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LTC4076 Dual Input Standalone Li-Ion Battery Charger
Charges Single-Cell Li-Ion Batteries from Wall Adapter and USB Inputs Automatic Input Power Detection and Selection Charge Current Programmable up to 950mA from Wall Adapter Input C/X Charge Current Termination Thermal Regulation Maximizes Charge Rate Without Risk of Overheating* Preset Charge Voltage with 0.6% Accuracy 18A USB Suspend Current in Shutdown Power Present Status Output Charge Status Output Automatic Recharge Available in a Thermally Enhanced, Low Profile (0.75mm) 10-Lead (3mm x 3mm) DFN Package The LTC(R)4076 is a standalone linear charger that is capable of charging a single-cell Li-Ion battery from both wall adapter and USB inputs. The charger can detect power at the inputs and automatically select the appropriate power source for charging. No external sense resistor or blocking diode is required for charging due to the internal MOSFET architecture. Internal thermal feedback regulates the battery charge current to maintain a constant die temperature during high power operation or high ambient temperature conditions. The float voltage is fixed at 4.2V and the charge current is programmed with an external resistor. The LTC4076 terminates the charge cycle when the charge current drops below the user programmed termination threshold after the final float voltage is reached. The LTC4076 can be put into shutdown mode reducing the DCIN supply current to 20A, the USBIN supply current to 10A, and the battery drain current to less than 2A even with power applied to both inputs. Other features include automatic recharge, undervoltage lockout, charge status output, power present status output to indicate the presence of wall adapter or USB power and high power/low power mode (C/5) for USB compatible applications.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Protected by U.S. patents, including 6522118

APPLICATIO S

Cellular Telephones Handheld Computers Portable MP3 Players Digital Cameras
Dual Input Battery Charger for Single-Cell Li-Ion
LTC4076 DCIN 1F USBIN IUSB ITERM GND 1k 1%
4076 TA01
WALL ADAPTER USB PORT 1F
800mA (WALL) 500mA (USB) BAT
BATTERY CHARGE VOLTAGE (V) CURRENT (mA)
HPWR
DCIN VOLTAGE (V)
2k IDC 1% 1.24k 1%
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TYPICAL APPLICATIO
Complete Charge Cycle (1100mAh Battery)
1000 800 600 400 200 0 4.2 4.0 3.8 3.6 3.4 5.0 2.5 0 0 0.5 1.0 1.5 2.0 TIME (HR) 2.5 3.0
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4.2V SINGLE CELL Li-Ion BATTERY
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CONSTANT VOLTAGE USBIN = 5V TA = 25C RIDC = 1.24k RIUSB = 2k HPWR = 5V
FEATURES
DESCRIPTIO
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LTC4076
(Notes 1, 7)
Input Supply Voltage (DCIN, USBIN) ......... -0.3V to 10V EN, CHRG, PWR, HPWR ............................ -0.3V to 10V BAT, IDC, IUSB, ITERM ................................ -0.3V to 7V DCIN Pin Current (Note 6) ..........................................1A USBIN Pin Current (Note 6) .................................700mA BAT Pin Current (Note 6) ............................................1A BAT Short-Circuit Duration............................ Continuous Maximum Junction Temperature .......................... 125C Operating Temperature Range (Note 2) .. -40C to 85C Storage Temperature Range.................. -65C to 125C
TOP VIEW USBIN IUSB ITERM PWR CHRG 1 2 3 4 5 11 10 DCIN 9 BAT 8 IDC 7 HPWR 6 EN
DD PACKAGE 10-LEAD (3mm x 3mm) PLASTIC DFN TJMAX = 125C, JA = 40C/W (NOTE 3) EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER PART NUMBER LTC4076EDD
DD PART MARKING LBWC
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges.
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDCIN = 5V, VUSBIN = 5V, HPWR = 5V unless otherwise noted.
SYMBOL VDCIN VUSBIN IDCIN PARAMETER Supply Voltage Supply Voltage DCIN Supply Current CONDITIONS

ELECTRICAL CHARACTERISTICS
MIN 4.3 4.3
TYP
MAX 8 8 800 100 40 800 100 36 20 4.225 4.242 840 500 105 108 -6 -2 2 1.05 1.05 110 55 12 6.5
UNITS V V A A A A A A A V V mA mA mA mA A A A V V mA mA mA mA
IUSBIN
USBIN Supply Current
VFLOAT IBAT
Regulated Output (Float) Voltage BAT Pin Current
VIDC VIUSB ITERMINATE
IDC Pin Regulated Voltage IUSB Pin Regulated Voltage Charge Current Termination Threshold
Charge Mode (Note 4), RIDC = 10k Standby Mode; Charge Terminated Shutdown Mode (EN = 5V) Charge Mode (Note 5), RIUSB = 10k, VDCIN = 0V Standby Mode; Charge Terminated, VDCIN = 0V Shutdown (VDCIN = 0V, EN = 5V) VDCIN > VUSBIN IBAT = 1mA (Note 7) IBAT = 1mA, 0C < TA < 85C, 4.3V < VCC < 8V RIDC = 1.25k, Constant-Current Mode RIUSB = 2.1k, Constant-Current Mode RIUSB = 2.1k, HPWR = 0V RIDC = 10k or RIUSB = 10k Standby Mode, Charge Terminated Shutdown Mode (Charger Disabled) Sleep Mode (VDCIN = 0V, VUSBIN = 0V) Constant-Current Mode Constant-Current Mode RITERM = 1k RITERM = 2k RITERM = 10k RITERM = 20k

4.175 4.158 760 450 84 92

0.95 0.95 90 45 8 3.5
250 50 20 250 50 18 10 4.2 4.2 800 476 95 100 -3 -1 1 1 1 100 50 10 5
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ABSOLUTE
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
LTC4076 ELECTRICAL CHARACTERISTICS
SYMBOL ITRIKL VTRIKL VUVDC VUVUSB VASD-DC VASD-USB VEN REN VHPWR RHPWR VCHRG VPWR VRECHRG tRECHRG tTERMINATE tSS RON-DC RON-USB TLIM PARAMETER Trickle Charge Current Trickle Charge Threshold Voltage DCIN Undervoltage Lockout Voltage USBIN Undervoltage Lockout Voltage VDCIN - VBAT Lockout Threshold VUSBIN - VBAT Lockout Threshold EN Input Threshold Voltage EN Pulldown Resistance HPWR Input Threshold Voltage HPWR Pulldown Resistance CHRG Output Low Voltage PWR Output Low Voltage Recharge Battery Threshold Voltage Recharge Comparator Filter Time Termination Comparator Filter Time Soft-Start Time Power FET "ON" Resistance (Between DCIN and BAT) Power FET "ON" Resistance (Between USBIN and BAT) Junction Temperature in Constant-Temperature Mode
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDCIN = 5V, VUSBIN = 5V, HPWR = 5V unless otherwise noted.
CONDITIONS VBAT < VTRIKL; RIDC = 1.25k VBAT < VTRIKL; RIUSB = 2.1k VBAT Rising Hysteresis From Low to High Hysteresis From Low to High Hysteresis VDCIN from Low to High, VBAT = 4.2V VDCIN from High to Low, VBAT = 4.2V VUSBIN from Low to High VUSBIN from High to Low

MIN 60 30 2.8 4 3.8 140 20 140 20 0.4 1 0.4 1
TYP 80 47.5 2.9 100 4.15 200 3.95 200 180 50 180 50 0.7 2 0.7 2 0.35 0.35 100 6 1.5 250 400 550 105
MAX 100 65 3 4.3 4.1 220 80 220 80 1 5 1 5 0.6 0.6 135 10 2.2 325
UNITS mA mA V mV V mV V mV mV mV mV mV V M V M V V mV ms ms s m m C
ICHRG = 5mA IPWR = 5mA VFLOAT - VRECHRG, 0C < TA < 85C VBAT from High to Low IBAT Drops Below Termination Threshold IBAT = 10% to 90% Full-Scale
65 3 0.8 175
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 2: The LTC4076E is guaranteed to meet the performance specifications from 0C to 85C. 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 backside of the package to the PC board will result in a thermal resistance much higher than 40C/W. See Thermal Considerations.
Note 4: Supply current includes IDC and ITERM pin current (approximately 100A each) but does not include any current delivered to the battery through the BAT pin. Note 5: Supply current includes IUSB and ITERM pin current (approximately 100A each) but does not include any current delivered to the battery through the BAT pin. Note 6: Guaranteed by long term current density limitations. Note 7: VCC is greater of DCIN or USBIN
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LTC4076 TYPICAL PERFOR A CE CHARACTERISTICS
Regulated Output (Float) Voltage vs Charge Current
4.26 4.24 4.22 VFLOAT (V) VFLOAT (V) 4.20 4.18 4.16 4.14 4.12 4.10 0 100 200 300 400 500 600 700 800 CHARGE CURRENT (mA)
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VDCIN = VUSBIN = 5V
VIDC (V)
RIDC = RIUSB = 2k
RIDC = 1.25k
IUSB Pin Voltage vs Temperature (Constant-Current Mode)
1.008 1.006 1.004 VIUSB (V) VIUSB (V) 1.002 1.000 0.998 0.996 0.994 0.992 -50 -25 0 25 50 TEMPERATURE (C) 75 100
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HPWR = 5V
IBAT (mA)
VUSBIN = 8V VUSBIN = 4.3V
Charge Current vs IUSB Pin Voltage
900 800 700 600 IBAT (mA) 500 400 300 200 100 0 0 0.2 0.4 RIUSB = 10k VUSBIN = 5V HPWR = 5V 250 RIUSB = 1.25k
IPWR (mA)
IBAT (mA)
RIUSB = 2k
0.6 0.8 VIUSB (V)
4
UW
1.0
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Regulated Output (Float) Voltage vs Temperature
4.220 4.215 4.210 4.205 4.200 4.195 4.190 4.185 4.180 -50 -25 0 25 50 TEMPERATURE (C) 75 100
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IDC Pin Voltage vs Temperature (Constant-Current Mode)
1.008 1.006 1.004 1.002 1.000 0.998 0.996 0.994 0.992 -50 -25 0 25 50 TEMPERATURE (C) 75 100
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VDCIN = VUSBIN = 5V
VDCIN = 8V VDCIN = 4.3V
IUSB Pin Voltage vs Temperature (Constant-Current Mode)
0.208 0.206 0.204 0.202 0.200 0.198 0.196 0.194 0.192 -50 -25 50 25 TEMPERATURE (C) 0 75 100
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Charge Current vs IDC Pin Voltage
900 800 700 600 VDCIN = 5V RIDC = 1.25k
HPWR = 0V
VUSBIN = 8V VUSBIN = 4.3V
500 400 300 200 100 0 0 0.2 0.4 0.6 0.8 VIDC (V)
RIDC = 2k
RIDC = 10k
1.0
1.2
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Charge Current vs IUSB Pin Voltage
VUSBIN = 5V HPWR = 0V RIUSB = 1k 35 30 25 20 15 10 5 0
PWR Pin I-V Curve
VDCIN = VUSBIN = 5V TA = - 40C TA = 25C TA = 90C
200
150 RIUSB = 2k RIUSB = 4k
100 50
1.2
0
0
50
150 100 VIUSBL (mV)
200
250
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0
1
2
4 3 VPWR (V)
5
6
7
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LTC4076 TYPICAL PERFOR A CE CHARACTERISTICS
CHRG Pin I-V Curve
35 30 25 ICHRG (mA) 20 15 10 5 0 0 4 3 VCHRG (V) 5 6 7
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VDCIN = VUSBIN = 5V
IBAT (mA)
IBAT (mA)
1
2
Charge Current vs Battery Voltage
1000 550 500 450 400 350 300
800 RDS(ON) (m)
IBAT (mA)
600
RDS(ON) (m)
400
200
0
VDCIN = VUSBIN = 5V JA = 40C/W RIDC = 1.25k 2.4 2.7 3.0 3.3 3.6 VBAT (V) 3.9 4.2 4.5
EN Pin Threshold (Rising) vs Temperature
900 VDCIN = VUSBIN = 5V 850 800 VHPWR (mV) VEN (mV) 750 700 650 600 -50 900
IDCIN (A)
-25
50 25 0 TEMPERATURE (C)
UW
TA = -40C TA = 25C TA = 90C 75
Charge Current vs Ambient Temperature
1000 ONSET OF THERMAL REGULATION RIDC = 1.25k 700 600 500 200 HPWR = 5V VDCIN = VUSBIN = 5V VBAT = 4V JA = 40C/W 50 25 75 0 TEMPERATURE (C) 100 125 400 900 800
Charge Current vs Supply Voltage
ONSET OF THERMAL REGULATION
800
600 RIDC = RIUSB = 2k
400
0 -50 -25
RIDC = 1.25k VBAT = 4V JA = 35C/W 5.0 5.5 6.0 6.5 VDCIN (V) 7.0 7.5 8.0
300 4.0 4.5
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DCIN Power FET "On" Resistance vs Temperature
VBAT = 4V IBAT = 200mA 800 750 700 650 600 550 500 450 400 50 25 75 0 TEMPERATURE (C) 100 125
USBIN Power FET "On" Resistance vs Temperature
VBAT = 4V IBAT = 200mA HPWR = 5V
250 -50 -25
350 -50 -25
50 25 75 0 TEMPERATURE (C)
100
125
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HPWR Pin Threshold (Rising) vs Temperature
50 VDCIN = VUSBIN = 5V 850 800 750 700 650 600 -50 45 40 35 30 25 20 15 10 5 -25 50 25 0 TEMPERATURE (C) 75 100
DCIN Shutdown Current vs Temperature
VDCIN = 8V
VDCIN = 5V VDCIN = 4.3V EN = 5V -25 25 0 TEMPERATURE (C) 50 75 100
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100
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0 -50
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LTC4076 TYPICAL PERFOR A CE CHARACTERISTICS
USBIN Shutdown Current vs Temperature
45 40 35 30 IUSBIN (A) 25 20 15 10 5 0 -50 -25 50 25 0 TEMPERATURE (C) VUSBIN = 4.3V EN = 5V 75 100
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VUSBIN = 8V REN (M)
RHPWR (M)
VUSBIN = 5V
Undervoltage Lockout Threshold vs Temperature
4.30 4.25 4.20 4.15 VUV (V) 4.10 4.05 4.00 3.95 3.90 -50 -25 0 25 50 TEMPERATURE (C) 75 100
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VRECHRG (V)
Battery Drain Current vs Temperature
5 4 3 IBAT (A) 2 1 0 -1 -50 EN 5V/DIV VBAT = 4.2V VDCIN, VUSBIN (OPEN) IBAT 500mA/DIV
-25
6
UW
EN Pin Pulldown Resistance vs Temperature
2.8 2.6 2.4 2.2 2.0 1.8 1.6 -50 2.8 2.6 2.4 2.2 2.0 1.8
HPWR Pin Pulldown Resistance vs Temperature
-25
50 25 0 TEMPERATURE (C)
75
100
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1.6 -50
-25
50 25 0 TEMPERATURE (C)
75
100
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Recharge Threshold Voltage vs Temperature
4.16
DCIN UVLO
4.14 4.12 4.10 4.08 4.06 4.04 -50 VDCIN = VUSBIN = 4.3V VDCIN = VUSBIN = 8V
USBIN UVLO
-25
0 25 50 TEMPERATURE (C)
75
100
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Charge Current at Turn-On and Turn-Off
0 25 50 TEMPERATURE (C)
75
100
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VDCIN = 5V RIDC = 1.25k
100 s/DIV
4076 G23
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LTC4076 PI FU CTIO S
USBIN (Pin 1): USB Input Supply Pin. Provides power to the battery charger. The maximum supply current is 650mA. This pin should be bypassed with a 1F capacitor. IUSB (Pin 2): Charge Current Program for USB Power. The charge current is set by connecting a resistor, RIUSB, to ground. When charging in constant-current mode, this pin servos to 1V. The voltage on this pin can be used to measure the battery current delivered from the USB input using the following formula: IBAT = IBAT VIUSB * 1000 (HPWR = HIGH) RIUSB V = IUSB * 200 (HPWR = LOW) RIUSB
ITERM (Pin 3): Termination Current Threshold Program. The termination current threshold, ITERMINATE, is set by connecting a resistor, RITERM, to ground. ITERMINATE is set by the following formula: ITERMINATE = 100V RITERM
When the battery current, IBAT, falls below the termination threshold, charging stops and the CHRG output becomes high impedance. This pin is internally clamped to approximately 1.5V. Driving this pin to voltages beyond the clamp voltage should be avoided. PWR (Pin 4): Open-Drain Power Supply Status Output. When the DCIN or USBIN pin voltage is sufficient to begin charging (i.e. when the supply is greater than the undervoltage lockout threshold and at least 180mV above the battery terminal), the PWR pin is pulled low by an internal N-channel MOSFET. Otherwise PWR is high impedance. This output is capable of sinking up to 10mA, making it suitable for driving an LED.
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CHRG (Pin 5): Open-Drain Charge Status Output. When the LTC4076 is charging, the CHRG pin is pulled low by an internal N-channel MOSFET. When the charge cycle is completed, CHRG becomes high impedance. This output is capable of sinking up to 10mA, making it suitable for driving an LED. EN (Pin 6): Charge Enable Input. A logic low on this pin enables the charger. If left floating, an internal 2M pulldown resistor defaults the LTC4076 to charge mode . Pull this pin high for shutdown. HPWR (Pin 7): HPWR Enable Input. Used to control the amount of current drawn from the USB port. A logic high on the HPWR pin sets the charge current to 100% of the current programmed by the IUSB pin. A logic low on the HPWR pin sets the charge current to 20% of the current programmed by the IUSB pin. An internal 2M pull-down resistor defaults the HPWR pin to its low current state. IDC (Pin 8): Charge Current Program for Wall Adapter Power. The charge current is set by connecting a resistor, RIDC, to ground. When charging in constant-current mode, this pin servos to 1V. The voltage on this pin can be used to measure the battery current delivered from the DC input using the following formula: IBAT = VIDC *1000 RIDC
BAT (Pin 9): Charger Output. This pin provides charge current to the battery and regulates the final float voltage to 4.2V. DCIN (Pin 10): Wall Adapter Input Supply Pin. Provides power to the battery charger. The maximum supply current is 950mA. This should be bypassed with a 1F capacitor. Exposed Pad (Pin 11): GND. The exposed backside of the package is ground and must be soldered to PC board ground for electrical connection and maximum heat transfer.
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LTC4076 W
DCIN 10 BAT 9 USBIN 1 CC/CV REGULATOR CC/CV REGULATOR
BLOCK DIAGRA
HPWR
7 RHPWR 4.15V
+ -
DCIN UVLO DC SOFT-START USB SOFT-START USBIN UVLO
+ - + -
BAT 3.95V
PWR
4
10mA MAX
+
BAT
CHRG
5
10mA MAX
-
+
LOGIC RECHRG TRICKLE TERM RECHARGE
4.1V
-
BAT DC_ENABLE USB_ENABLE
+
THERMAL REGULATION
EN
6 REN
TERMINATION
8
+ + -
TRICKLE CHARGE
-
2.9V 100mV IBAT/1000 3 11 RITERM
TDIE 105C
CHARGER CONTROL
-
IBAT/1000
IBAT/1000
ITERM GND 8
IDC 2 RIDC
IUSB
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RIUSB
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LTC4076
The LTC4076 is designed to efficiently manage charging of a single-cell lithium-ion battery from two separate power sources: a wall adapter and USB power bus. Using the constant-current/constant-voltage algorithm, the charger can deliver up to 950mA of charge current from the wall adapter supply or up to 650mA of charge current from the USB supply with a final float voltage accuracy of 0.6%. The LTC4076 has two internal P-channel power MOSFETs and thermal regulation circuitry. No blocking diodes or external sense resistors are required. Power Source Selection The LTC4076 can charge a battery from either the wall adapter input or the USB port input. The LTC4076 automatically senses the presence of voltage at each input. If both power sources are present, the LTC4076 defaults to the wall adapter source provided sufficient power is present at the DCIN input. "Sufficient power" is defined as: * Supply voltage is greater than the UVLO threshold. * Supply voltage is greater than the battery voltage by 50mV (180mV rising, 50mV falling). The open drain power status output (PWR) indicates that sufficient power is available. Table 1 describes the behavior of this status output.
Table 1. Power Source Selection
VUSBIN > 3.95V and VUSBIN > BAT + 50mV Device powered from wall adapter source; USBIN current < 25A PWR: LOW Device powered from USB source; PWR: LOW VUSBIN < 3.95V or VUSBIN < BAT + 50mV Device powered from wall adapter source PWR: LOW No charging PWR: Hi-Z
VDCIN > 4.15V and VDCIN > BAT + 50mV
VDCIN < 4.15V or VDCIN < BAT + 50mV
Programming and Monitoring Charge Current The charge current delivered to the battery from the wall adapter supply is programmed using a single resistor from the IDC pin to ground. RIDC = 1000 V ICHRG(DC) , ICHRG(DC) = 1000 V RIDC
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Similarly, the charge current from the USB supply is programmed using a single resistor from the IUSB pin to ground. Setting HPWR pin to its high state will select 100% of the programmed charge current, while setting HPWR to its low state will select 20% of the programmed charge current. RIUSB = 1000 V ICHRG(USB) (HPWR = HIGH) ICHRG(USB) = ICHRG(USB) = 1000 V (HPWR = HIGH) RIUSB 200 V (HPWR = LOW) RIUSB Charge current out of the BAT pin can be determined at any time by monitoring the IDC or IUSB pin voltage and using the following equations: IBAT = IBAT = IBAT = VIDC * 1000, (ch arg ing from wall adapter ) RIDC VIUSB * 1000, (ch arg ing from USB sup ply, RIUSB HPWR = HIGH) VIUSB * 200, (ch arg ing from USB sup ply, RIUSB HPWR = LOW) Programming Charge Termination The charge cycle terminates when the charge current falls below the programmed termination threshold during constant-voltage mode. This threshold is set by connecting an external resistor, RITERM, from the ITERM pin to ground. The charge termination current threshold (ITERMINATE) is set by the following equation: RITERM = 100V ITERMINATE , ITERMINATE = 100V RITERM
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OPERATIO
9
LTC4076
The termination condition is detected by using an internal filtered comparator to monitor the ITERM pin. When the ITERM pin voltage drops below 100mV* for longer than tTERMINATE (typically 1.5ms), the charge cycle terminates, charge current latches off and the LTC4076 enters standby mode. When charging, transient loads on the BAT pin can cause the ITERM pin to fall below 100mV for short periods of time before the DC charge current has dropped below the programmed termination current. The 1.5ms filter time (tTERMINATE) on the termination comparator ensures that transient loads of this nature do not result in premature charge cycle termination. Once the average charge current drops below the programmed termination threshold, the LTC4076 terminates the charge cycle and ceases to provide any current out of the BAT pin. In this state, any load on the BAT pin must be supplied by the battery. Low-Battery Charge Conditioning (Trickle Charge) This feature ensures that deeply discharged batteries are gradually charged before applying full charge current . If the BAT pin voltage is below 2.9V, the LTC4076 supplies 1/10th of the full charge current to the battery until the BAT pin rises above 2.9V. For example, if the charger is programmed to charge at 800mA from the wall adapter input and 500mA from the USB input, the charge current during trickle charge mode would be 80mA and 50mA, respectively. Automatic Recharge In standby mode, the charger sits idle and monitors the battery voltage using a comparator with a 6ms filter time (tRECHRG). A charge cycle automatically restarts when the battery voltage falls below 4.1V (which corresponds to approximately 80%-90% battery capacity). This ensures that the battery is kept at, or near, a fully charged condition and eliminates the need for periodic charge cycle initiations.
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If the battery is removed from the charger, a sawtooth waveform of approximately 100mV appears at the battery output. This is caused by the repeated cycling between termination and recharge events. This cycling results in pulsing at the CHRG output; an LED connected to this pin will exhibit a blinking pattern, indicating to the user that a battery is not present. The frequency of the sawtooth is dependent on the amount of output capacitance. Manual Shutdown The EN pin has a 2M pulldown resistor to GND. A logic low enables the charger and logic high disables it (the pulldown defaults the charger to the charging state). The DCIN input draws 20A when the charger is in shutdown. The USBIN input draws 18A during shutdown if no power is applied to DCIN, but draws only 10A when VDCIN > VUSBIN. Charge Current Soft-Start and Soft-Stop The LTC4076 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 full-scale current over a period of 250s. Likewise, internal circuitry slowly ramps the charge current from full-scale to zero in a period of approximately 30s when the charger shuts down or self terminates. This minimizes the transient current load on the power supply during start-up and shut-off. Status Indicators The charge status output (CHRG) has two states: pull-down and high impedance. The pull-down state indicates that the LTC4076 is in a charge cycle. Once the charge cycle has terminated or the LTC4076 is disabled, the pin state becomes high impedance. The pull-down state is capable of sinking up to 10mA.
*Any external sources that hold the ITERM pin above 100mV will prevent the LTC4076 from terminating a charge cycle.
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OPERATIO
LTC4076
The power supply status output (PWR) has two states: pull-down and high impedance. The pull-down state indicates that power is present at either DCIN or USBIN. If no power is applied at either pin, the PWR pin is high impedance, indicating that the LTC4076 lacks sufficient power to charge the battery. The pull-down state is capable of sinking up to 10mA. Thermal Limiting An internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above
STARTUP DCIN POWER APPLIED ONLY USB POWER APPLIED USBIN POWER REMOVED OR DCIN POWER APPLIED
BAT < 2.9V
2.9V < BAT
BAT < 4.1V
EN DRIVEN LOW
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a preset value of approximately 105C. This feature protects the LTC4076 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 device. The charge current can be set according to typical (not worst-case) ambient temperature with the assurance that the charger will automatically reduce the current in worstcase conditions. DFN power considerations are discussed further in the Applications Information section.
POWER SELECTION DCIN POWER REMOVED TRICKLE CHARGE MODE 1/10th FULL CURRENT CHRG STATE: PULLDOWN BAT > 2.9V CHARGE MODE FULL CURRENT CHRG STATE: PULLDOWN IBAT < ITERMINATE IN VOLTAGE MODE STANDBY MODE NO CHARGE CURRENT CHRG STATE: Hi-Z TRICKLE CHARGE MODE 1/10th FULL CURRENT CHRG STATE: PULLDOWN BAT > 2.9V CHARGE MODE FULL CURRENTHPWR = HIGH 1/5 FULL CURRENTHPWR = LOW CHRG STATE: PULLDOWN IBAT < ITERMINATE IN VOLTAGE MODE STANDBY MODE NO CHARGE CURRENT CHRG STATE: Hi-Z BAT < 4.1V 2.9V < BAT BAT < 2.9V SHUTDOWN MODE IDCIN DROPS TO 20A CHRG STATE: Hi-Z DCIN POWER REMOVED USBIN POWER REMOVED OR DCIN POWER APPLIED EN DRIVEN HIGH EN DRIVEN HIGH SHUTDOWN MODE IUSBIN DROPS TO 18A CHRG STATE: Hi-Z
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OPERATIO
EN DRIVEN LOW
Figure 1. LTC4076 State Diagram of a Charge Cycle
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LTC4076
Using a Single Charge Current Program Resistor In applications where the programmed wall adapter charge current and USB charge current are the same, a single program resistor can be used to set both charge currents. Figure 2 shows a charger circuit that uses one charge current program resistor. In this circuit, one resistor programs the same charge current for each input supply. 1000 V ICHRG(DC) = ICHRG(USB) = RISET
WALL ADAPTER USB PORT 1F 1F RISET 2k 1% LTC4076 DCIN USBIN IUSB IDC ITERM GND RITERM 1k 1%
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100mA (USB, HPWR = LOW) 500mA BAT
HPWR
+
Figure 2. Dual Input Charger Circuit. The Wall Adapter Charge Current and USB Charge Current are Both Programmed to be 500mA
WALL ADAPTER USB PORT
1F
RIUSB 2k 1%
RIDC 1.24k 1%
Figure 3. Full Featured Dual Input Charger Circuit
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The LTC4076 can also program the wall adapter charge current and USB charge current independently using two program resistors, RIDC and RIUSB. Figure 3 shows a charger circuit that sets the wall adapter charge current to 800mA and the USB charge current to 500mA. Stability Considerations The constant-voltage mode feedback loop is stable without any compensation provided a battery is connected to the charger output. However, a 1F capacitor with a 1 series resistor is recommended at the BAT pin to keep the ripple voltage low when the battery is disconnected. When the charger is in constant-current mode, the charge current program pin (IDC or IUSB) is in the feedback loop, not the battery. The constant-current mode stability is affected by the impedance at the charge current program pin. With no additional capacitance on this pin, the charger is stable with program resistor values as high as 20k (ICHRG = 50mA); however, additional capacitance on these nodes reduces the maximum allowed program resistor.
LTC4076 DCIN USBIN 1F HPWR IUSB IDC PWR CHRG ITERM GND RITERM 1k 1%
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APPLICATIO S I FOR ATIO W U U
800mA (WALL) 100mA/500mA (USB) BAT 1k 1k 4.2V 1-CELL Li-Ion BATTERY
+
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LTC4076
Power Dissipation When designing the battery charger circuit, it is not necessary to design for worst-case power dissipation scenarios because the LTC4076 automatically reduces the charge current during high power conditions. The conditions that cause the LTC4076 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 MOSFET pass device. Thus, the power dissipation is calculated to be: PD = (VIN - VBAT) * IBAT PD is the power dissipated, VIN is the input supply voltage (either DCIN or USBIN), 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 - (VIN - VBAT) * IBAT * JA Example: An LTC4076 operating from a 5V wall adapter (on the DCIN input) 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 LTC4076 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
U
The LTC4076 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: 105C - TA IBAT = (VIN - 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 LTC4076 applications do not need to be designed for worst-case thermal conditions, since the IC will automatically reduce power dissipation when 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 LTC4076 package is properly soldered to the PC board ground. When correctly soldered to a 2500mm2 double sided 1oz copper board, the LTC4076 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 correctly soldered LTC4076 can deliver over 800mA to a battery from a 5V supply at room temperature. Without a good backside thermal connection, this number would drop to much less than 500mA.
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APPLICATIO S I FOR ATIO W U U
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LTC4076
Protecting the USB Pin and Wall Adapter Input from Overvoltage Transients Caution must be exercised when using ceramic capacitors to bypass the USBIN pin or the wall adapter inputs. High voltage transients can be generated when the USB or wall adapter is hot plugged. When power is supplied via the USB bus or wall adapter, the cable inductance along with the self resonant and high Q characteristics of ceramic capacitors can cause substantial ringing which could exceed the maximum voltage ratings and damage the LTC4076. Refer to Linear Technology Application Note 88, entitled "Ceramic Input Capacitors Can Cause Overvoltage Transients" for a detailed discussion of this problem.
DRAIN-BULK DIODE OF FET WALL ADAPTER LTC4076 DCIN
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Figure 4. Low Loss Input Reverse Polarity Protection
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Always use an oscilloscope to check the voltage waveforms at the USBIN and DCIN pins during USB and wall adapter hot-plug events to ensure that overvoltage transients have been adequately removed. Reverse Polarity Input Voltage Protection In some applications, protection from reverse polarity voltage on the input supply pins is desired. If the supply voltage is high enough, a series blocking diode can be used. In other cases where the voltage drop must be kept low, a P-channel MOSFET can be used (as shown in Figure 4).
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APPLICATIO S I FOR ATIO W U U
LTC4076 U
DD Package 10-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115 TYP 6 0.675 0.05 0.38 0.10 10 3.00 0.10 (4 SIDES) PACKAGE OUTLINE 0.25 0.05 PIN 1 TOP MARK (SEE NOTE 6) 0.200 REF 0.75 0.05 5 2.38 0.10 (2 SIDES) BOTTOM VIEW--EXPOSED PAD 1 1.65 0.10 (2 SIDES)
(DD) DFN 1103
PACKAGE DESCRIPTIO
3.50 0.05 1.65 0.05 2.15 0.05 (2 SIDES)
0.50 BSC 2.38 0.05 (2 SIDES)
0.25 0.05 0.50 BSC
0.00 - 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 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
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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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LTC4076 RELATED PARTS
PART NUMBER LTC3455 LTC4053 LTC4054/LTC4054X LTC4055 LTC4058/LTC4058X LTC4061 LTC4061-4.4 LTC4062 LTC4065/LTC4065A LTC4066 LTC4068/LTC4068X LTC4075 DESCRIPTION Dual DC/DC Converter with USB Power Management and Li-Ion Battery Charger USB Compatible Monolithic Li-Ion Battery Charger Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOT USB Power Controller and Battery Charger Standalone 950mA Lithium-Ion Charger in DFN Standalone Li-Ion Charger with Thermistor Interface Standalone Li-Ion Charger with Thermistor Interface Standalone Li-Ion Charger with Micropower Comparator Standalone 750mA Li-Ion Charger in 2mm x 2mm DFN USB Power Controller and Li-Ion Linear Battery Charger with Low-Loss Ideal Diode Standalone Linear Li-Ion Battery Charger with Programmable Termination Dual Input Standalone Li-Ion Battery Charger COMMENTS Efficiency >96%, Accurate USB Current Limiting (500mA/100mA), 4mm x 4mm QFN-24 Package 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 Charges Single-Cell Li-Ion Batteries Directly from USB Port, Thermal Regulation, 4mm x 4mm QFN-16 Package C/10 Charge Termination, Battery Kelvin Sensing, 7% Charge Accuracy 4.2V, 0.35% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN-10 Package 4.4V, 0.4% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN-10 Package 4.2V, 0.35% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN-10 Package 4.2V, 0.6% Float Voltage, Up to 750mA Charge Current, 2mm x 2mm DFN-6 Package Seamless Transition Between Input Power Sources: Li-Ion Battery, USB and Wall Adapter, Low-Loss (50) Ideal Diode, 4mm x 4mm QFN-24 Package Charge Current up to 950mA, Thermal Regulation, 3mm x 3mm DFN-8 Package Charges Single-Cell Li-Ion Batteries from Wall Adapter and USB Inputs with Automatic Input Power Detection and Selection, 950mA Charger Current, Thermal Regulation, C/X Charge Termination, 3mm x 3mm DFN Package Charges Single-Cell Li-Ion Batteries from Wall Adapter and USB Inputs with Automatic Input Power Detection and Selection, 950mA Charger Current, Thermal Regulation, C/10 Charge Termination, 3mm x 3mm DFN Package Manages Total Power Between a USB Peripheral and Battery Charger, Ultralow Battery Drain: 1A, ThinSOTTM Package Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes
LTC4077
Dual Input Standalone Li-Ion Battery Charger
LTC4410 LTC4411/LTC4412
USB Power Manager and Battery Charger Low Loss PowerPathTM Controller in ThinSOT
ThinSOT and PowerPath are trademarks of Linear Technology Corporation
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16 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT 04/06 REV A PRINTED IN USA
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2005

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