LTC4075X

LTC4075/LTC4075X Dual Input USB/AC Adapter Standalone Li-Ion Battery Chargers FEATURES ■ ■ ■ DESCRIPTIO ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 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 No External MOSFET, Sense Resistor or Blocking Diode Needed Thermal Regulation Maximizes Charging Rate Without Risk of Overheating* Preset Charge Voltage with ±0.6% Accuracy Programmable Charge Current Termination 18µA USB Suspend Current in Shutdown Independent “Power Present” Status Outputs Charge Status Output Automatic Recharge Available Without Trickle Charge (LTC4075X) Available in a Thermally Enhanced, Low Profile (0.75mm) 10-Lead (3mm × 3mm) DFN Package The LTC®4075/LTC4075X are standalone linear chargers that are capable of charging a single-cell Li-Ion battery from both wall adapter and USB inputs. The chargers 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 LTC4075 terminates the charge cycle when the charge current drops below the programmed termination threshold after the final float voltage is reached. With power applied to both inputs, the LTC4075/LTC4075X can be put into shutdown mode reducing the DCIN supply current to 20µA, the USBIN supply current to 10µA, and the battery drain current to less than 2µA. Other features include automatic recharge, undervoltage lockout, charge status outputs, and “power present” status outputs to indicate the presence of wall adapter or USB power. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Protected by U.S. patents, including 6522118, 6700364 APPLICATIO S ■ ■ ■ ■ Cellular Telephones Handheld Computers Portable MP3 Players Digital Cameras TYPICAL APPLICATIO WALL ADAPTER USB PORT 1µF 1µF LTC4075 DCIN USBIN IUSB 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 –2.5 0 0.5 1.0 2.0 1.5 TIME (HR) 2.5 3.0 4075Xf 4075 TA01b Dual Input Battery Charger for Single-Cell Li-Ion 800mA (WALL) 500mA (USB) BAT BATTERY CHARGE VOLTAGE (V) CURRENT (mA) + 2k 1% 4075 TA01 DCIN VOLTAGE (V) 2k IDC 1% 1.24k 1% 4.2V SINGLE CELL Li-Ion BATTERY ITERM GND U CONSTANT VOLTAGE USBIN = 5V TA = 25°C RIDC = 1.25k RIUSB = 2k U U 1 LTC4075/LTC4075X ABSOLUTE (Note 1) AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW USBIN IUSB ITERM PWR CHRG 1 2 3 4 5 11 10 DCIN 9 BAT 8 IDC 7 USBPWR 6 ENABLE Input Supply Voltage (DCIN, USBIN) ........... –0.3 to 10V EN, ⎯C⎯H⎯R⎯G, ⎯P⎯W⎯R, USBPWR.......................... –0.3 to 10V BAT, IDC, IUSB, ITERM .................................. –0.3 to 7V DCIN Pin Current (Note 7) ..........................................1A USBIN Pin Current (Note 7) .................................700mA BAT Pin Current (Note 7) ............................................1A BAT Short-Circuit Duration............................Continuous Maximum Junction Temperature .......................... 125°C Operating Temperature Range (Note 2) .. –40°C to 85°C Storage Temperature Range.................. –65°C to 125°C ORDER PART NUMBER LTC4075EDD LTC4075XEDD DD PART MARKING LBSC LBRK DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 40°C/W (NOTE 3) EXPOSED PAD IS GND (PIN 11) MUST BE SOLDERED TO PCB Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS SYMBOL VDCIN VUSBIN IDCIN PARAMETER Supply Voltage Supply Voltage DCIN Supply Current The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VDCIN = 5V, VUSBIN = 5V unless otherwise noted. CONDITIONS ● ● MIN 4.3 4.3 TYP MAX 8 8 800 100 40 800 100 36 20 4.225 4.242 840 500 107 –6 –2 ±2 1.05 1.05 110 55 11.5 6 100 65 3 4.3 4.1 UNITS V V µA µA µA µA µA µA µA V V mA mA mA µA µA µA V V mA mA mA mA mA mA V mV V mV V mV 4075Xf Charge Mode (Note 4), RIDC = 10k Standby Mode; Charge Terminated Shutdown Mode (ENABLE = 5V) Charge Mode (Note 5), RIUSB = 10k, VDCIN = 0V Standby Mode; Charge Terminated, VDCIN = 0V Shutdown (VDCIN = 0V, ENABLE = 0V) VDCIN > VUSBIN IBAT = 1mA IBAT = 1mA, 0°C < TA < 85°C RIDC = 1.25k, Constant-Current Mode RIUSB = 2.1k, Constant-Current Mode 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 VBAT < VTRIKL; RIDC = 1.25k VBAT < VTRIKL; RIUSB = 2.1k VBAT Rising Hysteresis From Low to High Hysteresis From Low to High Hysteresis ● ● ● ● 250 50 20 250 50 18 10 4.2 4.2 800 476 100 –3 –1 ±1 1 1 100 50 10 5 80 47.5 2.9 100 4.15 200 3.95 200 IUSBIN USBIN Supply Current VFLOAT IBAT Regulated Output (Float) Voltage BAT Pin Current ● ● ● 4.175 4.158 760 450 93 VIDC VIUSB ITERMINATE IDC Pin Regulated Voltage IUSB Pin Regulated Voltage Charge Current Termination Threshold ● ● ● ● ITRIKL VTRIKL VUVDC VUVUSB Trickle Charge Current (Note 6) Trickle Charge Threshold (Note 6) DCIN Undervoltage Lockout Voltage USBIN Undervoltage Lockout Voltage 0.95 0.95 90 45 8.5 4 60 30 2.8 4 3.8 2 U W U U WW W LTC4075/LTC4075X ELECTRICAL CHARACTERISTICS SYMBOL VASD-DC VASD-USB VENABLE RENABLE V⎯C⎯H⎯R⎯G V⎯P⎯W⎯R VUSBPWR ΔVRECHRG tRECHRG tTERMINATE tSS RON-DC RON-USB TLIM PARAMETER VDCIN – VBAT Lockout Threshold VUSBIN – VBAT Lockout Threshold ENABLE Input Threshold Voltage ENABLE Pulldown Resistance ⎯C⎯H⎯R⎯G Output Low Voltage ⎯P⎯W⎯R Output Low Voltage USBPWR Output Low Voltage Recharge Battery Threshold 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 = 25°C. VDCIN = 5V, VUSBIN = 5V unless otherwise noted. CONDITIONS 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 140 20 140 20 0.4 1.2 TYP 180 50 180 50 0.7 2 0.35 0.35 0.35 100 6 1.5 250 400 550 105 MAX 220 80 220 80 1 5 0.6 0.6 0.6 135 9 2.2 325 UNITS mV mV mV mV V MΩ V V V mV ms ms µs mΩ mΩ °C I⎯C⎯H⎯R⎯G = 5mA I⎯P⎯W⎯R = 5mA IUSBPWR = 300µA VFLOAT – VRECHRG, 0°C < TA < 85°C VBAT from High to Low IBAT Drops Below Termination Threshold IBAT = 0 to Full-Scale 65 3 0.8 175 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC4075E/LTC4075XE are guaranteed to meet the performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Failure to correctly solder the exposed backside of the package to the PC board will result in a thermal resistance much higher than 40°C/W. See Thermal Considerations. Note 4: Supply current includes IDC and ITERM pin current (approximately 100µA 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 100µA each) but does not include any current delivered to the battery through the BAT pin. Note 6: This parameter is not applicable to the LTC4075X. Note 7: Guaranteed by long term current density limitations. 4075Xf 3 LTC4075/LTC4075X 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) 4075X G01 VDCIN = VUSBIN = 5V 4.200 4.195 4.190 4.185 4.180 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 4075X G02 VIDC (V) RIDC = RIUSB = 2k RIDC = 1.25k IUSB Pin Voltage vs Temperature (Constant-Current Mode) 1.008 1.006 1.004 VIUSB (V) IBAT (mA) 1.002 VUSBIN = 8V 1.000 0.998 0.996 0.994 0.992 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 VUSBIN = 4.3V 900 800 700 600 500 400 300 200 100 0 IBAT (mA) ⎯P⎯W⎯R Pin I-V Curve 35 VDCIN = VUSBIN = 5V 30 25 IPWR (mA) 20 15 10 5 0 0 1 2 4 3 VPWR (V) 5 6 7 TA = – 40°C TA = 25°C ICHRG (mA) TA = 90°C 35 30 25 20 15 10 5 0 IUSBPWR (mA) 4 UW 4075X G04 4075X G07 Regulated Output (Float) Voltage vs Temperature 4.220 4.215 4.210 4.205 VDCIN = VUSBIN = 5V 1.008 1.006 1.004 1.002 1.000 0.998 0.996 0.994 IDC Pin Voltage vs Temperature (Constant-Current Mode) VDCIN = 8V VDCIN = 4.3V 0.992 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 4075X G03 Charge Current vs IDC Pin Voltage VDCIN = 5V RIDC = 1.25k 900 800 700 600 RIDC = 2k 500 400 300 200 RIDC = 10k 100 0 0 0.2 0.4 0.6 0.8 VIDC (V) 1.0 1.2 Charge Current vs IUSB Pin Voltage VUSBIN = 5V RIUSB = 1.25k RIUSB = 2k RIUSB = 10k 0 0.2 0.4 0.6 0.8 VIUSB (V) 1.0 1.2 4075X G05 4075X G06 ⎯C⎯H⎯R⎯G Pin I-V Curve VDCIN = VUSBIN = 5V 6 TA = – 40°C 5 TA = 25°C TA = 90°C 4 3 2 1 0 USBPWR Pin I-V Curve VDCIN = 5V VUSBIN = 0V TA = – 40°C TA = 25°C TA = 90°C 0 1 2 4 3 VCHRG (V) 5 6 7 0 1 2 4 3 5 VUSBPWR (V) 6 7 4075X G08 4075X G09 4075Xf LTC4075/LTC4075X TYPICAL PERFOR A CE CHARACTERISTICS Charge Current vs Ambient Temperature 1000 ONSET OF THERMAL REGULATION 800 RIDC = 1.25k 700 IBAT (mA) IBAT (mA) 600 500 200 VDCIN = VUSBIN = 5V VBAT = 4V θJA = 40°C/W 50 25 75 0 TEMPERATURE (°C) 100 125 400 RIDC = 1.25k VBAT = 4V θJA = 35°C/W 5.0 5.5 6.0 6.5 VDCIN (V) 7.0 7.5 8.0 200 LTC4075 0 2.4 2.7 3.0 3.3 3.6 VBAT (V) 3.9 4.2 4.5 VDCIN = VUSBIN = 5V θJA = 40°C/W RIDC = 1.25k IBAT (mA) 600 RIDC = RIUSB = 2k 600 900 800 400 0 –50 –25 DCIN Power FET “On” Resistance vs Temperature 550 500 700 RDS(ON) (mΩ) RDS(ON) (mΩ) 450 400 350 300 400 250 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 650 600 550 500 450 VBAT = 4V IBAT = 200mA 800 750 VENABLE (mV) DCIN Shutdown Current vs Temperature 50 45 40 35 IDCIN (µA) 30 25 20 15 10 5 0 –50 –25 VDCIN = 5V VDCIN = 8V IUSBIN (µA) 45 40 35 25 20 15 VUSBIN = 5V RENABLE (MΩ) VDCIN = 4.3V ENABLE = 5V 50 25 0 TEMPERATURE (°C) 75 100 4075X G16 UW 4075X G10 4075X G13 Charge Current vs Supply Voltage 1000 ONSET OF THERMAL REGULATION 800 Charge Current vs Battery Voltage LTC4075X 400 300 4.0 4.5 4075X G11 4075X G12 USBIN Power “On” Resistance vs Temperature VBAT = 4V IBAT = 200mA 900 ENABLE Pin Threshold (On-to-Off) vs Temperature VDCIN = VUSBIN = 5V 850 800 750 700 650 350 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 600 –50 –25 50 25 0 TEMPERATURE (°C) 75 100 4075X G14 4075X G15 USBIN Shutdown Current vs Temperature 2.8 2.6 VUSBIN = 8V 2.4 2.2 2.0 1.8 ENABLE = 0V –25 50 25 0 TEMPERATURE (°C) 75 100 ENABLE Pin Pulldown Resistance vs Temperature 30 10 5 VUSBIN = 4.3V 0 –50 1.6 –50 –25 50 25 0 TEMPERATURE (°C) 75 100 4075X G17 4075X G18 4075Xf 5 LTC4075/LTC4075X TYPICAL PERFOR A CE CHARACTERISTICS Undervoltage Lockout Threshold vs Temperature 4.30 4.25 DCIN UVLO 4.20 VRECHRG (V) 4.15 VUV (V) 4.10 4.05 USBIN UVLO 4.00 3.95 3.90 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 4075X G19 Battery Drain Current vs Temperature 5 4 3 IBAT (µA) 2 1 0 –1 –50 ENABLE 5V/DIV VBAT = 4.2V VDCIN, VUSBIN (NOT CONNECTED) IBAT 500mA/DIV –25 6 UW Recharge Threshold vs Temperature 4.16 4.14 4.12 4.10 4.08 4.06 4.04 –50 VDCIN = VUSBIN = 4.3V VDCIN = VUSBIN = 8V –25 0 25 50 TEMPERATURE (°C) 75 100 4075X G20 Charge Current During Turn-On and Turn-Off 0 25 50 TEMPERATURE (°C) 75 100 VDCIN = 5V RIDC = 1.25k 100µs/DIV 4075X G22 4075X G21 4075Xf LTC4075/LTC4075X 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 1µF 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 = VIUSB •1000 RIUSB is capable of sinking up to 10mA, making it suitable for driving an LED. ENABLE (Pin 6): Enable Input. When the LTC4075 is charging from the DCIN source, a logic low on this pin enables the charger. When the LTC4075 is charging from the USBIN source, a logic high on this pin enables the charger. If this input is left floating, an internal 2MΩ pulldown resistor defaults the LTC4075 to charge when a wall adapter is applied and to shut down if only the USB source is applied. USBPWR (Pin 7): Open-Drain USB Power Status Output. When the voltage on the USBIN pin is sufficient to begin charging and there is insufficient power at DCIN, the USBPWR pin is high impedance. In all other cases, this pin is pulled low by an internal N-channel MOSFET, provided that there is power present at the DCIN, USBIN, or BAT inputs. This output is capable of sinking up to 1mA, making it suitable for driving high impedance logic inputs. 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 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 ⎯C⎯H⎯R⎯G output becomes high impedance. This pin is internally clamped to approximately 1.5V. Driving this pin to voltages beyond the clamp voltage can draw large currents and should be avoided. ⎯P⎯W⎯R (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 ⎯P⎯W⎯R pin is pulled low by an internal N-channel MOSFET. Otherwise ⎯P⎯W⎯R is high impedance. This output is capable of sinking up to 10mA, making it suitable for driving an LED. ⎯C⎯H⎯R⎯G (Pin 5): Open-Drain Charge Status Output. When the LTC4075 is charging, the ⎯C⎯H⎯R⎯G pin is pulled low by an internal N-channel MOSFET. When the charge cycle is completed, ⎯C⎯H⎯R⎯G becomes high impedance. This output U U U BAT (Pin 9): Charger Output and Regulator Input. 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 1μF 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. 4075Xf 7 LTC4075/LTC4075X BLOCK DIAGRA W DCIN 10 BAT 9 USBIN 1 CC/CV REGULATOR CC/CV REGULATOR USBPWR 7 1mA MAX + 4.15V + DC SOFT-START DCIN UVLO USB SOFT-START USBIN UVLO – – 3.95V PWR 4 10mA MAX + BAT CHRG 5 10mA MAX + – BAT – + RECHARGE LOGIC RECHRG 4.1V – BAT DC_ENABLE USB_ENABLE TRICKLE TERM *TRICKLE CHARGE ENABLE 6 RENABLE TERMINATION *TRICKLE CHARGE DISABLED ON THE LTC4075X RITERM RIDC RIUSB 8 – 2.9V + – TDIE CHARGER CONTROL THERMAL REGULATION 100mV IBAT/1000 IBAT/1000 IBAT/1000 105°C + + – ITERM GND 3 11 8 IDC 2 IUSB 4075 BD 4075Xf LTC4075/LTC4075X OPERATIO The LTC4075 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 LTC4075 has two internal P-channel power MOSFETs and thermal regulation circuitry. No blocking diodes or external sense resistors are required. Power Source Selection The LTC4075 can charge a battery from either the wall adapter input or the USB port input. The LTC4075 automatically senses the presence of voltage at each input. If both power sources are present, the LTC4075 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 outputs (⎯P⎯W⎯R and USBPWR) indicate which power source has been selected. Table 1 describes the behavior of these status outputs. Table 1. Power Source Selection VUSBIN > 3.95V and VUSBIN > BAT + 50mV VDCIN > 4.15V and VDCIN > BAT + 50mV Device powered from wall adapter source; USBIN current < 25µA ⎯P⎯W⎯R: LOW USBPWR: LOW Device powered from USB source; ⎯P⎯W⎯R: LOW USBPWR: Hi-Z VUSBIN < 3.95V or VUSBIN < BAT + 50mV Device powered from wall adapter source ⎯P⎯W⎯R: LOW USBPWR: LOW No charging ⎯P⎯W⎯R: Hi-Z USBPWR: LOW VDCIN < 4.15V or VDCIN < BAT + 50mV U 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. Likewise, the charge current from the USB supply is programmed using a single resistor from the IUSB pin to ground. The program resistor and the charge current (ICHRG) are calculated using the following equations: RIDC = RIUSB 1000V ICHRG−DC RIDC 1000V 1000V = , ICHRG−USB = ICHRG−USB RIUSB , ICHRG−DC = 1000V 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 VIDC • 1000, (ch arg ing fromwall adapter) RIDC V = IUSB • 1000, (ch arg ing fromUSB sup ply) RIUSB 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 4075Xf 9 LTC4075/LTC4075X OPERATIO 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), charging is terminated. The charge current is latched off and the LTC4075 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 LTC4075 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 near-dead batteries are gradually charged before reapplying full charge current . If the BAT pin voltage is below 2.9V, the LTC4075 supplies 1/10th of the full charge current to the battery until the BAT pin rises back 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. The LTC4075X does not include the trickle charge feature; it outputs full charge current to the battery when the BAT pin voltage is below 2.9V. The LTC4075X is useful in applications where the trickle charge current may be insufficient to supply the load during low battery voltage conditions. 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 condi*Any external sources that hold the ITERM pin above 100mV will prevent the LTC4075 from terminating a charge cycle. 10 U tion and eliminates the need for periodic charge cycle initiations. 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 ⎯C⎯H⎯R⎯G 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 ENABLE pin has a 2MΩ pulldown resistor to GND. The definition of this pin depends on which source is supplying power. When the wall adapter input is supplying power, logic low enables the charger and logic high disables it (the pulldown defaults the charger to the charging state). The opposite is true when the USB input is supplying power; logic high disables the charger and logic high enables it (the default is the shutdown state). The DCIN input draws 20µA when the charger is in shutdown. The USBIN input draws 18µA during shutdown if no power is applied to DCIN, but draws only 10µA when VDCIN > VUSBIN. Charge Current Soft-Start and Soft-Stop The LTC4075 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 250µs. Likewise, internal circuitry slowly ramps the charge current from full-scale to zero in a period of approximately 30µs 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 LTC4075 is in a charge cycle. Once the charge cycle has terminated or the LTC4075 is disabled, the pin state becomes high impedance. The pull-down state is capable of sinking up to 10mA. 4075Xf LTC4075/LTC4075X OPERATIO ⎯⎯ ⎯ The power supply status output (PWR) has two states: pulldown and high impedance. The pull-down state indicates that power is present at either DCIN or USBIN. This output is strong enough to drive an LED. If no power is applied at either pin, the ⎯P⎯W⎯R pin is high impedance, indicating that the LTC4075 lacks sufficient power to charge the battery. The pull-down state is capable of sinking up to 10mA. The USB power status output (USBPWR) has two states: pull-down and high impedance. The high impedance state indicates that the LTC4075 is being powered from the USBIN input. The pull-down state indicates that the charger is either powered from DCIN or is in a UVLO condition (see Table 1). The pull-down state is capable of sinking up to 1mA. DCIN POWER APPLIED POWER SELECTION DCIN POWER REMOVED TRICKLE CHARGE MODE* 1/10th FULL CURRENT CHRG STATE: PULLDOWN BAT > 2.9V 2.9V < BAT CHARGE MODE FULL CURRENT CHRG STATE: PULLDOWN IBAT < ITERMINATE IN VOLTAGE MODE STANDBY MODE BAT < 4.1V NO CHARGE CURRENT CHRG STATE: Hi-Z USBIN POWER REMOVED OR DCIN POWER APPLIED BAT < 2.9V ENABLE DRIVEN LOW *LTC4075 ONLY U Thermal Limiting An internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 105°C. This feature protects the LTC4075 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. STARTUP ONLY USB POWER APPLIED 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 BAT < 4.1V 2.9V < BAT BAT < 2.9V SHUTDOWN MODE IDCIN DROPS TO 20µA CHRG STATE: Hi-Z DCIN POWER REMOVED USBIN POWER REMOVED OR DCIN POWER APPLIED ENABLE DRIVEN HIGH ENABLE DRIVEN LOW SHUTDOWN MODE IUSBIN DROPS TO 18µA CHRG STATE: Hi-Z 4075 F01 ENABLE DRIVEN HIGH Figure 1. LTC4075 State Diagram of a Charge Cycle 4075Xf 11 LTC4075/LTC4075X APPLICATIO S I FOR ATIO Using a Single Charge Current Program Resistor The LTC4075 can program the wall adapter charge current and USB charge current independently using two program resistors, RIDC and RIUSB. Figure 2 shows a charger circuit that sets the wall adapter charge current to 800mA and the USB charge current to 500mA. WALL ADAPTER USB PORT 1µF 1µF RIUSB 2k 1% RIDC 1.24k 1% LTC4075 DCIN USBIN IUSB IDC ITERM GND RITERM 1k 1% 4075 F02 800mA (WALL) 500mA (USB) BAT Figure 2. Full Featured Dual Input Charger Circuit 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 3 shows a charger circuit that uses one charge current program resistor. WALL ADAPTER USB PORT 1µF 1µF RISET 2k 1% LTC4075 DCIN USBIN IUSB IDC ITERM GND RITERM 1k 1% 4075 F03 500mA BAT Figure 3. Dual Input Charger Circuit. The Wall Adapter Charge Current and USB Charge Current are Both Programmed to be 500mA 12 U In this circuit, the programmed charge current from both the wall adapter supply is the same value as the programmed charge current from the USB supply: ICHRG−DC = ICHRG−USB = Stability Considerations The constant-voltage mode feedback loop is stable without any compensation provided a battery is connected to the charger output. However, a 1µF capacitor with a 1Ω 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. Power Dissipation When designing the battery charger circuit, it is not necessary to design for worst-case power dissipation scenarios because the LTC4075 automatically reduces the charge current during high power conditions. The conditions that cause the LTC4075 to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the IC. Most of the power dissipation is generated from the internal charger MOSFET. Thus, the power dissipation is calculated to be: PD = (VIN – VBAT) • IBAT 1000V RISET + + 4075Xf W U U LTC4075/LTC4075X APPLICATIO S I FOR ATIO 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 = 105°C – PD • θJA TA = 105°C – (VIN – VBAT) • IBAT • θJA Example: An LTC4075 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 θJA is 40°C/W (see Thermal Considerations), the ambient temperature at which the LTC4075 will begin to reduce the charge current is approximately: TA = 105°C – (5V – 3.3V) • (800mA) • 40°C/W TA = 105°C – 1.36W • 40°C/W = 105°C – 54.4°C TA = 50.6°C The LTC4075 can be used above 50.6°C ambient, but the charge current will be reduced from 800mA. The approximate current at a given ambient temperature can be approximated by: 105°C – TA IBAT = (VIN – VBAT ) • θ JA Using the previous example with an ambient temperature of 60°C, the charge current will be reduced to approximately: IBAT = IBAT 105°C – 60°C 45°C = (5V – 3.3V)• 40°C / W 68°C / A = 662mA U It is important to remember that LTC4075 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 105°C. 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 LTC4075 package is properly soldered to the PC board ground. When correctly soldered to a 2500mm2 double sided 1oz copper board, the LTC4075 has a thermal resistance of approximately 40°C/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 40°C/W. As an example, a correctly soldered LTC4075 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. 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 pin ratings and damage the LTC4075. Refer to Linear Technology Application Note 88, entitled “Ceramic Input Capacitors Can Cause Overvoltage Transients” for a detailed discussion of this problem. The long cable lengths of most wall adapters and USB cables 4075Xf W U U 13 LTC4075/LTC4075X APPLICATIO S I FOR ATIO makes them especially susceptible to this problem. To bypass the USB pin and the wall adapter input, add a 1Ω resistor in series with a ceramic capacitor to lower the effective Q of the network and greatly reduce the ringing. A tantalum, OS-CON, or electrolytic capacitor can be used in place of the ceramic and resistor, as their higher ESR reduces the Q, thus reducing the voltage ringing. The oscilloscope photograph in Figure 4 shows how serious the overvoltage transient can be for the USB and wall adapter inputs. For both traces, a 5V supply is hot-plugged using a three foot long cable. For the top trace, only a 4.7µF capacitor (without the recommended 1Ω series resistor) is used to locally bypass the input. This trace shows excessive ringing when the 5V cable is inserted, with the overvoltage spike reaching 10V. For the bottom trace, a 1Ω resistor is added in series with the 4.7µF capacitor to locally bypass the 5V input. This trace shows the clean response resulting from the addition of the 1Ω resistor. Even with the additional 1Ω resistor, bad design techniques and poor board layout can often make the overvoltage 4.7µF ONLY 2V/DIV 4.7µF + 1Ω 2V/DIV 20µs/DIV 3455 F04 Figure 4. Waveforms Resulting from Hot-Plugging a 5V Input Supply 14 U problem even worse. System designers often add extra inductance in series with input lines in an attempt to minimize the noise fed back to those inputs by the application. In reality, adding these extra inductances only makes the overvoltage transients worse. Since cable inductance is one of the fundamental causes of the excessive ringing, adding a series ferrite bead or inductor increases the effective cable inductance, making the problem even worse. For this reason, do not add additional inductance (ferrite beads or inductors) in series with the USB or wall adapter inputs. For the most robust solution, 6V transorbs or zener diodes may also be added to further protect the USB and wall adapter inputs. Two possible protection devices are the SM2T from STMicroelectronics and the EDZ series devices from ROHM. 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 5). DRAIN-BULK DIODE OF FET WALL ADAPTER LTC4075 DCIN 4075 F05 W U U Figure 5. Low Loss Input Reverse Polarity Protection 4075Xf LTC4075/LTC4075X PACKAGE DESCRIPTIO U DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699) R = 0.115 TYP 6 0.675 ± 0.05 10 0.38 ± 0.10 3.00 ± 0.10 (4 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.38 ± 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS PIN 1 TOP MARK (SEE NOTE 6) 5 0.200 REF 0.75 ± 0.05 2.38 ± 0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 1 1.65 ± 0.10 (2 SIDES) (DD10) DFN 1103 3.50 ± 0.05 1.65 ± 0.05 2.15 ± 0.05 (2 SIDES) 0.25 ± 0.05 0.50 BSC 0.00 – 0.05 4075Xf 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. 15 LTC4075/LTC4075X TYPICAL APPLICATIO U Full Featured Li-Ion Charger LTC4075 DCIN USBIN 1µF 1µF PWR IUSB IDC 2.1k 1% 1.24k 1% CHRG ITERM GND 1k 1% 4075 TA03 WALL ADAPTER USB POWER 800mA (WALL) 475mA (USB) BAT 1k 1k + 1-CELL Li-Ion BATTERY RELATED PARTS PART NUMBER LTC3455 LTC4053 LTC4054/LTC4054X LTC4055 LTC4058/LTC4058X LTC4061 LTC4066 LTC4068/LTC4068X LTC4410 LTC4411/LTC4412 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 USB Power Controller and Li-Ion Linear Battery Charger with Low-Loss Ideal Diode Standalone Linear Li-Ion Battery Charger with Programmable Termination USB Power Manager and Battery Charger Low Loss PowerPathTM Controller in ThinSOT COMMENTS Efficiency >96%, Accurate USB Current Limiting (500mA/100mA), 4mm × 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 × 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 Seamless Transition Between Input Power Sources: Li-Ion Battery, USB and Wall Adapter, Low-Loss (50Ω) Ideal Diode, 4mm × 4mm QFN-24 Package Charge Current up to 950mA, Thermal Regulation, 3mm × 3mm DFN-8 Package Manages Total Power Between a USB Peripheral and Battery Charger, Ultralow Battery Drain: 1µA, ThinSOTTM Package Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes ThinSOT and PowerPath are trademarks of Linear Technology Corporation 4075Xf 16 Linear Technology Corporation (408) 432-1900 ● LT/TP 0405 500 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005