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LTC4055 USB Power Controller and Li-Ion Linear Charger
FEATURES
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DESCRIPTIO
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Charges Single Cell Li-Ion Batteries Directly from USB Port Load Dependent Charging Guarantees USB Input Current Compliance Automatic Battery Switchover When Input Supply is Removed Constant-Current/Constant-Voltage Operation with Thermal Feedback to Maximize Charging Rate Without Risk of Overheating* Selectable 100% or 20% Current Limit (e.g., 500mA/100mA) Low Loss Full PowerPathTM Control with Ideal Diode Operation (Reverse Current Blocking) Preset 4.2V Charge Voltage with 0.8% Accuracy USB Compliant Suspend Mode Programmable Charge Current and Termination Timer Automatic Recharge Soft-Start Limits Inrush Current NTC Thermistor Input for Temperature Qualified Charging Tiny (4mm x 4mm x 0.8mm) QFN Package
The LTC(R)4055 is a USB power manager and Li-Ion battery charger designed to work in portable battery-powered applications. The part manages and limits the total current used by the USB peripheral for operation and battery charging. Depending on the state of the current select pin (HPWR), total input current can be limited to either 100mA or 500mA. The voltage drop from the USB supply or battery to the USB peripheral is typically less than 100mV at 400mA and 20mV at 80mA. Other management features include: automatic switch over to battery when input is removed, inrush current limiting, reverse current blocking, undervoltage lockout and thermal shutdown. The LTC4055 includes a complete constant-current/constant-voltage linear charger for single cell Li-ion batteries. The float voltage applied to the battery is held to a tight 0.8% (typ) tolerance, and charge current is programmable using an external resistor to ground. Fully discharged cells are automatically trickle charged at 10% of the programmed current until the cell voltage exceeds 2.8V. Total charge time is programmable by an external capacitor to ground. When the battery drops 100mV below the float voltage, automatic recharging of the battery occurs. Also featured is an NTC thermistor input used to monitor battery temperature while charging. The LTC4055 is available in a 16-pin low profile (4mm x 4mm) QFN package.
APPLICATIO S
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Portable USB Devices: Cameras, MP3 Players, PDAs
, LTC and LT are registered trademarks of Linear Technology Corporation. PowerPath is a trademark of Linear Technology Corporation. *U.S. patent number 6522118
TYPICAL APPLICATIO
5V (NOM) FROM USB CABLE VBUS IN1 1 10F IN2 VNTC NTC WALL SHDN SUSPEND USB POWER 500mA/100mA SELECT SUSP HPWR TIMER PROG 0.1F
Input and Battery Current vs Load Current RPROG = RCLPROG = 97.6k
600
OUT BAT TO SYSTEM LOADS
500 400
+
10F
CURRENT (mA)
Li-Ion CELL
LTC4055
CHRG ACPR
300 200 100
CLPROG 97.6k
GND
0 -100
97.6k
4055 TA01
U
IIN ILOAD IBAT CHARGING IBAT (IDEAL DIODE) 0 100 200 300 400 ILOAD (mA) 500 600
4055 TA02
U
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1
LTC4055
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2, 3, 4, 5)
PACKAGE/ORDER INFORMATION
TOP VIEW CHRG ACPR VNTC NTC
Terminal Voltage IN1, IN2, OUT, BAT ................................ -0.3V to 6V NTC, VNTC, TIMER, PROG, CLPROG ..................... -0.3V to (VCC + 0.3V) CHRG, HPWR, SUSP, SHDN, WALL, ACPR .......................................... -0.3V to 6V IN2 .......................................................... VIN1 + 0.1V Pin Current (DC) IN1, IN2, OUT, BAT (Note 7) ............................. 1.6A Operating Temperature Range ............... - 40C to 85C Maximum Operating Junction Temperature......... 125C Storage Temperature Range ................ - 65C to 125C
ORDER PART NUMBER
12 TIMER
16 15 14 13 IN2 1 BAT 2 OUT 3 IN1 4 5 WALL 6 SHDN 7 SUSP 8 HPWR 17
LTC4055EUF
11 PROG 10 GND 9 CLPROG
UF PART MARKING 4055
UF PACKAGE 16-LEAD (4mm x 4mm) PLASTIC QFN TJMAX = 125C, JA = 37C/W EXPOSED PAD IS GND (PIN 17) MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL VIN VBAT IIN PARAMETER Input Supply Voltage Input Voltage Input Supply Current
The q indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN1 = VIN2 = 5V, VBAT = 3.5V, HPWR = 5V, WALL = 0V, RPROG = RCLPROG = 100k, unless otherwise noted.
CONDITIONS IN1, IN2 and OUT BAT VBAT = 4.2V Suspend Mode Suspend Mode, Wall = 2V, VOUT = 4.8V Shutdown VOUT = 5V, VIN1 = VIN2 = 0V, VBAT = 4.2V VBAT = 4.2V, Charging Stopped Suspend Mode Shutdown VIN1 = VIN2 = 0V, BAT Powers OUT, No Load (Note 8) VIN Powers Part, Rising Threshold VOUT Powers Part, Rising Threshold VIN Rising - VIN Falling or VOUT Rising - VOUT Falling RCLPROG = 100k, HPWR = 5V RCLPROG = 100k, HPWR = 0V HPWR = 5V, 400mA Load HPWR = 0V, 80mA Load RCLPROG = RPROG = 100k RCLPROG = RPROG = 50k IN or OUT VIN Rising VIN Rising - VIN Falling (VIN - VOUT) VIN Rising (VIN - VOUT) VIN Falling
q q q q q q q q q q q q q
MIN 4.35
TYP
IOUT IBAT
Output Supply Current Battery Drain Current
ILIM(MAX) VUVLO VUVLO Current Limit ILIM RON VPROG ISS VCLEN VCLEN VALEN
Maximum Current Limit Input or Output Undervoltage Lockout Input or Output Undervoltage Lockout Hysteresis Current Limit ON Resistance VIN to VOUT Programming Pin Voltage (PROG, CLPROG) Soft-Start Inrush Current Input Current Limit Enable Threshold Input Current Limit Enable Threshold Automatic Limit Enable Threshold Voltage
3.5 3.5
0.8 50 0.1 10 450 15 15 2.5 50 1 3.8 3.8 125
MAX 5.5 4.3 1.6 100 0.2 20 900 30 30 5 100 4 4
UNITS V V mA A mA A A A A A A A V V mV
q q
465 89
q q q
0.98 0.98 3.5 25 -75
490 97 0.2 0.2 1.000 1.000 5 3.8 125 50 -50
515 105
1.02 1.02 4 75 -25
mA mA V V mA/s V mV mV mV
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2
U
W
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U
WW
W
LTC4055
ELECTRICAL CHARACTERISTICS
SYMBOL Battery Charger VFLOAT IBAT PARAMETER Regulated BAT Voltage Current Mode Charge Current
The q indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN1 = VIN2 = 5V, VBAT = 3.5V, HPWR = 5V, WALL = 0V, RPROG = RCLPROG = 100k, unless otherwise noted.
CONDITIONS (0C to 85C)
q
MIN 4.165 4.158 445 45 445 900 900
TYP 4.200 4.200 485 80 485 980 980 1 1 45 2.85 70 80 70 80 4.3 100 10 50 25 105
MAX 4.235 4.242 525 110 525 1060 1060
UNITS V V mA mA mA mA mA A mA/mA mA V mV mV mV mV V mV % % % C
IBAT(MAX) IB/IO ITRKL VTRKL VCENI VCENO VUVCL VRECHRG tTIMER
TLIM Ideal Diode RFWD RDIO,ON VFWD
Maximum Charge Current Charge Current Load Dependency Trickle Charge Current Trickle Charge Threshold Voltage Input Charger Enable Threshold Voltage Output Charger Enable Threshold Voltage Input/Output Undervoltage Current Limit Recharge Battery Threshold Voltage TIMER Accuracy Recharge Time Low-Battery Trickle Charge Time Junction Temperature in Constant Temperature Mode On Resistance, VON Regulation On Resistance VBAT to VOUT Voltage Forward Drop (VBAT - VOUT)
RPROG = 100k, HPWR = 5V, No Load RPROG = 100k, HPWR = 0V, No Load RPROG = 100k, VOUT = 5V, VIN = 0V, VWALL = 2V RPROG = 50k, HPWR = 5V, No Load RPROG = 50k, VOUT = 5V, VIN = 0V, VWALL = 2V (Note 8) IBAT/IOUT, IOUT = 100mA VBAT = 2V, RPROG = 100k VBAT Rising (VIN - VBAT) High to Low (VIN - VBAT) Low to High (VOUT - VBAT) High to Low (VOUT - VBAT) Low to High IBAT = ICHG/2 VFLOAT - VRECHRG CTIMER = 0.1F Percent of Total Charge Time Percent of Total Charge Time, VBAT < 2.8V
q q q q q
q q
0.95 30 2.7
1.05 60 3
q q
4.23 65
4.37 135
VOFF IFWD IMAX Logic VOL VIH VIL IPULLDN VCHG,SD ICHG,SD VWALL VWALL,HYS IWALL
VBAT = 3.5V, 100mA Load VBAT = 3.5V, 600mA Load VBAT = 3.5V, 5mA Load VBAT = 3.5V, 100mA Load VBAT = 3.5V, 600mA Diode Disable Battery Voltage VBAT Falling Load Current Limit for VON Regulation VIN = 3.5V Diode Current Limit VBAT = 3.5V, VOUT = 2.8V, Pulsed with 10% Duty Cycle Output Low Voltage (CHRG, ACPR) Enable Input High Voltage Enable Input Low Voltage Logic Input Pull-Down Current Charger Shutdown Threshold Voltage on TIMER Charger Shutdown Pull-Up Current on TIMER Wall Input Threshold Voltage Wall Input Hysteresis Wall Input Leakage Current ISINK = 5mA SUSP, SHDN, HPWR Pin Low to High SUSP, SHDN, HPWR Pin High to Low SUSP, SHDN, HPWR TIMER Falling VTIMER = 0V VWALL Rising Threshold VWALL Rising - VWALL Falling Threshold VWALL = 1V
q
10
1.4
0.1 0.2 30 55 120 2.8 550 1.8
50
2.2
mV mV mV V mA A
q q q q q q
0.2 0.4 2 0.15 2 0.98 4 1.000 35 0
0.4 1.2
0.4
V V V A V A
1.02 50
V mV nA
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LTC4055
ELECTRICAL CHARACTERISTICS
SYMBOL NTC IVNTC VVNTC VCOLD VHOT VDIS VNTC Pin Current VNTC Bias Voltage Cold Temperature Fault Threshold Voltage Hot Temperature Fault Threshold Voltage NTC Disable Voltage PARAMETER
The q indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN1 = VIN2 = 5V, VBAT = 3.5V, HPWR = 5V, WALL = 0V, RPROG = RCLPROG = 100k, unless otherwise noted.
CONDITIONS VVNTC = 2.5V IVNTC = 500A Rising Threshold Falling Threshold Falling Threshold Rising Threshold NTC Input Voltage to GND (Falling) Hysteresis
q q q
MIN 1.5 3.4
TYP 2.5 3.8 0.74 * VVNTC 0.72 * VVNTC 0.29 * VVNTC 0.30 * VVNTC
MAX 3.5
UNITS mA V V V V V
75
100 50
125
mV mV
Note 1: Absolute Maximum Ratings are those beyond which the life of a device may be impaired. Note 2: VCC is the greater of VIN1, VOUT or VBAT Note 3: IN1 and IN2 should be tied together with a low impedance to ensure that the difference between the two pins does not exceed 100mV Note 4: All voltage values are with respect to GND. Note 5: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 6: The LTC4055EUF 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 7: Guaranteed by long term current density limitations. Note 8: Accuracy of programmed current may degrade for currents greater than 1A.
TYPICAL PERFOR A CE CHARACTERISTICS
Input Supply Current vs Temperature
900 800 700 600 VIN = 5V VBAT = 4.2V RPROG = RCLPROG = 100k
IBAT (A)
IIN (A)
500 400 300 200
IIN (A)
100 0 -50 -25 0 25 50 TEMPERATURE (C) 75 100
4
UW
4055 G01
Input Supply Current vs Temperature (Suspend Mode)
60 50 40 30 20
20
Battery Drain Current vs Temperature (BAT Powers OUT, No Load)
70 60 50 40 30 VIN = 0V VBAT = 4.2V
VIN = 5V VBAT = 4.2V RPROG = RCLPROG = 100k SUSP = 5V
10 0 -50
10 0 -50
-25
0 25 50 TEMPERATURE (C)
75
100
4055 G02
-25
50 25 0 TEMPERATURE (C)
75
100
4055 G03
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LTC4055 TYPICAL PERFOR A CE CHARACTERISTICS
Input Current Limit vs Temperature, HPWR = 5V
515 VIN = 5V VBAT = 3.5V RPROG = RCLPROG = 100k 105.0 102.5 100.0
505
RON (m)
IIN (mA)
IIN (mA)
495
485
475
465 -50
-25
50 25 0 75 TEMPERATURE (C)
PROG Pin Voltage vs Temperature
1.020 1.015 1.010 VCLPROG (V) VIN = 5V RPROG = 100k 1.020 1.015 1.010
1.000 0.995 0.990 0.985 0.980 -50 -25 50 25 TEMPERATURE (C) 0 75 100
4055 G07
1.000 0.995 0.990 0.985 0.980 -50 -25 50 25 TEMPERATURE (C) 0 75 100
4055 G08
VFLOAT (V)
VPROG (V)
1.005
Regulated Output VoltageRecharge Threshold Voltage vs Temperature
120 115 VIN = 5V 4.220 4.215 4.210
VFLOAT-VRECHARGE (V)
110
VFLOAT (V)
IBAT (mA)
105 100 95 90 85 80 -50 -25 50 25 TEMPERATURE (C) 0 75 100
4055 G10
UW
100
Input Current Limit vs Temperature, HPWR = 0V
VIN = 5V VBAT = 3.5V RPROG = RCLPROG = 100k
RON vs Temperature
250 225 VIN = 5V 200 VIN = 4.5V 175 VIN = 5.5V 150 125 100 -50 -25 ILOAD = 400mA
97.5 95.0 92.5 90.0 -50 -25
125
50 25 75 0 TEMPERATURE (C)
100
125
50 25 75 0 TEMPERATURE (C)
100
125
4055 G04
4055 G05
4055 G06
CLPROG Pin Voltage vs Temperature
VIN = 5V RCLPROG = 100k 4.220 4.215 4.210 4.205 4.200 4.195 4.190 4.185
Battery Regulated Output (Float) Voltage vs Temperature
VIN = 5V
1.005
4.180 -50
-25
0 50 25 TEMPERATURE (C)
75
100
4055 G09
Battery Regulated Output (Float) Voltage vs Supply Voltage
TA = 25C
Battery Current and Voltage vs Time
600 500 VBAT 400 300 200 100 0.8AHr CELL VIN = 5V TA = 25C RPROG = 105k 0 IBAT 1 4 3 2 CHRG 6 5
VBAT AND VCHRG (V)
4.205 4.200 4.195 4.190 4.185 4.180 4.5
0
4.75 5 5.25 VIN (V) 5.5 5.75 6
4055 G11
0 20 40 60 80 100 120 140 160 180 200 TIME (MINUTES)
4055 G12
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5
LTC4055 TYPICAL PERFOR A CE CHARACTERISTICS
Charging from USB, IBAT vs VBAT
600 500 400
IBAT (mA)
VIN = 5V VOUT = NO LOAD RPROG = 100k RCLPROG = 100k HPWR = 1 TA = 25C
IBAT (mA)
300 200 100 0 0 0.5 1 1.5 2 2.5 VBAT (V) 3 3.5 4 4.5
IBAT (A)
Charge Current vs Temperature (Thermal Regulation)
1.0 0.9 0.8 0.7 RPROG = 100k
IOUT (mA)
1000
RPROG = 50k
700 600 500 400 300 200 100 125C 75C
IOUT (mA), RDIO (m)
IBAT (A)
0.6 0.5 0.4 0.3 0.2 VIN = 5V 0.1 VBAT = 3.5V JA = 37C/W 0 50 25 0 75 -50 -25 TEMPERATURE (C)
Ideal Diode and Schottky Diode Forward Voltage vs Current
1000 VBAT = 3.5V 900 VIN = 0V T = 25C 800 A 700 VIN 5V/DIV VOUT 5V/DIV IIN 0.5A/DIV IBAT 0.5A/DIV
IOUT (mA)
600 500 400 300 200 100 0 0 50 100 150 200 250 300 350 400 450 VFWD (mV)
4055 G19
SCHOTTKY
6
UW
4055 G13
Charging from USB, Low Power, IBAT vs VBAT
100 VIN = 5V VOUT = NO LOAD RPROG = 100k RCLPROG = 100k HPWR = 0 TA = 25C
Undervoltage Current Limit, Charging from VIN, IBAT vs VIN
1.6 1.4 RPROG = 34k 1.2 RPROG = 50k 1.0 0.8 0.6 0.4 0.2 RPROG = 100k HPWR = 0 4.300 4.340 VIN (V) 4.380 4.420
4055 G15
TA = 25C
80
60
40
RPROG = 100
20
0 0 0.5 1 1.5 2 2.5 VBAT (V) 3 3.5 4 4.5
0 4.260
4055 G14
Ideal Diode Forward Voltage vs Current and Temperature
900 800 VBAT = 3.5V VIN = 0V 1000 25C 0C -50C 900 800 700 600 500 400 300 200 100 0 20 40 60 80 100 120 140 160 180 200 VFWD (mV)
4055 G17
Ideal Diode Forward Voltage and Resistance vs Current
VBAT = 3.5V VIN = 0V TA = 25C
RDIO(ON) RFWD
100
125
0
0
0
20 40 60 80 100 120 140 160 180 200 VFWD (mV)
4055 G18
4055 G16
Input Connect Waveforms
VIN 5V/DIV VOUT 5V/DIV IIN 0.5A/DIV IBAT 0.5A/DIV
VBAT = 3.5V IOUT = 100mA 1ms/DIV
4055 G20
Input Disconnect Waveforms
VBAT = 3.5V IOUT = 100mA
1ms/DIV
4055 G22
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LTC4055 TYPICAL PERFOR A CE CHARACTERISTICS
Response to HPWR
HPWR 5V/DIV
WALL 5V/DIV OUT 5V/DIV IWALL 0.5A/DIV IBAT 0.5A/DIV
IIN 0.5A/DIV IBAT 0.5A/DIV VBAT = 3.5V IOUT = 50mA 250s/DIV
Response to Suspend
SUSPEND 5V/DIV OUT 5V/DIV IIN 0.5A/DIV IBAT 0.5A/DIV VBAT = 3.5V IOUT = 50mA 1ms/DIV
4055 G23
UW
WALL Connect Waveforms VIN = 0V
WALL 5V/DIV OUT 5V/DIV IWALL 0.5A/DIV IBAT 0.5A/DIV
WALL Disconnect Waveforms VIN = 0V
4055 G21
VBAT = 3.5V IOUT = 100mA RPROG = 57.6k
1ms/DIV
4055 G24
VBAT = 3.5V IOUT = 100mA RPROG = 57.6k
1ms/DIV
4055 G25
WALL Connect Waveforms VIN = 5V
WALL 5V/DIV IIN 0.5A/DIV IWALL 0.5A/DIV IBAT 0.5A/DIV WALL 5V/DIV IIN 0.5A/DIV IWALL 0.5A/DIV IBAT 0.5A/DIV
WALL Disconnect Waveforms VIN = 5V
VBAT = 3.5V IOUT = 100mA RPROG = 57.6k
1ms/DIV
4055 G26
VBAT = 3.5V IOUT = 100mA RPROG = 57.6k
1ms/DIV
4055 G27
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LTC4055
PI FU CTIO S
BAT (Pin 2): Connect to a single cell Li-Ion battery. Used as an output when charging the battery and as an input when supplying power to OUT. When the OUT pin potential drops below the BAT pin potential, an ideal diode function connects BAT to OUT and prevents VOUT from dropping more than 100mV below VBAT. A precision internal resistor divider sets the final float potential on this pin. The internal resistor divider is disconnected when IN1/IN2 and OUT are in UVLO. OUT (Pin 3): Voltage Output. Used to provide controlled power to a USB device from either USB VBUS (IN1/IN2) or the battery (BAT) when the USB is not present. Can also be used as an input for battery charging when the USB is not present and a wall adaptor is applied to this pin. Should be bypassed with at least 10F to GND. IN1/IN2 (Pin 4/Pin 1): Input Supply. Connect to USB supply, VBUS. Used as main supply while connected to USB VBUS for power control to a USB device. Input current is limited to either 20% or 100% of the current programmed by the CLPROG pin as determined by the state of the HPWR pin. Charge current (to BAT pin) supplied through the inputs is set to the current programmed by the PROG pin but will be limited by the input current limit if set greater than the input current limit. Connect IN2 to IN1 with a resistance no greater than 0.05. WALL (Pin 5): Wall Adapter Present Input. Pulling this pin above 1V will disable charging from IN1/IN2 and disconnect the power path from IN1/IN2 to OUT. The ACPR pin will also be pulled low to indicate that a wall adapter has been detected. Requires the voltage on IN1/IN2 or OUT to be 100mV greater than VBAT and greater than VUVLO to activate this function. SHDN (Pin 6): Shutdown Input. Pulling this pin greater than 1.2V will disable the entire part and place it in a low supply current mode of operation. All power paths will be disabled. A weak pull-down current is internally applied to this pin to ensure it is low at power up when the input is not being driven externally. SUSP (Pin 7): Suspend Mode Input. Pulling this pin above 1.2V will disable charging from IN1/IN2 and disconnect the power path from IN1/IN2 to OUT. The supply current will be reduced to comply with the USB specification for Suspend mode. The BAT to OUT ideal diode function will remain active as well as the ability to charge the battery from OUT. Suspend mode will reset the charge timer if VOUT is less than VBAT while in suspend mode. If VOUT is kept greater than VBAT, such as when a wall adapter is present, the charge timer will not be reset when the part is put in suspend. A weak pull-down current is internally applied to this pin to ensure it is low at power up when the input is not being driven externally. HPWR (Pin 8): High Power Select. Used to control the amount of current drawn from the USB port. A voltage greater than 1.2V on the pin will set the current limit to 100% of the current programmed by the CLPROG pin and 100% of the charge current programmed by the PROG pin. A voltage less than 0.4V on the pin will set the current limit to 20% of the current programmed by the CLPROG pin and decrease battery charge current to 16% of the current programmed by the CLPROG pin. A weak pull-down current is internally applied to this pin to ensure it is low at power up when the input is not being driven externally. CLPROG (Pin 9): Current Limit Program. Connecting a resistor, RCLPROG to ground, programs the input to output current limit. The current limit is programmed as follows:
8
U
U
U
ICL ( A) =
VCLPROG 49, 000 V * 49, 000 = RCLPROG RCLPROG
In USB applications the resistor RCLPROG should be set to no less than 105k. GND (Pin 10): Ground. PROG (Pin 11): Charge Current Program. Connecting a resistor, RPROG, to ground programs the battery charge current. The battery charge current is programmed as follows:
ICHG( A) =
VPROG 48, 500 V * 48, 500 = RPROG RPROG
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LTC4055
PI FU CTIO S
TIMER (Pin 12): Timer Capacitor. Placing a capacitor CTIMER to GND sets the timer period. The timer period is:
CTIMER * RPROG * 3 Hours 0.1F * 100k Charge time is increased as charge current is reduced due to input voltage regulation, load current and current limit selection (HPWR). t TIMER(Hours) =
Shorting the TIMER pin to GND disables the battery charging functions. ACPR (Pin 13): Wall Adapter Present Output. Active low open-drain output pin. A low on this pin indicates that the wall adapter input comparator has had its input pulled above the input threshold and power is present on IN1/IN2 or OUT (i.e., above UVLO threshold). CHRG (Pin 14): Open-Drain Charge Status Output. When the battery is being charged, the CHRG pin is pulled low by an internal N-channel MOSFET. When the timer runs out or the input supply or output supply is removed, the CHRG pin is forced to a high impedance state.
U
U
U
VNTC (Pin 15): Output Bias Voltage for NTC. A resistor from this pin to the NTC pin will set up the bias for an NTC thermistor. NTC (Pin 16): Input to the NTC Thermistor Monitoring Circuits. Under normal operation, tie a thermistor from the NTC pin to ground and a resistor of equal value from NTC to VNTC. When the voltage on this pin is above 0.74 * VVNTC (Cold, 0C) or below 0.29 * VVNTC (Hot, 50C) the timer is suspended, but not cleared, the charging is disabled and the CHRG pin remains in its former state. When the voltage on NTC comes back between 0.74 * VVNTC and 0.29 * VVNTC, the timer continues where it left off and charging is re-enabled if the battery voltage is below the recharge threshold. There is approximately 3C of temperature hysteresis associated with each of the input comparators. If the NTC function is not to be used, connect the NTC to ground. This will disable all of the LTC4055 NTC functions. Exposed Pad (Pin 17): Ground. The Exposed Pad must be soldered to a good thermally conductive PCB ground.
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LTC4055
BLOCK DIAGRA
+ -
9 100k CLPROG
1V ILIM
+ -
11 100k 8 PROG HPWR 500mA/100mA 2u 13 ACPR
1V BATTERY CHARGER
5
WALL
+ -
1V
15
VNTC CONTROL LOGIC
100k
16
0.1V
-
10 GND 6 SHDN 7 SUSP
4055 BD
10
+
-
100k
+
NTC
NTC
+
NTC ENABLE 2u 2u
W
VBUS 4 IN1 3 OUT 2 BAT 1 IN2
-+
25mV IDEAL DIODE IN1 0.2 OUT 0.2 BAT 0.2 IN2
DIE TEMP
105C
4.35V
-
TA
+
-
VR
+
CURRENT LIMIT
SOFT-START ILIM CNTL ENABLE SENSE ICHRG SOFT-START2 CHARGER CC/CV REGULATOR I/O SEL ENABLE
CURRENT CONTROL
+ - +
0.25V
BAT UV
2.8V BATTERY UVLO
-
IN1 OUT BAT
+
VOLTAGE DETECT UVLO BAT UV RECHRG OSCILLATOR
4.1V RECHARGE
-
TIMER
12
-
2COLD NTCERR 2HOT
HOLD RESET
CLK COUNTER STOP
CHRG
14
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LTC4055
OPERATIO
The LTC4055 is a complete PowerPath controller for battery-powered USB applications. The LTC4055 is designed to provide device power and Li-ion battery charging from the USB VBUS while maintaining the current limits as specified in the USB specification. This is accomplished by reducing battery charge current as output/load current is increased. In this scenario, the available bus current is maximized in an effort to minimize battery charge time. An ideal diode function provides power from the battery when output/load current exceeds the input current limit set for the part or when input power is removed. The advantage to powering the load through the ideal diode (rather than connecting the load directly to the battery) is that when the bus is connected and the battery is fully charged, the battery remains fully charged until bus power is removed. Once bus 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.
WALL ADAPTER
VBUS
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Another advantage to powering the load from the bus when the bus is available is in cases where the load is a switching regulator. The input power to a switching regulator can be thought of as constant. A higher voltage across a constant power load will require less current. Less load current in USB applications means more available charge current. More charge current translates to shorter charge times. The LTC4055 also has the ability to accommodate power from a wall adapter. Wall adapter power can be connected to the output (load side) of the LTC4055 through an external device such as a power Schottky or FET, as shown in Figure 1. The LTC4055 has the unique ability to use the output, which is powered by the wall adapter, as an alternate path to charge the battery while providing power to the load. A wall adapter comparator on the LTC4055 can be configured to detect the presence of the wall adapter and shut off the connection to the USB to prevent reverse conduction out to the bus.
4 1 IN1 OUT 3 LOAD IN2 INPUT CHARGER CONTROL ENABLE CURRENT LIMIT CONTROL ENABLE OUTPUT CHARGER CONTROL ENABLE IDEAL BAT WALL 2
+ + -
UVLO
5
Li-Ion
1V
4055 F01
Figure 1. Simplified Block Diagram--PowerPath
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11
LTC4055
OPERATIO
WALL PRESENT Y X X X X X N WALL PRESENT Y X X X X X N WALL PRESENT N X X X X Y WALL PRESENT X X X X
Table 1. Operating Modes--PowerPath States Current Limited Input Power (IN1/IN2 to OUT)
SHUTDOWN X Y X X X X N SHUTDOWN X Y X X X X N SHUTDOWN X Y X X X N SHUTDOWN Y X X N SUSPEND X X Y X X X N SUSPEND X X Y X X X N SUSPEND X X X X X X SUSPEND X X X X VIN > 3.8V X X X N X X Y VIN > 4.35V X X X N X X Y VOUT > 4.35V X X N X X Y VBAT > 2.8V X N X Y VIN > (VOUT + 100mV) X X X X N X Y VIN > (VOUT + 100mV) X X X X N X Y VOUT > (VIN + 100mV) X X X N X Y VBAT > VOUT X X N Y VIN > (VBAT + 100mV) X X X X X N Y VIN > (VBAT + 100mV) X X X X X N Y VOUT > (VBAT + 100mV) X X X X N Y VIN X X X X CURRENT LIMIT ENABLED N N N N N N Y INPUT CHARGER ENABLED N N N N N N Y OUTPUT CHARGER ENABLED N N N N N Y DIODE ENABLED N N N Y
Input Powered Charger (IN1/IN2 to BAT)
Output Powered Charger (OUT to BAT)
Ideal Diode (BAT to OUT)
Table 2. Operating Modes--Pin Currents vs Programmed Currents (Charging from IN1/IN2)
PROGRAMMING ICL = ICHG OUTPUT CURRENT IOUT < ICL IOUT = ICL = ICHG IOUT > ICL IOUT < (ICL - ICHG) IOUT > (ICL - ICHG) IOUT = ICL IOUT > ICL IOUT < ICL IOUT > ICL* BATTERY CURRENT IBAT = ICHG - IOUT IBAT = 0 IBAT = ICL - IOUT IBAT = ICHG IBAT = ICL - IOUT IBAT = 0 IBAT = ICL - IOUT IBAT = ICL - IOUT IBAT = ICL - IOUT INPUT CURRENT IIN = IQ + ICL IIN = IQ + ICL IIN = IQ + ICL IIN = IQ + ICHG + IOUT IIN = IQ + ICL IIN = IQ + ICL IIN = IQ + ICL IIN = IQ + ICL IIN = IQ + ICL
ICHG < ICL
ICL < ICHG
*Charge current shuts off when VOUT drops below VBAT, i.e., when IOUT exceeds ICL.
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Operational State Diagram
SHUTDOWN SHUTDOWN * CHARGING DISABLED * ALL SWITCHES OPEN SHDN UVLO * CHARGING DISABLED * BATTERY POWERS VOUT BATTERY > 2.8V LOW BATTERY * CHRG IS HI-Z * BATTERY POWER TO VOUT--DISABLED POWER APPLIED TO VIN VIN POWERS PART WALL ADAPTER PRESENT * CURRENT LIMIT SWITCH FROM VIN TO VOUT--ON WALL ADAPTER PRESENT VOUT POWERS PART * CURRENT LIMIT SWITCH FROM VIN TO VOUT--OFF * ACPR PULLED LOW BATTERY < 2.8V
BATTERY POWERS VOUT
VOUT > VBAT
* CHARGING SUSPENDED * CHRG HIGH-Z
VOUT < VBAT
BATTERY < 4.1V
BATTERY > 4.1V AND CHARGER TIMED OUT
BATTERY > 4.1V AND CHARGER TIMED OUT
BATTERY < 4.1V
BATTERY POWERS VOUT * CURRENT LIMIT SWITCH FROM VIN TO VOUT--ON * BATTERY CHARGING ON * VIN CHARGE SWITCH OPEN * CHRG PULLED LOW WALL ADAPTER PRESENT
VOUT > VBAT
VIN CHARGING BATTERY
VOUT CHARGING BATTERY
* CHARGING SUSPENDED * CHRG PULLED LOW
VOUT < VBAT
* CURRENT LIMIT SWITCH FROM VIN TO VOUT--OFF * BATTERY CHARGING ON * VIN CHARGE SWITCH OPEN * CHRG PULLED LOW * ACPR PULLED LOW
TEMP OK AND BATTERY > 2.8V TEMP NOT OK NTC FAULT * BATTERY CHARGING SUSPENDED * CHRG PULLED LOW BATTERY < 2.8V
TEMP NOT OK
TEMP OK AND BATTERY > 2.8V NTC FAULT BATTERY < 2.8V * BATTERY CHARGING SUSPENDED * CHRG PULLED LOW BATTERY > 2.8V
BATTERY > 2.8V
TEMP OK AND BATTERY < 2.8V TEMP NOT OK VIN CHARGING LOW BATTERY
TEMP NOT OK
TEMP OK AND BATTERY < 2.8V VOUT CHARGING LOW BATTERY
* BATTERY CHARGING ON * CHARGE CURRENT C/10 * VOUT CHARGE SWITCH OPEN * CHRG PULLED LOW * BATTERY POWER TO VOUT IS OFF
WALL ADAPTER PRESENT
* CURRENT LIMIT SWITCH FROM VIN TO VOUT--OFF * BATTERY CHARGING ON * CHARGE CURRENT C/10 * VIN CHARGE SWITCH OPEN * CHRG PULLED LOW * ACPR PULLED LOW
4055 SD
BAD BATTERY * CHRG IS HI-Z * BATTERY POWER TO VOUT--DISABLED
1/4 TIMEOUT AND BATTERY < 2.8V
1/4 TIMEOUT AND BATTERY < 2.8V
BAD BATTERY * CHRG IS HI-Z * BATTERY POWER TO VOUT--DISABLED
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LTC4055
OPERATIO
(VIN AND VOUT) < UVLO
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LTC4055
OPERATIO
USB CURRENT LIMIT AND CHARGE CURRENT CONTROL The current limit and charger control circuits of the LTC4055 are designed to limit input current as well as control battery charge current as a function of IOUT. The programmed current limit, ICL is defined as:
49, 000 49, 000 V ICL = * VCLPROG = RCLPROG RCLPROG
The programmed battery charge current, ICHG, is defined as:
48, 500 48, 500 V ICHG = * VPROG = RPROG RPROG
Input current, IIN, is equal to the sum of the BAT pin output current and the OUT pin output current. IIN = IOUT + IBAT The current limiting circuitry in the LTC4055 can and should be configured to limit current to 500mA for USB applications (selectable using the HPWR pin and programmed using the CLPROG pin). When programmed for 500mA current limit and 500mA or more of charging current, powered from IN1/IN2 and battery charging is active, control circuitry within the
600 500 400
CURRENT (mA)
CURRENT (mA)
IIN
300 200 100 0 -100 IBAT CHARGING
60 40 20 0 -20
ILOAD
CURRENT (mA)
0
100
200
300 400 ILOAD (mA)
(2a) High Power Mode/Full Charge (RPROG = RCLPROG = 97.6k)
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LTC4055 reduces the battery charging current such that the sum of the battery charge current and the load current does not exceed 500mA (100mA when HPWR is low, see Figure 2) The battery charging current goes to zero when load current exceeds 500mA (80mA when HPWR is low). If the load current is greater than the current limit, the output voltage will drop to just under the battery voltage where the ideal diode circuit will take over and the excess load current will be drawn from the battery (shaded region in Figure 2). PROGRAMMING CURRENT LIMIT The formula for programming current limit is:
ICL = ICLPROG * 49, 000 =
VCLPROG * 49, 000 RCLPROG
where VCLPROG is the CLPROG pin voltage and RCLPROG is the total resistance from the CLPROG pin to ground. For example, if typical 490mA current limit is required, calculate: RCLPROG = 1V * 49, 000 = 100k 490mA
In USB applications, the minimum value for RCLPROG should be 105k. This will prevent the application current
600 500
120 100 80 ILOAD IIN
IIN 400 ILOAD 300 200 100 0 -100 IBAT CHARGING IBAT = ICL - IOUT IBAT = ICHG
IBAT CHARGING
500
600 IBAT (IDEAL DIODE)
4055 F02a
0
20
40
60 80 ILOAD (mA)
100
120 IBAT (IDEAL DIODE)
4055 F02b
0
100
200
300 400 ILOAD (mA)
500
600 IBAT (IDEAL DIODE)
4055 F02c
(2b) Low Power Mode/Full Charge (RPROG = RCLPROG = 97.6k)
(2c) High Power Mode with ICL = 500mA and ICHG = 250mA (RPROG = 196k, RCLPROG = 97.6k)
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Figure 2. Input and Battery Currents as a Function of Load Current
LTC4055
OPERATIO
from exceeding 500mA due to LTC4055 tolerances and quiescent currents. This will give a typical current limit of approximately 467mA in high power mode (HPWR = 1) or 92mA in low power mode (HPWR = 0). For best stability over temperature and time, 1% metal film resistors are recommended. Battery Charger The battery charger circuits of the LTC4055 are designed for charging single cell lithium-ion batteries. Featuring an internal P-channel power MOSFET, the charger uses a constant-current/constant-voltage charge algorithm with programmable current and a programmable timer for charge termination. Charge current can be programmed up to 1A. The final float voltage accuracy is 0.8% typical. No blocking diode or sense resistor is required when charging through IN1/IN2. The CHRG open-drain status output provides information regarding the charging status of the LTC4055 at all times. An NTC input provides the option of charge qualification using battery temperature. An internal thermal limit reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 105C. This feature protects the LTC4055 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 LTC4055. Another benefit of the LTC4055 thermal limit is that charge current can be set according to typical, not worst-case, ambient temperatures for a given application with the assurance that the charger will automatically reduce the current in worst-case conditions. An internal voltage regulation circuit, called undervoltage current limit, UVCL, reduces the programmed charge current to keep the voltage on VIN or VOUT at least 4.4V. This feature prevents the charger from cycling in and out of undervoltage lockout due to resistive drops in the USB or wall adapter cabling. The charge cycle begins when the voltage at the input (IN1/IN2) rises above the input UVLO level and the battery voltage is below the recharge threshold. No charge current actually flows until the input voltage is greater than the VUVCL level. At the beginning of the charge cycle, if the
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battery voltage is below 2.8V, the charger goes into trickle charge mode to bring the cell voltage up to a safe level for charging. The charger goes into the fast charge constantcurrent mode once the voltage on the BAT pin rises above 2.8V. In constant current mode, the charge current is set by RPROG. When the battery approaches the final float voltage, the charge current begins to decrease as the LTC4055 switches to constant-voltage mode. An external capacitor on the TIMER pin sets the total minimum charge time. When this time elapses the charge cycle terminates and the CHRG pin assumes a high impedance state. While charging in constant-current mode, if the charge current is decreased due to load current, undervoltage charge current limiting or thermal regulation the charging time is automatically increased. In other words, the charge time is extended inversely proportional to charge current delivered to the battery. For lithium-ion and similar batteries that require accurate final float potential, the internal bandgap reference, voltage amplifier and the resistor divider provide regulation with 1% maximum accuracy. TRICKLE CHARGE AND DEFECTIVE BATTERY DETECTION At the beginning of a charge cycle, if the battery voltage is low (below 2.8V) the charger goes into trickle charge reducing the charge current to 10% of the full-scale current. If the low battery voltage persists for one quarter of the total charge time, the battery is assumed to be defective, the charge cycle is terminated and the CHRG pin output assumes a high impedance state. If for any reason the battery voltage rises above ~2.8V, 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, cycle the TIMER pin to 0V or cycle the SHDN pin to 0V. PROGRAMMING CHARGE CURRENT The formula for programming the battery charge current, when not being limited, is:
ICHG = IPROG * 48, 500 = VPROG * 48, 500 RPROG
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15
LTC4055
OPERATIO
where VPROG is the PROG pin voltage and RPROG is the total resistance from the PROG pin to ground. For example, if typical 485mA charge current is required, calculate: RPROG = 1V * 48, 500 = 100k 485mA
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. 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 and is also a function of the resistance on PROG. Typically the charge time is:
C *R * 3 Hours t TIMER(Hours) = TIMER PROG 0.1F * 100k
The timer starts when an input voltage greater than the undervoltage lockout threshold level is applied, or when leaving shutdown and the voltage on the battery is less than 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 the recharge threshold, the timer will not start and charging 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. The LTC4055 has a feature that extends charge time automatically. Charge time is extended if the charge current in constant-current mode is reduced due to load current, undervoltage charge current limiting or thermal regulation. This change in charge time is inversely proportional to the change in charge current. As the LTC4055 approaches constant-voltage mode the charge current begins to drop. This change in charge current is part of the normal charging operation of the part and should not affect the timer duration. Therefore, the LTC4055 detects
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that the change in charge current is due to voltage mode, and increases the timer period back to its programmed operating period. 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 to indicate that the charging has stopped. Connecting the TIMER pin to ground disables the battery charger. CHRG STATUS OUTPUT PIN When the charge cycle starts, the CHRG pin is pulled to ground by an internal N-channel MOSFET capable of driving an LED. After a time-out occurs, the pin assumes a high impedance state. NTC Thermistor The battery temperature is measured by placing a negative temperature coefficient (NTC) thermistor close to the battery pack. The NTC circuitry is shown in Figure 3. To use this feature, connect the NTC thermistor, RNTC, between the NTC pin and ground and a resistor, RNOM, from the NTC pin to VNTC. RNOM should be a 1% resistor with a value equal to the value of the chosen NTC thermistor at 25C (this value is 10k for a Vishay NTHS0603N02N1002J thermistor). The LTC4055 goes into hold mode when the resistance, RHOT, of the NTC thermistor drops to 0.41 times the value of RNOM or approximately 4.1k, which should be at 50C. The hold mode freezes the timer and stops the charge cycle until the thermistor indicates a return to a valid temperature. As the temperature drops, the resistance of the NTC thermistor rises. The LTC4055 is designed to go into hold mode when the value of the NTC thermistor increases to 2.82 times the value of RNOM. This resistance is RCOLD. For a Vishay NTHS0603N02N1002J thermistor, this value is 28.2k which corresponds to approximately 0C. The hot and cold comparators each have approximately 3C of hysteresis to prevent oscillation about the trip point. Grounding the NTC pin disables the NTC function.
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LTC4055
OPERATIO
VNTC 15 RNOM 100k NTC 16
RNTC 100k 0.29 * VNTC
THERMISTORS The LTC4055 NTC trip points were designed to work with thermistors whose resistance-temperature characteristics follow Vishay Dale's "R-T Curve 2." 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 of RCOLD to RHOT is about 7.0 will also work (Vishay Dale R-T Curve 2 shows a ratio of RCOLD to RHOT of 2.815/0.4086 = 6.89). Power conscious designs may want to use thermistors whose room temperature value is greater than 10k. Vishay Dale has a number of values of thermistor from 10k to 100k that follow the "R-T Curve 1." Using these as indicated in the NTC Thermistor section will give temperature trip points of approximately 3C and 47C, a delta of 44C. This delta in temperature can be moved in either direction by changing the value of RNOM with respect to RNTC. Increasing RNOM will move both trip points to lower temperatures. Likewise a decrease in RNOM with respect to RNTC will move the trip points to higher temperatures. To
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LTC4055 NTC BLOCK 0.74 * VNTC VNTC 15 RNOM 121k NTC 16 0.74 * VNTC LTC4055 NTC BLOCK
-
TOO_COLD
-
TOO_COLD
+
+
-
TOO_HOT
R1 13.3k 0.29 * VNTC RNTC 100k
-
TOO_HOT
+
+
+
NTC_ENABLE 0.1V
+
NTC_ENABLE 0.1V
-
4055 F03a
-
4055 F03b
(3a) Figure 3. NTC Circuits
(3b)
calculate RNOM for a shift to lower temperature for example, use the following equation: RNOM = RCOLD * RNTC at 25C 2.815
where RCOLD is the resistance ratio of RNTC at the desired cold temperature trip point. If you want to shift the trip points to higher temperatures use the following equation: RNOM = RHOT * RNTC at 25C 0.4086
where RHOT is the resistance ratio of RNTC at the desired hot temperature trip point. Here is an example using a 100k R-T Curve 1 thermistor from Vishay Dale. The difference between the trip points is 44C, from before, and we want the cold trip point to be 0C, which would put the hot trip point at 44C. The RNOM needed is calculated as follows:
RNOM = RCOLD * RNTC at 25C 2.815 3.266 = * 100k = 116k 2.815
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LTC4055
OPERATIO
The nearest 1% value for RNOM is 115k. This is the value used to bias the NTC thermistor to get cold and hot trip points of approximately 0C and 44C respectively. To extend the delta between the cold and hot trip points a resistor, R1, can be added in series with RNTC (see Figure 3b). The values of the resistors are calculated as follows:
RCOLD - RHOT 2.815 - 0.4086 0.4086 R1 = * (RCOLD - RHOT ) - RHOT 2.815 - 0.4086 RNOM =
where RNOM is the value of the bias resistor, RHOT and RCOLD are the values of RNTC at the desired temperature trip points. Continuing the example from before with a desired hot trip point of 50C:
RNOM = RCOLD - RHOT 100k * (3.266 - 0.3602) = 2.815 - 0.4086 2.815 - 0.4086 = 120.8k, 121k is nearest 1%
0.4086 R1 = 100k * * (3.266 - 0.3602) - 0.3602 2.815 - 0.4086 = 13.3k, 13.3k is nearest 1%
The final solution is as shown if Figure 3b where RNOM = 121k, R1 = 13.3k and RNTC=100k at 25C. CURRENT LIMIT UNDERVOLTAGE LOCKOUT An internal undervoltage lockout circuit monitors the input voltage and keeps the current limit circuits of the part in shutdown mode until VIN rises above the undervoltage lockout threshold. The current limit UVLO circuit has a built-in hysteresis of 125mV. Furthermore, to protect against reverse current in the power MOSFET, the current limit UVLO circuit keeps the current limit shutdown if VOUT exceeds VIN. If the current limit UVLO comparator is tripped, the current limit circuits will not come out of shutdown until VOUT falls 50mV below the VIN voltage.
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CHARGER UNDERVOLTAGE LOCKOUT Internal undervoltage lockout circuits monitor the VIN and VOUT voltages and keep the charger circuits of the part shut down until VIN or VOUT rises above the under-voltage lockout threshold. The charger UVLO circuit has a built-in hysteresis of 125mV. Furthermore, to protect against reverse current in the power MOSFET, the charger UVLO circuit keeps the charger shutdown if VBAT exceeds VOUT. If the charger UVLO comparator is tripped, the charger circuits will not come out of shutdown until VOUT exceeds VBAT by 50mV. SHUTDOWN The LTC4055 can be shut down by forcing the SHDN pin greater than 1V. In shutdown, the currents on IN1/IN2, OUT and BAT are decreased to less than 2.5A and the internal battery charge timer is reset. All power paths are put in a Hi-Z state. SUSPEND The LTC4055 can be put in suspend mode by forcing the SUSP pin greater than 1V. In suspend mode the ideal diode function from BAT to OUT and the output charger are kept alive. The rest of the part is shut down to conserve current and the battery charge timer is reset if VOUT becomes less than VBAT. VIN and Wall Adapter 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 hot power source. For more information, refer to Application Note 88.
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LTC4055
OPERATIO
Selecting WALL Input Resistors The WALL input pin identifies the presence of a wall adapter. This information is used to disconnect the inputs IN1/IN2 from the OUT pin in order to prevent back conduction to whatever may be connected to the inputs. It also forces the ACPR pin low when the voltage at the WALL pin exceeds the input threshold. The WALL pin has a 1V rising threshold and approximately 30mV of hysteresis. It needs to be noted that this function is disabled when the only power applied to the part is from the battery. Therefore the 1V threshold only applies when the voltage on either IN1/IN2 or OUT is 100mV greater than the voltage on BAT and the voltage on IN1/IN2 or OUT is greater than the VUVLO (3.8V typ) threshold. The wall adapter detection threshold is set by the following equation:
R1 VTH( Adapter ) = VWALL * 1 + R2 R1 VHYST ( Adapter ) = VWALL-HYST * 1 + R2
where VTH(Adapter) is the wall adapter detection threshold, VWALL is the WALL pin rising threshold (typically 1V), R1 is the resistor from the wall adapter input to WALL and R2 is the resistor from WALL to GND. Consider an example where the VTH(Adapter) is to be set somewhere around 4.5V. Resistance on the WALL pin should be kept relatively low (~10k) in order to prevent false tripping of the wall comparator due to leakages associated with the switching element used to connect the adapter to OUT. Pick R2 to be 10k and solve for R1. V ( Adapter ) R1 = R2 * TH - 1 VWALL 4.5 - 1 = 10k * 3.5 = 35k R1 = 10k * 1
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The nearest 1% resistor is 34.8k. Therefore R1 = 34.8k and the rising trip point should be 4.48V. 34.8 VHYST ( Adapter ) 30mV * 1 + 134mV 10 The hysteresis is going to be approximately 134mV for this example. Power Dissipation The conditions that cause the LTC4055 to reduce charge current due to the thermal protection feedback can be approximated by considering the power dissipated in the part. For high charge currents and a wall adapter applied to VOUT, the LTC4055 power dissipation is approximately: PD = (VOUT - VBAT) * IBAT Where PD is the power dissipated, VOUT is the supply voltage, VBAT is the battery voltage and IBAT is the battery charge current. It is not necessary to perform any worstcase power dissipation scenarios because the LTC4055 will automatically reduce the charge current to maintain the die temperature at approximately 105C. However, the approximate ambient temperature at which the thermal feedback begins to protect the IC is: TA = 105C - PD * JA TA = 105C - (VOUT - VBAT) * IBAT * JA Example: An LTC4055 operating from a wall adapter with 5V at VOUT providing 0.8A to a 3V Li-Ion battery. The ambient temperature above, which the LTC4055 will begin to reduce the 0.8A charge current, is approximately: TA = 105C - (5V - 3V) * 0.8A * 37C/W TA = 105C - 1.6W * 37C/W = 105C - 59C = 46C
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LTC4055
OPERATIO
The LTC4055 can be used above 46C, but the charge current will be reduced below 0.8A. The charge current at a given ambient temperature can be approximated by:
IBAT
105C - TA = ( VOUT - VBAT ) * JA
Consider the above example with an ambient temperature of 55C. The charge current will be reduced to approximately:
IBAT =
105C - 55C 50C = = 0.675A (5V - 3V) * 37C / W 74C /A
Board Layout Considerations In order to be able to deliver maximum charge current under all conditions, it is critical that the exposed pad on the backside of the LTC4055 package is soldered to the board. Correctly soldered to a 2500mm2 double-sided 1oz. copper board, the LTC4055 has a thermal resistance of approximately 37C/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 37C/W. As an example, a correctly soldered LTC4055 can deliver over 1A to a battery from a 5V supply
CURRENT (A)
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at room temperature. Without a backside thermal connection, this number could drop to less than 500mA. STABILITY The constant-voltage mode feedback loop is stable without any compensation when a battery is connected. However, a 1F capacitor with a 1 series resistor to GND is recommended at the BAT pin to keep ripple voltage low when the battery is disconnected. Ideal Diode from BAT to OUT Forward regulation for the LTC4055 from BAT to OUT has three operational ranges, depending on the magnitude of the load current. For small load currents, the LTC4055 will provide a constant voltage drop; this operating mode is referred to as "constant VON" regulation. As the current exceeds IFWD, the voltage drop will increase linearly with the current with a slope of 1/RDIO,ON; this operating mode is referred to as "constant RON" regulation. As the current increases further, exceeding IMAX, the forward voltage drop will increase rapidly; this operating mode is referred to as "constant ION" regulation. The characteristics for the following parameters: RFWD, RON, VFWD, and IFWD are specified with the aid of Figure 4.
LTC4055 IMAX CONSTANT ION SLOPE: 1/RDIO,ON CONSTANT RON IFWD SCHOTTKY DIODE SLOPE: 1/RFWD CONSTANT VON 0 VFWD
4055 F04
FORWARD VOLTAGE (V)
Figure 4. LTC4055 vs Schottky Diode Forward Voltage Drop
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LTC4055
TYPICAL APPLICATIO S
LTC4055 Configured for USB Application with Wall Adapter Figure 5 shows an LTC4055 configured for USB applications with the optional wall adapter input. The programming resistor (RCLPROG) is set to 105k which sets up a nominal current limit of 467mA in high power mode (92mA in low power). This is done to prevent the various tolerances in the part and programming resistors from
5V WALL ADAPTER INPUT 5V (NOM) FROM USB CABLE VBUS
R3 1 10F R1 34.8k R2 10k
Figure 5. USB Power Control Application with Wall Adapter Input
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allowing the input current supplied by VBUS to exceed the 500mA/100mA limits. The programming resistor (RPROG) with a value of 60.4k sets up a nominal charge current of approximately 800mA. Note that this is the charge current when the wall adapter is present. When the wall adapter is absent, the current limit supersedes the charge current programming and charge current is limited to 467mA.
IN1 IN2 CHRG ACPR WALL RNTCBIAS 100k NTC C TIMER 100k 0.1F VNTC NTC TIMER PROG CLPROG LTC4055
OUT BAT
TO LDOs, REGs, ETC
+
10F Li-Ion CELL SUSPEND USB POWER 500mA/100mA SELECT SHUTDOWN
SUSP HPWR SHDN GND
RPROG 60.4k
RCLPROG 105k
4055 F05
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21
LTC4055
TYPICAL APPLICATIO S
USB Hosting Application: The LTC4055's IN1 and IN2 are Set Hi-Z by Pulling the SUSP Pin Above 1.2V In applications where the power is required to go back out on to the USB VBUS the LTC4055 can be configured to turn off its input power path, IN1 and IN2. Forcing the SUSP input pin above 1.2V does this. Figure 6 shows the
5V (NOM) FROM USB CABLE VBUS 5V WALL ADAPTER INPUT IN1 R1 34.8k R2 10k SUSP USB CONTROLLER R3 100k NTC C TIMER 100k 0.1F VNTC NTC TIMER PROG CLPROG RPROG 100k IN2 WALL LTC4055 CHRG ACPR HPWR SHDN GND 500mA/100mA SELECT SHUTDOWN OUT BAT 10F TO LDOs, REGs, ETC
1F
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application circuit. The wall adapter or the battery can still provide power to OUT, which in turn can provide power to VBUS when commanded from the USB controller. The ability to charge the battery is enabled when the wall adapter is present.
DC/DC VOUT CONVERTER VIN EN
+
Li-Ion CELL
RCLPROG 105k
4055 F06
Figure 6. USB Hosting Application
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LTC4055
PACKAGE DESCRIPTIO
4.35 0.05 2.15 0.05 2.90 0.05 (4 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS BOTTOM VIEW--EXPOSED PAD 4.00 0.10 (4 SIDES) PIN 1 TOP MARK (NOTE 6) 2.15 0.10 (4-SIDES) 0.75 0.05 R = 0.115 TYP 0.55 0.20 15 16
NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC) 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
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.
U
UF Package 16-Lead Plastic QFN (4mm x 4mm)
(Reference LTC DWG # 05-08-1692)
0.72 0.05 PACKAGE OUTLINE 0.30 0.05 0.65 BSC 1 2
(UF) QFN 1103
0.200 REF 0.00 - 0.05
0.30 0.05 0.65 BSC
4055f
23
LTC4055
TYPICAL APPLICATIO
ADAPTER 4.5V TO 5.5V
Adapter Diode Replaced with LTC4411 "Ideal Diode" for Improved Efficiency
LTC4411 1 C5 1F R10 35.8k C1 10F 5 R9 10k 6 7 8 17 2 3 VIN GND CTL STAT 4 VOUT 5 C3 10F SYSTEM LOAD OUTPUT
USB 4.35V TO 5.5V
RELATED PARTS
PART NUMBER Battery Chargers LTC1733 LTC1734 LTC1734L LTC4002 LTC4052 LTC4053 LTC4054 LTC4057 LTC4058 LTC4059 LTC4411/LTC4412 DESCRIPTION Monolithic Lithium-Ion Linear Battery Charger Lithium-Ion Linear Battery Charger in ThinSOTTM Lithium-Ion Linear Battery Charger in ThinSOT Switch Mode Lithium-Ion Battery Charger 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 Low Loss PowerPathTM Controller in ThinSOT COMMENTS Standalone Charger with Programmable Timer, Up to 1.5A Charge Current 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 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 Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes 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, MS10 Package 95% Efficiency, VIN = 2.5V to 5.5V, VOUT = 2.5V, IQ = 25A, ISD < 1A, MS Package Seamless Transition Between Power Sources: USB, Wall Adapter and Battery; 95% Efficient DC/DC Conversion
4055f
Power Management LTC3405/LTC3405A 300mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter LTC3406/LTC3406A 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter LTC3411 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter LTC3440 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter LTC3455 Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger 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 q FAX: (408) 434-0507
q
U
+Li-Ion 4 IN1 WALL NTC SHDN VNTC SUSP HPWR ACPR EXPOSED PAD CLPROG GND PROG TIMER 9 R2 105k 10 11 R3 68.1k 12 C2 0.1F
4055 TA03
3 OUT
2 BAT
1 IN2 16 15 R5 10k 14 13 USB CURRENT 100mA-500mA ADAPTER CURRENT 700mA
NTC
LTC4055 CHRG
LT/TP 0404 1K * PRINTED IN THE USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2004

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