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LTC4062 Standalone Linear Li-Ion Battery Charger with Micropower Comparator
FEATURES

DESCRIPTIO
Charge Current Programmable up to 1A Charges Single Cell Li-Ion Batteries Directly from USB Port Preset Float Voltage with 0.35% Accuracy Micropower Comparator for Battery Monitoring Thermal Regulation Maximizes Charge Rate Without Risk of Overheating* Programmable Charge Current Detection/ Termination Programmable Charge Termination Timer Smart Pulsing Error Feature SmartStartTM Prolongs Battery Life 20A Charger Quiescent Current in Shutdown Available in a Low Profile (0.75mm) 10-Lead (3mm x 3mm) DFN Package
The LTC(R)4062 is a full-featured, flexible, standalone linear charger for single-cell Lithium-Ion batteries. It is capable of operating within USB power specifications. Both programmable time and programmable current based termination schemes are available. Furthermore, the CHRG open-drain status pin can be programmed to indicate the battery charge state according to the needs of the application. A precise low power comparator is available even with no power applied as long as battery voltage is higher than 2.5V. Additional safety features designed to maximize battery lifetime and reliability include the SmartStart charging algorithm. No external sense resistor or external blocking diode is required for charging due to the internal MOSFET architecture. Internal thermal feedback regulates the charge current to maintain a constant die temperature during high power operation or high ambient temperature conditions. The charge current is programmed with an external resistor. With power applied, the LTC4062 can be put into shutdown mode to reduce the supply current to 20A and the battery drain current to less than 2A. Without power applied, the internal low power comparator can work sinking only 10A from the battery. Other features include smart recharge, USB C/5 current programming input and undervoltage lockout.
APPLICATIO S

Handheld Computers Portable MP3 Players Digital Cameras
, LTC and LT are registered trademarks of Linear Technology Corporation. SmartStart is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Protected by U.S. Patents, including 6522118.
TYPICAL APPLICATIO
Complete Charge Cycle (1100mAh Battery)
900 800 4.3 4.2 4.1
800mA Single Cell Li-Ion Battery Charger (C/10 Termination)
VIN 4.3V TO 8V CHARGE CURRENT (mA) VCC OUT 100k BAT > 3V BAT < 3V 800mA LTC4062 EN C/5 BAT TIMER PROG IDET IN+ GND
700 600 500 400 300 200 100 VCC = 5V TA = 25C 0 0.5 1.5 1.0 2.0 TIME (HOURS) 2.5 BATTERY VOLTAGE BATTERY CURRENT
1F
715k
+
347k
4062 TA01
619
SINGLE CELL Li-Ion BATTERY
0
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BATTERY VOLTAGE (V)
4.0 3.9 3.8 3.7 3.6 3.5 3.4 3.0
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LTC4062
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW BAT IN+ TIMER OUT CHRG 1 2 3 4 5 11 10 VCC 9 PROG 8 IDET 7 EN 6 C/5
Input Supply Voltage (VCC) ........................ -0.3V to 10V EN, OUT, CHRG, IN+, PROG, C/5, BAT ....... -0.3V to 10V TIMER, IDET ..................................... -0.3V to VCC +0.3V BAT Short-Circuit Duration ...........................Continuous VCC Pin Current ......................................................... 1A BAT Pin Current ......................................................... 1A Maximum Junction Temperature .......................... 125C Operating Temperature Range (Note 2) ... -40C to 85C Storage Temperature Range .................. -65C to 125C
ORDER PART NUMBER LTC4062EDD DD PART MARKING LBJT
DD PACKAGE 10-LEAD (3mm x 3mm) PLASTIC DFN TJMAX = 125C, JA = 40C/W (NOTE 3) EXPOSED PAD IS GROUND (PIN 11) MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL VCC ICC PARAMETER Input Supply Voltage Input Supply Current
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, unless otherwise noted.
CONDITIONS
MIN 4.3

TYP 240 130 20
MAX 8 500 300 50 4.215 4.225 107 840 2 2 1.03 1.03 0.25 0.26 0.25 14 100 3 3.9 230 75 5 1 1
UNITS V A A A V V mA mA A A V V V V V mA mA V mV V V mV mV M V mV V mV V mV
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Charge Mode (Note 4), RPROG = 10k Standby Mode, Charge Terminated Shutdown (EN = 5V, VCC < VBAT or VCC < VUV) 0 < TA < 85C
VFLOAT IBAT
VBAT Regulated Output Voltage BAT Pin Current RPROG = 10k, Constant Current Mode RPROG = 1.25k, Constant Current Mode Standby Mode, Charge Terminated Shutdown Mode RPROG = 10k, Constant Current Mode RPROG = 1.25k, Constant Current Mode IOUT = 5mA IOUT = 5mA, VCC = 0V, VBAT = 2.55V ICHRG = 5mA VBAT < VTRIKL, RPROG = 10k VBAT < VTRIKL, RPROG = 1.25k VBAT Rising Hysteresis From Low to High Hysteresis VCC from Low to High, VBAT = 4.3V VCC from High to Low, VBAT = 4.3V

4.185 4.175 93 760
4.2 4.2 100 800 1 1 1 1 0.10 0.16 0.1
VPROG VOUT VCHRG ITRIKL VTRIKL VUV VASD REN VEN VCT VUT
PROG Pin Voltage OUT Output Low Voltage CHRG Output Low Voltage Trickle Charge Current Trickle Charge Threshold Voltage VCC Undervoltage Lockout Voltage VCC - VBAT Lockout Threshold Voltage EN Pin Pull-Down Resistor EN Input Threshold Voltage Charge Termination Mode Threshold Voltage User Termination Mode Threshold Voltage
0.97 0.97
6 60 2.8 3.7 145 10 2 0.4 0.4 3.9
10 80 2.9 100 3.8 200 190 45 3.4 0.7 70 0.7 50 4.2 50
EN Rising, 4.3V < VCC < 8V Hysteresis VTIMER from High to Low Hysteresis VTIMER from Low to High Hysteresis
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LTC4062
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, unless otherwise noted.
SYMBOL IDETECT PARAMETER Charge Current Detection Threshold CONDITIONS RDET = 1k, 0 TA 85C RDET = 2k, 0 TA 85C RDET = 10k, 0 TA 85C RDET = 20k, 0 TA 85C VFLOAT - VRECHRG, 0 TA 85C IBAT from 0 to ICHG Current Termination Mode CTIMER = 0.1F
ELECTRICAL CHARACTERISTICS
MIN 90 45 8 3.8 65 0.8 3 2.55 2 0.4
TYP 100 50 10 5 100 100 1.5 7 3 3.4 0.7 70 105
MAX 110 55 12 6.2 135 2.5 14 3.45 5 1
UNITS mA mA mA mA mV s ms ms hr M V mV C m
VRECHRG tSS tTERM tRECHRG tTIMER RC/5 VC/5 TLIM RON Comparator VIN+ VBAT-MIN IBAT
Recharge Threshold Voltage Soft-Start Time Termination Comparator Filter Time Recharge Comparator Filter Time Charge Cycle Time C/5 Pin Pull-Down Resistor C/5 Input Threshold Voltage Junction Temperature in Constant Temperature Mode Power FET "ON" Resistance (Between VCC and BAT) IN+ Pin Threshold Voltage Minimum VBAT Supply Voltage for the Low Power Comparator Supply Current for the Low Power Comparator
C/5 Rising, 4.3V < VCC < 8V Hysteresis
VBAT = 3.85V, ICC = 175mA, RPROG = 2k
375
VIN+ Falling Hysteresis VCC = 0V, VBAT Falling Hysteresis VCC = 0V, VBAT = 2.5V
0.988 2.4 7
1 50 2.5 100 9
1.012 2.6 13
V mV V mV A
Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The LTC4062 is guaranteed to meet performance specifications from 0C to 70C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Failure to correctly solder the exposed pad of the package to the PC board will result in a thermal resistance much higher than 40C/W.
Note 4: Supply current includes PROG pin current and IDET pin current (approximately 100A each) but does not include any current delivered to the battery through the BAT pin (approximately 100mA). Note 5: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Overtemperature protection will become active at a junction temperature greater than the maximum operating temperature. Continuous operation above the specified maximum operating junction temperature may impair device reliability.
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LTC4062 TYPICAL PERFOR A CE CHARACTERISTICS
Battery Regulated Output (Float) Voltage vs Charge Current
4.26 4.24 4.22
VFLOAT (V) VFLOAT (V) VFLOAT (V)
VCC = 5V RPROG = 1k
4.20 4.18 4.16 4.14 4.12 4.10 0 200 800 600 CHARGE CURRENT (mA) 400 1000
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Charge Current vs PROG Pin Voltage
1200 1000 800
IBAT (mA)
VCC = 5V RPROG = 1k C/5 = 5V VTIMER = 5V
VPROG (V)
600 400 200 0
VPROG (V)
0
0.2
0.4
0.6 VPROG (V)
0.8
Trickle Charge Current vs Temperature
84 VCC = 5V VBAT = 2.5V RPROG = 1.25k 2.96 2.94 2.92
VTRICKLE (V)
82
ITRICKLE (mA) IBAT (mA)
80
78 2.86 76 -50 2.84 -50
-25
0 25 50 TEMPERATURE (C)
4
UW
1.0
4062 G04
TA = 25C unless otherwise noted Battery Regulated Output (Float) Voltage vs Supply Voltage
4.26 4.24 4.22 RPROG = 1k TA = 25C IBAT = 10mA
Battery Regulated Output (Float) Voltage vs Temperature
4.215 4.210 4.205 4.200 4.195 4.14 4.190 4.185 -50 4.12 VCC = 5V RPROG = 10k
4.20 4.18 4.16
-25
0 25 50 TEMPERATURE (C)
75
100
4062 G02
4.10 4.0 4.5
5.0 5.5
6.0 6.5 VCC (V)
7.0 7.5
8.0
4062 G03
PROG Pin Voltage vs Temperature (Constant-Current Mode)
1.006 1.004 1.002 VCC = 8V 1.000 VCC = 4.3V 0.998 0.996 0.994 -50 RPROG = 10k C/5 = VCC 1.006 1.004 1.002 1.000 0.998 0.996
PROG Pin Voltage vs VCC (Constant-Current Mode)
VCC = 5V VBAT = 4V RPROG = 10k C/5 = 5V
1.2
-25
0 25 50 TEMPERATURE (C)
75
100
4062 G05
0.994 4.0
4.5 5.0
5.5
6.0 VCC (V)
6.5
7.0
7.5
8.0
4062 G06
Trickle Charge Threshold Voltage vs Temperature
VCC = 5V RPROG = 1.25k 550
Charge Current vs Battery Voltage
C/5 = 5V 450
350
2.90 2.88
250 VCC = 5V RPROG = 2k
150 C/5 = 0V 50 3.2 3.0
75
100
4062 G07
-25
0 25 50 TEMPERATURE (C)
75
100
4062 G08
3.6 3.4 VBAT (V)
3.8
4.0
4062 G09
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LTC4062 TYPICAL PERFOR A CE CHARACTERISTICS
Internal Charge Timer vs Temperature
195 190
tTIMER (MINUTES)
VCC = 4.3V VCC = 8V
185
IBAT (mA)
180 175 170 165 -50 CTIMER = 0.1F -25 0 25 50 TEMPERATURE (C) 75 100
4062 G10
RPROG = 2k
IBAT (mA)
Recharge Threshold Voltage vs Temperature
4.16 4.14 4.12 VCC = 8V VCC = 4.3V 4.10 4.08 4.06 4.04 -50 300 500
VRECHARGE (V)
RDS(ON) (m)
VUV (V)
-25
0 25 50 TEMPERATURE (C)
Charge Current vs Battery Voltage
900 800 700 600
IBAT (mA)
VCC = 5V C/5 = 5V RPROG = 1.25k JA = 40C/W
REN (M)
500 400 300 200
3.5 3.0 2.5
RC/5 (M)
100 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 VBAT (V)
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UW
75
TA = 25C unless otherwise noted
Charge Current vs Ambient Temperature with Thermal Regulation
1000 ONSET OF THERMAL REGULATION 800 RPROG = 1.25k 102 104
Charge Current vs Supply Voltage
VCC = 5V VBAT = 4V C/5 = 5V RPROG = 10k
600
100
400
200
98 VCC = 5V VBAT = 4V JA = 40C/W -25 50 25 0 75 TEMPERATURE (C) 100 125
0 -50
96
4.0
4.5 5.0
5.5
6.0 VCC (V)
6.5
7.0
7.5
8.0
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Power FET "ON" Resistance vs Temperature
VCC = 4V IBAT = 200mA 450 3.850 400 3.825 3.800 3.775 3.750 3.725 100 250 -50 -25 0 25 50 TEMPERATURE (C) 75 100
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Undervoltage Lockout Voltage vs Temperature
3.900 3.875
350
3.700 - 50
-25
50 25 0 TEMPERATURE (C)
75
100
4062 G17
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EN Pin Pulldown Resistance vs Temperature
5.0 4.5 4.0 5.0 4.5 4.0 3.5 3.0 2.5
C/5 Pin Pulldown Resistance vs Temperature
2.0 -50
-25
50 25 0 TEMPERATURE (C)
75
100
4062 G19
2.0 -50
-25
50 25 0 TEMPERATURE (C)
75
100
4062 G20
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LTC4062 TYPICAL PERFOR A CE CHARACTERISTICS
EN Pin Threshold Voltage (On-to-Off) vs Temperature
900 VCC = 5V 850 800 VC/5 (mV) VEN (mV) 750 700 650 600 -50 850 800 ICC (A) 750 700 650 600 -50 900
-25
0 25 50 TEMPERATURE (C)
OUT Pin I-V Curve
160 140 120 IOUT (mA) 100 80 60 40 20 0 0 1 2 VOUT (V)
4062 G24
VCC = 5V VBAT = 4V
VCHRG (V)
OUT Pin Output Low Voltage vs Temperature
0.6 0.5 0.4 ICHRG (mA) VOUT (V) 0.3 0.2 0.1 0 -50 VCC = 5V IOUT = 5mA IN+ 1.05V 160 140 120 100 80 60 40 20 -25 50 25 0 TEMPERATURE (C) 75 100
4062 G26
6
UW
75
4062 G21
TA = 25C unless otherwise noted Shutdown Supply Current vs Temperature and VCC
70 EN = VCC 60 50 40 30 20 10 -50 VCC = 5V VCC = 4.3V
C/5 Pin Threshold Voltage (High-to-Low) vs Temperature
VCC = 5V
VCC = 8V
100
-25
50 25 0 TEMPERATURE (C)
75
100
4062 G22
-25
0 25 50 TEMPERATURE (C)
75
100
4062 G23
CHRG Pin Output Low Voltage vs Temperature
0.6 TA = -40C TA = 25C TA = 90C 0.4 0.3 0.2 0.1 0 -50 0.5 VCC = 5V ICHRG = 5mA
3
4
-25
50 25 0 TEMPERATURE (C)
75
100
4062 G25
CHRG Pin I-V Curve
VCC = 5V VBAT = 4V TA = -40C TA = 25C TA = 90C
0
0
1
2 VCHRG (V)
3
4
4062 G27
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LTC4062
PI FU CTIO S
BAT (Pin 1): Charge Current Output. This pin provides charge current to the battery and regulates the final float voltage to 4.2V. IN+ (Pin 2): Positive Input of the Micropower Comparator. The negative input is tied internally to a precise bandgap voltage reference of 1V. There is approximately 50mV of hysteresis associated with the input comparator threshold (rising edge). TIMER (Pin 3): Timer Program and Termination Select Pin. This pin selects which method is used to terminate the charge cycle. Connecting a capacitor, CTIMER, to ground selects charge time termination. The charge time is set by the following formula: CTIMER or 0.1F TIME (HOURS) CTIMER = 0.1F * 3 (HOURS) TIME (HOURS) = 3 (HOURS) * Connecting the TIMER pin to ground selects charge current termination, while connecting the pin to VCC selects user termination. See Applications Information for more information on current and user termination. OUT (Pin 4): Low Power Comparator Open-Drain Output. This comparator output pin has two states; pull-down and high impedance. This output can be used as a logic interface or as an LED driver. In the pull-down state, an NMOS transistor capable of sinking 10mA pulls down on the OUT pin. The state of this pin is dependent on the value of IN+. When IN+ is greater than 1V the output pin is in pulldown state, if IN+ is less than 1V the output pin is in high impedance state. See Applications Information. CHRG (Pin 5): Open-Drain Charge Status Output. The charge status indicator pin has three states: pull-down, pulse at 6Hz and high impedance. This output can be used as a logic interface or as a LED driver. In the pull-down state, an NMOS transistor capable of sinking 10mA pulls down on the CHRG pin. The state of this pin depends on the value of IDETECT as well as the termination method being used. See Applications Information. C/5 (Pin 6): C/5 Enable Input. Used to control the amount of current drawn by the charger when powered from a USB port. A logic high on the C/5 pin sets the current limit to 100% of the current programmed by the PROG pin. A logic low on the C/5 pin sets the current limit to 20% of the current programmed by the PROG pin. An internal 3M pull-down resistor defaults the C/5 pin to its low current state. EN (Pin 7): Charger Enable Input. A logic high on the EN pin places the charger into shutdown mode, where the input quiescent current is less than 50A. A logic low on this pin enables charging. An internal 3M pull-down resistor to ground defaults the charger to its enabled state. IDET (Pin 8): Current Detection Threshold Program Pin. The current detection threshold, IDETECT, is set by connecting a resistor, RDETECT, to ground. IDETECT is set by the following formula:
IDETECT = RDET = RPROG 100V * ICHG = or 10RDET RDET 100V
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IDETECT
The CHRG pin becomes high impedance when the charge current drops below IDETECT. IDETECT can be set to 1/10th the programmed charge current by connecting IDET directly to PROG. If the IDET pin is not connected, the CHRG output remains in its pull-down state until the charge time elapses and terminates the charge cycle. See Applications Information. This pin is clamped to approximately 2.4V. Driving this pin to voltages beyond the clamp voltage should be avoided. PROG (Pin 9): Charge Current Program and Charge Current Monitor. The charge current is set by connecting a resistor, RPROG, to ground. When charging in constant current mode, this pin servos to 1V. The voltage on this pin can be used to measure the charge current using the following formula:
IBAT = VPROG * 1000 RPROG
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LTC4062
PI FU CTIO S
VCC (Pin 10): Positive Input Supply Voltage. Provides power to the battery charger. This pin should be bypassed with a 1F capacitor. GND (Exposed Pad) (Pin 11): Ground. This pin is the back of the exposed metal pad package and must be soldered to the PCB copper for minimal thermal resistance.
BLOCK DIAGRA
4.1V
TO BAT IN+
MA 4
C4
5
CHRG 1V STOP 0.2V RECHRG C/5 3M LOGIC EN 3M 0.1V C/5 LOGIC 1.2V
6
7
EN
TERM
SEL
+
COUNTER 0.1V OSCILLATOR
TIMER 3 CTIMER 8
8
-
+
OUT
1V
C2
C3
-
+
TO BAT
-
2.9V TA
IDET 9 RDET
PROG
RPROG
+
-
2
W
+
-
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10 VCC
C1 1x 1x 1000x BAT
1
CA
VA
-
+
-
+
C/5
+ -
TDIE
105C SHDN GND 11
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LTC4062 OPERATIO
The LTC4062 is designed to charge single cell lithium-ion batteries. Using the constant current/constant voltage algorithm, the charger can deliver up to 1A of charge current with a final float voltage accuracy of 0.35%. The LTC4062 includes an internal P-channel power MOSFET and thermal regulation circuitry. No blocking diode or external sense resistor is required; thus, the basic charger circuit requires only two external components. Normal Operation The charge cycle begins when the voltage at the VCC pin rises above the UVLO level and a discharged battery is connected to BAT. If the BAT pin voltage is below 2.9V, the charger enters trickle charge mode. In this mode, the LTC4062 supplies 1/10th of the programmed charge current in order to bring the battery voltage up to a safe level for full current charging. Once the BAT pin voltage rises above 2.9V, the charger enters constant current mode, where the programmed charge current is supplied to the battery. When the BAT pin approaches the final float voltage (4.2V), the LTC4062 enters constant voltage mode and the charge current decreases as the battery becomes fully charged. The LTC4062 offers several methods with which to terminate a charge cycle. Connecting an external capacitor to the TIMER pin activates an internal timer that stops the charge cycle after the programmed time period has elapsed. Grounding the TIMER pin and connecting a resistor to the IDET pin causes the charge cycle to terminate once the charge current falls below a set threshold when the charger is in constant voltage mode. Connecting the TIMER pin to VCC disables internal termination, allowing external charge user termination through the EN input. See Applications Information for more information on charge termination methods.
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Programming Charge Current The charge current is programmed using a single resistor from the PROG pin to ground. When the charger is in the constant current mode, the voltage on the PROG pin is 1V. The battery charge current is 1000 times the current out of the PROG pin. The program resistor and the charge current are calculated by the following equations:
RPROG =
1000 V 1000 V , ICHG = ICHG RPROG
The charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage and applying the following equation:
IBAT = VPROG * 1000 RPROG
SmartStart When the LTC4062 is initially powered on or brought out of shutdown mode, the charger checks the battery voltage. If the BAT pin is below the recharge threshold of 4.1V (which corresponds to approximately 80-90% battery capacity), the LTC4062 enters charge mode and begins a full charge cycle. If the BAT pin is above 4.1V, the LTC4062 enters standby mode and does not begin charging. This feature reduces the number of unnecessary charge cycles, prolonging battery life. Automatic Recharge When the charger is in standby mode, the LTC4062 continuously monitors the voltage on the BAT pin. When the BAT pin voltage drops below 4.1V, the charge cycle is automatically restarted and the internal timer is reset to 50% of the programmed charge time (if time termination
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LTC4062 OPERATIO
is being used). This feature eliminates the need for periodic charge cycle initiations and ensures that the battery is always fully charged. Automatic recharge is disabled in user termination mode. Thermal Regulation An internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 105C. This feature protects the LTC4062 from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damaging the LTC4062. The charge current can be set according to typical (not worst-case) ambient temperatures with the assurance that the charger will automatically reduce the current in worst-case conditions. Undervoltage Lockout (UVLO) An internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until VCC rises above the undervoltage lockout threshold (3.8V). The UVLO circuit has a built-in hysteresis of 200mV. Furthermore, to protect against reverse current in the power MOSFET, the UVLO circuit keeps the charger in shutdown mode if VCC falls to less than 45mV above the battery voltage. Hysteresis of 145mV prevents the charger from cycling in and out of shutdown. Manual Shutdown At any point in the charge cycle, the charger can be put into shutdown mode by pulling the EN pin high. This reduces the supply current to less than 50A and the battery drain current of the charger to less than 2A. A new charge cycle can be initiated by floating the EN pin or pulling it low.
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If shutdown is not required, leaving the pin disconnected continuously enables the circuit. Trickle-Charge and Defective Battery Detection When the BAT pin voltage is below the 2.9V trickle charge threshold (VTRIKL), the charger reduces the charge current to 10% of the programmed value. If the battery remains in trickle charge for more than 25% of the total programmed charge time, the charger stops charging and enters a FAULT state, indicating that the battery is defective1. The LTC4062 indicates the FAULT state by driving the CHRG open-drain output with a square wave. The duty cycle of this oscillation is 50% and the frequency is set by CTIMER:
fCHRG = 0.1F * 6Hz CTIMER
A LED driven by the CHRG output exhibits a pulsing pattern, indicating to the user that the battery needs replacing. To exit the FAULT state, the charger must be restarted either by toggling the EN input or removing and reapplying power to VCC. Charge Status Output (CHRG) The charge status indicator pin has three states: pulldown, pulse at 6Hz and high impedance. In the pull-down state, an NMOS transistor pulls down on the CHRG pin capable of sinking up to 10mA. A pull-down state indicates that the LTC4062 is charging a battery and the charge current is greater than IDETECT (which is set by the external component RDET). A high impedance state indicates that the charge current has dropped below IDETECT. In the case where the IDET pin is left unconnected (RDET = , IDETECT = 0), a high impedance state on CHRG indicates that the LTC4062 is not charging.
1The Defective Battery Detection Feature is only available when time termination is being used.
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LTC4062 OPERATIO
Smart Pulsing Error Feature LTC4062 has a pulsing state at the CHRG pull-down pin of 6Hz (50% duty cycle) due to defective battery detection (see Trickle-Charge and Defective Battery Detection section). Low Power Comparator (IN+; OUT) The low power, low offset comparator is designed with an internal 1V reference connected to the negative input. This reference is generated by a precise bandgap circuit. The
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comparator output drives a pull down NMOS transistor able to sink up to 10mA. Voltages lower than 1V at the IN+ pin set the OUT pin to a high impedance state. Voltages higher than 1V plus a built-in 50mV hysteresis at the IN+ pin set the OUT pin to a low impedance state. The comparator is operational even when VCC is not applied provided the BAT pin voltage is greater than 2.5V. When the voltage at the BAT pin drops below 2.5V, the comparator shuts down and the current at the BAT pin is reduced to <1A.
4 2 IN+ OUT
+
1V
-
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LTC4062
Figure 1. Low Power Comparator Circuit
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LTC4062
APPLICATIO S I FOR ATIO
Programming Charge Termination
The LTC4062 can terminate a charge cycle using one of several methods, allowing the designer considerable flexibility in choosing an ideal charge termination algorithm. Table 1 shows a brief description of the different termination methods and their behaviors. Charge Time Termination Connecting a capacitor (CTIMER) to the TIMER pin enables the timer and selects charge time termination. The total charge time is set by:
TIME (HOURS) =
CTIMER * 3 HOURS 0.1F
When the programmed time has elapsed, the charge cycle terminates and the charger enters standby mode. Subsequent recharge cycles terminate when 50% of the programmed time has elapsed. The IDET pin determines the behavior of the CHRG output. Connecting a resistor (RDET) from the IDET pin to ground sets the charge current detection threshold, IDETECT:
Table 1
METHOD Charge Time Termination Mode TIMER 0.1F to GND IDET RDET to GND
CHARGER DESCRIPTION Charges for 3 Hours. After 3 Hours, the Charger Stops Charging and Enters Standby Mode. Recharge Cycles Last for 1.5 Hours. Charges for 3 Hours. After 3 Hours, the Charger Stops Charging and Enters Standby Mode. Recharge Cycles Last for 1.5 Hours. Charges Until Charge Current Drops Below IDET, Then Enters Standby Mode. Charges Indefinitely.
0.1F to GND Charge Current Termination GND
NC
RDET to GND NC
GND
User Selectable Charge Termination
VCC
RDET to GND
Charges Indefinitely. SmartStart Is Disabled.
VCC
NC
Charges Indefinitely. SmartStart Is Disabled.
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IDETECT = RDET = RPROG 100V * ICHG = or 10RDET RDET 100V IDETECT
When the charge current (I BAT ) is greater than IDETECT, the CHRG output is in its pull-down state. When the charger enters constant voltage mode operation and the charge current falls below IDETECT, the CHRG output becomes high impedance, indicating that the battery is almost fully charged. The CHRG output will also become high impedance once the charge time elapses. If the IDET pin is not connected, the CHRG output remains in its pulldown state until the charge time elapses and terminates the charge cycle. Figure 2 shows a charger circuit using charge time termination that is programmed to charge at 500mA. Once the charge current drops below 100mA in constant voltage mode (as set by RDET), the CHRG output turns off the LED. This indicates to the user that the battery is almost fully charged and ready to use. The LTC4062 continues to
CHRG OUTPUT DESCRIPTION Pull-Down State While IBAT > IDET. High Impedance State While IBAT < IDETECT or When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. Pull-Down State When Charging. High Impedance State When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. Pull-Down State When Charging. High Impedance State When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. Pull-Down State When Charging. High Impedance State When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. Pull-Down State While IBAT > IDETECT. High Impedance State While IBAT < IDETECT or When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. Pull-Down State When Charging. High Impedance State When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging.
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LTC4062
APPLICATIO S I FOR ATIO
charge the battery until the internal timer reaches 3 hours (as set by CTIMER). During recharge cycles, the LTC4062 charges the battery until the internal timer reaches 1.5 hours. Figure 3 describes the operation of the LTC4062 charger when charge time termination is used.
500mA VIN VCC CHRG PROG RPROG 2k IDET RDET 1k GND TIMER CTIMER 0.1F
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BAT
C/5 LTC4062
+
Figure 2. Time Termination Mode. The Charge Cycle Ends After 3 Hours
POWER ON
BAT < 2.9V BAT > 2.9V CHARGE MODE FULL CURRENT CHRG STATE: 2.9V < BAT < 4.1V PULL-DOWN IF IBAT > IDETECT Hi-Z IF IBAT < IDETECT CHARGE TIME ELAPSES STANDBY MODE BAT > 4.1V NO CHARGE CURRENT EN = 5V OR UVLO CONDITION SHUTDOWN MODE ICC DROPS TO 20A CHRG STATE: Hi-Z
1/2 CHARGE TIME ELAPSES
Figure 3. State Diagram of a Charge Cycle Using Charge Time Termination
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Charge Current Termination Connecting the TIMER pin to ground selects charge current termination. With this method, the timer is disabled and a resistor (RDET) must be connected from the IDET pin to ground. IDETECT is programmed using the same equation stated in the previous section. The charge cycle terminates when the charge current falls below IDETECT. This condition is detected using an internal filtered comparator to monitor the IDET pin. When the IDET pin falls below 100mV for longer than tTERM (typically 1.5ms), charging is terminated. When charging, transient loads on the BAT pin can cause the IDET pin to fall below 100mV for short periods of time before the DC current has dropped below the IDETECT
DEFECTIVE BATTERY FAULT MODE NO CHARGE CURRENT CHRG STATE: PULSING 1/4 CHARGE TIME ELAPSES TRICKLE CHARGE MODE 1/10TH FULL CURRENT EN = 0V OR UVLO CONDITION STOPS CHRG STATE: PULL-DOWN CHRG STATE: Hi-Z BAT < 4.1V RECHARGE MODE FULL CURRENT CHRG STATE: PULL-DOWN IF IBAT > IDETECT Hi-Z IF IBAT < IDETECT
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LTC4062
APPLICATIO S I FOR ATIO
threshold. The 1.5ms filter time (tTERM) on the internal comparator ensures that transient loads of this nature do not result in premature charge cycle termination. Once the average charge current drops below IDETECT, the charger terminates the charge cycle. The CHRG output is in a pull-down state while charging and in a high impedance state once charging has stopped. Figure 4 describes the operation of the LTC4062 charger when charge current termination is used.
POWER ON TRICKLE CHARGE MODE 1/10TH FULL CURRENT EN = 0V OR UVLO CONDITION STOPS
BAT < 2.9V BAT > 2.9V CHARGE MODE 2.9V < BAT < 4.1V FULL CURRENT
BAT < 4.1V
BAT > 4.1V
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Figure 4. State Diagram of a Charge Cycle Using Charge Current Termination
POWER ON TRICKLE CHARGE MODE 1/10TH FULL CURRENT EN = 0V OR UVLO CONDITION STOPS SHUTDOWN MODE CHRG STATE: PULL-DOWN BAT < 2.9V BAT > 2.9V CHARGE MODE FULL CURRENT CHRG STATE: 2.9V < BAT PULL-DOWN IF IBAT > IDETECT Hi-Z IF IBAT < IDETECT EN = 5V OR UVLO CONDITION CHRG STATE: Hi-Z ICC DROPS TO 20A
Figure 5. State Diagram of a Charge Cycle Using User-Selectable Termination
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When the charger is set for charge current termination and the battery is removed from the charger, a sawtooth waveform of several hundred mV will appear at the charger output. This is caused by the repeated cycling between termination and recharge events. This cycling results in pulsing at the CHRG output. If an LED is connected to this pin, it will exhibit a pulsing pattern, indicating to the user that a battery is not present. The frequency of the sawtooth is dependent on the amount of output capacitance.
CHRG STATE: PULL-DOWN SHUTDOWN MODE ICC DROPS TO 20A CHRG STATE: Hi-Z CHRG STATE: PULL-DOWN IBAT < IDETECT IN VOLTAGE MODE STANDBY MODE NO CHARGE CURRENT EN = 5V OR UVLO CONDITION CHRG STATE: Hi-Z
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LTC4062
APPLICATIO S I FOR ATIO
User-Selectable Charge Termination Connecting the TIMER pin to VCC selects user-selectable charge termination, in which all of the internal termination features are disabled. The charge cycle continues indefinitely until the charger is shut down through the EN pin. The IDET pin programs the behavior of the CHRG output in the same manner as when using charge time termination. If the IDET pin is not connected, the CHRG output remains in its pull-down state until the charger is shut down. With user-selectable charge termination, the SmartStart feature is disabled; when the charger is powered on or enabled, the LTC4062 automatically begins charging, regardless of the battery voltage. Figure 5 describes charger operation when user-selectable charge termination is used. Programming C/10 Current Detection/Termination In most cases, an external resistor, RDET, is needed to set the charge current detection threshold, IDETECT. However, when setting IDETECT to be 1/10th of ICHG, the IDET pin can be connected directly to the PROG pin. This reduces the component count, as shown in Figure 6.
500mA VIN VCC PROG RPROG 2k IDET RDET 2k TIMER GND BAT C/5 LTC4062
+
500mA VIN VCC BAT C/5 LTC4062 PROG RPROG 1k IDET TIMER GND
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Figure 6. Two Circuits That Charge at 500mA Full-Scale Current and Terminate at 50mA
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When PROG and IDET are connected in this way, the fullscale charge current, ICHG, is programmed with a different equation:
RPROG = 500V 500V , ICHG = ICHG RPROG
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Stability Considerations The battery charger constant voltage mode feedback loop is stable without any compensation provided a battery is connected. However, a 1F capacitor with a 1 series resistor to GND is recommended at the BAT pin to reduce noise when no battery is present. When the charger is in constant current mode, the PROG pin is in the feedback loop, not the battery. The constant current stability is affected by the impedance at the PROG pin. With no additional capacitance on the PROG pin, the charger is stable with program resistor values as high as 10k; however, additional capacitance on this node reduces the maximum allowed program resistor value. Power Dissipation When designing the battery charger circuit, it is not necessary to design for worst-case power dissipation scenarios because the LTC4062 automatically reduces the charge current during high power conditions. The conditions that cause the LTC4062 to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the IC. Most of the power dissipation is generated from the internal charger MOSFET. Thus, the power dissipation is calculated to be approximately: PD = (VCC - VBAT) * IBAT PD is the power dissipated, VCC is the input supply voltage, VBAT is the battery voltage and IBAT is the charge current. The approximate ambient temperature at which the thermal feedback begins to protect the IC is: TA = 105C - PD * JA TA = 105C - (VCC - VBAT) * IBAT * JA
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LTC4062
APPLICATIO S I FOR ATIO
Example: An LTC4062 operating from a 5V wall adapter is programmed to supply 800mA full-scale current to a discharged Li-Ion battery with a voltage of 3.3V. Assuming JA is 40C/W (see Thermal Considerations), the ambient temperature at which the LTC4062 will begin to reduce the charge current is approximately: TA = 105C - (5V - 3.3V) * (800mA) * 40C/W TA = 105C - 1.36W * 40C/W = 105C - 54.4C TA = 50.6C The LTC4062 can be used above 50.6C ambient, but the charge current will be reduced from 800mA. The approximate current at a given ambient temperature can be approximated by:
IBAT =
105C - TA (VCC - VBAT )* JA
Using the previous example with an ambient temperature of 60C, the charge current will be reduced to approximately:
IBAT = IBAT
105C - 60C 45C = (5V - 3.3V)* 40C /W 68C /A = 662mA
It is important to remember that LTC4062 applications do not need to be designed for worst-case thermal conditions, since the IC will automatically reduce power dissipation if the junction temperature reaches approximately 105C. Thermal Considerations In order to deliver maximum charge current under all conditions, it is critical that the exposed metal pad on the backside of the LTC4062 package is properly soldered to the PC board ground. Correctly soldered to a 2500mm2 double sided 1oz copper board, the LTC4062 has a thermal resistance of approximately 40C/W. Failure to make thermal contact between the exposed pad on the backside of the package and the copper board will result in thermal resistances far greater than 40C/W. As an example, a
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correctly soldered LTC4062 can deliver over 800mA to a battery from a 5V supply at room temperature. Without a good backside thermal connection, this number could drop to less than 500mA. VCC Bypass Capacitor Many types of capacitors can be used for input bypassing; however, caution must be exercised when using multilayer 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 connecting the charger input to a live power source. Adding a 1.5 resistor in series with an X5R ceramic capacitor will minimize start-up voltage transients. For more information, see Application Note 88. Charge Current Soft-Start and Soft-Stop The LTC4062 includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. When a charge cycle is initiated, the charge current ramps from zero to the full-scale current over a period of approximately 100s. Likewise, internal circuitry slowly ramps the charge current from full-scale to zero when the charger is shut off or self terminates. This has the effect of minimizing the transient current load on the power supply during start-up and charge termination. Reverse Polarity Input Voltage Protection In some applications, protection from reverse polarity on VCC is desired. If the supply voltage is high enough, a series blocking diode can be used. In other cases, where the diode voltage drop must be kept low, a P-channel MOSFET can be used (as shown in Figure 7).
DRAIN-BULK DIODE OF FET LTC4062 VIN VCC
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Figure 7. Low Loss Input Reverse Polarity Protection
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APPLICATIO S I FOR ATIO
USB and Wall Adapter Power
The LTC4062 allows charging from both a wall adapter and a USB port. Figure 8 shows an example of how to combine wall adapter and USB power inputs. A P-channel MOSFET, MP1, is used to prevent back conducting into the USB port when a wall adapter is present and a Schottky diode, D1, is used to prevent USB power loss through the 1k pull-down resistor.
5V WALL ADAPTER ICHG = 800mA USB POWER ICHG = 500mA
MP1
Figure 8. Combining Wall Adapter and USB Power
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Typically a wall adapter can supply more current than the 500mA limited USB port. Therefore, an N-channel MOSFET, MN1, and an extra 3.3k program resistor are used to increase the charge current to 800mA when the wall adapter is present.
D1 VCC BAT SYSTEM LOAD LTC4062 IDET C/5 PROG 3.3k 1k MN1 2k 1.24k
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Li-Ion BATTERY
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LTC4062
TYPICAL APPLICATIO S
Full-Featured Li-Ion Charger with Low-Battery Comparator (Using Time Termination)
VIN 4.3V TO 8V VCC LTC4062 EN C/5 BAT TIMER PROG IDET IN+ GND 100k 800mA OUT
5V WALL ADAPTER 400mA USB POWER 1F C/5 VCC LTC4062 PROG BAT
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BAT > 3V BAT < 3V
1F
715k
+
347k
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0.1F
1.24k
619
SINGLE CELL Li-Ion BATTERY
USB/Wall Adapter Power Li-Ion Charger (Using Charge Current Termination)
+
Li-Ion CELL
TIMER IDET GND
2k
2.5k
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PACKAGE DESCRIPTIO U
DD Package 10-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1669)
0.675 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.38 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 6 0.38 0.10 10 3.00 0.10 (4 SIDES) PIN 1 TOP MARK (SEE NOTE 6) 5 0.200 REF 0.75 0.05 2.38 0.10 (2 SIDES) BOTTOM VIEW--EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 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 THE TOP AND BOTTOM OF PACKAGE 1 0.25 0.05 0.50 BSC 1.65 0.10 (2 SIDES)
(DD10) DFN 1103
3.50 0.05 1.65 0.05 2.15 0.05 (2 SIDES)
0.00 - 0.05
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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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LTC4062
RELATED PARTS
PART NUMBER Battery Chargers LTC1734 LTC1734L LTC4002 LTC4050 LTC4052 LTC4053 LTC4054 LTC4057 LTC4058 LTC4059 LTC4061/ LTC4061-4.4 LTC4063 LTC4411/LTC4412 Power Management LTC3405/LTC3405A LTC3406/LTC3406A LTC3411 LTC3440 LTC4413 300mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter Dual Ideal Diode in DFN 95% Efficiency, VIN: 2.7V to 6V, VOUT = 0.8V, IQ = 20A, ISD < 1A, ThinSOT Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.6V, IQ = 20A, ISD < 1A, ThinSOT Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.8V, IQ = 60A, ISD < 1A, MS Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 2.5V, IQ = 25A, ISD < 1A, MS Package 2-Channel Ideal Diode ORing, Low Forward ON Resistance, Low Regulated Forward Voltage, 2.5V VIN 5.5V Lithium-Ion Linear Battery Charger in ThinSOTTM Lithium-Ion Linear Battery Charger in ThinSOT Switch Mode Lithium-Ion Battery Charger Lithium-Ion Linear Battery Charger Controller Monolithic Lithium-Ion Battery Pulse Charger USB Compatible Monolithic Li-Ion Battery Charger Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOT Lithium-Ion Linear Battery Charger Standalone 950mA Lithium-Ion Charger in DFN 900mA Linear Lithium-Ion Battery Charger Standalone Li-Ion Chargers with Thermistor Li-Ion Charger with Linear Regulator Low Loss PowerPath Controller in ThinSOT
TM
DESCRIPTION
COMMENTS Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed Low Current Version of LTC1734, 50mA ICHRG 180mA Standalone, 4.7V VIN 24V, 500kHz Frequency, 3 Hour Charge Termination Features Preset Voltages, C/10Charger Detection and Programmable Timer, Input Power Good Indication, Thermistor Interface No Blocking Diode or External Power FET Required, 1.5A Charge Current Standalone Charger with Programmable Timer, Up to 1.25A Charge Current Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA Charge Current Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package C/10 Charge Termination, Battery Kelvin Sensing, 7% Charge Accuracy 2mm x 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output 4.2V/4.4V, 0.35%/0.4% Float Voltage, Up to 1A Charge Current Interface Up to 1A Charge Current, 100mA, 125mV LDO, 3mm x 3mm DFN Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT/TP 0205 1K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2005

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