LTC4090 [Linear]
USB Power Manager with 2A High Voltage Bat-Track Buck Regulator; 与2A高电压电池跟踪降压型稳压器的USB电源管理器
| 型号： | LTC4090 |
| 厂家： | 
Linear |
| 描述： | USB Power Manager with 2A High Voltage Bat-Track Buck Regulator |
| 文件： | 总28页 (文件大小：394K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4090/LTC4090-5
USB Power Manager with
2A High Voltage Bat-Track
Buck Regulator
FEATURES
DESCRIPTION
The LTC®4090/LTC4090-5 are USB power managers plus
highvoltageLi-Ion/Polymerbatterychargers. Thedevices
control the total current used by the USB peripheral for
operation and battery charging. Battery charge current is
automaticallyreducedsuchthatthesumoftheloadcurrent
and the charge current does not exceed the programmed
input current limit. The LTC4090/LTC4090-5 also accom-
modate high voltage power supplies, such as 12V AC/DC
wall adapters, FireWire, or automotive power.
■
Seamless Transition Between Power Sources: Li-
Ion Battery, USB, and 6V to 36V Supply (60V Max)
■
2A Output High Voltage Buck Regulator with Bat-
TrackTM Adaptive Output Control (LTC4090)
Internal 215mΩ Ideal Diode Plus Optional External
■
Ideal Diode Controller Provides Low Loss Power
Path When External Supply / USB Not Present
■
Load Dependent Charging from USB Input Guaran-
tees Current Compliance
Full Featured Li-Ion Battery Charger
■
The LTC4090 provides a Bat-Track adaptive output that
tracksthebatteryvoltageforhighefficiencychargingfrom
the high voltage input. The LTC4090-5 provides a fixed 5V
output from the high voltage input to charge single cell
Li-Ionbateries.Thechargecurrentisprogrammableandan
■
1.5A Maximum Charge Current with Thermal Limiting
■
NTC Thermistor Input for Temperature Qualified
Charging
■
Tiny (3mm × 6mm × 0.75mm) 22-Pin DFN Package
⎯
⎯
⎯
⎯
end-of-charge status output (CHRG) indicates full charge.
Alsofeaturedareprogrammabletotalchargetime, anNTC
thermistorinputusedtomonitorbatterytemperaturewhile
charging and automatic recharging of the battery.
APPLICATIONS
■
HDD-Based Media Players
■
Personal Navigation Devices
■
Other USB-Based Handheld Products
Automotive Accessories
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Bat-Track is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
■
TYPICAL APPLICATION
0.47μF
6.8μH
LTC4090/LTC4090-5 High Voltage
Battery Charger Efficiency
BOOST
SW
HIGH (6V-36V)
HVIN
IN
22μF
VOLTAGE INPUT
1μF
90
80
70
60
50
40
30
20
HVOUT
5V WALL
ADAPTER
FIGURE 12 SCHEMATIC
WITH R = 52k
LTC4090
PROG
HVPR
NO OUTPUT LOAD
4.7μF
USB
LTC4090
1k
V
C
OUT
LOAD
LTC4090-5
4.7μF
TIMER
BAT
R
CLPROG
2k
GND PROG
T
59k
+
40.2k
100k
270pF
0.1μF
Li-Ion BATTERY
HVIN = 8V
HVIN = 12V
HVIN = 24V
HVIN = 36V
V
(TYP)
+ 0.3V
5V
5V
AVAILABLE INPUT
HV INPUT (LTC4090)
HV INPUT (LTC4090-5)
USB ONLY
OUT
V
BAT
2.0
2.5
3.0
3.5
(V)
4.0
4.5
V
BAT
V
BAT ONLY
BAT
4090 TAO1
4090 TA01b
4090fa
1
LTC4090/LTC4090-5
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 2, 3, 4)
TOP VIEW
HVIN, HVEN (Note 9) ................................................60V
BOOST ......................................................................56V
BOOST above SW .....................................................30V
PG, SYNC..................................................................30V
IN, OUT, HVOUT
SYNC
PG
1
2
3
4
5
6
7
8
9
22 HVEN
21 HVIN
20 SW
R
T
V
19 BOOST
18 HVOUT
17 TIMER
16 SUSP
15 HPWR
14 CLPROG
13 OUT
C
NTC
VNTC
HVPR
CHRG
PROG
t < 1ms and Duty Cycle < 1% .................. –0.3V to 7V
Steady State............................................. –0.3V to 6V
23
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
BAT, HPWR, SUSP, V , CHRG, HVPR........... –0.3V to 6V
C
NTC, TIMER, PROG, CLPROG..........–0.3V to V + 0.3V
I , I , I (Note 5) ..............................................2.5A
CC
IN OUT BAT
GATE 10
BAT 11
Operating Temperature Range .....................–40 to 85°C
Junction Temperature ........................................... 110°C
Storage Temperature Range.......................–65 to 125°C
12 IN
DJC PACKAGE
22-LEAD (6mm × 3mm) PLASTIC DFN
T
= 110°C, θ = 47°C/W
JMAX
JA
EXPOSED PAD (PIN 23) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC4090EDJC#PBF
LTC4090EDJC-5#PBF
TAPE AND REEL
PART MARKING
4090
PACKAGE DESCRIPTION
22-Lead (6mm × 3mm) Plastic DFN
22-Lead (6mm × 3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
LTC4090EDJC#TRPBF
LTC4090EDJC-5#TRPBF
40905
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V,
RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
USB Input Current Limit
●
V
USB Input Supply Voltage
Input Bias Current
4.35
5.5
V
IN
●
●
I
I
I
I
= 0 (Note 6)
0.5
50
1
100
mA
μA
IN
BAT
Suspend Mode; SUSP = 5V
●
●
Current Limit
HPWR = 5V
HPWR = 0V
475
90
500
100
525
110
mA
mA
LIM
Maximum Input Current Limit
(Note 7)
2.4
A
IN(MAX)
Ω
R
ON
On-Resistance V to V
I = 80mA
OUT
0.215
IN
OUT
●
●
V
CLPROG Servo Voltage in Current Limit
R
R
= 2k
= 1k
0.98
0.98
1.00
1.00
1.02
1.02
V
V
CLPROG
CLPROG
CLPROG
I
Soft-Start Inrush Current
10
mA/μs
SS
4090fa
2
LTC4090/LTC4090-5
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V,
RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
(V - V ) Rising
MIN
TYP
MAX
UNITS
V
Input Current Limit Enable Threshold
20
–80
50
–50
80
–20
mV
mV
CLEN
IN
OUT
Voltage (V - V
)
(V - V ) Falling
IN
OUT
IN
OUT
●
V
Input Undervoltage Lockout
V
Rising
3.6
3.8
4
V
UVLO
IN
IN
ΔV
Input Undervoltage Lockout Hysteresis
V
Rising – V Falling
130
mV
UVLO
IN
High Voltage Regulator
●
●
V
HVIN Supply Voltage
6
60
45
V
V
HVIN
OVLO
HVIN
V
HVIN Overvoltage Lockout Threshold
HVIN Bias Current
36
41.5
I
Shutdown; HVEN = 0.2V
Not Switching, HVOUT = 3.6V
0.01
130
0.5
200
μA
μA
●
V
V
Output Voltage with HVIN Present
Output Voltage with HVIN Present
Switching Frequency
Assumes HVOUT to OUT Connection,
3.45
4.85
V
+ 0.3
BAT
4.6
V
OUT
OUT
0 ≤ V ≤ 4.2V (LTC4090)
BAT
Assumes HVOUT to OUT Connection
(LTC4090-5)
5
5.15
V
f
R = 8.66k
2.1
0.9
160
2.4
1.0
200
2.7
1.15
240
MHz
MHz
kHz
SW
T
R = 29.4k
T
R = 187k
T
●
●
t
I
Minimum Switch Off-Time
Switch Current Limit
60
3.5
500
0.02
1.5
22
150
4.0
ns
A
OFF
Duty Cycle = 5%
3.0
SW(MAX)
V
Switch V
I = 2A
SW
mV
μA
V
SAT
CESAT
I
Boost Schottky Reverse Leakage
Minimum Boost Voltage (Note 8)
BOOST Pin Current
SW = 10V, HVOUT = 0V
2
R
V
2.1
35
B(MIN)
BST
I
I
SW
= 1A
mA
Battery Management
Battery Drain Current
●
●
●
I
V
= 4.3V, Charging Stopped
15
22
60
27
35
100
μA
μA
μA
BAT
BAT
Suspend Mode, SUSP = 5V
V
IN
= 0V, BAT Powers OUT, No Load
V
FLOAT
V
Regulated Output Voltage
I
I
= 2mA
4.165
4.158
4.200
4.200
4.235
4.242
V
V
BAT
BAT
BAT
= 2mA; 0 ≤ T ≤ 85°C
A
●
I
I
Constant-Current Mode Charge Current,
No Load
R
R
= 100k
465
900
500
535
mA
mA
CHG
PROG
PROG
= 50k, 0 ≤ T ≤ 85°C
1000
1080
A
Maximum Charge Current
PROG Pin Servo Voltage
1.5
A
CHG(MAX)
●
●
V
R
PROG
R
PROG
= 100k
= 50k
0.98
0.98
1.00
1.00
1.02
1.02
V
V
PROG
●
●
●
k
Ratio of End-of-Charge Indication
Current to Charge Current
V
= V
(4.2V)
FLOAT
0.085
0.1
0.11
mA/mA
EOC
BAT
I
Trickle Charge Current
BAT = 2V
35
50
60
mA
V
TRKL
V
V
Trickle Charge Threshold Voltage
Charge Enable Threshold Voltage
BAT Rising
2.75
2.9
3.0
TRKL
CEN
(V
(V
– V ) Falling; V = 4V
55
80
mV
mV
OUT
OUT
BAT
BAT
BAT
BAT
– V ) Rising; V = 4V
ΔV
Recharge Battery Threshold Voltage
Threshold Voltage Relative to V
–65
–100
–135
mV
RECHRG
FLOAT
4090fa
3
LTC4090/LTC4090-5
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V,
RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
= 4.3V
MIN
TYP
MAX
UNITS
%
t
TIMER Accuracy
V
–10
10
TIMER
BAT
Recharge Time
Percent of Total Charge Time
Percent of Total Charge Time,
50
25
%
Low Battery Trickle Charge Time
%
V
<2.9V
BAT
T
Junction Temperature in Constant
Temperature Mode
105
°C
LIM
Internal Ideal Diode
R
R
Incremental Resistance, V Regulation
I
I
= 100mA
= 600mA
125
215
mΩ
mΩ
FWD
ON
OUT
OUT
On-Resistance V to V
OUT
DIO, ON
FWD
BAT
●
V
Voltage Forward Drop (V – V
)
I
I
I
= 5mA
= 100mA
= 600mA
10
30
55
160
50
mV
mV
mV
BAT
OUT
OUT
OUT
OUT
V
Diode Disable Battery Voltage
2.7
550
2.2
V
mA
A
OFF
I
I
Load Current Limit for V Regulation
FWD
ON
Diode Current Limit
D(MAX)
External Ideal Diode
External Diode Forward Voltage
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
V
20
mV
FWD, EXT
Logic (CHRG, HVPR, TIMER, SUSP, HPWR, HVEN, PG, SYNC)
●
●
●
V
Charger Shutdown Threshold Voltage
on TIMER
0.14
5
0.4
V
CHG, SD
I
Charger Shutdown Pull-Up Current on
TIMER
V
= 0V
14
μA
CHG, SD
TIMER
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
V
V
V
V
V
Output Low Voltage
Input High Voltage
Input Low Voltage
HVEN High Threshold
HVEN Low Threshold
Logic Input Pull-Down Current
HVEN Pin Bias Current
PG Threshold
(CHRG, HVPR); I
SUSP, HPWR
SUSP, HPWR
= 5mA
0.1
0.4
0.4
0.3
10
V
V
OL
SINK
1.2
2.3
IH
V
IL
V
HVEN, H
HVEN, L
PULLDN
HVEN
V
I
I
SUSP, HPWR
HVEN = 2.5V
HVOUT Rising
2
5
μA
μA
V
V
2.8
35
0.1
900
PG
ΔV
PG Hysteresis
mV
μA
μA
V
PG
PGLK
PG
I
I
PG Leakage
PG = 5V
1
●
PG Sink Current
PG = 0.4V
100
0.5
V
V
SYNC Low Threshold
SYNC High Threshold
SYNC Pin Bias Current
SYNC, L
SYNC, H
SYNC
0.8
V
I
V
= 0V
0.1
μA
SYNC
4090fa
4
LTC4090/LTC4090-5
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V,
RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted.
SYMBOL
NTC
PARAMETER
CONDITIONS
MIN
TYP
MAX
3.5
1
UNITS
●
●
I
VNTC Pin Current
VNTC = 2.5V
1.4
4.4
2.5
4.85
0
mA
V
VNTC
V
VNTC Bias Voltage
I
= 500μA
VNTC
NTC
VNTC
I
NTC Input Leakage Current
NTC = 1V
μA
V
V
V
Cold Temperature Fault Threshold
Voltage
Rising NTC Voltage
Hysteresis
0.738 • VNTC
0.02 • VNTC
V
V
COLD
HOT
DIS
Hot Temperature Fault Threshold
Voltage
Falling NTC Voltage
Hysteresis
0.29 • VNTC
0.01 • VNTC
V
V
●
NTC Disable Threshold Voltage
Falling NTC Voltage
Hysteresis
75
100
35
125
mV
mV
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.
Note 4: V is the greater of V , V , and V
CC IN OUT BAT
Note 5: Guaranteed by long term current density limitations.
Note 6: Total input current is equal to this specification plus 1.002 • I
BAT
where I is the charge current.
BAT
Note 2: The LTC4090/LTC4090-5 are guaranteed to meet performance
specifications from 0°C to 85°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperatures will exceed 110°C when overtemperature protection is
active. Continuous operation above the specified maximum operating
junction temperature may result in device degradation or failure.
Note 7: Accuracy of programmed current may degrade for currents
greater than 1.5A.
Note 8: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
Note 9: Absolute Maximum Voltage at HVIN and HVEN pins is for non-
repetative 1 second transients; 40V for continuous operation.
TYPICAL PERFORMANCE CHARACTERISTICS
Battery Regulation (Float)
Voltage vs Temperature
Battery Current and Voltage vs
Time (LTC4090)
VFLOAT Load Regulation
4.30
4.25
4.220
4.215
4.210
4.205
5
4
3
2
1
0
1500
1200
900
600
300
0
R
= 34k
V
BAT
= 5V
PROG
IN
I
= 2mA
V
BAT
V
V
OUT
CHRGB
BAT
4.20
4.15
I
4.200
4.195
C/10
4.10
4.05
4.00
4.190
4.185
4.180
1250mAh
CELL
TERMINATION
150
HVIN = 12V
R
= 50k
PROG
0
200
400
I
600
(mA)
800
1000
–25
0
50
–50
75
100
25
100
0
50
200
TEMPERATURE (°C)
BAT
TIME (MIN)
4090 G01
4090 G02
4090 G03
4090fa
5
LTC4090/LTC4090-5
TYPICAL PERFORMANCE CHARACTERISTICS
Ideal Diode Current vs Forward
Voltage and Temperature (No
External Device)
Charge Current vs Temperature
Charging from USB, IBAT vs VBAT
(Thermal Regulation)
1000
900
800
700
600
500
400
300
200
100
0
600
500
600
500
400
300
V
V
R
R
= 5V
V
V
= 3.7V
IN
OUT
BAT
IN
= NO LOAD
= 100k
= 0V
HPWR = 5V
PROG
= 2k
CLPROG
400
300
200
200
100
0
–50°C
0°C
R
V
= 2.1k
= 3.5V
PROG
IN
HPWR = 0V
100
0
= 5V
50°C
100°C
V
BAT
θ
= 40°C/W
JA
0
50
100
(mV)
150
200
0
0.5
1
1.5
2
2.5
(V)
3
3.5
4
4.5
–50
25
50
75
100 125
–25
0
V
V
TEMPERATURE (°C)
FWD
BAT
4090 G06
4090 G04
4090 G05
Ideal Diode Current vs Forward
Voltage and Temperature with
External Device
LTC4090 High Voltage Regulator
Efficiency vs Output Load
LTC4090-5 High Voltage Regulator
Efficiency vs Output Load
100
95
90
85
80
75
70
65
60
55
50
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
100
95
90
85
80
75
70
65
60
55
50
FIGURE 12 SCHEMATIC
FIGURE 12 SCHEMATIC
V
V
= 3.7V
BAT
IN
V
= 4.21V (I
= 0)
V
= 4.21V (I
= 0)
BAT
BAT
BAT
BAT
= 0V
Si2333 PFET
–50°C
0°C
50°C
100°C
HVIN = 8V
HVIN = 12V
HVIN = 24V
HVIN = 36V
HVIN = 8V
HVIN = 12V
HVIN = 24V
HVIN = 36V
0
0
0.2
0.4
0.6
(A)
0.8
1.0
0
20
40
V
60
80
100
0
0.2
0.4
0.6
(A)
0.8
1.0
I
(mV)
I
OUT
FWD
OUT
4090 G08
4090 G07
4090 G29
High Voltage Regulator Minimum
Switch On-Time vs Temperature
High Voltage Regulator Switch
Voltage Drop
High Voltage Regulator Maximum
Load Current
140
120
3.0
2.8
2.6
2.4
2.2
2.0
1.8
700
600
FIGURE 12 SCHEMATIC
V
= 4.21V (I
= 0)
BAT
BAT
TYPICAL
100
500
400
300
200
100
80
60
40
20
MINIMUM
0
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (˚C)
4090 G10
5
15
20
25
30
35
10
0
500
1000
1500
2000
2500
HVIN (V)
SWITCH CURRENT (mA)
4090 G09
4090 G11
4090fa
6
LTC4090/LTC4090-5
TYPICAL PERFORMANCE CHARACTERISTICS
High Voltage Regulator
Frequency Foldback
High Voltage Regulator Switch
Frequency
High Voltage Regulator Soft-Start
1000
900
800
700
600
500
400
300
200
100
0
4.0
1100
1000
900
800
700
600
500
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
75 100
0
1
2
3
4
0.5
1
2
2.5
3
3.5
–50 –25
0
25 50
125 150
0
1.5
TEMPERATURE (°C)
HVOUT (V)
RUN/SS PIN VOLTAGE (V)
4090 G13
4090 G12
4090 G14
High Voltage Regulator Switch
Current Limit
High Voltage Regulator Minimum
Input Voltage
High Voltage Regulator Switch
Current Limit
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
4.0
3.5
3.0
DUTY CYCLE = 10 %
TO START
DUTY CYCLE = 90 %
2.5
2.0
TO RUN
1.5
1.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
4090 G16
1
10
100
1000
20
60
40
DUTY CYCLE (%)
80
100
0
LOAD CURRENT (mA)
4090 G17
4090 G15
High Voltage Regulator VC
Voltages
High Voltage Regulator Power
Good Threshold
High Voltage Regulator Boost
Diode VF vs IF
2.90
2.50
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
2.85
2.80
2.00
1.50
CURRENT LIMIT CLAMP
SWITCHING THRESHOLD
2.75
2.70
2.65
1.00
0.50
0
50
–50 –25
0
25
75 100 125 150
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
4090 G19
0
0.5
1.0
1.5
2.0
TEMPERATURE (°C)
BOOST DIODE CURRENT (A)
4090 G20
4090 G18
4090fa
7
LTC4090/LTC4090-5
TYPICAL PERFORMANCE CHARACTERISTICS
LTC4090 Input Connect
Waveforms
LTC4090 Input Disconnect
Waveforms
LTC4090 Response to Suspend
V
SUSP
5V/DIV
V
IN
IN
5V/DIV
5V/DIV
V
V
V
OUT
OUT
OUT
5V/DIV
5V/DIV
5V/DIV
I
IN
I
IN
I
IN
0.5A/DIV
0.5A/DIV
0.5A/DIV
I
I
I
BAT
BAT
BAT
0.5A/DIV
0.5A/DIV
0.5A/DIV
1ms/DIV
1ms/DIV
1ms/DIV
4090 G22
4090 G23
4090 G21
V
I
= 3.85V
= 100mA
V
I
= 3.85V
= 50mA
V
I
= 3.85V
= 100mA
BAT
OUT
BAT
OUT
BAT
OUT
LTC4090 High Voltage Input
Connect Waveforms
LTC4090 High Voltage Input
Disconnect Waveforms
LTC4090 Response to HPWR
V
V
HPWR
5V/DIV
HVIN
HVIN
10V/DIV
5V/DIV
V
V
OUT
OUT
I
IN
5V/DIV
5V/DIV
0.5A/DIV
I
I
HVIN
HVIN
1A/DIV
1A/DIV
I
BAT
0.5A/DIV
I
I
BAT
1A/DIV
BAT
1A/DIV
2ms/DIV
2ms/DIV
100μs/DIV
4090 G24
4090 G25
4090 G26
V
= 3.85V
= 100mA
V
= 3.85V
= 100mA
V
= 3.85V
= 50mA
BAT
OUT
BAT
OUT
BAT
OUT
I
I
I
LTC4090 High Voltage Regulator
Load Transient
LTC4090 High Voltage Regulator
Load Transient
HVOUT
50mV/DIV
HVOUT
50mV/DIV
I
I
OUT
L
1A/DIV
1A/DIV
4090 G28
4090 G27
25μs/DIV
25μs/DIV
I
= 500mA
LOAD
I
= 500mA
LOAD
4090fa
8
LTC4090/LTC4090-5
PIN FUNCTIONS
SYNC (Pin 1): External Clock Synchronization Input. See
synchronizing section in the Applications Information
section. Ground pin when not used.
PROG (Pin 9): Charge Current Program Pin. Connecting
a resistor from PROG to ground programs the charge
current:
PG (Pin 2): The PG pin is the open collector output of an
internal comparator. PG remains low until the HVOUT pin
is above 2.8V. PG output is valid when HVIN is above 3.6V
and HVEN is high.
50,000V
ICHG(A)=
RPROG
GATE (Pin 10): External Ideal Diode Gate Connection. This
pin controls the gate of an optional external P-channel
MOSFET transistor used to supplement the internal ideal
diode. The source of the P-channel MOSFET should be
connected to OUT and the drain should be connected to
BAT. When not in use, this pin should be left floating. It
is important to maintain high impedance on this pin and
minimize all leakage paths.
R (Pin3):OscillatorResistorInput. Connectingaresistor
T
to ground from this pin sets the switching frequency.
V (Pin 4): High Voltage Buck Regulator Control Pin. The
C
voltage on this pin controls the peak switch current in the
high voltage regulator. Tie an RC network from this pin to
ground to compensate the control loop.
NTC (Pin 5): Input to the NTC Thermistor Monitoring
Circuits. The NTC pin connects to a negative temperature
coefficient thermistor which is typically co-packaged with
thebatterypacktodetermineifthebatteryistoohotortoo
cold to charge. If the battery temperature is out of range,
charging is paused until the battery temperature re-enters
the valid range. A low drift bias resistor is required from
VNTC to NTC and a thermistor is required from NTC to
ground. If the NTC function is not desired, the NTC pin
should be grounded.
BAT (Pin 11): Single-Cell Li-Ion Battery. This pin is used
as an output when charging the battery and as an input
whensupplyingpowertoOUT.WhentheOUTpinpotential
drops below the BAT pin potential, an ideal diode function
connects BAT to OUT and prevents OUT from dropping
more than 100mV below BAT. A precision internal resistor
divider sets the final float (charging) potential on this pin.
The internal resistor divider is disconnected when IN and
HVIN are in undervoltage lockout.
IN (Pin 12): Input Supply. Connect to USB supply, V
.
BUS
VNTC(Pin6):OutputBiasVoltageforNTC.Aresistorfrom
this pin to the NTC pin will bias the NTC thermistor.
Input current to this pin is limited to either 20% or 100%
of the current programmed by the CLPROG pin as deter-
minedbythestateoftheHPWRpin. Chargecurrent(tothe
BAT pin) supplied through the input is set to the current
programmed by the PROG pin but will be limited by the
input current limit if charge current is set greater than the
input current limit or if the sum of charge current plus load
current is greater than the input current limit.
⎯
⎯
⎯
⎯
HVPR (Pin 7): High Voltage Present Output (Active Low).
A low on this pin indicates that the high voltage regulator
has sufficient voltage to charge the battery. This feature
is enabled if power is present on HVIN, IN, or BAT (i.e.,
above UVLO thresholds).
⎯
⎯
⎯
⎯
CHRG(Pin8):Open-DrainChargeStatusOutput.Whenthe
OUT (Pin 13): Voltage Output. This pin is used to provide
⎯
⎯
⎯
⎯
battery is being charged, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the timer runs out or
the charge current drops below 10% of the programmed
controlled power to a USB device from either USB V
BUS
(IN), anexternalhighvoltagesupply(HVIN), orthebattery
(BAT) when no other supply is present. The high voltage
⎯
⎯
⎯
⎯
charge current or the input supply is removed, the CHRG
pin is forced to a high impedance state.
supply is prioritized over the USB V
input. OUT should
BUS
be bypassed with at least 4.7μF to GND.
4090fa
9
LTC4090/LTC4090-5
PIN FUNCTIONS
CLPROG (Pin 14): Current Limit Program and Input Cur-
Charge time is increased if charge current is reduced
due to load current, thermal regulation and current limit
selection (HPWR low).
rent Monitor. Connecting a resistor, R
programs the input to output current limit. The current
limit is programmed as follows:
, to ground
CLPROG
Shorting the TIMER pin to GND disables the battery
charging functions.
1000V
ICL(A)=
RCLPROG
HVOUT (Pin 18): Voltage Output of the High Voltage
Regulator. When sufficient voltage is present at HVOUT,
the low voltage power path from IN to OUT will be discon-
In USB applications, the resistor R
should be set
CLPROG
to no less than 2.1k. The voltage on the CLPROG pin is
always proportional to the current flowing through the
IN to OUT power path. This current can be calculated as
follows:
⎯
⎯
⎯
⎯
nected and the HVPR pin will be pulled low to indicate
that a high voltage wall adapter has been detected. The
LTC4090 high voltage regulator will maintain just enough
differential voltage between HVOUT and BAT to keep the
battery charger MOSFET out of dropout (typically 300mV
from OUT to BAT). The LTC4090-5 high voltage regulator
will provide a 5V output to the battery charger MOSFET.
HVOUT should be bypassed with at least 22μF to GND.
V
CLPROG
IIN(A)=
•1000
RCLPROG
HPWR(Pin15):HighPowerSelect.Thislogicinputisused
to control the input current limit. A voltage greater than
1.2V on the pin will set the input current limit to 100% of
the current programmed by the CLPROG pin. A voltage
less than 0.4V on the pin will set the input current limit to
20% of the current programmed by the CLPROG pin. A
2μA pull-down current is internally connected to this pin
to ensure it is low at power up when the pin is not being
driven externally.
BOOST (Pin 19): This pin is used to provide drive voltage,
higher than the input voltage, to the internal bipolar NPN
power switch.
SW (Pin 20): The SW pin is the output of the internal high
voltage power switch. Connect this pin to the inductor,
catch diode and boost capacitor.
HVIN(Pin21):HighVoltageRegulatorInput.TheHVINpin
suppliescurrenttotheinternalhighvoltageregulationand
to the internal high voltage power switch. The presence
SUSP (Pin 16): Suspend Mode Input. Pulling this pin
above 1.2V will disable the power path from IN to OUT.
The supply current from IN will be reduced to comply
with the USB specification for suspend mode. Both the
ability to charge the battery from HVIN and the ideal diode
function (from BAT to OUT) will remain active. Suspend
mode will reset the charge timer if OUT is less than BAT
while in suspend mode. If OUT is kept greater than BAT,
such as when the high voltage input is present, the charge
timer will not be reset when the part is put in suspend. A
2μA pull-down current is internally connected to this pin
to ensure it is low at power up when the pin is not being
driven externally.
of a high voltage input takes priority over the USB V
BUS
input (i.e., when a high voltage input supply is detected,
the USB IN to OUT path is disconnected). This pin must
be locally bypassed.
HVEN (Pin 22): High Voltage Regulator Enable Input. The
HVEN pin is used to disable the high voltage input path.
Tie to ground to disable the high voltage input or tie to at
least 2.3V to enable the high voltage path. If this feature
is not used, tie HVEN to the HVIN pin. This pin can also
be used to soft-start the high voltage regulator; see the
Applications Information section for more information.
TIMER (Pin 17): Timer Capacitor. Placing a capacitor,
TIMER
is:
Exposed Pad (Pin 23): Ground. The exposed package pad
is ground and must be soldered to the PC board for proper
functionality and for maximum heat transfer (use several
vias directly under the LTC4090/LTC4090-5).
C
, to GND sets the timer period. The timer period
CTIMER •RPROG •3hours
tTIMER(hours)=
0.1µF •100k
4090fa
10
LTC4090/LTC4090-5
BLOCK DIAGRAM
C2
BOOST
L1
HVIN
10
SW
Q1
INTERNAL
D1
REFERENCE
+
–
HVEN
10
I
L
+
–
R
S
Q
Q
SOFT-START
DRIVER
R
T
OSCILLATOR
200kHz - 2.4MHz
10
R
T1
SYNC
HVOUT
10
10
–
V
C
C1
V
SET
GM
+
+
3.6V (LTC4090)
5V (LTC4090-5)
R
C
C
F
–
VC CLAMP
C
C
75mV (RISING)
25mV (FALLING)
350mV
(LTC4090)
+
+
+
–
–
PG
IN
10
10
+
+
–
2.8V
–
HVPR
4.25V (RISING)
3.15V (FALLING)
19
CURRENT LIMIT
CNTL
IN
I
LIM
SOFT-START
I
IN
1V
+
–
OUT
OUT
I
LIM
CURRENT
CONTROL
ENABLE
1000
CLPROG
21
21
21
CL
–
+
22
13
20mV
–
+
CC/CV REGULATOR
CHARGER
–
+
DIE
R
30mV
CLPROG
GATE
105°C
TEMP
ENABLE
500mA/100mA
EDA
HPWR
IDEAL
DIODE
+
–
IN OUT BAT
2μA
TA
BAT
BAT
+
–
I
CHG
CHARGE CONTROL
0.25V
2.9V
BATTERY
UVLO
SOFT-START2
+
–
1V
CHG
+
–
PROG
23
15
14
R
PROG
VOLTAGE DETECT
UVLO
4.1V
RECHARGE
+
–
V
NTC
BAT UV
–
+
10k
TOO
COLD
RECHRG
TIMER
CHRG
NTCERR
NTC
21
18
OSCILLATOR
CONTROL LOGIC
C
TIMER
HOLD
CLK
10k
T
–
+
STOP
RESET
TOO
HOT
COUNTER
EOC
C/10
+
NTC ENABLE
2μA
0.1V
–
GND
16
SUSP
11
4090 BD
4090fa
11
LTC4090/LTC4090-5
OPERATION
Introduction
the ideal diode instead of connecting the load directly to
the battery allows a fully charged battery to remain fully
charged until external power is removed. Once external
power is removed the output drops until the ideal diode is
forward biased. The forward biased ideal diode will then
provide the output power to the load from the battery.
The LTC4090/LTC4090-5 are complete PowerPathTM
controllers for battery powered USB applications. The
LTC4090/LTC4090-5 are designed to receive power from
a low voltage source (e.g., USB or 5V wall adapter), a
high voltage source (e.g., FireWire/IEEE1394, automotive
battery, 12V wall adapter, etc.), and a single-cell Li-Ion
battery. They can then deliver power to an application
connected to the OUT pin and a battery connected to the
BAT pin (assuming that an external supply other than
the battery is present). Power supplies that have limited
The LTC4090/LTC4090-5 also include a high voltage
switching regulator which has the ability to receive power
fromahighvoltageinput. Thisinputtakespriorityoverthe
USB V
input (i.e., if both HVIN and IN are present, load
BUS
current and charge current will be delivered via the high
voltage path). When enabled, the high voltage regulator
regulates the HVOUT voltage using a constant frequency,
currentmoderegulator. AnexternalPFETbetweenHVOUT
current resources (such as USB V
supplies) should
BUS
be connected to the IN pin which has a programmable
current limit. Battery charge current will be adjusted to
ensure that the sum of the charge current and load cur-
rent does not exceed the programmed input current limit
(see Figure 1).
⎯
⎯
⎯
⎯
(drain) and OUT (source) is turned on via the HVPR pin
allowing OUT to charge the battery and/or supply power
to the application. The LTC4090’s Bat-Track maintains
approximately 300mV between the OUT pin and the BAT
pin, while the LTC4090-5 provides a fixed 5V output.
An ideal diode function provides power from the battery
whenoutput/loadcurrentexceedstheinputcurrentlimitor
when input power is removed. Powering the load through
PowerPath is a trademark of Linear Technology Corporation
HVIN
SW
L1
Q1
D1
HIGH VOLTAGE
BUCK REGULATOR
HVOUT
C1
+
4.25V (RISING)
–
3.15V (FALLING)
HVPR
19
+
–
LOAD
75mV (RISING)
+
25mV (FALLING)
–
ENABLE
IN
OUT
OUT
21
21
USB CURRENT LIMIT
–
+
30mV
–
+
30mV
+
–
GATE
BAT
CC/CV REGULATOR
CHARGER
EDA
IDEAL
DIODE
BAT
21
+
Li-Ion
4090 F01
Figure 1. Simplified PowerPath Block Diagram
4090fa
12
LTC4090/LTC4090-5
OPERATION
USB Input Current Limit
andquiescentcurrents. A2.1kCLPROGresistorwillgivea
typical current limit of 476mA in high power mode (when
HPWR is high) or 95mA in low power mode (when HPWR
is low).
The input current limit and charge control circuits of the
LTC4090/LTC4090-5aredesignedtolimitinputcurrentas
well as control battery charge current as a function of I
OUT drives the external load and the battery charger.
.
OUT
When SUSP is driven to a logic high, the input power
path is disabled and the ideal diode from BAT to OUT will
supply power to the application.
If the combined load at OUT does not exceed the pro-
grammed input current limit, OUT will be connected to IN
through an internal 215mΩ P-channel MOSFET.
High Voltage Step Down Regulator
IfthecombinedloadatOUTexceedstheprogrammedinput
currentlimit,thebatterychargerwillreduceitschargecur-
rent by the amount necessary to enable the external load
to be satisfied while maintaining the programmed input
current. Even if the battery charge current is set to exceed
the allowable USB current, a correctly programmed input
currentlimitwillensurethattheUSBspecificationisnever
violated. Furthermore, load current at OUT will always be
prioritized and only excess available current will be used
to charge the battery.
The power delivered from HVIN to HVOUT is controlled by
a constant frequency, current mode step down regulator.
An external P-channel MOSFET directs this power to OUT
andpreventsreverseconductionfromOUTtoHVOUT(and
ultimately HVIN).
An oscillator, with frequency set by R , enables an RS flip-
T
flop,turningontheinternalpowerswitch.Anamplifierand
comparatormonitorthecurrentflowingbetweenHVINand
SW pins, turning the switch off when this current reaches
a level determined by the voltage at V . An error amplifier
C
The input current limit, I , can be programmed using the
CL
servos the V node to maintain approximately 300mV
C
following formula:
between OUT and BAT (LTC4090). By keeping the voltage
across the battery charger low, efficiency is optimized be-
cause power lost to the battery charger is minimized and
power available to the external load is maximized. If the
BAT pin voltage is less than approximately 3.3V, then the
⎛
⎞
1000
1000V
RCLPROG
ICL =
• V
=
CLPROG
⎜
⎟
R
⎝
⎠
CLPROG
where V
is the CLPROG pin voltage (typically 1V)
CLPROG
erroramplifierwillservotheV nodetoprovideaconstant
C
and R
is the total resistance from the CLPROG pin
CLPROG
HVOUT output voltage of about 3.6V (LTC4090). An active
to ground. For best stability over temperature and time,
1% metal film resistors are recommended.
clamp on the V node provides current limit. The V node
C
C
is also clamped to the voltage on the HVEN pin; soft-start
is implemented by generating a voltage ramp at the HVEN
pin using an external resistor and capacitor.
The programmed battery charge current, I , is defined
CHG
as:
⎛
⎞
The switch driver operates from either the high voltage
input or from the BOOST pin. An external capacitor and
internal diode are used to generate a voltage at the BOOST
pin that is higher than the input supply. This allows the
driver to fully saturate the internal bipolar NPN power
switch for efficient operation.
50,000
50,000V
RPROG
ICHG
=
• V
=
PROG
⎜
⎟
R
⎝
⎠
PROG
Input current, I , is equal to the sum of the BAT pin output
IN
current and the OUT pin output current. V
will track
CLPROG
the input current according to the following equation:
V
To further optimize efficiency, the high voltage buck regu-
lator automatically switches to Burst Mode® operation in
lightloadsituations.Betweenbursts,allcircuitryassociated
with controlling the output switch is shut down reducing
the input supply current.
CLPROG
IIN =IOUT +IBAT
=
•1000
RCLPROG
In USB applications, the maximum value for R
CLPROG
should be 2.1k. This will prevent the input current from
exceeding 500mA due to LTC4090/LTC4090-5 tolerances
4090fa
13
LTC4090/LTC4090-5
OPERATION
I
I
IN
IN
500
400
300
200
100
100
80
60
40
20
0
500
400
300
200
100
I
IN
I
I
LOAD
I
LOAD
LOAD
I
= I
BAT CHG
I
= I = I
BAT CL OUT
I
I
I
BAT
(CHARGING)
BAT
(CHARGING)
BAT
(CHARGING)
0
0
100
200
20
40
100
200
0
300
400
500
BAT
0
60
80
100
BAT
0
300
400
500
BAT
I
I
I
I
I
I
LOAD (mA)
LOAD(mA)
LOAD(mA)
(IDEAL DIODE)
(IDEAL DIODE)
(IDEAL DIODE)
4090 F02a
4090 F02b
4090 F02c
(a) High Power Mode/Full Charge
RPROG = 100k and RCLPROG = 2k
(a) Low Power Mode/Full Charge
RPROG = 100k and RCLPROG = 2k
(a) High Power Mode with
ICL = 500mA and ICHG = 250mA
RPROG = 100k and RCLPROG = 2k
Figure 2. Input and Battery Currents as a Function of Load Current
The oscillator reduces the switch regulator’s operating
frequency when the voltage at the HVOUT pin is low (be-
low 2.95V). This frequency foldback helps to control the
output current during start-up and overload.
If the desired input current increases beyond the pro-
grammedinputcurrentlimitadditionalcurrentwillbedrawn
from the battery via the internal ideal diode. Furthermore,
if power to IN (USB V ) or HVIN (high voltage input) is
BUS
removed, then all of the application power will be provided
by the battery via the ideal diode. A 4.7μF capacitor at
OUT is sufficient to keep a transition from input power
to battery power from causing significant output voltage
droop.Theidealdiodeconsistsofaprecisionamplifierthat
enablesalargeP-channelMOSFETtransistorwheneverthe
The high voltage regulator contains a power good com-
parator which trips when the HVOUT pin is at 2.8V. The PG
output is an open-collector transistor that is off when the
output is in regulation, allowing an external resistor to pull
the PG pin high. Power good is valid when the switching
regulator is enabled and HVIN is above 3.6V.
voltage at OUT is approximately 20mV (V
) below the
FWD
voltage at BAT. The resistance of the internal ideal diode
Ideal Diode From BAT to OUT
is approximately 215mΩ.
The LTC4090/LTC4090-5 have an internal ideal diode as
well as a controller for an optional external ideal diode. If
a battery is the only power supply available, or if the load
current exceeds the programmed input current limit, then
the battery will automatically deliver power to the load via
an ideal diode circuit between the BAT and OUT pins. The
ideal diode circuit (along with the recommended 4.7μF
capacitor on the OUT pin) allows the LTC4090/LTC4090-5
to handle large transient loads and wall adapter or USB
If this is sufficient for the application then no external
componentsarenecessary. Howeverifmoreconductance
is needed, an external P-channel MOSFET can be added
fromBATtoOUT.TheGATEpinoftheLTC4090/LTC4090-5
drives the gate of the external PFET for automatic ideal
diode control. The source of the external MOSFET should
be connected to OUT and the drain should be connected
to BAT. In order to help protect the external MOSFET in
overcurrentsituations,itshouldbeplacedinclosethermal
contact to the LTC4090/LTC4090-5.
V
connect/disconnect scenarios without the need for
BUS
large bulk capacitors. The ideal diode responds within
a few microseconds and prevents the OUT pin voltage
from dropping significantly below the BAT pin voltage.
A comparison of the I-V curve of the ideal diode and a
Schottky diode can be seen in Figure 3.
Burst Mode is a registered trademark of Linear Technology Corporation
4090fa
14
LTC4090/LTC4090-5
OPERATION
Suspend Mode
trickle charge mode to bring the cell voltage up to a safe
level for charging. The charger goes into the fast charge
constant current mode once the voltage on the BAT pin
rises above 2.9V. In constant current mode, the charge
When SUSP is pulled above V the LTC4090/LTC4090-5
IH
entersuspendmodetocomplywiththeUSBspecification.
In this mode, the power path between IN and OUT is put
in a high impedance state to reduce the IN input current to
50μA. If no other power source is available to drive HVIN,
the system load connected to OUT is supplied through the
ideal diodes connected to BAT.
current is set by R
. When the battery approaches the
PROG
final float voltage, the charge current begins to decrease
as the LTC4090/LTC4090-5 switch to constant voltage
mode. When the charge current drops below 10% of the
programmed value while in constant voltage mode the
⎯
⎯
⎯
⎯
CHRG pin assumes a high impedance state.
Battery Charger
An external capacitor on the TIMER pin sets the total
minimum charge time. When this time elapses, the
The battery charger circuits of the LTC4090/LTC4090-5
are designed for charging single cell lithium-ion batteries.
FeaturinganinternalP-channelpowerMOSFET,thecharger
usesaconstantcurrent/constantvoltagechargealgorithm
with programmable charge current and a programmable
timer for charge termination. Charge current can be
programmed up to 1.5A. The final float voltage accuracy
is 0.8% typical. No blocking diode or sense resistor is
required when powering either the IN or the HVIN pins.
The CHRG open-drain status output provides information
regarding the charging status of the LTC4090/LTC4090-5
at all times. An NTC input provides the option of charge
qualification using battery temperature.
⎯
⎯
⎯
⎯
charge cycle terminates and the CHRG pin assumes a
high impedance state, if it has not already done so. While
charging in constant current mode, if the charge current
is decreased by thermal regulation or in order to maintain
the programmed input current limit, the charge time is
automaticallyincreased.Inotherwords,thechargetimeis
extendedinverselyproportionaltotheactualchargecurrent
deliveredtothebattery.ForLi-Ionandsimilarbatteriesthat
require accurate final float potential, the internal bandgap
reference,voltageamplifierandtheresistordividerprovide
regulation with 0.8% accuracy.
⎯
⎯
⎯
⎯
The charge cycle begins when the voltage at the OUT
pin rises above the battery voltage and the battery volt-
age is below the recharge threshold. No charge current
actually flows until the OUT voltage is 100mV above
the BAT voltage. At the beginning of the charge cycle, if
the battery voltage is below 2.9V, the charger goes into
Trickle Charge and Defective Battery Detection
At the beginning of a charge cycle, if the battery voltage
is below 2.9V, the charger goes into trickle charge reduc-
ing the charge current to 10% of the full-scale current.
If the low battery voltage persists for one quarter of the
programmed total charge time, the battery is assumed
to be defective, the charge cycle is terminated and the
CONSTANT
0N
LTC4090/LTC4090-5
⎯
⎯
⎯
⎯
CHRG pin output assumes a high impedance state. If
for any reason the battery voltage rises above ~2.9V the
charge cycle will be restarted. To restart the charge cycle
(i.e., when the dead battery is replaced with a discharged
battery), simply remove the input voltage and reapply it
or cycle the TIMER pin to 0V.
I
I
MAX
CONSTANT
0N
SLOPE: 1/R
DIO(ON)
R
I
FWD
SCHOTTKY
DIODE
CONSTANT
0N
SLOPE: 1/R
FWD
Programming Charge Current
V
The formula for the battery charge current is:
0
FORWARD VOLTAGE (V)
V
V
FWD
4090 F03
PROG
ICHG =IPROG •50,000=
•50,000
RPROG
Figure 3. LTC4090/LTC4090-5 Versus Schottky Diode Forward
Voltage Drop
4090fa
15
LTC4090/LTC4090-5
OPERATION
where V
is the PROG pin voltage and R
is the
PROG
As the LTC4090/LTC4090-5 approach constant voltage
mode the charge current begins to drop. This change in
charge current is due to normal charging operation and
does not affect the timer duration.
PROG
total resistance from the PROG pin to ground. Keep in
mind that when the LTC4090/LTC4090-5 are powered
from the IN pin, the programmed input current limit takes
precedence over the charge current. In such a scenario,
the charge current cannot exceed the programmed input
current limit.
Consider, for example, a USB charge condition where
R
= 2k, R
= 100k and C
= 0.1μF. This
CLPROG
PROG
TIMER
corresponds to a three hour charge cycle. However, if the
HPWR input is set to a logic low, then the input current
limit will be reduced from 500mA to 100mA. With no ad-
ditional system load, this means the charge current will
be reduced to 100mA. Therefore, the termination timer
will automatically slow down by a factor of five until the
For example, if typical 500mA charge current is required,
calculate:
1V
500mA
RPROG
=
•50,000=100k
charger reaches constant voltage mode (i.e. V
ap-
BAT
For best stability over temperature and time, 1% metal
film resistors are recommended. Under trickle charge
conditions, this current is reduced to 10% of the full-
scale value.
proaches 4.2V) or HPWR is returned to a logic high. The
charge cycle is automatically lengthened to account for
the reduced charge current. The exact time of the charge
cycle will depend on how long the charger remains in
constant current mode and/or how long the HPWR pin
remains logic low.
The Charge Timer
The programmable charge timer is used to terminate the
charge cycle. The timer duration is programmed by an
external capacitor at the TIMER pin. The charge time is
typically:
Once a time-out occurs and the voltage on the battery is
greater than the recharge threshold, the charge current
⎯
⎯
⎯
⎯
stops, and the CHRG output assumes a high impedance
state if it has not already done so.
CTIMER •RPROG •3hours
tTIMER(hours)=
Connecting the TIMER pin to ground disables the battery
charger.
0.1µF •100k
The timer starts when an input voltage greater than the
undervoltage lockout threshold level is applied or when
leavingshutdownandthevoltageonthebatteryislessthan
the recharge threshold. At power-up or exiting shutdown
with the battery voltage less than the recharge threshold,
the charge time is a full cycle. If the battery is greater than
therechargethresholdthetimerwillnotstartandcharging
is prevented. If after power-up the battery voltage drops
below the recharge threshold, or if after a charge cycle
the battery voltage is still below the recharge threshold,
the charge time is set to one-half of a full cycle.
⎯ ⎯ ⎯ ⎯
CHRG Status Output Pin
⎯
⎯
⎯
⎯
When the charge cycle starts, the CHRG pin is pulled to
ground by an internal N-channel MOSFET capable of driv-
ing an LED. When the charge current drops below 10%
of the programmed full charge current while in constant
voltage mode, the pin assumes a high impedance state,
but charge current continues to flow until the charge
time elapses. If this state is not reached before the end
of the programmable charge time, the pin will assume a
⎯
⎯
⎯
⎯
high impedance state when a time-out occurs. The CHRG
current detection threshold can be calculated by the fol-
lowing equation:
TheLTC4090/LTC4090-5haveafeaturethatextendscharge
time automatically. Charge time is extended if the charge
current in constant current mode is reduced due to load
current or thermal regulation. This change in charge time
is inversely proportional to the change in charge current.
0.1V
RPROG
5000V
RPROG
IDETECT
=
•50,000=
4090fa
16
LTC4090/LTC4090-5
OPERATION
For example, if the full charge current is programmed
of the LTC4090/LTC4090-5 thermal regulation loop is that
charge current can be set according to actual conditions
rather than worst-case conditions with the assurance that
the battery charger will automatically reduce the current
in worst-case conditions.
⎯
⎯
⎯
⎯
to 500mA with a 100k PROG resistor the CHRG pin will
change state at a battery charge current of 50mA.
Note: The end-of-charge (EOC) comparator that moni-
tors the charge current latches its decision. Therefore,
the first time the charge current drops below 10% of the
programmed full charge current while in constant volt-
Undervoltage Lockout
Aninternalundervoltagelockoutcircuitmonitorstheinput
voltage (IN) and the output voltage (OUT) and disables
either the input current limit or the battery charger circuits
or both. The input current limit circuitry is disabled until
V risesabovetheundervoltagelockoutthresholdandV
⎯
⎯
⎯
⎯
age mode, it will toggle CHRG to a high impedance state.
If, for some reason the charge current rises back above
⎯
⎯
⎯
⎯
the threshold, the CHRG pin will not resume the strong
pull-down state. The EOC latch can be reset by a recharge
cycle (i.e., V
drops below the recharge threshold) or
IN
IN
BAT
exceedsV by50mV.Thebatterychargercircuitsaredis-
toggling the input power to the part.
OUT
ableduntilV
exceedsV by50mV.Bothundervoltage
OUT
BAT
Automatic Recharge
lockout comparators have built-in hysteresis.
After the battery charger terminates, it will remain off
drawing only microamperes of current from the battery. If
the product remains in this state long enough, the battery
will eventually self discharge. To ensure that the battery is
always topped off, a charge cycle will automatically begin
NTC Thermistor
The battery temperature is measured by placing a nega-
tive temperature coefficient (NTC) thermistor close to
the battery pack. To use this feature connect the NTC
thermistor, R , between the NTC pin and ground and a
when the battery voltage falls below V
(typically
from
NTC
RECHRG
bias resistor, R
, from VNTC to NTC. R
should be
4.1V). To prevent brief excursions below V
NOM
NOM
RECHRG
a 1% resistor with a value equal to the value of the chosen
resetting the safety timer, the battery voltage must be
below V for more than a few milliseconds. The
NTC thermistor at 25°C (denoted R ).
25C
RECHRG
charge cycle and safety timer will also restart if the IN
UVLO cycles low and then high (e.g. IN, is removed and
then replaced).
The LTC4090/LTC4090-5 will pause charging when the
resistance of the NTC thermistor drops to 0.41 times the
value of R or approximately 4.1k (for a Vishay “Curve
25C
2” thermistor, this corresponds to approximately 50°C).
The safety timer also pauses until the thermistor indicates
a return to a valid temperature. As the temperature drops,
the resistance of the NTC thermistor rises. The LTC4090/
LTC4090-5arealsodesignedtopausecharging(andtimer)
when the value of the NTC thermistor increases to 2.82
Thermal Regulation
To prevent thermal damage to the IC or surrounding
components, an internal thermal feedback loop will
automatically decrease the programmed charge current
if the die temperature rises to approximately 105°C.
Thermal regulation protects the LTC4090/LTC4090-5
from excessive temperature due to high power operation
or high ambient thermal conditions and allows the user
to push the limits of the power handling capability with a
given circuit board design without risk of damaging the
LTC4090/LTC4090-5 or external components. The benefit
times the value of R . For a Vishay “Curve 2” thermistor
25C
this resistance, 28.2k, corresponds to approximately 0°C.
The hot and cold comparators each have approximately
3°Cofhysteresistopreventoscillationaboutthetrippoint.
Grounding the NTC pin disables all NTC functionality.
4090fa
17
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
USB and 5V Wall Adapter Power
5V WALL
ADAPTER
I
CHG
BAT
850mA I
CHG
Although the LTC4090/LTC4090-5 are designed to draw
power from a USB port, a higher power 5V wall adapter
can also be used to power the application and charge the
battery (higher voltage wall adapters can be connected
directlytoHVIN).Figure4showsanexampleofcombining
a 5V wall adapter and a USB power input. With its gate
grounded by 1k, P-channel MOSFET MP1 provides USB
power to the LTC4090/LTC4090-5 when 5V wall power is
not available. When 5V wall power is available, diode D1
supplies power to the LTC4090/LTC4090-5, pulls the gate
of MN1 high to increase the charge current (by increasing
the input current limit), and pulls the gate of MP1 high to
disable it and prevent conduction back to the USB port.
D1
LTC4090
USB POWER
IN
PROG
500mA I
+
CHG
Li-Ion
BATTERY
MP1
1k
CLPROG
2.87k
MN1
2k
59k
4090 F04
Figure 4. USB or 5V Wall Adapter Power
Operating Frequency Tradeoffs
Selection of the operating frequency for the high voltage
buckregulatorisatradeoffbetweenefficiency,component
size, minimum dropout voltage, and maximum input volt-
age. The advantage of high frequency operation is that
smaller inductor and capacitor values may be used. The
disadvantages are lower efficiency, lower maximum input
voltage,andhigherdropoutvoltage.Thehighestacceptable
Setting the Switching Frequency
The high voltage switching regulator uses a constant
frequency PWM architecture that can be programmed to
switch from 200kHz to 2.4MHz by using a resistor tied
switchingfrequency(f
)foragivenapplicationcan
from the R pin to ground. A table showing the necessary
SW(MAX)
be calculated as follows:
T
R value for a desired switching frequency is in Table 1.
T
V + V
D
HVOUT
Table 1. Switching Frequency vs RT Value
SWITCHING FREQUENCY (MHz)
f
=
SW(MAX)
tON(MIN) • V + VHVIN – VSW
(
)
R VALUE (kΩ)
D
T
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
187
121
where V
HVOUT
is the typical high voltage input voltage,
HVIN
V
is the output voltage of the switching regulator, V
D
88.7
68.1
56.2
46.4
40.2
34.0
29.4
23.7
19.1
16.2
13.3
11.5
9.76
8.66
is the catch diode drop (~0.5V), and V is the internal
SW
switch drop (~0.5V at max load). This equation shows
that slower switching frequency is necessary to safely
accommodate high V
/V
ratio. Also, as shown in
HVIN HVOUT
the next section, lower frequency allows a lower dropout
voltage. The reason input voltage range depends on the
switching frequency is because the high voltage switch
has finite minimum on and off times. The switch can turn
on for a minimum of ~150ns and turn off for a minimum
of ~150ns. This means that the minimum and maximum
duty cycles are:
DC
DC
= f • t
SW ON(MIN)
MIN
= 1 – f • t
MAX
SW OFF(MIN)
where f
is the switching frequency, t
is the
is the
SW
ON(MIN)
OFF(MIN)
minimum switch-on time (~150ns), and t
4090fa
18
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
minimumswitch-offtime(~150ns).Theseequationsshow
that duty cycle range increases when switching frequency
is decreased.
may enter pulse skipping operation where some switch-
ing pulses are skipped to maintain output regulation. In
this mode the output voltage ripple and inductor current
ripplewillbehigherthaninnormaloperation.Above41.5V,
switching will stop.
A good choice of switching frequency should allow ad-
equate input voltage range (see next section) and keep
the inductor and capacitor values small.
Theminimuminputvoltageisdeterminedbyeitherthehigh
voltageregulator’sminimumoperatingvoltageof~6Vorby
itsmaximumdutycycle(seeequationinprevioussection).
The minimum input voltage due to duty cycle is:
HVIN Input Voltage Range
The maximum input voltage range for the LTC4090/
LTC4090-5 applications depends on the switching fre-
V
HVOUT + V
D
V
=
− V + VSW
D
HVIN(MIN)
quency, the Absolute Maximum Ratings of the V
BOOST pins, and the operating mode.
and
HVIN
1− f t
SW OFF(MIN)
where V
OFF(MIN)
is the minimum input voltage, and
The high voltage switching regulator can operate from
input voltages up to 36V, and safely withstand input volt-
HVIN(MIN)
t
is the minimum switch off time (150ns). Note
thathigherswitchingfrequencywillincreasetheminimum
input voltage. If a lower dropout voltage is desired, a lower
switching frequency should be used.
ages up to 60V. Note that while V
> 41.5V (typical),
HVIN
the LTC4090/LTC4090-5 will stop switching, allowing the
output to fall out of regulation.
While the high voltage regulator output is in start-up,
short-circuit, or other overload conditions, the switching
frequency should be chosen according to the following
discussion.
Inductor Selection and Maximum Output Current
A good choice for the inductor value is L = 6.8μH (assum-
ing a 800kHz operating frequency). With this value the
maximum load current will be ~2.4A. The RMS current
rating of the inductor must be greater than the maximum
load current and its saturation current should be about
30% higher. Note that the maximum load current will be
programmed charge current plus the largest expected
application load current. For robust operation in fault
conditions, the saturation current should be ~3.5A. To
keep efficiency high, the series resistance (DCR) should
be less than 0.1Ω. Table 2 lists several vendors and types
that are suitable.
For safe operation at inputs up to 60V the switching fre-
quency must be low enough to satisfy V
≥ 45V
HVIN(MAX)
HVIN(MAX)
according to the following equation. If lower V
is desired, this equation can be used directly.
V
HVOUT + V
D
V
=
– V + VSW
D
HVIN(MAX)
fSW • tON(MIN)
whereV
HVOUT
isthemaximumoperatinginputvoltage,
HVIN(MAX)
V
is the high voltage regulator output voltage, V is
D
the catch diode drop (~0.5V), V is the internal switch
SW
Table 2. Inductor Vendors
drop (~0.5V at max load), f is the switching frequency
SW
VENDOR URL
PART SERIES
TYPE
(set by R ), and t
is the minimum switch-on time
T
ON(MIN)
Murata
TDK
www.murata.com
LQH55D
Open
(~150ns). Note that a higher switching frequency will de-
press the maximum operating input voltage. Conversely,
a lower switching frequency will be necessary to achieve
safe operation at high input voltages.
www.componenttdk.com SLF7045
Shielded
Shielded
SLF10145
Toko
www.toko.com
D62CB
D63CB
D75C
Shielded
Shielded
Shielded
Open
D75F
If the output is in regulation and no short-circuit, start-
up, or overload events are expected, then input voltage
transients of up to 60V are acceptable regardless of the
switchingfrequency.Inthismode,theLTC4090/LTC4090-5
Sumida www.sumida.com
CR54
Open
CDRH74
CDRH6D38
CR75
Shielded
Shielded
Open
4090fa
19
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
Catch Diode
100
VOUT SW
wheref isinMHz, andC
COUT
=
The catch diode conducts current only during switch-off
time. Average forward current in normal operation can
be calculated from:
f
istherecommendedoutput
OUT
SW
capacitance in μF. Use X5R or X7R types. This choice will
provide low output ripple and good transient response.
Transientperformancecanbeimprovedwithahighervalue
capacitor if the compensation network is also adjusted
to maintain the loop bandwidth. A lower value of output
capacitor can be used to save space and cost but transient
performance will suffer. See the High Voltage Regulator
FrequencyCompensationsectiontochooseanappropriate
compensation network.
V
HVIN – V
(
•
)
HVOUT
ID(AVG) =IHVOUT
whereI
V
HVIN
istheoutputloadcurrent. Theonlyreasonto
HVOUT
consideradiodewithalargercurrentratingthannecessary
for nominal operation is for the worst-case condition of
shorted output. The diode current will then increase to the
typical peak switch current. Peak reverse voltage is equal
to the regulator input voltage. Use a Schottky diode with a
reverse voltage rating greater than the input voltage. The
overvoltageprotectionfeatureinthehighvoltageregulator
When choosing a capacitor, look carefully through the
data sheet to find out what the actual capacitance is under
operating conditions (applied voltage and temperature).
A physically larger capacitor, or one with a higher voltage
rating, may be required. High performance tantalum or
electrolyticcapacitorscanbeusedfortheoutputcapacitor.
Low ESR is important, so choose one that is intended for
use in switching regulators. The ESR should be specified
by the supplier, and should be 0.05Ω or less. Such a
capacitor will be larger than a ceramic capacitor and will
have a larger capacitance, because the capacitor must be
large to achieve low ESR.
will keep the switch off when V
the use of 45V rated Schottky even when V
up to 60V. Table 3 lists several Schottky diodes and their
manufacturers.
> 45V which allows
HVIN
ranges
HVIN
Table 3. Diode Vendors
V
(V)
I
V AT 1A V AT 2A
F F
R
AVE
PART NUMBER
(A)
(MV)
(MV)
On Semiconductor
MBRM120E
MBRM140
20
40
1
1
530
550
595
Diodes Inc.
B130
Ceramic Capacitors
30
20
30
60
40
1
2
2
3
2
500
500
B220
500
500
550
500
Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can cause problems
when used with the high voltage switching regulator
due to their piezoelectric nature. When in Burst Mode
operation, theLTC4090/LTC4090-5’sswitchingfrequency
depends on the load current, and at very light loads the
LTC4090/LTC4090-5 can excite the ceramic capacitor at
audio frequencies, generating audible noise. Since the
LTC4090/LTC4090-5operateatalowercurrentlimitduring
Burst Mode operation, the noise is typically very quiet to a
casual ear. If this is unacceptable, use a high performance
tantalum or electrolytic capacitor at the output.
B230
B360
DFLS240L
International Rectifier
10BQ030
20BQ030
30
30
1
2
420
470
470
High Voltage Regulator Output Capacitor Selection
The high voltage regulator output capacitor has two es-
sential functions. Along with the inductor, it filters the
square wave generated at the switch pin to produce the
DC output. In this role it determines the output ripple, and
low impedance at the switching frequency is important.
The second function is to store energy in order to satisfy
transient loads and stabilize the LTC4090/LTC4090-5’s
control loop. Ceramic capacitors have very low equiva-
lent series resistance (ESR) and provide the best ripple
performance. A good starting value is:
High Voltage Regulator Frequency Compensation
The LTC4090/LTC4090-5 high voltage regulator uses
current mode control to regulate the output. This simpli-
fies loop compensation. In particular, the high voltage
4090fa
20
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
regulator does not require the ESR of the output capacitor Toenhanceefficiencyatlightloads,theLTC4090/LTC4090-5
for stability, so you are free to use ceramic capacitors to can be operated in low ripple Burst Mode operation which
achieve low output ripple and small circuit size. Frequency keeps the output capacitor charged to the proper voltage
compensation is provided by the components tied to the whileminimizingtheinputquiescentcurrent.DuringBurst
V pin, as shown in Figure 1. Generally a capacitor (C ) Mode operation, the LTC4090/LTC4090-5 deliver single
C
C
and a resistor (R ) in series to ground are used. In ad- cycle bursts of current to the output capacitor followed
C
dition, there may be a lower value capacitor in parallel. by sleep periods where the output power is delivered to
This capacitor (C ) is not part of the loop compensation the load by the output capacitor. Because the LTC4090/
F
but is used to filter noise at the switching frequency, and LTC4090-5deliverpowertooutputwithsingle,lowcurrent
is required only if a phase-lead capacitor is used or if the pulses, the output ripple is kept below 15mV for a typical
output capacitor has high ESR.
application. As the load current decreases towards a no
load condition, the percentage of time that the high volt-
age regulator operates in sleep mode increases and the
average input current is greatly reduced resulting in high
efficiency even at very low loads. See Figure 6.
Loop compensation determines the stability and transient
performance.Designingthecompensationnetworkisabit
complicatedandthebestvaluesdependontheapplication
and in particular the type of output capacitor. A practical
approachistostartwiththefrontpageschematicandtune At higher output loads (above 70mA for the front page
thecompensationnetworktooptimizeperformance.Stabil- application) the LTC4090/LTC4090-5 will be running at
ityshouldthenbecheckedacrossalloperatingconditions, the frequency programmed by the R resistor, and will be
T
includingloadcurrent, inputvoltageandtemperature. The operating in standard PWM mode. The transition between
LTC1375 datasheet contains a more thorough discussion PWM and low ripple Burst Mode operation is seamless,
of loop compensation and describes how to test the sta- and will not disturb the output voltage.
bility using a transient load. Figure 5 shows the transient
If low quiescent current is not required, the LTC4090/
response when the load current is stepped from 500mA
LTC4090-5 can operate in pulse-skip mode. The benefit
to 1500mA and back to 500mA.
of this mode is that the LTC4090/LTC4090-5 will enter full
frequency standard PWM operation at a lower output load
Low Ripple Burst Mode Operation and Pulse-Skip
Mode
currentthanwheninBurstModeoperation.Thefrontpage
application circuit will switch at full frequency at output
TheLTC4090/LTC4090-5arecapableofoperatingineither
lowrippleBurstModeoperationorpulse-skipmodewhich
are selected using the SYNC pin. Tie the SYNC pin below
loads higher than about 60mA.
V
LOAD
= 12V; FIGURE 12 SCHEMATIC
IN
I
= 10mA
V
(typically0.5V)forlowrippleBurstModeoperation
SYNC,L
or above V
I
L
(typically 0.8V) for pulse-skip mode.
0.5A/DIV
SYNC,H
FIGURE 12 SCHEMATIC
V
SW
HVOUT
50mV/DIV
5V/DIV
V
OUT
10mV/DIV
I
L
1A/DIV
4090 F06
5μs/DIV
4090 F05
25μs/DIV
Figure 6. High Voltage Regulator Burst Mode Operation
Figure 5. Transient Load Response of the LTC4090 High Voltage
Regulator Front Page Application as the Load Current is Stepped
from 500mA to 1500mA.
4090fa
21
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
Boost Pin Considerations
lowerthantheexternalsynchronizationfrequencytoensure
adequate slope compensation. While synchronized, the
high voltage regulator will turn on the power switch on
positive going edges of the clock. When the power good
(PG) output is low, such as during start-up, short-circuit,
andoverloadconditions,theLTC4090/LTC4090-5willdis-
able the synchronization feature. The SYNC pin should be
grounded when synchronization is not required.
Capacitor C2 (see Block Diagram) and an internal diode
are used to generate a boost voltage that is higher than
the input voltage. In most cases, a 0.47μF capacitor will
work well. The BOOST pin must be at least 2.3V above
the SW pin for proper operation.
High Voltage Regulator Soft-Start
The HVEN pin can be used to soft-start the high voltage
regulator of the LTC4090/LTC4090-5, reducing maximum
input current during start-up. The HVEN pin is driven
through an external RC filter to create a voltage ramp at
this pin. Figure 7 shows the start-up and shutdown wave-
forms with the soft-start circuit. By choosing a large RC
time constant, the peak start-up current can be reduced
to the current that is required to regulate the output, with
no overshoot. Choose the value of the resistor so that it
can supply 20μA when the HVEN pin reaches 2.3V.
Alternate NTC Thermistors and Biasing
The LTC4090/LTC4090-5 provide temperature qualified
charging if a grounded thermistor and a bias resistor are
connected to NTC (see Figure 8). By using a bias resistor
whose value is equal to the room temperature resistance
ofthethermistor(R )theupperandlowertemperatures
25C
are pre-programmed to approximately 50°C and 0°C,
respectively (assuming a Vishay “Curve 2” thermistor).
The upper and lower temperature thresholds can be ad-
justed by either a modification of the bias resistor value
or by adding a second adjustment resistor to the circuit.
If only the bias resistor is adjusted, then either the upper
or the lower threshold can be modified but not both. The
other trip point will be determined by the characteristics
of the thermistor. Using the bias resistor in addition to an
adjustmentresistor,boththeupperandthelowertempera-
ture trip points can be independently programmed with
the constraint that the difference between the upper and
lower temperature thresholds cannot decrease. Examples
of each technique are given below.
I
L
RUN
15k
1A/DIV
HVEN
GND
V
RUN/SS
0.22μF
2V/DIV
V
OUT
2V/DIV
4090 F07
2ms/DIV
NTC thermistors have temperature characteristics which
areindicatedonresistance-temperatureconversiontables.
The Vishay-Dale thermistor NTHS0603N02N1002J, used
in the following examples, has a nominal value of 10k
and follows the Vishay “Curve 2” resistance-temperature
characteristic. The LTC4090/LTC4090-5’s trip points are
designedtoworkwiththermistorswhoseresistance-tem-
peraturecharacteristicsfollowVishayDale’s“R-TCurve2.”
The Vishay NTHS0603N02N1002J is an example of such
a thermistor. However, Vishay Dale has many thermistor
products that follow the “R-T Curve 2” characteristic in a
variety of sizes. Furthermore, any thermistor whose ratio
Figure 7. To Soft-Start the High Voltage Regulator, Add a Resistor
and Capacitor to the HVEN Pin
Synchronization and Mode
The SYNC pin allows the high voltage regulator to be
synchronized to an external clock.
Synchronizing the LTC4090/LTC4090-5 internal oscilla-
tor to an external frequency can be done by connecting a
square wave (with 20% to 80% duty cycle) to the SYNC
pin. The square wave amplitude should be such that the
valleys are below 0.3V and the peaks are above 0.8V (up
to 6V). The high voltage regulator may be synchronized
of R
to R
is about 7.0 will also work (Vishay Dale
COLD
HOT
over a 300kHz to 2MHz range. The R resistor should be
T
R-T Curve 2 shows a ratio of 2.815/0.409 = 6.89).
chosen such that the LTC4090/LTC4090-5 oscillate 25%
4090fa
22
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
In the explanation below, the following notation is used.
SolvingtheseequationsforR
in the following:
andR
results
NTC|COLD
NTC|HOT
R
R
R
= Value of the Thermistor at 25°C
25C
R
= 0.409 • R
NOM
NTC|HOT
= Value of Thermistor at the Cold Trip Point
NTC|COLD
and
= Value of the Thermistor at the Hot Trip Point
NTC|HOT
R
= 2.815 • R
NOM
NTC|COLD
rcold = Ratio of R
to R
NTC|COLD
to R
NTC|HOT
25C
By setting R
equal to R , the above equations result
25C
NOM
=0.409andr
r
= Ratio of R
HOT
25C
inr
=2.815.Referencingtheseratios
HOT
COLD
R
NOM
= Primary Thermistor Bias Resistor (see Figure 8)
to the Vishay Resistance-Temperature Curve 2 chart gives
a hot trip point of about 50°C and a cold trip point of about
0°C. The difference between the hot and cold trip points
is approximately 50°C.
R1 = Optional Temperature Range Adjustment resistor
(see Figure 9)
The trip points for the LTC4090/LTC4090-5’s tempera-
ture qualification are internally programmed at 0.29 •
VNTC for the hot threshold and 0.74 • VNTC for the cold
threshold.
By using a bias resistor, R
25C
, different in value from
NOM
R
, the hot and cold trip points can be moved in either
direction.Thetemperaturespanwillchangesomewhatdue
to the non-linear behavior of the thermistor. The following
equations can be used to easily calculate a new value for
the bias resistor:
Therefore, the hot trip point is set when:
RNTC|HOT
• VNTC= 0.29• VNTC
RNOM +RNTC|HOT
rHOT
0.409
rCOLD
RNOM
RNOM
=
=
•R25C
•R25C
and the cold trip point is set when:
2.815
RNTC|COLD
• VNTC= 0.74• VNTC
RNOM +RNTC|COLD
VNTC
6
VNTC
6
NTC BLCOK
NTC BLCOK
0.738 • VNTC
0.738 • VNTC
R
R
NOM
13.2k
NTC
NOM
–
+
–
+
10k
TOO_COLD
TOO_HOT
TOO_COLD
TOO_HOT
NTC
5
5
R
10k
R1
1.97k
NTC
–
+
–
+
0.29 • VNTC
0.29 • VNTC
R
NTC
10k
+
–
+
–
NTC_ENABLE
NTC_ENABLE
0.1V
0.1V
4090 F08
4090 F09
Figure 8. Typical NTC Thermistor Circuit
Figure 9. NTC Thermistor Circuit with Additional Bias Resistor
4090fa
23
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
where r
and r
are the resistance ratios at the de-
Ingeneral,iftheLTC4090/LTC4090-5isbeingpoweredfrom
IN the power dissipation can be calculated as follows:
HOT
COLD
sired hot and cold trip points. Note that these equations
are linked. Therefore, only one of the two trip points can
be chosen, the other is determined by the default ratios
designed in the IC. Consider an example where a 40°C
hot trip point is desired.
P = (V – V ) • I + (V – V ) • I
D
IN
BAT
BAT
IN
OUT
OUT
where P is the power dissipated, I
is the battery
BAT
D
charge current, and I
is the application load current.
OUT
For a typical application, an example of this calculation
would be:
FromtheVishayCurve2R-Tcharacteristics,r is0.5758
HOT
should be set
, the cold trip point is
at 40°C. Using the above equation, R
NOM
P
= (5V – 3.7V) • 0.4A + (5V – 4.75V) • 0.1A
to 14.0k. With this value of R
D
NOM
= 545mW
about -7°C. Notice that the span is now 47°C rather than
the previous 50°C. This is due to the increase in “tem-
perature gain” of the thermistor as absolute temperature
decreases.
This examples assumes V = 5V, V
= 4.75V, V =
BAT
IN
OUT
3.7V, I = 400mA, and I
= 100mA resulting in slightly
BAT
OUT
more than 0.5W total dissipation.
The upper and lower temperature trip points can be inde-
pendentlyprogrammedbyusinganadditionalbiasresistor
as shown in Figure 9. The following formulas can be used
If the LTC4090 is being powered from HVIN, the power
dissipation can be estimated by calculating the regulator
powerlossfromanefficiencymeasurement,andsubtract-
ing the catch diode loss.
to compute the values of R
and R1:
NOM
r
COLD –rHOT
P =(1− η)• VHVOUT •(IBAT +IOUT
)
⎤
⎡
RNOM
=
•R25C
D
⎣
⎦
2.815
⎛
⎞
V
V
HVOUT
R1= 0.409•RNOM –rHOT •R25C
−V • 1−
• IBAT +IOUT)+0.3V •IBAT
(
)
D
⎜
⎟
⎝
⎠
HVIN
For example, to set the trip points to -5°C and 55°C with
a Vishay Curve 2 thermistor choose
where η is the efficiency of the high voltage regulator and
V is the forward voltage of the catch diode at I = I
D
BAT
3.532–0.3467
2.815–0.409
+ I . The first term corresponds to the power lost in
RNOM
=
•10k =13.2k
OUT
converting V
to V , the second term subtracts
HVOUT
HVIN
the catch diode loss, and the third term is the power dis-
sipated in the battery charger. For a typical application,
an example of this calculation would be:
the nearest 1% value is 13.3k.
R1 = 0.409 • 13.3k – 0.3467 • 10k = 1.97k
the nearest 1% value is 1.96k. The final solution is shown
in Figure 9 and results in an upper trip point of 55°C and
a lower trip point of -5°C.
P =(1−0.87)• 4V •(1A +0.6A)
[
]
D
4V
⎛
⎞
−0.4V • 1−
• 1A +0.6A +0.3V •1A = 0.7W
(
)
⎜
⎟
⎠
⎝
12V
Power Dissipation and High Temperature
Considerations
This example assumes 87% efficiency, V
= 12V, V
BAT
OUT
HVIN
= 1A, I
= 3.7V (V
is about 4V), I
= 600mA
HVOUT
BAT
The die temperature of the LTC4090/LTC4090-5 must be
lower than the maximum rating of 110°C. This is generally
not a concern unless the ambient temperature is above
85°C. The total power dissipated inside the LTC4090/
LTC4090-5dependonmanyfactors,includinginputvoltage
(INorHVIN),batteryvoltage,programmedchargecurrent,
programmed input current limit, and load current.
resulting in about 0.7W total dissipation. If the LTC4090-5
is being powered from HVIN, the power dissipation can
be estimated by calculating the regulator power loss from
an efficiency measurement, and subtracting the catch
diode loss.
4090fa
24
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
thermal resistance from die (i.e., junction) to ambient can
⎛
⎞
5V
VHVIN
P = 1– η • 5V • IBAT +IOUT – V • 1–
•
(
)
(
)
be reduced to θ = 40°C/W.
(
)
D
D
⎜
⎟
JA
⎝
⎠
I
BAT +IOUT + 5V – V
•I
Board Layout Considerations
(
) (
)
BAT
BAT
As discussed in the previous section, it is critical that
the exposed metal pad on the backside of the LTC4090/
LTC4090-5 package be soldered to the PC board ground.
Furthermore,properoperationandminimumEMIrequires
acarefulprintedcircuitboard(PCB)layout.Notethatlarge,
switched currents flow in the power switch (between the
HVIN and SW pins), the catch diode and the HVIN input
capacitor. These components, along with the inductor and
output capacitor, should be placed on the same side of
the circuit board, and their connections should be made
on that layer. Place a local, unbroken ground plane below
thesecomponents.Theloopformedbythesecomponents
should be as small as possible.
The difference between this equation and that for the
LTC4090 is the last term, which represents the power
dissipationinthebatterycharger. Foratypicalapplication,
an example of this calculation would be:
⎛
⎝
⎞
5V
12V
P = 1– 0.87 • 5V • 1A + 0.6A – 0.4V • 1–
•
(
)
(
)
(
)
D
⎜
⎟
⎠
1A + 0.6A + 5V – 3.7V •1A = 1.97W
(
) (
)
Like the LTC4090 example, this examples assumes 87%
efficiency, V = 12V, V = 3.7V, I = 1A and I
=
OUT
HVIN
BAT
BAT
600mA resulting in about 2W total power dissipation.
It is important to solder the exposed backside of the pack-
age to a ground plane. This ground should be tied to other
copper layers below with thermal vias; these layers will
spread the heat dissipated by the LTC4090/LTC4090-5.
Additional vias should be placed near the catch diode.
Adding more copper to the top and bottom layers and
tying this copper to the internal planes with vias can
reduce thermal resistance further. With these steps, the
Additionally, the SW and BOOST nodes should be kept
as small as possible. Figure 10 shows the recommended
component placement with trace and via locations.
High frequency currents, such as the high voltage input
current of the LTC4090/LTC4090-5, tend to find their way
along the ground plane on a mirror path directly beneath
theincidentpathonthetopoftheboard. Ifthereareslitsor
cuts in the ground plane due to other traces on that layer,
the current will be forced to go around the slits. If high
frequency currents are not allowed to flow back through
their natural least-area path, excessive voltage will build
up and radiated emissions will occur. See Figure 11.
C1 AND D1
GND PADS
SIDE-BY-SIDE
AND SEPERATED
WITH C3 GND PAD
MINIMIZE D1, L1,
C3, U1, SW PIN LOOP
U1 THERMAL PAD
SOLDERED TO PCB.
4090 F11
VIAS CONNECTED TO ALL
GND PLANES WITHOUT
MINIMIZE TRACE LENGTH
THERMAL RELIEF
Figure 11. Ground Currents Follow Their Incident Path at High
Speed.SlicesintheGroundPlaneCauseHighVoltageandIncreased
Emissions.
4090 F10
Figure 10. Suggested Board Layout
4090fa
25
LTC4090/LTC4090-5
APPLICATIONS INFORMATION
IN and HVIN Bypass Capacitor
Battery Charger Stability Considerations
Many types of capacitors can be used for input bypassing;
however,cautionmustbeexercisedwhenusingmultilayer
ceramic capacitors. Because of the self-resonant and high
Q characteristics of some types of ceramic capacitors,
high voltage transients can be generated under some
start-up conditions, such as from connecting the charger
input to a hot power source. For more information, refer
to Application Note 88.
Theconstant-voltagemodefeedbackloopisstablewithout
any compensation when a battery is connected with low
impedanceleads.Excessiveleadlength,however,mayadd
enough series inductance to require a bypass capacitor
of at least 1μF from BAT to GND. Furthermore, a 4.7μF
capacitor with a 0.2Ω to 1Ω series resistor to GND is
recommended at the BAT pin to keep ripple voltage low
when the battery is disconnected.
TYPICAL APPLICATIONS
L1
0.47μF
HIGH
6.8μH
16V
(6V TO 36V)
HVIN
BOOST SW
VOLTAGE
INPUT
C1
C3
1μF
D1
22μF
6.3V
1206
HVEN
IN
50V
1206
USB
680Ω
4.7μF
6.3V
HVOUT
LTC4090
HPWR
59k
1%
V
C
270pF
SUSP
HVPR
OUT
Q1
0.1μF
1k
TIMER
CLPROG
PROG
2.1k
1%
LOAD
4.7μF
6.3V
71.5k
1%
GATE
BAT
Q2
40.2k
1%
R
T
+
VNTC
NTC
Li-Ion
BATTERY
PG
10k
1%
SYNC
T
10k
680Ω
D: DIODES INC. B360A
L: SUMIDA CDR6D28MN-GR5
Q1, Q2: SILICONIX Si2333DS
CHRG
4090 F12
Figure 12. 800kHz Switching Frequency
L
L
0.47μF
10μH
0.47μF
2.2μH
BOOST
SW
HIGH (6V TO 36V)
HVIN
IN
BOOST
SW
4.7μF
HIGH (6V TO 16V)
VOLTAGE INPUT
TRANSIENT TO 60V*
HVIN
22μF
1μF
1μF
HVOUT
HVOUT
Q1
USB
HVPR
LTC4090
Q1
IN
V
USB
HVPR
4.7μF
LTC4090
1k
4.7μF
1k
V
C
OUT
BAT
LOAD
OUT
BAT
GND PROG
LOAD
C
4.7μF
R
T
4.7μF
R
T
TIMER
CLPROG
2.1k
GND PROG
TIMER
CLPROG
2.1k
35k
330pF
88.7k
+
30k
11.5k
71.5k
+
Li-Ion BATTERY
0.1μF
71.5k
330pF
0.1μF
Li-Ion BATTERY
L: SUMIDA CDRH8D28/HP-100
* USE SCHOTTKY DIODE RATED AT V > 45V
L: SUMIDA CDRH4D22/HP-2R2
R
4090 TAO4
4090 TAO3
Figure 13. 400kHz Switching Frequency
Figure 14. 2MHz Switching Frequency
4090fa
26
LTC4090/LTC4090-5
PACKAGE DESCRIPTION
DJC Package
22-Lead Plastic DFN (6mm × 3mm)
(Reference LTC DWG # 05-08-1714)
0.889
0.70 0.05
R = 0.10
0.889
3.60 0.05
1.65 0.05
2.20 0.05
(2 SIDES)
PACKAGE
OUTLINE
0.25 0.05
0.50 BSC
5.35 0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. APPLY SOLDER MASK TO AREAS THAT
ARE NOT SOLDERED
3. DRAWING IS NOT TO SCALE
R = 0.115
0.40 0.05
6.00 0.10
(2 SIDES)
TYP
0.889
12
22
R = 0.10
TYP
0.889
3.00 0.10
(2 SIDES)
1.65 0.10
(2 SIDES)
PIN 1
TOP MARK
(NOTE 6)
PIN #1 NOTCH
R0.30 TYP OR
0.25mm × 45°
CHAMFER
11
1
0.25 0.05
0.50 BSC
0.75 0.05
0.200 REF
5.35 0.10
(2 SIDES)
(DJC) DFN 0605
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WXXX)
IN JEDEC PACKAGE OUTLINE M0-229
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 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON TOP AND BOTTOM OF PACKAGE
4090fa
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.
27
LTC4090/LTC4090-5
RELATED PARTS
PART NUMBER
Battery Chargers
LTC1733
DESCRIPTION
COMMENTS
Monolithic Lithium-Ion Linear Battery
Charger
Standalone Charger with Programmable Timer, Up to 1.5A Charge Current
Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed
LTC1734
LTC4002
LTC4053
LTC4054
Lithium-Ion Linear Battery Charger in
ThinSOTTM
Switch Mode Lithium-Ion Battery
Charger
Standalone, 4.7V ≤ V ≤ 24V, 500kHz Frequency, 3 Hour Charge Termination
IN
USB Compatible Monolithic Li-Ion
Battery Charger
Standalone Charger with Programmable Timer, Up to 1.25A Charge Current
Standalone Linear Li-Ion Battery
Charger with Integrated Pass Transistor Charge Current
in ThinSOT
Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA
LTC4057
LTC4058
Lithium-Ion Linear Battery Charger
Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package
Standalone 950mA Lithium-Ion Charger C/10 Charge Termination, Battery Kelvin Sensing, 7% Charge Accuracy
in DFN
LTC4059
900mA Linear Lithium-Ion Battery
Charger
2mm 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output
LTC4065/LTC4065A Standalone Li-Ion Battery Chargers
in 2mm 2mm DFN
4.2V, 0.6% Float Voltage, Up to 750mA Charge Current, 2mm 2mm DFN,
“A” Version has ACPR Function.
LTC4095
Standalone USB Lithium-Ion/Polymer
950mA Charge Current, Timer Termination + C/10 Detection Output, 4.2V, 0.6% Accurate
⎯
⎯
⎯
⎯
Battery Charger in in 2mm 2mm DFN Float Voltage, 4 CHRG Pin Indicator States
Power Management
LTC3406/LTC3406A 600mA (I ), 1.5MHz, Synchronous
95% Efficiency, V = 2.5V to 5.5V, V
= 0.6V, I = 20μA, I < 1μA, ThinSOT Package
Q SD
OUT
IN
OUT
OUT
OUT
Step-Down DC/DC Converter
LTC3411
LTC3440
LTC3455
LT3493
1.25A (I ), 4MHz, Synchronous
95% Efficiency, V = 2.5V to 5.5V, V
= 0.8V, I = 60μA, I < 1μA, MS10 Package
Q SD
OUT
IN
Step-Down DC/DC Converter
600mA (I ), 2MHz, Synchronous
95% Efficiency, V = 2.5V to 5.5V, V
= 2.5V, I = 25μA, I < 1μA, MS Package
Q SD
OUT
IN
Buck-Boost DC/DC Converter
Dual DC/DC Converter with USB Power Seamless Transition Between Power Sources: USB, Wall Adapter and Battery; 95%
Manager and Li-Ion Battery Charger
Efficient DC/DC Conversion
1.2A, 750kHz Step-Down Switching
Regulator
88% Efficiency, V = 3.6V to 36V (40V Maximum), V
= 0.8V, I < 2μA, 2mm 3mm
OUT SD
IN
DFN Package
LTC4055
LTC4066
LTC4067
LTC4085
USB Power Controller and Battery
Charger
Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation,
200m Ideal Diode, 4mm 4mm QFN16 Package
USB Power Controller and Li-Ion Battery Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation, 50m
Charger with Low-Loss Ideal Diode
Ideal Diode, 4mm 4mm QFN24 Package
USB Power Controller with OVP, Ideal
Diode and Li-Ion Battery Charger
13V Overvoltage Transient Protection, Thermal Regulation, 200mΩ Ideal Diode with
<50mΩ Option, 4mm × 3mm DFN-14 Package
USB Power Manager with Ideal Diode
Controller and Li-Ion Charger
Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation,
200mΩ Ideal Diode with <50mΩ Option, 4mm 3mm DFN14 Package
LTC4089/
LTC4089-5
USB Power Manager with Ideal Diode
Controller and High Efficiency Li-Ion
Battery Charger
High Efficiency 1.2A Charger from 6V to 36V (40V Max) Input Charges Single-Cell Li-Ion
Batteries Directly from a USB Port, Thermal Regulation, 200mΩ Ideal Diode with <50mΩ
Option, Bat-Track Adaptive Output Control (LTC4089), Fixed 5V Output (LTC4089-5),
6mm × 3mm DFN-22 Package
LTC4411/LTC4412 Low Loss PowerPath Controller in
ThinSOT
Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diode
LTC4412HV
High Voltage Power Path Controllers in
ThinSOT
V = 3V to 36V, More Efficient than Diode ORing, Automatic Switching Between DC
IN
Sources, Simplified Load Sharing, ThinSOT Package.
ThinSOT is a trademark of Linear Technology Corporation.
4090fa
LT 0208 REV A • PRINTED IN USA
28 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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