LTC4055/LTC USB Power Controller and Li-Ion Charger DESCRIPTION FEATURES APPLICATIONS TYPICAL APPLICATION

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1 FEATURES n Charges Singe-Ce Li-Ion Batteries Directy from USB Port n Load Dependent Charging Guarantees USB Input Current Compiance n Automatic Battery Switchover When Input Suppy is Removed n Constant-Current/Constant-otage Operation with Therma Feedback to Maximize Charging Rate Without Risk of Overheating* n Seectabe 5mA/1mA Current Limit n Low Loss Fu PowerPath Contro with Idea Diode Operation (Reverse Current Bocking) n Preset 4.2 Charge otage with.8% Accuracy (4.1 for LTC455-1) n 4.1 Foat otage (LTC455-1) Improves Battery Life and High Temperature Safety Margin n USB-Compiant Suspend Mode n Programmabe Charge Current and Termination Timer n Soft-Start Limits Inrush Current n NTC Thermistor Input for Temperature Quaified Charging n Tiny (4mm 4mm.75mm) QFN Package APPLICATIONS n Portabe USB Devices: Cameras, MP3 Payers, PDAs L, LT, LTC and LTM are registered trademarks of Linear Technoogy Corporation. PowerPath is a trademark of Linear Technoogy Corporation. A other trademarks are the property of their respective owners. *Protected by U.S. Patent, incuding DESCRIPTION LTC455/LTC455-1 USB Power Controer and Li-Ion Charger The LTC 455/LTC455-1 are USB power manager and Li-Ion battery chargers designed to work in portabe battery-powered appications. The parts manage and imit the tota current used by the USB periphera for operation and battery charging. Depending on the state of the current seect pin (HPWR), tota input current can be imited to either 1mA or 5mA. The votage drop from the USB suppy or battery to the USB periphera is typicay ess than 1m at 4mA and 2m at 8mA. Other management features incude: automatic switchover to battery when input is removed, inrush current imiting, reverse current bocking, undervotage ockout and therma shutdown. The LTC455/LTC455-1 incude a compete constantcurrent/constant-votage inear charger for singe-ce Li-ion batteries. The foat votage appied to the battery is hed to a tight.8% toerance, and charge current is programmabe using an externa resistor to ground. Fuy discharged ces are automaticay tricke charged at 1% of the programmed current unti the ce votage exceeds 2.8. Tota charge time is programmabe by an externa capacitor to ground. When the battery drops 1m beow the f oat votage, automatic recharging of the battery occurs. Aso featured is an NTC thermistor input used to monitor battery temperature whie charging. The LTC455/LTC455-1 are avaiabe in a 16-pin ow profie (4mm 4mm) QFN package. TYPICAL APPLICATION 5 (NOM) FROM USB CABLE BUS 1Ω 1μF SUSPEND USB POWER 5mA/1mA SELECT IN1 IN2 NTC NTC WALL SHDN SUSP HPWR TIMER PROG LTC455 CLPROG.1μF 97.6k 97.6k OUT BAT CHRG ACPR GND 455 TA1 Li-Ion CELL TO SYSTEM LOADS 1μF Input and Battery Current vs Load Current R PROG = R CLPROG = 97.6k CURRENT (ma) I IN I LOAD (ma) I LOAD CHARGING 455 TA2 (IDEAL DIODE) 1

2 LTC455/LTC455-1 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2, 3, 4, 5) Termina otage IN1, IN2, OUT, BAT....3 to 6 NTC, NTC, TIMER, PROG, CLPROG....3 to (CC.3) CHRG, HPWR, SUSP, SHDN, WALL, ACPR....3 to 6 IN2... IN1.1 Pin Current (DC) IN1, IN2, OUT, BAT (Note 7) A Operating Temperature Range... 4 C to 85 C Maximum Operating Junction Temperature C Storage Temperature Range C to 125 C PIN CONFIGURATION IN2 BAT OUT IN TOP IEW NTC NTC CHRG ACPR WALL SHDN SUSP HPWR 12 TIMER 11 PROG 1 GND 9 CLPROG UF PACKAGE 16-LEAD (4mm 4mm) PLASTIC QFN T JMAX = 125 C, θ JA = 37 C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC455EUF#PBF LTC455EUF#TRPBF Lead (4mm 4mm) Pastic QFN 4 C to 85 C LTC455EUF-1#PBF LTC455EUF-1#TRPBF Lead (4mm 4mm) Pastic QFN 4 C to 85 C Consut LTC Marketing for parts specifi ed with wider operating temperature ranges. Consut LTC Marketing for information on non-standard ead based fi nish parts. For more information on ead free part marking, go to: For more information on tape and ree specifi cations, go to: ELECTRICAL CHARACTERISTICS The denotes the specifi cations which appy over the fu operating temperature range, otherwise specifi cations are at T A = 25 C. IN1 = IN2 = 5, BAT = 3.5, HPWR = 5, WALL =, R PROG = R CLPROG = 1k, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IN Input Suppy otage IN1, IN2 and OUT BAT Input otage BAT 4.3 I IN Input Suppy Current BAT = 4.2 Suspend Mode Suspend Mode, Wa = 2, OUT = 4.8 Shutdown I OUT Output Suppy Current OUT = 5, IN1 = IN2 =, BAT = μa Battery Drain Current BAT = 4.2, Charging Stopped Suspend Mode Shutdown IN1 = IN2 =, BAT Powers OUT, No Load I LIM(MAX) Maximum Current Limit (Note 8) 1 A ULO Input or Output Undervotage Lockout IN Powers Part, Rising Threshod OUT Powers Part, Rising Threshod Δ ULO Input or Output Undervotage Lockout Hysteresis IN Rising IN Faing or OUT Rising OUT Faing ma μa ma μa μa μa μa μa 125 m 2

3 LTC455/LTC455-1 ELECTRICAL CHARACTERISTICS The denotes the specifi cations which appy over the fu operating temperature range, otherwise specifi cations are at T A = 25 C. IN1 = IN2 = 5, BAT = 3.5, HPWR = 5, WALL =, R PROG = R CLPROG = 1k, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Current Limit I LIM Current Limit R CLPROG = 1k, HPWR = 5 R CLPROG = 1k, HPWR = R ON ON Resistance IN to OUT HPWR = 5, 4mA Load HPWR =, 8mA Load PROG Programming Pin otage (PROG, CLPROG) R CLPROG = R PROG = 1k R CLPROG = R PROG = 5k I SS Soft-Start Inrush Current IN or OUT 5 ma/μs CLEN Input Current Limit Enabe Threshod IN Rising Δ CLEN Input Current Limit Enabe Threshod IN Rising IN Faing 125 m ALEN Automatic Limit Enabe Threshod otage ( IN OUT ) IN Rising ( IN OUT ) IN Faing m m Battery Charger FLOAT Reguated BAT otage ( C to 85 C) = 2mA (LTC455) = 2mA (LTC455) ( C to 85 C). = 2mA (LTC455-1) = 2mA (LTC455-1) Current Mode Charge Current R PROG = 1k, HPWR = 5, No Load R PROG = 1k, HPWR =, No Load R PROG = 1k, OUT = 5, IN =, WALL = 2 R PROG = 5k, HPWR = 5, No Load R PROG = 5k, OUT = 5, IN =, WALL = (MAX) Maximum Charge Current (Note 8) 1 A ΔI B /ΔI O Charge Current Load Dependency Δ /ΔI OUT, I OUT = 1mA ma/ma I TRKL Tricke-Charge Current BAT = 2, R PROG = 1k ma TRKL Tricke-Charge Threshod otage BAT Rising CENI Input Charger Enabe Threshod otage ( IN BAT ) High to Low ( IN BAT ) Low to High 7 8 m m CENO Output Charger Enabe Threshod otage ( OUT BAT ) High to Low ( OUT BAT ) Low to High UCL Input/Output Undervotage Current Limit = I CHG / RECHRG Recharge Battery Threshod otage FLOAT RECHRG m t TIMER TIMER Accuracy C TIMER =.1μF ±1 % Recharge Time Percent of Tota Charge Time 5 % Low Battery Tricke-Charge Time Percent of Tota Charge Time, BAT < % T LIM Junction Temperature in Constant 15 C Temperature Mode Idea Diode R FWD On Resistance, ON Reguation BAT = 3.5, 1mA Load.1 Ω R DIO,ON On Resistance BAT to OUT BAT = 3.5, 6mA Load.2 Ω FWD otage Forward Drop ( BAT OUT ) BAT = 3.5, 5mA Load BAT = 3.5, 1mA Load BAT = 3.5, 6mA ma ma Ω Ω ma ma ma ma ma m m 5 m m m OFF Diode Disabe Battery otage BAT Faing 2.8 I FWD Load Current Limit for ON Reguation IN = ma I MAX Diode Current Limit BAT = 3.5, OUT = 2.8, Pused with 1% Duty Cyce A 3

4 LTC455/LTC455-1 ELECTRICAL CHARACTERISTICS The denotes the specifi cations which appy over the fu operating temperature range, otherwise specifi cations are at T A = 25 C. IN1 = IN2 = 5, BAT = 3.5, HPWR = 5, WALL =, R PROG = R CLPROG = 1k, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Logic OL Output Low otage (CHRG, ACPR) I SINK = 5mA.2.4 IH Enabe Input High otage SUSP, SHDN, HPWR Pin Low to High 1.2 IL Enabe Input Low otage SUSP, SHDN, HPWR Pin High to Low.4 I PULLDN Logic Input Pu-Down Current SUSP, SHDN, HPWR 2 μa CHG,SD Charger Shutdown Threshod otage on TIMER TIMER Faing.15.4 I CHG,SD Charger Shutdown Pu-Up Current TIMER = 2 4 μa on TIMER WALL Wa Input Threshod otage WALL Rising Threshod WALL,HYS Wa Input Hysteresis WALL Rising WALL Faing Threshod 35 m I WALL Wa Input Leakage Current WALL = 1 ±5 na NTC I NTC NTC Pin Current NTC = ma NTC NTC Bias otage I NTC = 5μA COLD Cod Temperature Faut Threshod otage Rising Threshod Faing Threshod.74 NTC.72 NTC HOT Hot Temperature Faut Threshod otage Faing Threshod Rising Threshod DIS NTC Disabe otage NTC Input otage to GND (Faing) Hysteresis NTC.3 NTC 125 m m Note 1: Stresses beyond those isted under Absoute Maximum Ratings may cause permanent damage to the device. Exposure to any Absoute Maximum Rating condition for extended periods may affect device reiabiity and ifetime. Note 2: CC is the greater of IN1, OUT or BAT. Note 3: IN1 and IN2 shoud be tied together with a ow impedance to ensure that the difference between the two pins does not exceed 1m. Note 4: A votage vaues are with respect to GND. Note 5: This IC incudes overtemperature protection that is intended to protect the device during momentary overoad conditions. Junction temperature wi exceed 125 C when overtemperature protection is active. Continuous operation above the specifi ed maximum operating junction temperature may impair device reiabiity. Note 6: The LTC455EUF/LTC455EUF-1 are guaranteed to meet performance specifi cations from C to 85 C. Specifi cations over the 4 C to 85 C operating temperature range are assured by design, characterization and correation with statistica process contros. Note 7: Guaranteed by ong-term current density imitations. Note 8: Accuracy of programmed current may degrade for currents greater than 1A. 4

5 TYPICAL PERFORMANCE CHARACTERISTICS LTC455/LTC Input Suppy Current vs Temperature IN = 5 BAT = 4.2 R PROG = R CLPROG = 1k Input Suppy Current vs Temperature (Suspend Mode) IN = 5 BAT = 4.2 R PROG = R CLPROG = 1k SUSP = Battery Drain Current vs Temperature (BAT Powers OUT, No Load) IN = BAT = 4.2 I IN (μa) 5 4 I IN (μa) 3 (μa) TEMPERATURE ( C) TEMPERATURE ( C) TEMPERATURE ( C) 455 G1 455 G2 455 G3 I IN (ma) Input Current Limit vs Temperature, HPWR = 5 IN = 5 BAT = 3.5 R PROG = R CLPROG = 1k I IN (ma) Input Current Limit vs Temperature, HPWR = IN = 5 BAT = 3.5 R PROG = R CLPROG = 1k R ON (mω) R ON vs Temperature 25 I LOAD = 4mA 225 IN = 5 2 IN = IN = TEMPERATURE ( C) TEMPERATURE ( C) TEMPERATURE ( C) 455 G4 455 G5 455 G PROG Pin otage vs Temperature IN = 5 R PROG = 1k CLPROG Pin otage vs Temperature IN = 5 R CLPROG = 1k 4.3 Battery Reguated Output (Foat) otage vs Temperature IN = 5 PROG () CLPROG () FLOAT () LTC455 LTC TEMPERATURE ( C) TEMPERATURE ( C) TEMPERATURE ( C) 455 G7 455 G8 455 G9 5

6 LTC455/LTC455-1 TYPICAL PERFORMANCE CHARACTERISTICS Reguated Output otage- Recharge Threshod otage vs Temperature Battery Reguated Output (Foat) otage vs Suppy otage Battery Current and otage vs Time (LTC455) FLOAT - RECHARGE () IN = TEMPERATURE ( C) 1 FLOAT () T A = 25 C LTC455 LTC IN () 6 (ma) BAT CHRG 2 2.8AHr CELL 1 IN = 5 T A = 25 C 1 R PROG = 15k TIME (MINUTES) BAT AND CHRG () 455 G1 455 G G12 (ma) Charging from USB, vs BAT (LTC455) IN = 5 OUT = NO LOAD R PROG = 1k R CLPROG = 1k HPWR = 1 T A = 25 C (ma) Charging from USB, Low Power, vs BAT (LTC455) IN = 5 OUT = NO LOAD R PROG = 1k R CLPROG = 1k HPWR = T A = 25 C (A) Undervotage Current Limit, Charging from IN, vs IN T A = 25 C R PROG = 5k R PROG = 34k R PROG = 1k R PROG = 1k HPWR = BAT () BAT () IN () G G G15 (A) Charge Current vs Temperature (Therma Reguation) 5 IN = 5 BAT = 3.5 JA = 37 C/W R PROG = 5k R PROG = 1k TEMPERATURE ( C) I OUT (ma) Idea Diode Forward otage vs Current and Temperature BAT = 3.5 IN = 5 C 25 C C 125 C 75 C FWD (m) I OUT (ma), R DIO (mω) Idea Diode Forward otage and Resistance vs Current BAT = 3.5 IN = T A = 25 C R FWD R DIO(ON) FWD (m) 455 G G G18 6

7 LTC455/LTC455-1 TYPICAL PERFORMANCE CHARACTERISTICS Idea Diode and Schottky Diode Forward otage vs Current Input Connect Waveforms Input Disconnect Waveforms BAT = 3.5 IN = T A = 25 C IN 5/DI IN 5/DI I OUT (ma) SCHOTTKY OUT 5/DI I IN.5A/DI.5A/DI OUT 5/DI I IN.5A/DI.5A/DI 2 1 BAT = 3.5 I OUT = 1mA 1ms/DI 455 G2 BAT = 3.5 I OUT = 1mA 1ms/DI 455 G FWD (m) 455 G19 Response to HPWR WALL Connect Waveforms ( IN = ) WALL Disconnect Waveforms ( IN = ) HPWR 5/DI I IN.5A/DI.5A/DI WALL 5/DI OUT 5/DI I WALL.5A/DI.5A/DI WALL 5/DI OUT 5/DI I WALL.5A/DI.5A/DI BAT = 3.5 I OUT = 5mA 25μs/DI 455 G21 BAT = 3.5 I OUT = 1mA R PROG = 57.6k 1ms/DI 455 G24 BAT = 3.5 I OUT = 1mA R PROG = 57.6k 1ms/DI 455 G25 Response to Suspend WALL Connect Waveforms ( IN = 5) WALL Disconnect Waveforms ( IN = 5) SUSPEND 5/DI OUT 5/DI I IN.5A/DI.5A/DI WALL 5/DI I IN.5A/DI I WALL.5A/DI.5A/DI WALL 5/DI I IN.5A/DI I WALL.5A/DI.5A/DI BAT = 3.5 I OUT = 5mA 1ms/DI 455 G23 BAT = 3.5 I OUT = 1mA R PROG = 57.6k 1ms/DI 455 G26 BAT = 3.5 I OUT = 1mA R PROG = 57.6k 1ms/DI 455 G27 7

8 LTC455/LTC455-1 PIN FUNCTIONS BAT (Pin 2): Connect to a singe-ce Li-Ion battery. Used as an output when charging the battery and as an input when suppying power to OUT. When the OUT pin potentia drops beow the BAT pin potentia, an idea diode function connects BAT to OUT and prevents OUT from dropping more than 1m beow BAT. A precision interna resistor divider sets the fina f oat potentia on this pin. The interna resistor divider is disconnected when IN1/IN2 and OUT are in ULO. OUT (Pin 3): otage Output. Used to provide controed power to a USB device from either USB BUS (IN1/IN2) or the battery (BAT) when the USB is not present. Can aso be used as an input for battery charging when the USB is not present and a wa adaptor is appied to this pin. Shoud be bypassed with at east 1μF to GND. IN1/IN2 (Pin 4/Pin 1): Input Suppy. Connect to USB suppy, BUS. Used as main suppy whie connected to USB BUS for power contro to a USB device. Input current is imited to either 2% or 1% of the current programmed by the CLPROG pin as determined by the state of the HPWR pin. Charge current (to BAT pin) suppied through the inputs is set to the current programmed by the PROG pin but wi be imited by the input current imit if set greater than the input current imit. Connect IN2 to IN1 with a resistance no greater than.5ω. WALL (Pin 5): Wa Adapter Present Input. Puing this pin above 1 wi disabe charging from IN1/IN2 and disconnect the power path from IN1/IN2 to OUT. The ACPR pin wi aso be pued ow to indicate that a wa adapter has been detected. Requires the votage on IN1/IN2 or OUT to be 1m greater than BAT and greater than ULO to activate this function. SHDN (Pin 6): Shutdown Input. Puing this pin greater than 1.2 wi disabe the entire part and pace it in a ow suppy current mode of operation. A power paths wi be disabed. A weak pu-down current is internay appied to this pin to ensure it is ow at power-up when the input is not being driven externay. 8 SUSP (Pin 7): Suspend Mode Input. Puing this pin above 1.2 wi disabe charging from IN1/IN2 and disconnect the power path from IN1/IN2 to OUT. The suppy current wi be reduced to compy with the USB specification for Suspend mode. The BAT to OUT idea diode function wi remain active as we as the abiity to charge the battery from OUT. Suspend mode wi reset the charge timer if OUT is ess than BAT whie in suspend mode. If OUT is kept greater than BAT, such as when a wa adapter is present, the charge timer wi not be reset when the part is put in suspend. A weak pu-down current is internay appied to this pin to ensure it is ow at power-up when the input is not being driven externay. HPWR (Pin 8): High Power Seect. Used to contro the amount of current drawn from the USB port. A votage greater than 1.2 on the pin wi set the current imit to 1% of the current programmed by the CLPROG pin and 1% of the charge current programmed by the PROG pin. A votage ess than.4 on the pin wi set the current imit to 2% 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 pu-down current is internay appied to this pin to ensure it is ow at power-up when the input is not being driven externay. CLPROG (Pin 9): Current Limit Program. Connecting a resistor, R CLPROG to ground, programs the input to output current imit. The current imit is programmed as foows: I CL CLPROG 49, ( A) = 49, = R R CLPROG CLPROG In USB appications the resistor R CLPROG shoud be set to no ess than 15k. GND (Pin 1): Ground. PROG (Pin 11): Charge Current Program. Connecting a resistor, R PROG, to ground programs the battery charge current. The battery charge current is programmed as foows: I CHG PROG 48, 5 ( A) = 48, 5 = R R PROG PROG

9 LTC455/LTC455-1 PIN FUNCTIONS TIMER (Pin 12): Timer Capacitor. Pacing a capacitor C TIMER to GND sets the timer period. The timer period is: t TIMER CTIMER RPROG 3Hours ( Hours) =. 1μ F 1k Charge time is increased as charge current is reduced due to input votage reguation, oad current and current imit seection (HPWR). Shorting the TIMER pin to GND disabes the battery charging functions. ACPR (Pin 13): Wa Adapter Present Output. Active ow open-drain output pin. A ow on this pin indicates that the wa adapter input comparator has had its input pued above the input threshod and power is present on IN1/IN2 or OUT (i.e., above ULO threshod). CHRG (Pin 14): Open-Drain Charge Status Output. When the battery is being charged, the CHRG pin is pued ow by an interna N-channe MOSFET. When the timer runs out or the input suppy or output suppy is removed, the CHRG pin is forced to a high impedance state. NTC (Pin 15): Output Bias otage for NTC. A resistor from this pin to the NTC pin wi set up the bias for an NTC thermistor. NTC (Pin 16): Input to the NTC Thermistor Monitoring Circuits. Under norma operation, tie a thermistor from the NTC pin to ground and a resistor of equa vaue from NTC to NTC. When the votage on this pin is above.74 NTC (Cod, C) or beow.29 NTC (Hot, 5 C) the timer is suspended, but not ceared, the charging is disabed and the CHRG pin remains in its former state. When the votage on NTC comes back between.74 NTC and.29 NTC, the timer continues where it eft off and charging is re-enabed if the battery votage is beow the recharge threshod. There is approximatey 3 C 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 wi disabe a of the LTC455/LTC455-1 NTC functions. Exposed Pad (Pin 17): Ground. The Exposed Pad must be sodered to a good thermay conductive PCB ground. 9

10 LTC455/LTC455-1 BLOCK DIAGRAM BUS 4 IN1 3 2 OUT BAT 25m IDEAL DIODE IN1.2Ω OUT.2Ω BAT.2Ω IN2 1 IN2 DIE TEMP 15 C 4.35 CURRENT LIMIT TA R 1 I LIM SOFT-START I LIM CNTL ENABLE 1k 9 CLPROG 1 CURRENT CONTROL SENSE I CHRG SOFT-START2 CHARGER CC/C REGULATOR I/O SEL ENABLE BATTERY CHARGER 11 PROG 1k 8 HPWR 5mA/1mA.25 ACPR 13 2μ BAT U 2.8 BATTERY ULO 5 WALL 1 IN1 OUT BAT OLTAGE DETECT 4.1 RECHARGE (4. LTC455-1) ULO NTC 15 1k 16 NTC BAT U 2COLD NTCERR CONTROL LOGIC RECHRG HOLD RESET OSCILLATOR CLK COUNTER STOP TIMER CHRG NTC 1k 2HOT.1 NTC ENABLE 2μ 2μ GND SHDN SUSP BD 1

11 LTC455/LTC455-1 OPERATION The LTC455/LTC455-1are compete PowerPath controers for battery-powered USB appications. The LTC455/ LTC455-1 are designed to provide device power and Li-ion battery charging from the USB BUS whie maintaining the current imits as specified in the USB specifi cation. This is accompished by reducing battery charge current as output/oad current is increased. In this scenario, the avaiabe bus current is maximized in an effort to minimize battery charge time. An idea diode function provides power from the battery when output/oad current exceeds the input current imit set for the part or when input power is removed. The advantage to powering the oad through the idea diode (rather than connecting the oad directy to the battery) is that when the bus is connected and the battery is fuy charged, the battery remains fuy charged unti bus power is removed. Once bus power is removed the output drops unti the idea diode is forward biased. The forward biased idea diode wi then provide the output power to the oad from the battery. Another advantage to powering the oad from the bus when the bus is avaiabe is in cases where the oad is a switching reguator. The input power to a switching reguator can be thought of as constant. A higher votage across a constant power oad wi require ess current. Less oad current in USB appications means more avaiabe charge current. More charge current transates to shorter charge times. The LTC455/LTC455-1 aso have the abiity to accommodate power from a wa adapter. Wa adapter power can be connected to the output (oad side) of the LTC455/LTC455-1 through an externa device such as a power Schottky or FET, as shown in Figure 1. The LTC455/ LTC455-1 have the unique abiity to use the output, which is powered by the wa adapter, as an aternate path to charge the battery whie providing power to the oad. A wa adapter comparator on the LTC455/LTC455-1 can be configured to detect the presence of the wa adapter and shut off the connection to the USB to prevent reverse conduction out to the bus. WALL ADAPTER BUS 4 IN1 OUT 3 1 IN2 LOAD INPUT CHARGER CONTROL ENABLE CURRENT LIMIT CONTROL ENABLE OUTPUT CHARGER CONTROL ENABLE IDEAL 5 WALL BAT 2 Li-Ion 1 ULO 455 F1 Figure 1. Simpifi ed Bock Diagram PowerPath 11

12 LTC455/LTC455-1 OPERATION Tabe 1. Operating Modes PowerPath States Current Limited Input Power (IN1/IN2 to OUT) WALL PRESENT SHUTDOWN SUSPEND IN > 3.8 IN > ( OUT 1m) IN > ( BAT 1m) CURRENT LIMIT ENABLED Y X X X X X N X Y X X X X N X X Y X X X N X X X N X X N X X X X N X N X X X X X N N N N N Y Y Y Y Input Powered Charger (IN1/IN2 to BAT) WALL PRESENT SHUTDOWN SUSPEND IN > 4.35 IN > ( OUT 1m) IN > ( BAT 1m) INPUT CHARGER ENABLED Y X X X X X N X Y X X X X N X X Y X X X N X X X N X X N X X X X N X N X X X X X N N N N N Y Y Y Y Output Powered Charger (OUT to BAT) WALL PRESENT SHUTDOWN SUSPEND IN > 4.35 OUT > ( IN 1m) OUT > ( BAT 1m) OUTPUT CHARGER ENABLED N X X X X X N X Y X X X X N X X X N X X N X X X X N X N X X X X X N N Y N X Y Y Y Y Idea Diode (BAT to OUT) WALL PRESENT SHUTDOWN SUSPEND BAT > 2.8 BAT > OUT IN DIODE ENABLED X Y X X X X N X X X N X X N X X X X N X N X N X Y Y X Y Tabe 2. Operating Modes Pin Currents vs Programmed Currents (Charging from IN1/IN2) PROGRAMMING OUTPUT CURRENT BATTERY CURRENT INPUT CURRENT I CL = I CHG I OUT < I CL I OUT = I CL = I CHG I OUT > I CL I CHG < I CL I OUT < (I CL I CHG ) I OUT > (I CL I CHG ) I OUT = I CL I OUT > I CL I CL < I CHG I OUT < I CL I OUT > I CL * = I CHG I OUT = = I CL I OUT = I CHG = I CL I OUT = = I CL I OUT I IN = I Q I CL I IN = I Q I CL I IN = I Q I CL I IN = I Q I CHG I OUT I IN = I Q I CL I IN = I Q I CL I IN = I Q I CL = I CL I OUT = I CL I OUT I IN = I Q I CL I IN = I Q I CL *Charge current shuts off when OUT drops beow BAT, i.e., when I OUT exceeds I CL. 12

13 LTC455/LTC455-1 OPERATION BATTERY POWERS OUT CHARGING SUSPENDED CHRG Hi-Z BATTERY POWERS OUT CHARGING SUSPENDED CHRG PULLED LOW Operationa State Diagram SHUTDOWN SHUTDOWN CHARGING DISABLED ALL SWITCHES OPEN ( IN AND OUT) < ULO SHDN ULO CHARGING DISABLED BATTERY POWERS OUT BATTERY > 2.8 BATTERY < 2.8 LOW BATTERY CHRG IS Hi-Z BATTERY POWER TO OUT DISABLED POWER APPLIED TO IN WALL ADAPTER PRESENT OUT > BAT OUT < BAT IN POWERS PART CURRENT LIMIT SWITCH FROM IN TO OUT ON WALL ADAPTER PRESENT OUT POWERS PART CURRENT LIMIT SWITCH FROM IN TO OUT OFF ACPR PULLED LOW BATTERY < 4.1 (4. LTC455-1) BATTERY > 4.1 (4. LTC455-1) AND CHARGER TIMED OUT BATTERY > 4.1 (4. LTC455-1) AND CHARGER TIMED OUT BATTERY < 4.1 (4. LTC455-1) OUT > BAT OUT < BAT IN CHARGING BATTERY CURRENT LIMIT SWITCH FROM IN TO OUT ON BATTERY CHARGING ON IN CHARGE SWITCH OPEN CHRG PULLED LOW WALL ADAPTER PRESENT OUT CHARGING BATTERY CURRENT LIMIT SWITCH FROM IN TO OUT OFF BATTERY CHARGING ON IN CHARGE SWITCH OPEN CHRG PULLED LOW ACPR PULLED LOW TEMP OK AND BATTERY > 2.8 TEMP NOT OK TEMP NOT OK TEMP OK AND BATTERY > 2.8 NTC FAULT NTC FAULT BATTERY > 2.8 BATTERY CHARGING SUSPENDED CHRG PULLED LOW BATTERY < 2.8 BATTERY < 2.8 BATTERY CHARGING SUSPENDED CHRG PULLED LOW BATTERY > 2.8 TEMP OK AND BATTERY < 2.8 TEMP NOT OK TEMP NOT OK TEMP OK AND BATTERY < 2.8 IN CHARGING LOW BATTERY OUT CHARGING LOW BATTERY BATTERY CHARGING ON CHARGE CURRENT C/1 OUT CHARGE SWITCH OPEN CHRG PULLED LOW BATTERY POWER TO OUT IS OFF BAD BATTERY WALL ADAPTER PRESENT 1/4 TIMEOUT AND BATTERY < 2.8 1/4 TIMEOUT AND BATTERY < 2.8 CURRENT LIMIT SWITCH FROM IN TO OUT OFF BATTERY CHARGING ON CHARGE CURRENT C/1 IN CHARGE SWITCH OPEN CHRG PULLED LOW ACPR PULLED LOW BAD BATTERY 455 SD CHRG IS Hi-Z BATTERY POWER TO OUT DISABLED CHRG IS Hi-Z BATTERY POWER TO OUT DISABLED 13

14 LTC455/LTC455-1 OPERATION USB CURRENT LIMIT AND CHARGE CURRENT CONTROL The current imit and charger contro circuits of the LTC455/LTC455-1 are designed to imit input current as we as contro battery charge current as a function of I OUT. The programmed current imit, I CL is defi ned as: I CL = 49, CLPROG R = 49, R CLPROG CLPROG The programmed battery charge current, I CHG, is defined as: I CHG = 48, 5 PROG R = 48, 5 R PROG PROG Input current, I IN, is equa to the sum of the BAT pin output current and the OUT pin output current. I IN = I OUT The current imiting circuitry in the LTC455/LTC455-1 can and shoud be confi gured to imit current to 5mA for USB appications (seectabe using the HPWR pin and programmed using the CLPROG pin). When programmed for 5mA current imit and 5mA or more of charging current, powered from IN1/IN2 and battery charging is active, contro circuitry within the LTC455/LTC455-1 reduces the battery charging current such that the sum of the battery charge current and the oad current does not exceed 5mA (1mA when HPWR is ow, see Figure 2) The battery charging current goes to zero when oad current exceeds 5mA (8mA when HPWR is ow). If the oad current is greater than the current imit, the output votage wi drop to just under the battery votage where the idea diode circuit wi take over and the excess oad current wi be drawn from the battery (shaded region in Figure 2). PROGRAMMING CURRENT LIMIT The formua for programming current imit is: I CL CLPROG = ICLPROG 49, = 49, R CLPROG where CLPROG is the CLPROG pin votage and R CLPROG is the tota resistance from the CLPROG pin to ground. For exampe, if typica 49mA current imit is required, cacuate: 1 RCLPROG = 49, = 1k 49mA In USB appications, the minimum vaue for R CLPROG shoud be 15k. This wi prevent the appication current from I IN 1 5 CURRENT (ma) I LOAD CHARGING CURRENT (ma) I IN I LOAD CHARGING CURRENT (ma) = I CHG I IN CHARGING I LOAD = I CL I OUT I I LOAD (ma) BAT (IDEAL DIODE) 455 F2a (2a) High Power Mode/Fu Charge (R PROG = R CLPROG = 97.6k) I I LOAD (ma) BAT (IDEAL DIODE) 455 F2b (2b) Low Power Mode/Fu Charge (R PROG = R CLPROG = 97.6k) Figure 2. Input and Battery Currents as a Function of Load Current I I LOAD (ma) BAT (IDEAL DIODE) 455 F2c (2c) High Power Mode with I CL = 5mA and I CHG = 25mA (R PROG = 196k, R CLPROG = 97.6k) 14

15 LTC455/LTC455-1 OPERATION exceeding 5mA due to LTC455/LTC455-1 toerances and quiescent currents. This wi give a typica current imit of approximatey 467mA in high power mode (HPWR = 1) or 92mA in ow power mode (HPWR = ). For best stabiity over temperature and time, 1% meta fim resistors are recommended. Battery Charger The battery charger circuits of the LTC455/LTC455-1 are designed for charging singe-ce ithium-ion batteries. Featuring an interna P-channe power MOSFET, the charger uses a constant-current/constant-votage charge agorithm with programmabe current and a programmabe timer for charge termination. Charge current can be programmed up to 1A. The fina f oat votage accuracy is ±.8% typica. No bocking 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 LTC455/LTC455-1 at a times. An NTC input provides the option of charge quaification using battery temperature. An interna therma imit reduces the programmed charge current if the die temperature attempts to rise above a preset vaue of approximatey 15 C. This feature protects the LTC455/LTC455-1 from excessive temperature, and aows the user to push the imits of the power handing capabiity of a given circuit board without risk of damaging the LTC455/LTC Another benefit of the LTC455/LTC455-1 therma imit is that charge current can be set according to typica, not worst-case, ambient temperatures for a given appication with the assurance that the charger wi automaticay reduce the current in worst-case conditions. An interna votage reguation circuit, caed undervotage current imit, UCL, reduces the programmed charge current to keep the votage on IN or OUT at east 4.4. This feature prevents the charger from cycing in and out of undervotage ockout due to resistive drops in the USB or wa adapter cabing. The charge cyce begins when the votage at the input (IN1/IN2) rises above the input ULO eve and the battery votage is beow the recharge threshod. No charge current actuay f ows unti the input votage is greater than the UCL eve. At the beginning of the charge cyce, if the battery votage is beow 2.8, the charger goes into tricke-charge mode to bring the ce votage up to a safe eve for charging. The charger goes into the fast charge constant-current mode once the votage on the BAT pin rises above 2.8. In constant current mode, the charge current is set by R PROG. When the battery approaches the fi na foat votage, the charge current begins to decrease as the LTC455/LTC455-1 switches to constant-votage mode. An externa capacitor on the TIMER pin sets the tota minimum charge time. When this time eapses the charge cyce terminates and the CHRG pin assumes a high impedance state. Whie charging in constant-current mode, if the charge current is decreased due to oad current, undervotage charge current imiting or therma reguation the charging time is automaticay increased. In other words, the charge time is extended inversey proportiona to charge current deivered to the battery. For ithium-ion and simiar batteries that require accurate fina foat potentia, the interna bandgap reference, votage ampifier and the resistor divider provide reguation with ±1% maximum accuracy. TRICKLE CHARGE AND DEFECTIE BATTERY DETECTION At the beginning of a charge cyce, if the battery votage is ow (beow 2.8) the charger goes into tricke-charge reducing the charge current to 1% of the fu-scae current. If the ow battery votage persists for one quarter of the tota charge time, the battery is assumed to be defective, the charge cyce is terminated and the CHRG pin output assumes a high impedance state. If for any reason the battery votage rises above ~2.8, the charge cyce wi be restarted. To restart the charge cyce (i.e., when the dead battery is repaced with a discharged battery), simpy remove the input votage and reappy it, cyce the TIMER pin to or cyce the SHDN pin to. PROGRAMMING CHARGE CURRENT The formua for programming the battery charge current, when not being imited, is: I CHG PROG = IPROG 48, 5 = 48, 5 R PROG 15

16 LTC455/LTC455-1 OPERATION where PROG is the PROG pin votage and R PROG is the tota resistance from the PROG pin to ground. For exampe, if typica 485mA charge current is required, cacuate: 1 RPROG = 48, 5 = 1k 485mA For best stabiity over temperature and time, 1% meta fim resistors are recommended. Under tricke-charge conditions, this current is reduced to 1% of the fuscae vaue. THE CHARGE TIMER The programmabe charge timer is used to terminate the charge cyce. The timer duration is programmed by an externa capacitor at the TIMER pin and is aso a function of the resistance on PROG. Typicay the charge time is: t TIMER CTIMER RPROG 3Hours ( Hours) =. 1μ F 1k The timer starts when an input votage greater than the undervotage ockout threshod eve is appied, or when eaving shutdown and the votage on the battery is ess than the recharge threshod. At power-up or exiting shutdown with the battery votage ess than the recharge threshod, the charge time is a fu cyce. If the battery is greater than the recharge threshod, the timer wi not start and charging is prevented. If after power-up the battery votage drops beow the recharge threshod, or if after a charge cyce the battery votage is sti beow the recharge threshod, the charge time is set to one haf of a fu cyce. The LTC455/LTC455-1 have a feature that extends charge time automaticay. Charge time is extended if the charge current in constant-current mode is reduced due to oad current, undervotage charge current imiting or therma reguation. This change in charge time is inversey proportiona to the change in charge current. As the LTC455/LTC455-1 approach constant-votage mode the charge current begins to drop. This change in charge current is part of the norma charging operation of the part and shoud not affect the timer duration. Therefore, the LTC455/LTC455-1 detect that the change in charge current is due to votage mode, and increase the timer period back to its programmed operating period. Once a time-out occurs and the votage on the battery is greater than the recharge threshod, 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 disabes the battery charger. CHRG STATUS OUTPUT PIN When the charge cyce starts, the CHRG pin is pued to ground by an interna N-channe MOSFET capabe of driving an LED. After a time-out occurs, the pin assumes a high impedance state. NTC Thermistor The battery temperature is measured by pacing a negative temperature coefficient (NTC) thermistor cose to the battery pack. The NTC circuitry is shown in Figure 3. To use this feature, connect the NTC thermistor, R NTC, between the NTC pin and ground and a resistor, R NOM, from the NTC pin to NTC. R NOM shoud be a 1% resistor with a vaue equa to the vaue of the chosen NTC thermistor at 25 C (this vaue is 1k for a ishay NTHS63N2N12J thermistor). The LTC455/LTC455-1 go into hod mode when the resistance, R HOT, of the NTC thermistor drops to.41 times the vaue of R NOM or approximatey 4.1k, which shoud be at 5 C. The hod mode freezes the timer and stops the charge cyce unti the thermistor indicates a return to a vaid temperature. As the temperature drops, the resistance of the NTC thermistor rises. The LTC455/ LTC455-1 are designed to go into hod mode when the vaue of the NTC thermistor increases to 2.82 times the vaue of R NOM. This resistance is R COLD. For a ishay NTHS63N2N12J thermistor, this vaue is 28.2k which corresponds to approximatey C. The hot and cod comparators each have approximatey 3 C of hysteresis to prevent osciation about the trip point. Grounding the NTC pin disabes the NTC function. 16

17 LTC455/LTC455-1 OPERATION NTC 15 LTC455/LTC455-1 NTC BLOCK NTC 15 LTC455/LTC455-1 NTC BLOCK R NOM 1k NTC NTC TOO_COLD R NOM 121k NTC NTC TOO_COLD R NTC 1k R1 13.3k.29 NTC TOO_HOT R NTC 1k.29 NTC TOO_HOT.1 NTC_ENABLE.1 NTC_ENABLE 455 F3a 455 F3b (3a) (3b) Figure 3. NTC Circuits THERMISTORS The LTC455/LTC455-1 NTC trip points were designed to work with thermistors whose resistance-temperature characteristics foow ishay Dae s R-T Curve 2. The ishay NTHS63N2N12J is an exampe of such a thermistor. However, ishay Dae has many thermistor products that foow the R-T Curve 2 characteristic in a variety of sizes. Furthermore, any thermistor whose ratio of R COLD to R HOT is about 7. wi aso work (ishay Dae R-T Curve 2 shows a ratio of R COLD to R HOT of 2.815/.486 = 6.89). Power conscious designs may want to use thermistors whose room temperature vaue is greater than 1k. ishay Dae has a number of vaues of thermistor from 1k to 1k that foow the R-T Curve 1. Using these as indicated in the NTC Thermistor section wi give temperature trip points of approximatey 3 C and 47 C, a deta of 44 C. This deta in temperature can be moved in either direction by changing the vaue of R NOM with respect to R NTC. Increasing R NOM wi move both trip points to ower temperatures. Likewise a decrease in R NOM with respect to R NTC wi move the trip points to higher temperatures. To cacuate R NOM for a shift to ower temperature for exampe, use the foowing equation: R NOM RCOLD = RNTC at25 C where R COLD is the resistance ratio of R NTC at the desired cod temperature trip point. If you want to shift the trip points to higher temperatures use the foowing equation: R NOM RHOT = RNTC at25 C. 486 where R HOT is the resistance ratio of R NTC at the desired hot temperature trip point. Here is an exampe using a 1k R-T Curve 1 thermistor from ishay Dae. The difference between the trip points is 44 C, from before, and we want the cod trip point to be C, which woud put the hot trip point at 44 C. The R NOM needed is cacuated as foows: R NOM RCOLD = RNTC at25 C = 1k = 116k

18 LTC455/LTC455-1 OPERATION The nearest 1% vaue for R NOM is 115k. This is the vaue used to bias the NTC thermistor to get cod and hot trip points of approximatey C and 44 C respectivey. To extend the deta between the cod and hot trip points a resistor, R1, can be added in series with R NTC (see Figure 3b). The vaues of the resistors are cacuated as foows: RCOLD RHOT RNOM = R = R R R ( ) COLD HOT HOT where R NOM is the vaue of the bias resistor, R HOT and R COLD are the vaues of R NTC at the desired temperature trip points. Continuing the exampe from before with a desired hot trip point of 5 C: R NOM ( ) RCOLD RHOT 1k = = = 12.8k, 121k is nearest 1%. 486 R1= 1k ( ) = 13.3k, 13.3k is nearest 1% The fi na soution is as shown if Figure 3b where R NOM = 121k, R1 = 13.3k and R NTC = 1k at 25 C. CURRENT LIMIT UNDEROLTAGE LOCKOUT An interna undervotage ockout circuit monitors the input votage and keeps the current imit circuits of the part in shutdown mode unti IN rises above the undervotage ockout threshod. The current imit ULO circuit has a buit-in hysteresis of 125m. Furthermore, to protect against reverse current in the power MOSFET, the current imit ULO circuit keeps the current imit shutdown if OUT exceeds IN. If the current imit ULO comparator is tripped, the current imit circuits wi not come out of shutdown unti OUT fas 5m beow the IN votage. CHARGER UNDEROLTAGE LOCKOUT Interna undervotage ockout circuits monitor the IN and OUT votages and keep the charger circuits of the part shut down unti IN or OUT rises above the undervotage ockout threshod. The charger ULO circuit has a buitin hysteresis of 125m. Furthermore, to protect against reverse current in the power MOSFET, the charger ULO circuit keeps the charger shutdown if BAT exceeds OUT. If the charger ULO comparator is tripped, the charger circuits wi not come out of shutdown unti OUT exceeds BAT by 5m. SHUTDOWN The LTC455/LTC455-1 can be shut down by forcing the SHDN pin greater than 1. In shutdown, the currents on IN1/IN2, OUT and BAT are decreased to ess than 2.5μA and the interna battery charge timer is reset. A power paths are put in a Hi-Z state. SUSPEND The LTC455/LTC455-1 can be put in suspend mode by forcing the SUSP pin greater than 1. In suspend mode the idea diode function from BAT to OUT and the output charger are kept aive. The rest of the part is shut down to conserve current and the battery charge timer is reset if OUT becomes ess than BAT. IN and Wa Adapter Bypass Capacitor Many types of capacitors can be used for input bypassing. However, caution must be exercised when using mutiayer ceramic capacitors. Because of the sef resonant and high Q characteristics of some types of ceramic capacitors, high votage 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 Appication Note

19 LTC455/LTC455-1 OPERATION Seecting WALL Input Resistors The WALL input pin identifies the presence of a wa 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 aso forces the ACPR pin ow when the votage at the WALL pin exceeds the input threshod. The WALL pin has a 1 rising threshod and approximatey 3m of hysteresis. It needs to be noted that this function is disabed when the ony power appied to the part is from the battery. Therefore the 1 threshod ony appies when the votage on either IN1/IN2 or OUT is 1m greater than the votage on BAT and the votage on IN1/IN2 or OUT is greater than the ULO (3.8 typ) threshod. The wa adapter detection threshod is set by the foowing equation: R1 TH( Adapter) = WALL 1 R2 R1 HYST( Adapter) = WALL HYST 1 R2 where TH (Adapter) is the wa adapter detection threshod, WALL is the WALL pin rising threshod (typicay 1), R1 is the resistor from the wa adapter input to WALL and R2 is the resistor from WALL to GND. Consider an exampe where the TH (Adapter) is to be set somewhere around 4.5. Resistance on the WALL pin shoud be kept reativey ow (~1k) in order to prevent fase tripping of the wa comparator due to eakages associated with the switching eement used to connect the adapter to OUT. Pick R2 to be 1k and sove for R1. Adapter R R TH( ) 1= 2 1 WALL 45. R1= 1k 1 = 1k 3. 5= 35k 1 The nearest 1% resistor is 34.8k. Therefore R1 = 34.8k and the rising trip point shoud be HYST ( Adapter ) m m 1 The hysteresis is going to be approximatey 134m for this exampe. Power Dissipation The conditions that cause the LTC455/LTC455-1 to reduce charge current due to the therma protection feedback can be approximated by considering the power dissipated in the part. For high charge currents and a wa adapter appied to OUT, the LTC455/LTC455-1 power dissipation is approximatey: P D = ( OUT BAT ) where P D is the power dissipated, OUT is the suppy votage, BAT is the battery votage and is the battery charge current. It is not necessary to perform any worstcase power dissipation scenarios because the LTC455/ LTC455-1 wi automaticay reduce the charge current to maintain the die temperature at approximatey 15 C. However, the approximate ambient temperature at which the therma feedback begins to protect the IC is: T A = 15 C P D θ JA T A = 15 C ( OUT BAT ) θ JA Exampe: An LTC455/LTC455-1 operating from a wa adapter with 5 at OUT providing.8a to a 3 Li-Ion battery. The ambient temperature above, which the LTC455/LTC455-1 wi begin to reduce the.8a charge current, is approximatey: T A = 15 C (5 3).8A 37 C/W T A = 15 C 1.6W 37 C/W = 15 C 59 C = 46 C 19

20 LTC455/LTC455-1 OPERATION The LTC455/LTC455-1 can be used above 46 C, but the charge current wi be reduced beow.8a. The charge current at a given ambient temperature can be approximated by: I BAT 15 C T = A ( ) θ OUT BAT JA Consider the above exampe with an ambient temperature of 55 C. The charge current wi be reduced to approximatey: C C C IBAT = = =.675A C/ W 74 CA / ( ) Board Layout Considerations In order to be abe to deiver maximum charge current under a conditions, it is critica that the Exposed Pad on the backside of the LTC455/LTC455-1 package is sodered to the board. Correcty sodered to a 25mm 2 doube-sided 1oz. copper board, the LTC455/LTC455-1 has a therma resistance of approximatey 37 C/W. Faiure to make therma contact between the Exposed Pad on the backside of the package and the copper board wi resut in therma resistances far greater than 37 C/W. As an exampe, a correcty sodered LTC455/LTC455-1 can deiver over 1A to a battery from a 5 suppy at room temperature. Without a backside therma connection, this number coud drop to ess than 5mA. STABILITY The constant-votage mode feedback oop is stabe without any compensation when a battery is connected. However, a 1μF capacitor with a 1Ω series resistor to GND is recommended at the BAT pin to keep rippe votage ow when the battery is disconnected. Idea Diode from BAT to OUT Forward reguation for the LTC455/LTC455-1 from BAT to OUT has three operationa ranges, depending on the magnitude of the oad current. For sma oad currents, the LTC455/LTC455-1 wi provide a constant-votage drop; this operating mode is referred to as constant ON reguation. As the current exceeds I FWD, the votage drop wi increase ineary with the current with a sope of 1/R DIO,ON ; this operating mode is referred to as constant R ON reguation. As the current increases further, exceeding I MAX, the forward votage drop wi increase rapidy; this operating mode is referred to as constant I ON reguation. The characteristics for the foowing parameters: R FWD, R ON, FWD, and I FWD are specifi ed with the aid of Figure 4. I MAX LTC455 CONSTANT I ON SLOPE: 1/R DIO,ON CONSTANT R ON CURRENT (A) I FWD SLOPE: 1/R FWD SCHOTTKY DIODE CONSTANT ON FWD FORWARD OLTAGE () 455 F4 Figure 4. LTC455/LTC455-1 vs Schottky Diode Forward otage Drop 2

21 LTC455/LTC455-1 TYPICAL APPLICATIONS LTC455/LTC455-1 Confi gured for USB Appication with Wa Adapter Figure 5 shows an LTC455/LTC455-1 confi gured for USB appications with the optiona wa adapter input. The programming resistor (R CLPROG ) is set to 15k which sets up a nomina current imit of 467mA in high power mode (92mA in ow power). This is done to prevent the various toerances in the part and programming resistors from aowing the input current suppied by BUS to exceed the 5mA/1mA imits. The programming resistor (R PROG ) with a vaue of 6.4k sets up a nomina charge current of approximatey 8mA. Note that this is the charge current when the wa adapter is present. When the wa adapter is absent, the current imit supersedes the charge current programming and charge current is imited to 467mA. 5 WALL ADAPTER INPUT 5 (NOM) FROM USB CABLE BUS R3 1Ω 1μF R1 34.8k R2 1k R NTCBIAS 1k NTC 1k C TIMER.1μF IN1 IN2 CHRG ACPR LTC455 WALL NTC NTC TIMER PROG CLPROG R PROG 6.4k R CLPROG 15k OUT BAT SUSP HPWR SHDN GND Li-Ion CELL TO LDOs, REGs, ETC 1μF SUSPEND USB POWER 5mA/1mA SELECT SHUTDOWN 455 F5 Figure 5. USB Power Contro Appication with Wa Adapter Input 21

22 LTC455/LTC455-1 TYPICAL APPLICATIONS USB Hosting Appication: The LTC455/LTC455-1 s IN1 and IN2 are Set Hi-Z by Puing the SUSP Pin Above 1.2 In appications where the power is required to go back out on to the USB BUS the LTC455/LTC455-1 can be configured to turn off its input power path, IN1 and IN2. Forcing the SUSP input pin above 1.2 does this. Figure 6 shows the appication circuit. The wa adapter or the battery can sti provide power to OUT, which in turn can provide power to BUS when commanded from the USB controer. The abiity to charge the battery is enabed when the wa adapter is present. 5 (NOM) FROM USB CABLE BUS 1μF DC/DC OUT CONERTER EN IN 5 WALL ADAPTER INPUT R1 34.8k R2 1k IN1 IN2 WALL SUSP LTC455 OUT BAT CHRG ACPR 1μF Li-Ion CELL TO LDOs, REGs, ETC USB CONTROLLER R3 1k NTC 1k C TIMER.1μF NTC NTC TIMER PROG R PROG 1k CLPROG R CLPROG 15k HPWR SHDN GND 5mA/1mA SELECT SHUTDOWN 455 F6 Figure 6. USB Hosting Appication 22

23 LTC455/LTC455-1 PACKAGE DESCRIPTION UF Package 16-Lead Pastic QFN (4mm 4mm) (Reference LTC DWG # ).72 ± ± ± ±.5 (4 SIDES) PACKAGE OUTLINE.3 ±.5.65 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS PIN 1 TOP MARK (NOTE 6) 4. ±.1 (4 SIDES).75 ±.5 R =.115 TYP 2.15 ±.1 (4-SIDES) BOTTOM IEW EXPOSED PAD PIN 1 NOTCH R =.2 TYP OR CHAMFER.55 ± REF..5 NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-22 ARIATION (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.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 (UF16) QFN 14.3 ±.5.65 BSC Information furnished by Linear Technoogy Corporation is beieved to be accurate and reiabe. However, no responsibiity is assumed for its use. Linear Technoogy Corporation makes no representation that the interconnection of its circuits as described herein wi not infringe on existing patent rights. 23

24 LTC455/LTC455-1 TYPICAL APPLICATION Adapter Diode Repaced with LTC4411 Idea Diode for Improved Effi ciency ADAPTER 4.5 TO 5.5 USB 4.35 TO 5.5 C5 1μF C1 1μF R1 35.8k R9 1k IN GND CTL LTC OUT STAT WALL SHDN SUSP HPWR IN1 OUT BAT IN2 EXPOSED PAD LTC455 1 NTC NTC CHRG ACPR C3 1μF R5 1k SYSTEM LOAD OUTPUT Li-Ion USB CURRENT 1mA-5mA ADAPTER CURRENT 7mA NTC CLPROG 9 R2 15k GND PROG TIMER R3 68.1k C2.1μF 455 TA3 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS Battery Chargers LTC475HX Dua Input USB/AC Adapter Li-Ion Battery Charger with Overvotage Protection Both USB and AC Adapter Inputs Protected up to 22, Standaone Operation, 3mm 3mm DFN LTC495 95mA USB Linear Lithium-Ion Battery Charger 2mm 2mm DFN Package, therma Reguation, Standaone Operation LTC497 USB/Wa Adapter Standaone Li-Ion/Poymer Battery Charger Dua Input, Therma Reguation, 3mm 2mm DFN LTC4413 Dua Monoithic Idea Diodes 3mm 3mm DFN Package, Low Loss Repacement for ORing Diodes Power Management LTC466/ LTC466-1 LTC485/ LTC485-1 USB Power Controer and Battery Charger USB Power Manager with Idea Diode Controer and Li-Ion Charger Instant On Operation, 5mΩ Idea Diode, 4.1 Foat otage (LTC466-1), 4mm 4mm QFN24 Package Instant On Operation, 2mΩ Idea Diode with <5mΩ Option, 4.1 Foat otage (LTC485-1), 4mm 3mm DFN14 Package LTC488 High Effi ciency USB Power Manager and Battery Charger Maximizes Avaiabe Power from USB Port, Bat-Track, Instant On Operation, 1.5A Max Charge Current, 18mΩ Idea Diode with <5mΩ Option, 3.3/25mA Aways-On LDO, 4mm 3mm DFN14 Package LTC488-1/ LTC488-2 LTC489/ LTC489-5/ LTC489-1 LTC49/ LTC49-5 High Effi ciency USB Power Manager and Battery Charger with Reguated Output otage USB Power Manager with Idea Diode Controer and High otage High Effi ciency Li-Ion Battery Charger USB Power Manager with Idea Diode Controer and High otage High Effi ciency Li-Ion Battery Charger Bat-Track is a trademark of Linear Technoogy Corporation. Maximizes Avaiabe Power from USB Port, Bat-Track, Instant On Operation, 1.5A Max Charge Current, 18mΩ Idea Diode with <5mΩ Option, Automatic Charge Current Reduction Maintains 3.6 OUT, No 3.3 LDO, 4mm 3mm DFN14 Package High Effi ciency 1.2A Charger from 6 to 36 (4 Max) Input, 2mΩ Idea Diode with <5mΩ Option, 6mm 3mm DFN22, Bat-Track Adaptive Output Contro (LTC489), Fixed 5 Output (LTC489-5), 4.1 Foat otage (LTC489-1) High Effi ciency 1.2A Charger from 6 to 38 (6 Max) Input (2A Avaiabe to Load). 2mΩ Idea Diode with <5mΩ Option, 6mm 3mm DFN22, Bat-Track Adaptive Output Contro (LTC489), Fixed 5 Output (LTC489-5) 24 LT 118 RE B PRINTED IN USA Linear Technoogy Corporation 163 McCarthy Bvd., Mipitas, CA (48) FAX: (48) LINEAR TECHNOLOGY CORPORATION 24