatesseveraldegreesofchargecurrent
control freedom. The overall maximum charge current
is set using an external inductor current sense resistor.
A maximum charge current programming pin allows
dynamic manipulation of the battery charge current. The
LT3650 also incorporates a system input supply current
limit control feature that servos the battery charge current
to accommodate overall system load requirements.
The LT3650 contains two digital open-collector outputs,
which provide charger status and signal fault conditions.
These binary coded pins signal battery charging, standby
or shutdown modes, battery temperature faults and bad-
battery faults.
General Operation (See Block Diagram)
The LT3650 automatically enters a battery precondi-
tion mode if the sensed battery voltage is very low. In
this mode, the charge current is reduced to 15% of the
programmed maximum, as set by the inductor sense
The LT3650 uses average current mode control architec-
ture, such that the IC servos directly to average charge
current. The LT3650 senses charger output voltage via
the BAT pin. The difference between the voltage on this
pin and an internal float voltage reference is integrated by
thevoltageerroramplifier(V-EA).Thisamplifiergenerates
resistor, R
. Once the battery voltage climbs above
SENSE
the internally set precondition threshold of 2.9V, the IC
automatically increases the maximum charge current to
the full programmed value.
an error voltage on its output (I ), which corresponds
TH
to the average current sensed across the inductor cur-
The LT3650 can use a charge current based C/10 ter-
mination scheme, which ends a charge cycle when the
battery charge current falls to one-tenth the programmed
maximum charge current. The LT3650 also contains an
internalchargecyclecontroltimer,fortimer-basedtermina-
tion. When using the internal timer, the IC combines C/10
detection with a programmable time constraint, during
which the charging cycle can continue beyond the C/10
leveltotop-off abattery.Thechargecycleterminateswhen
a specific time elapses, typically three hours. When the
rent sense resistor, R
, which is connected between
SENSE
the SENSE and BAT pins. The I voltage is then divided
TH
down by a factor of 10, and imposed on the input of the
currenterroramplifier(C-EA).Thedifferencebetweenthis
imposed voltage and the current sense resistor voltage
is integrated, with the resulting voltage (V ) used as a
C
threshold that is compared against an internally gener-
ated ramp. The output of this comparison controls the
charger’s switch.
36504142fb
9
LT3650-4.1/LT3650-4.2
OPERATION
The I error voltage corresponds linearly to average
timing capacitor value (C
). When timer termination
TH
TIMER
current sensed across the inductor current sense resistor,
is used, the charge cycle does not terminate after C/10
is achieved. Because the CHRG status pin responds to
the C/10 current level, the IC will indicate a fully charged
battery status, but the charger will continue to source
low currents into the battery until the programmed EOC
time has elapsed, at which time the charge cycle will
terminate. At EOC, when the charging cycle terminates, if
the battery did not achieve at least 97.5% of the full float
voltage, charging is deemed unsuccessful. The LT3650
will then re-initiate, and charging will continue for another
full timer cycle.
allowing maximum charge current control by limiting the
effective voltage range of I . A clamp limits this voltage
TH
to 1V which, in turn, limits the current sense voltage to
100mV. This sets the maximum charge current, or the
current delivered while the charger is operating in con-
stant-current (CC) mode, which corresponds to 100mV
across R . This maximum charge current level can
SENSE
also be manipulated through the RNG/SS pin (see the
RNG/SS: Dynamic Charge Current Adjust and RNG/SS:
Soft-Start sections).
IfthevoltageontheBATpinisbelowV
,theLT3650
BAT(PRE)
Use of the timer function also enables bad-battery detec-
tion. This fault condition is achieved if the battery does
not respond to preconditioning and the charger remains
in (or enters) precondition mode after one-eighth of the
programmed charge cycle time. A bad-battery fault halts
the charging cycle, the CHRG status pin goes high imped-
ance and the FAULT pin is pulled low.
engagespreconditionmode.Duringthepreconditioninter-
val, the charger continues to operate in constant-current
mode,butthemaximumchargecurrentisreducedto15%
of the maximum programmed value as set by R
.
SENSE
WhenthechargeroutputvoltageontheBATpinapproaches
the float voltage (V ), the charger transitions into
BAT(FLT)
constant-voltage(CV)mode,andchargecurrentisreduced
When the LT3650 terminates a charging cycle, whether
through C/10 detection or by reaching timer EOC, the
average current mode analog loop remains active but
the internal float voltage reference is reduced by 2.5%.
Because the voltage on a successfully charged battery
is at the full float voltage, the voltage error amp detects
an overvoltage condition and rails low. When the voltage
error amp output drops below 0.3V, the IC enters standby
mode, where most of the internal circuitry is disabled, and
from the maximum value. As this occurs, the I voltage
TH
falls from the limit clamp and servos to lower voltages.
The IC monitors the I voltage as it is reduced, and
TH
detection of the C/10 charge current is achieved when
I
= 0.1V. If the charger is configured for C/10 termina-
TH
tion, this threshold is used to terminate the charge cycle.
Once the charge cycle is terminated, the CHRG status
pin becomes high impedance and the charger enters low
current standby mode.
the V bias current is reduced to 85μA. When the voltage
IN
on the BAT pin drops below the reduced float reference
level, the output of the voltage error amp will climb, at
which point the IC comes out of standby mode and a new
charging cycle is initiated.
The LT3650 contains an internal charge cycle timer that
terminates a successful charge cycle after a programmed
amount of time. This timer is typically programmed to
achieve end-of-cycle (EOC) in three hours, but can be
configuredforanyamountoftimebysettinganappropriate
36504142fb
10
LT3650-4.1/LT3650-4.2
APPLICATIONS INFORMATION
V Input Supply
IN
V /BOOST Start-Up Requirement
IN
The LT3650 is biased directly from the charger input
The LT3650 operates with a V range of 4.75V to 32V,
IN
supply through the V pin. This supply provides large
however, a start-up voltage requirement exists due to
the nature of the nonsynchronous step-down switcher
topology used for the charger. If there is no BOOST supply
IN
switched currents, so a high quality, low ESR decoupling
capacitor is recommended to minimize voltage glitches
on V . The V decoupling capacitor (C ) absorbs all
available, the internal switch requires (V – V ) > 3V
IN
IN
VIN
IN SW
input switching ripple current in the charger, so it must
to operate. This requirement does not exist if the BOOST
supply is available and (V – V ) > 2V.
haveanadequateripplecurrentrating. RMSripplecurrent
BOOST
SW
(I
) is:
CVIN(RMS)
When an LT3650 charger is not switching, the SW pin is at
the same potential as the battery, which can be as high as
1
⎛
⎞ 2
⎛
⎞
⎡
⎢
⎤
⎥
VBAT
V
IN
V
. For reliable start-up, the V supply must be at
BAT(FLT)
IN
ICVIN(RMS) ~ICHG(MAX)
•
•
− 1
⎜
⎟
⎜
⎟
V
V
least 3V above the SW pin. The minimum start-up speci-
⎝
⎠
⎝
⎠
IN
⎣ BAT ⎦
fication of V at or above 7.5V provides ample margin to
IN
satisfythisrequirement.Onceswitchingbegins,theBOOST
which has a maximum at V = 2 • V , where:
IN
BAT
supply capacitor gets charged such that (V
– V
)
SW
BOOST
I
= I
/2
CVIN(RMS)
CHG(MAX)
> 2V, and the V requirement no longer applies.
IN
The simple worst-case of 1/2 • I
used for design.
is commonly
CHG(MAX)
InlowV applications, theBOOSTsupplycanbepowered
IN
by an external source for start-up, eliminating the V
IN
start-up requirement.
Bulk capacitance is a function of desired input ripple volt-
age (ΔV ), and follows the relation:
IN
V
BAT
Output Decoupling
⎛
⎜
⎝
⎞
VBAT / V
IN
An LT3650 charger output requires bypass capacitance
CIN(BULK) = IMAX
•
(μF)
⎟
⎠
ΔV
IN
connected from the BAT pin to ground (C ). A 10μF ce-
BAT
ramic capacitor is required for all applications. In systems
where the battery can be disconnected from the charger
output, additional bypass capacitance may be desired for
visual indication of a no-battery condition (see the Status
Pins section).
10μF is typically adequate for most charger applications.
BOOST Supply
The BOOST bootstrapped supply rail drives the internal
switch and facilitates saturation of switch transistor. Oper-
ating range of the BOOST pin is 0V to 4.5V, as referenced
to the SW pin. Connect a 1μF or greater capacitor from
the BOOST pin to the SW pin.
If it is desired to operate a system load from the LT3650
chargeroutputwhenthebatteryisdisconnected,additional
bypass capacitance is required. In this type of application
with the charger being used as a DC/DC converter, exces-
sive ripple and/or low amplitude oscillations can occur
without additional output bulk capacitance. For these ap-
plications, place a 100μF low ESR nonceramic capacitor
(chip tantalum or organic semiconductor capacitors such
as Sanyo OS-CONs or POSCAPs) from BAT to ground,
in parallel with the 10μF ceramic bypass capacitor. This
additional bypass capacitance may also be required in
systems where the battery is connected to the charger
The voltage on the decoupling capacitor is refreshed
through a diode, with the anode connected to/from either
the battery output voltage or an external source, and the
cathode connected to the BOOST pin. Rate the diode av-
erage current greater than 0.1A, and its reverse voltages
greater than V
.
IN(MAX)
through long wires. The voltage rating on C must meet
BAT
or exceed the battery float voltage.
36504142fb
11
LT3650-4.1/LT3650-4.2
APPLICATIONS INFORMATION
R
SENSE
: Charge Current Programming
to 35% of I
, so an inductor value can be determined
MAX
by setting 0.25 < ΔI
< 0.35.
MAX
The LT3650 charger is configurable to charge at average
currents as high as 2A. Maximum charge current is set by
choosing an inductor sense resistor such that the desired
maximum average current through that sense resistor
creates a 100mV drop, or:
Magnetics vendors typically specify inductors with
maximum RMS and saturation current ratings. Select an
inductorthathasasaturationcurrentratingatorabove(1+
ΔI
/2) • I
, and an RMS rating above I
. Inductors
MAX
MAX
MAX
must also meet a maximum volt-second product require-
ment. If this specification is not in the data sheet of an
inductor, consult the vendor to make sure the maximum
volt-secondproductisnotbeingexceededbyyourdesign.
The minimum required volt-second product is:
0.1
IMAX(AVG)
RSENSE
=
where I
is the maximum average charge current.
A 2A charger, for example, would use a 0.05Ω sense
MAX(AVG)
resistor.
⎛
⎞
⎟
VBAT
VBAT • 1−
V • μs
(
)
⎜
V
⎝
⎠
IN(MAX)
SW
10
BOOST
LT3650
8
6
4
2
SENSE
R
SENSE
BAT
365042 F01
Figure 1. Programming Maximum Charge Current Using RSENSE
0
0
Inductor Selection
6
12
24
30
18
MAXIMUM OPERATIONAL V VOLTAGE (V)
IN
365042 F02
The primary criteria for inductor value selection in an
LT3650chargeristheripplecurrentcreatedinthatinductor.
Oncetheinductancevalueisdetermined,aninductormust
also have a saturation current equal to or exceeding the
maximum peak current in the inductor. An inductor value
(L), given the desired amount of ripple current (ΔI
can be approximated using the relation:
Figure 2. 2A Charger Switched Inductor Value
(RSENSE = 0.05Ω) 25% to 35% IMAX Ripple Current
16
12
8
)
MAX
⎛
⎜
⎝
⎞
⎟
⎠
10
L =
•RSENSE • VBAT + VF
(
)
ΔI
MAX
⎛
⎞
⎡
⎢
⎤
⎥
VBAT + VF
⎢ IN(MAX) + VF ⎥
• 1−
μH
(
)
⎜
⎟
V
⎝
⎠
⎣
⎦
4
6
12
24
0
30
18
MAXIMUM OPERATIONAL V VOLTAGE (V)
In the previous relation, ΔI
is the normalized ripple
IN
MAX
365042 F03
current, V
as the maximum operational voltage,
IN(MAX)
and V is the forward voltage of the rectifying Schottky
Figure 3. 1.3A Charger Switched Inductor Value
(RSENSE = 0.075Ω) 25% to 35% IMAX Ripple Current
F
diode. Ripple current is typically set within a range of 25%
36504142fb
12
LT3650-4.1/LT3650-4.2
APPLICATIONS INFORMATION
Rectifier Selection
CLP: System Current Limit
The rectifier diode in an LT3650 battery charger provides a
current path for the inductor current when the main power
switch is disabled. The rectifier is selected based upon
forward voltage, reverse voltage, and maximum current.
ASchottkydiodeisrequired, aslowforwardvoltageyields
the lowest power loss and highest efficiency. The rectifier
diode must be rated to withstand reverse voltages greater
The LT3650 contains a PowerPathTM control feature to
supportmultipleloadsystems.Thechargeradjustsoutput
currentinresponsetoasystemloadifoverallinputsupply
current exceeds the programmed maximum value.
Maximum input supply current is set by choosing a sense
resistor (R ) such that the desired maximum current
CLP
through that sense resistor creates a 50mV drop, or:
than the maximum V voltage.
IN
0.05
IMAX(IN)
RCLP
=
Theminimumaveragediodecurrentrating(I
)is
DIODE(MAX)
calculatedwithmaximumoutputcurrent(I ),maximum
MAX
operational V , and output at the precondition threshold
IN
whereI
isthemaximuminputcurrent.A1.5Asystem
MAX(IN)
(V
):
BAT(PRE)
limit, for example, would use a 33mΩ sense resistor.
IMAX • VIN(MAX) − VBAT(PRE)
(
)
TheLT3650integratestheCLPsignalinternally,soaverage
current limiting is performed in most cases without the
need for external filter elements.
IDIODE(MAX)
>
A
( )
V
IN(MAX)
For example, a rectifier diode for a 4.2V, 1.5A charger with
a 20V maximum input voltage would require:
PowerPath is a trademark of Linear Technology Corporation.
1.5 •(20 − 2.9)
IDIODE(MAX)
>
, or :
20
IDIODE(MAX) > 1.3A
SYSTEM LOAD
CURRENT
1.5A
SYSTEM LOAD
LT3650 INPUT
CURRENT (I
)
VIN
R
CLP
1.0A
0.5A
V
INPUT SUPPLY
IN
LT3650
CLP
365042 F04
365042 F05
Figure 4. RCLP Sets the Input Supply Current Limit
Figure 5. CLP Limit: Charger Current vs
System Load Current with 1.5A Limit
36504142fb
13
LT3650-4.1/LT3650-4.2
APPLICATIONS INFORMATION
RNG/SS: Dynamic Charge Current Adjust
This feature could be used, for example, to switch in a
reduced charge current level. Active servos can also be
usedtoimposevoltagesontheRNG/SSpin, providedthey
can only sink current. Active circuits that source current
cannotbeusedtodrivetheRNG/SSpin. Resistivepull-ups
can be used, but extreme care must be taken not to exceed
the 2.5V absolute maximum voltage on the pin.
TheLT3650givestheuserthecapabilitytoadjustmaximum
charge current dynamically through the RNG/SS pin. The
voltage on the RNG/SS pin corresponds to ten times the
maximum voltage acrossthe sense resistor(R
). The
SENSE
default maximum sense voltage is 100mV, so maximum
charge current can be expressed as:
I
= I
• V
RNG/SS
RNG/SS: Soft-Start
MAX(RNG/SS)
MAX
where I
RNG/SS
is the maximum charge current if
Soft-start functionality is also supported by the RNG/SS
pin. 50μA is sourced from the RNG/SS pin, so connecting
MAX(RNG/SS)
V
is within 0V to 1V. Voltages higher than 1V have
no effect on the maximum charge current.
a capacitor from the RNG/SS pin to ground (C
) cre-
RNG/SS
ates a linear voltage ramp. The maximum charge current
follows this voltage. Thus, the charge current increases
from zero to the fully programmed value as the capacitor
The LT3650 sources 50μA from the RNG/SS pin, such that
a current control voltage can be set by simply connecting
an appropriately valued resistor to ground, following the
relation:
charges from 0V to 1V. The value of C
is calculated
RNG/SS
based on the desired time to full current (t ) following
SS
VRNG/SS
the relation:
RRNG/SS
=
50μA
C
= 50μA • t
SS
RNG/SS
Forexample,toreducethemaximumchargecurrentto50%
of the original value, which corresponds to a maximum
sense voltage of 50mV, RNG/SS would be set to 0.5V.
The RNG/SS pin is pulled to ground internally when charg-
ing is terminated so each new charging cycle begins with
a soft-start cycle. RNG/SS is also pulled to ground during
bad-batteryandNTCfaultconditions,soagracefulrecovery
from these faults is possible.
0.5V
RRNG/SS
=
= 10kΩ
50μA
LT3650
LT3650
RNG/SS
RNG/SS
10k
+
SERVO REFERENCE
–
365042 F06
365042 F07
LOGIC HIGH = HALF CURRENT
Figure 6. Using the RNG/SS Pin for Digital
Control of Maximum Charge Current
Figure 7. Driving the RNG/SS Pin with a
Current-Sink Active Servo Amplifier
LT3650
RNG/SS
C
PROG
365042 F08
Figure 8. Using the RNG/SS Pin for Soft-Start
36504142fb
14
LT3650-4.1/LT3650-4.2
APPLICATIONS INFORMATION
Status Pins
voltage is achieved, the charge current falls until the C/10
thresholdisreached, atwhichtimethechargerterminates
and the LT3650 enters standby mode. The CHRG status
pin follows the charger cycle and is high impedance when
the charger is not actively charging.
The LT3650 reports charger status through two open-col-
lector outputs, the CHRG and FAULT pins. These pins can
accept voltages as high as V , and can sink up to 10mA
IN
when enabled.
When V
drops below 97.5% of the full-charged float
BAT
The CHRG pin indicates that the charger is delivering
current at greater than a C/10 rate, or one-tenth of the
programmed maximum charge current. The FAULT pin
signals bad-battery and NTC faults. These pins are binary
coded, and signal following the table below, where On
indicates the pin pulled low, and Off indicates pin high
impedance:
voltage, whether by battery loading or replacement of the
battery, the charger automatically re-engages and starts
charging.
There is no provision for bad-battery detection if C/10
termination is used.
Timer Termination
Table 1. Status Pins State Table
STATUS PINS STATE
TheLT3650supportsatimer-basedterminationscheme,in
which a battery charge cycle is terminated after a specific
amount of time elapses. Timer termination is engaged
CHRG
Off
FAULT
Off
CHARGER STATUS
Not Charging—Standby or Shutdown Mode
when a capacitor (C
) is connected from the TIMER
TIMER
Off
On
Bad-Battery Fault
(Precondition Timeout/EOC Failure)
pin to ground. The timer cycle EOC (t ) occurs based
EOC
On
On
Off
On
Normal Charging at C/10 or Greater
NTC Fault (Pause)
on C
following the relation:
TIMER
–7
C
= t
• 2.27 • 10 (Hours)
TIMER
EOC
If the battery is removed from an LT3650 charger that is
configured for C/10 termination, a sawtooth waveform
of approximately 100mV appears at the charger output,
due to cycling between termination and recharge events.
This cycling results in pulsing at the CHRG output. An
LED connected to this pin will exhibit a blinking pattern,
indicating to the user that a battery is not present. The
frequency of this blinking pattern is dependent on the
output capacitance.
Timer EOC is typically set to three hours, which requires
a 0.68μF capacitor.
The CHRG status pin continues to signal charging at a
C/10 rate, regardless of which termination scheme is
used. When timer termination is used, the CHRG status
pin is pulled low during a charging cycle until the charger
output current falls below the C/10 threshold. The charger
continues to top off the battery until timer EOC, when the
LT3650 terminates the charging cycle and enters standby
mode.
C/10 Termination
Termination at the end of the timer cycle only occurs if
the charging cycle was successful. A successful charge
cycle occurs when the battery is charged to within 2.5%
of the full-charge float voltage. If a charge cycle is not
successful at EOC, the timer cycle resets and charging
continues for another full timer cycle.
The LT3650 supports a low current based termination
scheme, where a battery charge cycle terminates when
the current output from the charger falls to below one-
tenth the maximum current, as programmed with R
.
SENSE
The C/10 threshold current corresponds to 10mV across
R
. This termination mode is engaged by shorting
SENSE
the TIMER pin to ground.
When V
drops below 97.5% of the full-charge float
BAT
voltage, whether by battery loading or replacement of
the battery, the charger automatically re-engages and
starts charging.
WhenC/10terminationisused,anLT3650chargersources
battery charge current as long as the average current level
remains above the C/10 threshold. As the full-charge float
36504142fb
15
LT3650-4.1/LT3650-4.2
APPLICATIONS INFORMATION
Preconditioning and Bad-Battery Fault
Battery Temperature Fault: NTC
An LT3650 charger has a precondition mode, in which
The LT3650 can accommodate battery temperature moni-
toring by using an NTC (negative temperature coefficient)
thermistor close to the battery pack. The temperature
monitoring function is enabled by connecting a 10kΩ,
B=3380NTCthermistorfromtheNTCpintoground. Ifthe
NTC function is not desired, leave the pin unconnected.
charge current is limited to 15% of the programmed I
,
MAX
as set by R
. The precondition current corresponds
SENSE
to 15mV across R
.
SENSE
PreconditionmodeisengagedwhilethevoltageontheBAT
pin is below the precondition threshold (V ). Once
BAT(PRE)
the BAT voltage rises above the precondition threshold,
normal full-current charging can commence. The LT3650
incorporates 3% of threshold hysteresis to prevent mode
glitching.
The NTC pin sources 50μA, and monitors the voltage
dropped across the 10kΩ thermistor. When the voltage
on this pin is above 1.36V (0°C) or below 0.29V (40°C),
the battery temperature is out of range, and the LT3650
triggersanNTCfault.TheNTCfaultconditionremainsuntil
the voltage on the NTC pin corresponds to a temperature
within the 0°C to 40°C range. Both hot and cold thresholds
incorporate hysteresis that corresponds to 5°C.
When the internal timer is used for termination, bad-bat-
tery detection is engaged. This fault detection feature is
designed to identify failed cells. A bad-battery fault is
triggered when the voltage on BAT remains below the
precondition threshold for greater than one-eighth of a
full timer cycle (one-eighth EOC). A bad-battery fault is
also triggered if a normally charging battery re-enters
precondition mode after one-eighth EOC.
If higher operational charging temperatures are desired,
the temperature range can be expanded by adding se-
ries resistance to the 10k NTC resistor. Adding a 0.91k
resistor will increase the effective temperature threshold
to 45°C.
When a bad-battery fault is triggered, the charging cycle
is suspended, so the CHRG status pin becomes high
impedance. The FAULT pin is pulled low to signal a fault
detection. The RNG/SS pin is also pulled low during this
fault, to accommodate a graceful restart, in the event that
a soft-start function is incorporated (see the RNG/SS:
Soft-Start section).
During an NTC fault, charging is halted and both status
pins are pulled low. If timer termination is enabled, the
timer count is suspended and held until the fault condition
is relieved. The RNG/SS pin is also pulled low during this
fault, to accommodate a graceful restart in the event that a
soft-start function is being incorporated (see the RNG/SS:
Soft-Start section).
Cycling the charger’s power or SHDN function initiates
a new charging cycle, but an LT3650 charger does not
require a reset. Once a bad-battery fault is detected, a new
timer charging cycle initiates when the BAT pin exceeds
the precondition threshold voltage. During a bad-battery
fault, 0.5mA is sourced from the charger; removing the
failed battery allows the charger output voltage to rise and
initiate a charge cycle reset. As such, removing a bad bat-
tery resets the LT3650, so a new charging cycle is started
by connecting another battery to the charger output.
Thermal Foldback
The LT3650 contains a thermal foldback protection feature
that reduces maximum charger output current if the IC
junction temperature approaches 125°C. In most cases,
on-chiptemperaturesservosuchthatanyovertemperature
conditions are relieved with only slight reductions in
maximum charger current.
In some cases, the thermal foldback protection feature
can reduce charger currents below the C/10 threshold. In
applications that use C/10 termination (TIMER = 0V), the
LT3650 will suspend charging and enter standby mode
until the overtemperature condition is relieved.
36504142fb
16
LT3650-4.1/LT3650-4.2
APPLICATIONS INFORMATION
Layout Considerations
effectively steer these high currents such that the battery
reference does not get corrupted. Figure 9 illustrates an
effective grounding scheme using component placement
to control ground currents. When the switch is enabled
(loop #1), current flows from the input bypass capacitor
The LT3650 switch node has rise and fall times that are
typicallylessthan10nstomaximizeconversionefficiency.
The switched node (Pin SW) trace should be kept as short
as possible to minimize high frequency noise. The input
(C ) through the switch and inductor to the battery posi-
IN
capacitor(C )shouldbeplacedclosetotheICtominimize
IN
tive terminal. When the switch is disabled (loop #2), the
this switching noise. Short, wide traces on these nodes
also help to avoid voltage stress from inductive ringing.
The BOOST decoupling capacitor should also be in close
proximity to the IC to minimize inductive ringing. The
SENSE and BAT traces should be routed together and
kept as short as possible. Shielding these signals from
switching noise with ground is recommended.
current to the battery positive terminal is provided from
ground through the freewheeling Schottky diode (D ). In
F
both cases, these switched currents return to ground via
the output bypass capacitor (C ).
BAT
The LT3650 packaging has been designed to efficiently
remove heat from the IC via the Exposed Pad on the
backside of the package, which is soldered to a copper
footprint on the PCB. This footprint should be made as
large as possible to reduce the thermal resistance of the
IC case to ambient air.
High current paths and transients should be kept iso-
lated from battery ground, to assure an accurate output
voltage reference. Effective grounding can be achieved
by considering switched current in the ground plane,
and careful component placement and orientation can
C
C
V
BAT
IN
BAT
R
SENSE
1
2
D
F
+
LT3650
V
IN
SW
SENSE
BAT
365042 F09
Figure 9. Component Orientation Isolates High Current Paths From Sensitive Nodes
36504142fb
17
LT3650-4.1/LT3650-4.2
TYPICAL APPLICATIONS
5V to 32V 1.5A Charger with Three Hour EOC Termination. The LTC1515 Provides
Boost Start-Up Requirement. Status Pins Use LED Indicators.
2N3904
10k
10k
BZX84C6V2L
(6.2V)
SHDN
POR
FB
V
OUT
100k
20k
100k
10μF
10μF
V
IN
+
LTC1515
C1
C1
0.1μF
–
GND
1N4148
1k
B240A
SW
V
IN
1μF
10μF
INPUT SUPPLY
5V TO 32V
CLP
BOOST
SENSE
BAT
10μH
LT3650
1N4148
SHDN
CHRG
5.1k
0.068Ω
5.1k
FAULT
10μF
NTC
B = 3380
10k
TIMER
RNG/SS
+
0.68μF
0.1μF
365042 TA02
12V to 32V 2A Charger with Three Hour EOC Termination and
Removable Battery Pack. The RNG/SS Pin Is Used to Reduce the
Maximum Charger Current if 12V < VIN < 20V; Input UVLO = 10V.
NTC Range Is Extended to +45C. The Charger Can Supply Loads Up
to the Maximum Charger Current with No Battery Connected.
RNG/SS Pin Foldback:
ICHG(MAX) vs VIN
CMSH3-40MA
V
IN
SW
V
IN
12V TO
32V
10μF
1μF
2.0
1.5
1.0
0.5
0
CLP
BOOST
6.8μH
0.05Ω
MM5Z9V1ST1
(9.1V)
LT3650
CMPSH1-4
SENSE
BAT
SHDN
CHRG
FAULT
36k
+
10μF
100μF
SYSTEM
LOAD
0.91k
NTC
RNG/SS
TIMER
10
12
14
16
18
20
22
32
3k
0.1μF
B=3380
10k
+
0.68μF
V
IN
365042 TA03b
365042 TA03a
36504142fb
18
LT3650-4.1/LT3650-4.2
PACKAGE DESCRIPTION
DD Package
12-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1725 Rev A)
R = 0.115
TYP
7
0.40 p 0.10
12
0.70 p0.05
2.38 p0.10
2.38 p0.05
1.65 p0.05
3.50 p0.05
2.10 p0.05
3.00 p0.10
(4 SIDES)
1.65 p0.10
PIN 1 NOTCH
PIN 1
R = 0.20 OR
0.25 s 45o
CHAMFER
PACKAGE
OUTLINE
TOP MARK
(SEE NOTE 6)
6
1
0.23 p 0.05
0.45 BSC
0.75 p0.05
0.200 REF
0.25 p 0.05
0.45 BSC
2.25 REF
(DD12) DFN 0106 REV
A
2.25 REF
0.00 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD AND TIE BARS SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
3. ALL DIMENSIONS ARE IN MILLIMETERS
MSE Package
12-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1666 Rev B)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.845 p 0.102
(.112 p .004)
2.845 p 0.102
(.112 p .004)
0.889 p 0.127
(.035 p .005)
1
6
0.35
REF
5.23
(.206)
MIN
1.651 p 0.102
(.065 p .004)
3.20 – 3.45
(.126 – .136)
0.12 REF
DETAIL “B”
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
DETAIL “B”
12
4.039 p 0.102
(.159 p .004)
(NOTE 3)
7
NO MEASUREMENT PURPOSE
0.65
(.0256)
BSC
0.42 p 0.038
(.0165 p .0015)
TYP
0.406 p 0.076
RECOMMENDED SOLDER PAD LAYOUT
(.016 p .003)
12 11 10 9 8 7
REF
DETAIL “A”
0o – 6o TYP
0.254
(.010)
3.00 p 0.102
(.118 p .004)
(NOTE 4)
4.90 p 0.152
(.193 p .006)
GAUGE PLANE
0.53 p 0.152
(.021 p .006)
1
2 3 4 5 6
DETAIL “A”
0.86
(.034)
REF
1.10
(.043)
MAX
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.1016 p 0.0508
(.004 p .002)
MSOP (MSE12) 0608 REV B
0.650
(.0256)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
36504142fb
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-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LT3650-4.1/LT3650-4.2
TYPICAL APPLICATION
10V to 32V 1.5A Charger with C/10 Termination and 1A Input Supply Limit.
Status Pins Use LED Indicators
SYSTEM LOAD
INPUT SUPPLY
10V TO 32V
AT 1A
B240A
SW
V
IN
10μF
1μF
0.05Ω
CLP
BOOST
SENSE
BAT
10μH
330k
47k
LT3650
BAS40
SHDN
CHRG
0.0687
10k
10k
+
10μF
FAULT
NTC
RNG/SS
TIMER
B = 3380
10k
0.1μF
365042 TA04
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LT1511
LT1513
LT1571
LT1769
3A Constant-Current/Constant-Voltage
Battery Charger
High Efficiency, Minimum External Components to Fast Charge Lithium, NIMH and NiCd
Batteries, 24-Lead SO Package
SEPIC Constant or Programmable Current/ Charger Input Voltage May Be Higher, Equal to or Lower Than Battery Voltage, 500kHz
Constant-Voltage Battery Charger
Switching Frequency, DD Pak and TO-220 Packages
1.5A Switching Charger
1- or 2-Cell Li-Ion, 500kHz or 200kHz Switching Frequency, Termination Flag, 16- and
28-Lead SSOP Packages
2A Switching Charger
Constant-Current/Constant-Voltage Switching Regulator, Input Current Limiting
Maximizes Charge Current, 20-Lead TSSOP and 28-Lead SSOP Packages
LT3650-8.2/
LT3650-8.4
Monolithic 2A Switch Mode
Nonsynchronous 2-Cell Li-Ion
Battery Charger
Standalone, 9V ≤ V ≤ 32V (40V Abs Max), 1MHz, 2A Programmable Charge Current,
IN
Timer or C/10 Termination, Small and Few External Components, LT3650-8.2 for 2 × 4.1V
Float Voltage Batteries, LT3650-8.4 for 2 × 4.2V Float Voltage Batteries, 3mm × 3mm
DFN-12 Package
LTC4001/
LTC4001-1
Monolithic 2A Switch Mode Synchronous
Li-Ion Battery Charger
Standalone, 4V ≤ V ≤ 5.5V (6V Abs Max, 7V Transient), 1.5MHz, Synchronous
IN
Rectification Efficiency >90%, Adjustable Timer Termination, Small and Few External
Components, LTC4001-1 for 4.1V Float Voltage Batteries, 4mm × 4mm QFN-16 Package
LTC4002
LTC4006
LTC4007
LTC4008
Standalone Li-Ion Switch Mode
Battery Charger
Complete Charger for 1- or 2-Cell Li-Ion Batteries, Onboard Timer Termination,
Up to 4A Charge Current, 10-Lead DFN and SO-8 Packages
Small, High Efficiency, Fixed Voltage Li-Ion Complete Charger for 2-, 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit and
Battery Charger with Termination
Thermistor Sensor, 16-Lead Narrow SSOP Package
High Efficiency, Programmable Voltage
Battery Charger with Termination
Complete Charger for 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit, Thermistor
Sensor and Indicator Outputs, 24-Lead SSOP Package
4A, High Efficiency, Multi-Chemistry
Battery Charger
Complete Charger for 2- to 6-Cell Li-Ion Batteries or 4- to 18-Cell Nickel Batteries,
Up to 96% Efficiency, 20-Lead SSOP Package
LTC4009/
LTC4009-1/
LTC4009-2
4A, High Efficiency, Multi-Chemistry
Battery Charger
Constant-Current/Constant-Voltage Switching Regulator Charger, Resistor Voltage/
Current Programming, AC Adapter Current Limit and Thermistor Sensor and Indicator
Outputs 1- to 4-Cell Li, Up to 18-Cell Ni, SLA and Supercap Compatible; 4mm × 4mm
QFN-20 Package, LTC4009-1 Version for 4.1V Float Voltage Li-Ion, LTC4009-2 Version for
4.2V Float Voltage Li-Ion Cells.
36504142fb
LT 0809 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
© LINEAR TECHNOLOGY CORPORATION 2009
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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