LTC4098EPDC-TRPBF

FEATURES n LTC4098/LTC4098-1 USB Compatible Switching Power Managers/Li-Ion Chargers with Overvoltage Protection DESCRIPTION The LTC®4098/LTC4098-1 are high efficiency USB PowerPath controllers and full-featured Li-Ion/Polymer battery chargers. They seamlessly manage power distribution from multiple sources including USB, wall adapter, automotive, Firewire or other high voltage DC/DC converters, and a Li-Ion/Polymer battery. The LTC4098/LTC4098-1’s internal switching regulator automatically limits its input current for USB compatibility. For automotive and other high voltage applications, the LTC4098/LTC4098-1 interface with a Linear Technology external switching regulator to provide a high efficiency high voltage power path. Both the USB and the optional high voltage inputs feature Bat-Track optimized charging to provide maximum power to the application and ease thermal issues in high power density applications with input supplies from 5V to as high as 38V. An overvoltage circuit protects the LTC4098/LTC4098-1 from high voltage damage on the USB/wall adaptor inputs with an N-channel FET and a resistor. The LTC4098/LTC4098-1 are available in the ultra-thin (0.55mm) 20-lead 3mm × 4 mm QFN surface mount package. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Bat-Track and PowerPath are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. n n n n n n n n n Switching Regulator with Bat-TrackTM Adaptive Output Control Makes Optimal Use of Limited Power Available from USB Port to Charge Battery and Power Application Overvoltage Protection Guards Against Damage Bat-Track External Step-Down Switching Regulator Control Maximizes Efficiency from Automotive, Firewire and Other High Voltage Input Sources 180mΩ Internal Ideal Diode Plus External Ideal Diode Controller Seamlessly Provide Low Loss PowerPathTM when Input Power is Limited or Unavailable Preset 4.2V Charge Voltage with 0.5% Accuracy (4.1V for LTC4098-1) 4.1V Float Voltage (LTC4098-1) Improves Battery Life and High Temperature Safety Margin Instant-On Operation with Discharged Battery 700mA Maximum Load Current from USB Port 1.5A Maximum Charge Current with Thermal Limiting Ultra-Thin (0.55mm) 20-Lead 3mm × 4mm QFN APPLICATIONS n n n n Media Players GPS PDAs Smart Phones TYPICAL APPLICATION High Efficiency USB/Automotive Battery Charger with Overvoltage Protection INPUT AUTOMOTIVE, FIREWIRE, ETC. LT3653 3.3μH INPUT USB SYSTEM LOAD EFFICIENCY (%) USB Switching Regulator Efficiency to System Load (PVOUT/PVBUS) 100 90 80 70 60 50 40 30 BAT = 4.2V BAT = 3.3V VBUS 10μF OVGATE OVSENS TO μC 3 D0-D2 CLPROG VC WALL SW 6.04k LTC4098/LTC4098-1 VOUT BAT PROG GND BATSENS 10μF 20 10 0.1μF 3.01k 1k + Li-Ion 40981 TA01a 0 0.01 VBUS = 5V IBAT = 0mA 10x MODE 0.1 IVOUT (A) 1 40981 TA01b 40981fb 1 LTC4098/LTC4098-1 ABSOLUTE MAXIMUM RATINGS (Note 1) PIN CONFIGURATION TOP VIEW WALL ACPR D2 16 D1 15 D0 21 14 SW 13 VBUS 12 VOUT 11 BAT 7 PROG 8 CHRG 9 10 IDGATE GND VC OVSENS 1 OVGATE 2 CLPROG 3 NTCBIAS 4 NTC 5 BATSENS 6 VBUS, WALL (Transient) t < 1ms, Duty Cycle < 1% .......................................... –0.3V to 7V VBUS, WALL (Static), BAT, BATSENS, CHRG, NTC, ................................................. –0.3V to 6V D0, D1, D2 .........–0.3V to Max (VBUS, VOUT, BAT) + 0.3V IOVSENS.................................................................±10mA ICLPROG ....................................................................3mA IPROG ........................................................................2mA ICHRG ......................................................................50mA IVOUT, ISW, IBAT ............................................................2A IACPR ......................................................................10mA Operating Temperature Range.................. –40°C to 85°C Junction Temperature ........................................... 125°C Storage Temperature Range................... –65°C to 125°C 20 19 18 17 PDC PACKAGE 20-LEAD (3mm 4mm) PLASTIC UTQFN TJMAX = 125°C, θJA = 43°C/W EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH LTC4098EPDC#PBF LTC4098EPDC-1#PBF TAPE AND REEL LTC4098EPDC#TRPBF LTC4098EPDC-1#TRPBF PART MARKING DDVT DSZT PACKAGE DESCRIPTION 20-Lead (3mm × 4mm) Plastic UTQFN 20-Lead (3mm × 4mm) Plastic UTQFN TEMPERATURE RANGE –40°C to 85°C –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, RCLPROG = 3.01k, unless otherwise noted. SYMBOL VBUS IVBUS(LIM) PARAMETER Input Supply Voltage Total Input Current 1x Mode 5x Mode 10x Mode Low Power Suspend Mode High Power Suspend Mode 1x Mode 5x Mode 10x Mode Low Power Suspend Mode High Power Suspend Mode 1x Mode 5x Mode 10x Mode Low Power Suspend Mode High Power Suspend Mode CONDITIONS l l l l l l ELECTRICAL CHARACTERISTICS MIN 4.35 92 445 815 0.32 1.6 TYP MAX 5.5 UNITS V mA mA mA mA mA mA mA mA mA mA mA/mA mA/mA mA/mA mA/mA mA/mA 40981fb Input Power Supply 97 473 883 0.39 2.05 6 15 15 0.042 0.042 230 1164 2210 11.6 60 100 500 1000 0.5 2.5 IVBUSQ (Note 4) Input Quiescent Current hCLPROG (Note 4) Ratio of Measured VBUS Current to CLPROG Program Current 2 LTC4098/LTC4098-1 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, RCLPROG = 3.01k, unless otherwise noted. SYMBOL IVOUT PARAMETER VOUT Current Available Before Discharging Battery CONDITIONS 1x Mode, BAT = 3.3V 5x Mode, BAT = 3.3V 10x Mode, BAT = 3.3V Low Power Suspend Mode High Power Suspend Mode 1x, 5x, 10x Modes Suspend Modes Rising Threshold Falling Threshold Rising Threshold Falling Threshold 1x, 5x, 10x Modes, 0V < BAT ≤ 4.2V, IVOUT = 0mA, Battery Charger Off USB Suspend Modes, IVOUT = 250μA fOSC RPMOS RNMOS IPEAK Switching Frequency PMOS On-Resistance NMOS On-Resistance Peak Inductor Current Clamp 1x Mode 5x Mode 10x Mode 3.5 4.5 1.96 3.95 MIN TYP 135 659 1231 0.32 2.04 1.188 100 4.30 4.00 200 50 BAT + 0.3 4.6 2.25 0.18 0.30 1.2 1.7 3 15 Rising Threshold Falling Threshold WALL-BAT Rising Threshold WALL-BAT Falling Threshold 4.2 4.3 3.2 90 30 BAT + 0.3 100 IACPR = 0mA IACPR = 0mA Rising Threshold, ROVSENS = 6.04k Input Below VOVP Input Above VOVP COVGATE = 1nF 4.179 4.165 4.080 4.066 980 192 6.20 VOUT 0 6.35 1.88 • VOVSENSE 0 2.2 4.200 4.200 4.100 4.100 1030 206 3.7 4.221 4.235 4.121 4.134 1080 220 5 6.50 12 4.4 4.7 4.7 2.65 4.35 MAX UNITS mA mA mA mA mA V mV V V mV mV V V MHz Ω Ω A A A Ω V V mV mV V μA V V V V V ms V V V V mA mA μA ELECTRICAL CHARACTERISTICS 0.26 1.6 0.41 2.46 VCLPROG VUVLO VDUVLO VOUT CLPROG Servo Voltage in Current Limit VBUS Undervoltage Lockout VBUS to BAT Differential Undervoltage Lockout VOUT Voltage RSUSP VWALL ΔVWALL Suspend LDO Output Resistance Absolute WALL Input Threshold Differential WALL Input Threshold Regulation Target WALL Quiescent Current ACPR High Voltage ACPR Low Voltage Bat-Track External Switching Regulator Control 0 3.5 45 Overvoltage Protection VOVP VOVGATE tRISE Battery Charger VFLOAT LTC4098 BAT Regulated Output Voltage 0°C ≤ TA ≤ 85°C LTC4098-1 BAT Regulated Output Voltage ICHG IBAT Constant-Current Mode Charge Current Battery Drain Current 0°C ≤ TA ≤ 85°C RPROG = 1k, 10x Mode RPROG = 5k, 5x, 10x Modes VBUS > VUVLO, PowerPath Switching Regulator On, Battery Charger Off, IVOUT = 0μA VBUS = 0V, IVOUT = 0μA (Ideal Diode Mode) Overvoltage Protection Threshold OVGATE Output Voltage OVGATE Time to Reach Regulation 25 35 μA 40981fb 3 LTC4098/LTC4098-1 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, RCLPROG = 3.01k, unless otherwise noted. SYMBOL VPROG VPROG,TRKL hPROG VTRKL ΔVTRKL VRECHRG tTERM tBADBAT hC/10 VCHRG ICHRG RON_CHG TLIM NTC VCOLD VHOT VDIS INTC Ideal Diode VFWD RDROPOUT IMAX VIL VIH IPD Forward Voltage Detection Internal Diode On-Resistance, Dropout Diode Current Limit Input Low Voltage Input High Voltage Static Pull-Down Current VPIN = 1V 1.2 2 IVOUT = 10mA IVOUT = 200mA 2 0.4 15 0.18 mV Ω A V V μA Cold Temperature Fault Threshold Voltage Hot Temperature Fault Threshold Voltage NTC Disable Threshold Voltage NTC Leakage Current Rising Threshold Hysteresis Falling Threshold Hysteresis Falling Threshold Hysteresis NTC = 5V 75.0 33.4 0.7 –50 76.5 1.5 34.9 1.5 1.7 50 78.0 36.4 2.7 50 %NTCBIAS %NTCBIAS %NTCBIAS %NTCBIAS %NTCBIAS mV nA PARAMETER PROG Pin Servo Voltage PROG Pin Servo Voltage in Trickle Charge Ratio of IBAT to PROG Pin Current Trickle Charge Threshold Voltage Trickle Charge Hystersis Voltage Recharge Battery Threshold Voltage Safety Timer Termination Period Bad Battery Termination Time End of Charge Indication Current Ratio CHRG Pin Output Low Voltage CHRG Pin Input Current Battery Charger Power FET On-Resistance (Between VOUT and BAT) Junction Temperature in ConstantTemperature Mode Threshold Voltage Relative to VFLOAT Timer Starts When BAT = VFLOAT BAT < VTRKL (Note 5) ICHRG = 5mA BAT = 4.5V, VCHRG = 5V IBAT = 200mA –80 3.4 0.43 0.09 BAT Rising 2.7 BAT < VTRKL CONDITIONS MIN TYP 1.000 0.100 1030 2.85 130 –100 4 0.5 0.1 65 0 0.18 110 –120 4.6 0.58 0.11 100 1 3 MAX UNITS V V mA/mA V mV mV Hour Hour mA/mA mV μA Ω °C ELECTRICAL CHARACTERISTICS Logic (D0, D1, D2) Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTC4098E/LTC4098E-1 are guaranteed to meet performance specifications from 0°C to 85°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: The LTC4098E/LTC4098E-1 include overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 4: Total input current is the sum of quiescent current, IVBUSQ, and measured current given by VCLPROG/RCLPROG • (hCLPROG + 1) Note 5: hC/10 is expressed as a fraction of measured full charge current with a 5k PROG resistor. 40981fb 4 LTC4098/LTC4098-1 TYPICAL PERFORMANCE CHARACTERISTICS Ideal Diode V-I Characteristics 1.0 INTERNAL IDEAL DIODE WITH SUPPLEMENTAL EXTERNAL VISHAY Si2333 PMOS RESISTANCE ( ) 0.25 TA = 25°C unless otherwise noted. USB Compliant Load Current Available Before Discharging Battery 800 750 Ideal Diode Resistance vs Battery Voltage 0.8 CURRENT (A) 0.20 CURRENT (mA) 4.2 40981 G02 0.6 INTERNAL IDEAL DIODE ONLY 0.4 INTERNAL IDEAL DIODE 0.15 700 650 600 550 VBUS = 5V RCLPROG = 3.01k 5x USB SETTING 500 3.0 3.3 2.7 0.10 INTERNAL IDEAL DIODE WITH SUPPLEMENTAL EXTERNAL VISHAY Si2333 PMOS 0.2 0.05 0 0 0.04 0.12 0.16 0.08 FORWARD VOLTAGE (V) 0.20 40981 G01 0 2.7 3.0 3.6 3.9 3.3 BATTERY VOLTAGE (V) 3.6 3.9 4.2 40981 G03 BATTERY VOLTAGE (V) VOUT Voltage vs VOUT Current (Battery Charger Disabled) 4.50 BAT = 4V 4.25 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 3.75 VOUT Voltage vs VOUT Current (Battery Charger Enabled) 700 Battery Charge Current vs VOUT Current (Battery Charger Enabled) 4.00 BAT = 3.4V CHARGE CURRENT (mA) 3.50 450 3.25 200 3.75 3.00 3.50 VBUS = 5V 5x MODE 3.25 0 200 600 400 OUTPUT CURRENT (mA) 800 40981 G04 VBUS = 5V BAT = 3V RCLPROG = 3.01k RPROG = 2k 5x USB SETTING 0 200 600 400 OUTPUT CURRENT (mA) 800 40981 G05 –50 VBUS = 5V BAT = 3V RCLPROG = 3.01k RPROG = 2k 5x USB SETTING 0 200 600 400 OUTPUT CURRENT (mA) 800 40981 G06 2.75 –300 USB Compliant Load Current Available Before Discharging Battery 160 150 CHARGE CURRENT (mA) 140 130 120 110 VBUS = 5V RCLPROG = 3.01k 1x USB SETTING 100 3.0 3.3 2.7 700 600 500 400 300 USB Limited Battery Charge Current vs Battery Voltage 150 125 CHARGE CURRENT (mA) VBUS = 5V RPROG = 1k RCLPROG = 3.01k 100 75 USB Limited Battery Charge Current vs Battery Voltage CURRENT (mA) VBUS = 5V RPROG = 1k RCLPROG = 3.01k LTC4098 LTC4098 200 LTC4098-1 100 5x USB SETTING, BATTERY CHARGER SET FOR 1A 0 3.0 3.3 3.6 3.9 2.7 BATTERY VOLTAGE (V) 50 LTC4098-1 25 0 1x USB SETTING, BATTERY CHARGER SET FOR 1A 2.7 3.0 3.3 3.6 3.9 BATTERY VOLTAGE (V) 4.2 40981 G09 3.6 3.9 4.2 40981 G07 4.2 40981 G08 BATTERY VOLTAGE (V) 40981fb 5 LTC4098/LTC4098-1 TYPICAL PERFORMANCE CHARACTERISTICS Battery Drain Current vs Battery Voltage 30 25 BATTERY CURRENT (μA) VBUS = 0V EFFICIENCY (%) EFFICIENCY (%) 20 15 10 5 0 2.7 3.0 3.3 3.6 3.9 BATTERY VOLTAGE (V) 4.2 40981 G10 TA = 25°C unless otherwise noted. Battery Charging Efficiency vs Battery Voltage with No External Load (PBAT/PVBUS) 100 RCLPROG = 3.01k RPROG = 1k IVOUT = 0mA 90 LTC4098 5x CHARGING EFFICIENCY PowerPath Switching Regulator Efficiency vs Output Current 100 90 80 70 60 50 40 0.01 BAT = 3.8V 1x MODE 5x, 10x MODE IVOUT = 0μA 80 1x CHARGING EFFICIENCY VBUS = 5V (SUSPEND MODE) 70 0.1 OUTPUT CURRENT (A) 1 40981 G11 60 2.7 3.0 3.6 3.9 3.3 BATTERY VOLTAGE (V) 4.2 40981 G12 VBUS Current vs VBUS Voltage (Suspend) 50 BAT = 3.8V IVOUT = 0mA OUTPUT VOLTAGE (V) 5.0 VOUT Voltage vs VOUT Current in Suspend 2.5 SUSPEND HIGH 4.5 VBUS CURRENT (mA) 2.0 VBUS Current vs VOUT Current in Suspend VBUS = 5V BAT = 3.3V RCLPROG = 3.01k SUSPEND HIGH 40 VBUS CURRENT (μA) 30 4.0 1.5 20 3.5 SUSPEND LOW VBUS = 5V BAT = 3.3V RCLPROG = 3.01k 0 0.5 1.5 2 1 OUTPUT CURRENT (mA) 2.5 40981 G14 1.0 10 3.0 0.5 SUSPEND LOW 0 0 0.5 1.5 2 1 OUTPUT CURRENT (mA) 2.5 40981 G15 0 2.5 1 2 4 3 VBUS VOLTAGE (V) 5 6 40981 G13 Automatic Battery Charge Current Reduction 120 % PROGRAMMED CHARGE CURRENT 100 CHARGE CURRENT (mA) 80 60 40 20 0 3.2 600 500 400 Battery Charge Current vs Temperature RPROG = 2k NORMALIZED FLOAT VOLTAGE 1.003 1.002 1.001 1.000 0.999 0.998 Normalized Battery Charger Float Voltage vs Temperature THERMAL REGULATION 300 200 100 0 –40 –20 3.3 3.4 VOUT (V) 3.5 3.6 40981 G16 0 20 40 60 80 TEMPERATURE (°C) 100 120 40981 G17 0.997 –40 –15 35 10 TEMPERATURE (°C) 60 85 40981 G18 40981fb 6 LTC4098/LTC4098-1 TYPICAL PERFORMANCE CHARACTERISTICS Low Battery (Instant-On) Output Voltage vs Temperature 3.68 BAT = 2.7V IVOUT = 100mA 5x MODE OUTPUT VOLTAGE (V) 3.66 FREQUENCY (MHz) 2.350 TA = 25°C unless otherwise noted. Oscillator Frequency vs Temperature 20 17 QUIESCENT CURRENT (mA) VBUS Quiescent Current vs Temperature VBUS = 5V IVOUT = 0μA 5x MODE 14 11 8 1x MODE 5 2 –40 2.300 2.250 3.64 2.200 3.62 2.150 3.60 –40 –15 35 10 TEMPERATURE ( C) 60 85 40981 G19 2.100 –40 –15 35 10 TEMPERATURE (°C) 60 85 40981 G20 –15 –10 35 TEMPERATURE (°C) 60 85 40981 G21 Quiescent Current in Suspend vs Temperature 45 42 QUIESCENT CURRENT (μA) 39 36 33 30 27 –40 CHRG PIN CURRENT (mA) VBUS = 5V IVOUT = 0μA 100 CHRG Pin Current vs Voltage (Pull-Down State) VBUS = 5V BAT = 3.8V 80 60 40 20 0 –15 10 35 TEMPERATURE (°C) 60 85 40981 G22 0 1 3 4 2 CHRG PIN VOLTAGE (V) 5 40981 G23 Suspend LDO Transient Response (500μA to 1.5mA) OVP Connection Waveform IOUT 500μA/DIV 0mA VOUT 20mV/DIV AC COUPLED VBUS 5V/DIV OVGATE 5V/DIV OVP INPUT VOLTAGE 0V TO 5V STEP 5V/DIV 500μs/DIV 40981 G24 500μs/DIV 40981 G25 40981fb 7 LTC4098/LTC4098-1 TYPICAL PERFORMANCE CHARACTERISTICS OVP Protection Waveform VBUS 5V/DIV OVGATE 5V/DIV OVGATE 5V/DIV OVP INPUT VOLTAGE 5V TO 10V STEP 5V/DIV 500μs/DIV 40981 G26 TA = 25°C unless otherwise noted. OVP Reconnection Waveform VBUS 5V/DIV OVP INPUT VOLTAGE 10V TO 5V STEP 5V/DIV 500μs/DIV 40981 G27 OVSENS Quiescent Current vs Temperature 37 VOVSENS = 5V 6.280 Rising Overvoltage Threshold vs Temperature 12 OVGATE vs OVSENS OVSENS CONNECTED TO INPUT THROUGH 10 6.04k RESISTOR 8 QUIESCENT CURRENT (μA) 35 OVP THRESHOLD (V) 6.275 33 6.270 OVGATE (V) –15 35 10 TEMPERATURE (°C) 60 85 40981 G29 6 4 31 6.265 29 6.260 2 0 0 2 4 6 INPUT VOLTAGE (V) 8 40981 G30 27 –40 –15 35 10 TEMPERATURE (°C) 60 85 40981 G28 6.255 –40 40981fb 8 LTC4098/LTC4098-1 PIN FUNCTIONS OVSENS (Pin 1): Overvoltage Protection Sense Input. OVSENS should be connected through a 6.04k resistor to the input power connector and the drain of an external N-channel MOS pass transistor. When the voltage on this pin exceeds a preset level, the OVGATE pin will be pulled to GND to disable the pass transistor and protect downstream circuitry. If overvoltage protection is not desired, connect OVSENS to GND. OVGATE (Pin 2): Overvoltage Protection Gate Output. Connect OVGATE to the gate pin of an external N-channel MOS pass transistor. The source of the transistor should be connected to VBUS and the drain should be connected to the product’s DC input connector. This pin is connected to an internal charge pump capable of creating sufficient overdrive to fully enhance the pass transistor. If an overvoltage condition is detected, OVGATE is brought rapidly to GND to prevent damage to downstream circuitry. OVGATE works in conjunction with OVSENS to provide this protection. If overvoltage protection is not desired, leave OVGATE open. CLPROG (Pin 3): USB Current Limit Program and Monitor Pin. A 1% resistor from CLPROG to ground determines the upper limit of the current drawn from the VBUS pin. A precise fraction of the input current, hCLPROG, is sent to the CLPROG pin when the high side switch is on. The switching regulator delivers power until the CLPROG pin reaches 1.188V. Therefore, the current drawn from VBUS will be limited to an amount given by hCLPROG and RCLPROG. There are several ratios for hCLPROG available, two of which correspond to the 500mA and 100mA USB specifications. A multilayer ceramic averaging capacitor is also required at CLPROG for filtering. NTCBIAS (Pin 4): NTC Thermistor Bias Output. If NTC operation is desired, connect a bias resistor between NTCBIAS and NTC, and an NTC thermistor between NTC and GND. To disable NTC operation, connect NTC to GND and leave NTCBIAS open. NTC (Pin 5): Input to the NTC Thermistor Monitoring Circuits. The NTC pin connects to a negative temperature coefficient thermistor which is typically co-packaged with the battery pack to determine if the battery is too hot or too cold to charge. If the battery’s temperature is out of range, charging is paused until the battery temperature re-enters the valid range. A low drift bias resistor is required from NTCBIAS to NTC and a thermistor is required from NTC to ground. If the NTC function is not desired, the NTC pin should be grounded. BATSENS (Pin 6): Battery Voltage Sense Input. For proper operation, this pin must always be connected to BAT. For best performance, connect BATSENS to BAT physically close to the Li-Ion cell. PROG (Pin 7): Charge Current Program and Charge Current Monitor Pin. Connecting a 1% resistor from PROG to ground programs the charge current. If sufficient input power is available in constant-current mode, this pin servos to 1V. The voltage on this pin always represents the actual charge current by using the following formula: IBAT = VPROG • 1030 RPROG CHRG (Pin 8): Open-Drain Charge Status Output. The CHRG pin indicates the status of the battery charger. Four possible states are represented by CHRG: charging, not charging, unresponsive battery and battery temperature out of range. CHRG is modulated at 35kHz and switches between a low and a high duty cycle for easy recognition by either humans or microprocessors. CHRG requires a pull-up resistor and/or LED to provide indication. GND (Pin 9, 21): Exposed Pad and pin must be soldered to the PCB to provide a low electrical and thermal impedance connection to ground. IDGATE (Pin 10): Ideal Diode Amplifier Output. This pin controls the gate of an external P-channel MOSFET transistor used to supplement the internal ideal diode. The source of the P-channel MOSFET should be connected to VOUT and the drain should be connected to BAT. BAT (Pin 11): Single-Cell Li-Ion Battery Pin. Depending on available power and load, a Li-Ion battery on BAT will either deliver system power to VOUT through the ideal diode or be charged from the battery charger. The LTC4098 will charge to a maximum voltage of 4.200V. The LTC4098-1 will charge to a maximum voltage of 4.100V. 40981fb 9 LTC4098/LTC4098-1 PIN FUNCTIONS VOUT (Pin 12): Output Voltage of the Switching PowerPath Controller and Input Voltage of the Battery Charger. The majority of the portable product should be powered from VOUT. The LTC4098/LTC4098-1 will partition the available power between the external load on VOUT and the internal battery charger. Priority is given to the external load and any extra power is used to charge the battery. An ideal diode from BAT to VOUT ensures that VOUT is powered even if the load exceeds the allotted power from VBUS or if the VBUS power source is removed. VOUT should be bypassed with a low impedance multilayer ceramic capacitor. VBUS (Pin 13): Input Voltage for the Switching PowerPath Controller. VBUS will usually be connected to the USB port of a computer or a DC output wall adapter. VBUS should be bypassed with a low impedance multilayer ceramic capacitor. SW (Pin 14): The SW pin delivers power from VBUS to VOUT via the step-down switching regulator. An inductor should be connected from SW to VOUT. See the Applications Information section for a discussion of inductance value and current rating. D0 (Pin 15): Mode Select Input Pin. D0, in combination with the D1 pin and the D2 pin, controls the current limit and battery charger functions of the LTC4098/LTC4098-1 (see Table 1). This pin is pulled low by a weak current sink. D1 (Pin 16): Mode Select Input Pin. D1, in combination with the D0 pin and the D2 pin, controls the current limit and battery charger functions of the LTC4098/LTC4098-1 (see Table 1). This pin is pulled low by a weak current sink. D2 (Pin 17): Mode Select Input Pin. D2, in combination with the D0 pin and D1 pin, controls the current limit and battery charger functions of the LTC4098/LTC4098-1 (see Table 1). This pin is pulled low by a weak current sink. WALL (Pin 18): External Power Source Sense Input. WALL should be connected to the output of the external high voltage switching regulator and to the drain of an external P-channel MOS transistor. It is used to determine when power is applied to the external regulator. When power is detected, ACPR is driven low and the USB input is automatically disabled. ACPR (Pin 19): External Power Source Present Output (Active Low). ACPR indicates that the output of the external high voltage step-down switching regulator is suitable for use by the LTC4098/LTC4098-1. It should be connected to the gate of an external P-channel MOS transistor whose source is connected to VOUT and whose drain is connected to WALL. ACPR has a high level of VOUT and a low level of GND. VC (Pin 20): Bat-Track External Switching Regulator Control Output. This pin drives the VC pin of a Linear Technology external step-down switching regulator. In concert with WALL and ACPR, it will regulate VOUT to maximize battery charger efficiency. Exposed Pad (Pin 21): Ground. The Exposed Pad must be soldered to the PCB. 40981fb 10 TO AUTOMOTIVE, FIREWIRE, ETC. VIN VC HVOK VOUT LT3653 ISENSE SW 20 VC WALL ACPR 19 OVERVOLTAGE PROTECTION VOUT 3.6V BAT + 0.3V 4.3V 18 BLOCK DIAGRAM TO USB OR WALL ADPAPTER SW NONOVERLAP AND DRIVE LOGIC VOUT 13 VBUS ISWITCH /N ILDO /M 100mV SUSPEND LDO 4.6V + – –+ 3 S Q CONSTANT-CURRENT CONSTANT-VOLTAGE BATTERY CHARGER R PWM CLPROG 0.3V 3.6V AVERAGE INPUT CURRENT LIMIT CONTROLLER AVERAGE OUTPUT VOLTAGE LIMIT CONTROLLER NTCBIAS VOUT UNDERTEMP NTC FAULT LOGIC OSC 4 0.1V D0 15 LTC4098/LTC4098-1 + – T NTC OVERTEMP NTC ENABLE D1 16 D2 17 + – 5 NTC + – GND 9 GND 21 + – + + – + – 1.188V +– 100mV – + 1V IBAT/1030 NTC BAD CELL CHRG 8 PWM PROG 7 40981 BD + – + – +– 14 12 IDEAL DIODE 0V 2 OVGATE 2 6V 15mV + – OPTIONAL EXTERNAL IDEAL DIODE PMOS + + – + – IDGATE 10 BATSENS BAT 6 11 SINGLECELL Li-Ion 1 OVSENS TO SYSTEM LOAD + 11 40981fb LTC4098/LTC4098-1 OPERATION Introduction The LTC4098/LTC4098-1 are high efficiency power management and Li-Ion charger solutions designed to make optimal use of the power available from a variety of sources, while minimizing power dissipation and easing thermal budgeting constraints. The innovative PowerPath architecture ensures that the application is powered immediately after external voltage is applied, even with a completely dead battery by prioritizing power to the application over the battery. The LTC4098/LTC4098-1 include a Bat-Track monolithic step-down switching regulator for USB, wall adapters and other 5V sources. Designed specifically for USB applications, the switching regulator incorporates a precision average input current limit for USB compatibility. Because power is conserved, the LTC4098/LTC4098-1 allow the load current on VOUT to exceed the current drawn by the USB port, making maximum use of the allowable USB power for battery charging. The switching regulator and battery charger communicate to ensure that the average input current never exceeds the USB specifications. For automotive, Firewire, and other high voltage applications, the LTC4098/LTC4098-1 provide Bat-Track control of an external LTC step-down switching regulator to maximize battery charger efficiency and minimize heat production. When power is available from both the USB and high voltage inputs, the high voltage input is prioritized and the USB input is automatically disabled. The LTC4098/LTC4098-1 feature an overvoltage protection circuit which is designed to work with an external N-channel FET to prevent damage to its inputs caused by accidental application of high voltage. The LTC4098/LTC4098-1 contain both an internal 180mΩ ideal diode and an ideal diode controller designed for use with an external P-channel FET. The ideal diodes from BAT to VOUT guarantee that ample power is always available to VOUT even if there is insufficient or absent power at VBUS or WALL. Finally, to prevent battery drain when a device is connected to a suspended USB port, an LDO from VBUS to VOUT provides either low power or high power USB suspend current to the application. Bat-Track Input Current Limited Step Down Switching Regulator The power delivered from VBUS to VOUT is controlled by a 2.25MHz constant-frequency step-down switching regulator. To meet the USB maximum load specification, the switching regulator contains a measurement and control system that ensures that the average input current remains below the level programmed at CLPROG. VOUT drives the combination of the external load and the battery charger. If the combined load does not cause the switching power supply to reach the programmed input current limit, VOUT will track approximately 0.3V above the battery voltage. By keeping the voltage across the battery charger at this low level, power lost to the battery charger is minimized. Figure 1 shows the power path components. If the combined external load plus battery charge current is large enough to cause the switching power supply to reach the programmed input current limit, the battery charger will reduce its charge current by precisely the amount necessary to enable the external load to be satisfied. Even if the battery charge current is programmed to exceed the allowable USB current, the USB specification for average input current will not be violated; the battery charger will reduce its current as needed. Furthermore, if the load current at VOUT exceeds the programmed power from VBUS, load current will be drawn from the battery via the ideal diodes even when the battery charger is enabled. The current at CLPROG is a precise fraction of the VBUS current. When a programming resistor and an averaging capacitor are connected from CLPROG to GND, the voltage on CLPROG represents the average input current of the switching regulator. As the input current approaches the programmed limit, CLPROG reaches 1.188V and power delivered by the switching regulator is held constant. Several ratios of current are available which can be set to correspond to USB low and high power modes with a single programming resistor. The input current limit is programmed by various combinations of the D0, D1 and D2 pins as shown in Table 1. 40981fb 12 OPERATION TO AUTOMOTIVE, FIREWIRE, ETC. VIN VC HVOK VOUT LT3653 ISENSE SW 20 OVERVOLTAGE PROTECTION ACPR 19 VOUT 3.6V BAT + 0.3V 4.3V Bat-Track HV CONTROL VC WALL 18 6V FROM USB OR WALL ADAPTER ISWITCH /N PWM AND GATE DRIVE IDEAL DIODE CONSTANT-CURRENT CONSTANT-VOLTAGE BATTERY CHARGER OmV 15mV 0.3V 3.6V 13 VBUS 3 1.188V CLPROG +– AVERAGE INPUT CURRENT LIMIT CONTROLLER AVERAGE OUTPUT VOLTAGE LIMIT CONTROLLER Figure 1. Simplified Power Flow Diagram + – + + – + – +– SW 14 VOUT 12 2 OVGATE 2 + – + – IDGATE 10 BAT 11 BATSENS 6 40981 F01 + + – USB INPUT BATTERY POWER HV INPUT 1 OVSENS 3.5V TO (BAT + 0.3V) TO SYSTEM LOAD OPTIONAL EXTERNAL IDEAL DIODE PMOS + – + SINGLE-CELL Li-Ion LTC4098/LTC4098-1 13 40981fb LTC4098/LTC4098-1 OPERATION The switching input regulator can also be deactivated (USB suspend). The average input current will be limited by the CLPROG programming resistor according to the following expression: IVBUS = IVBUSQ + VCLPROG • (hCLPROG + 1) RCLPROG Notice that when D0 is high and D1 is low, the switching regulator is set to a higher current limit for increased charging and power availability at VOUT. These modes will typically be used when there is line power available from a wall adapter. While not in current limit, the switching regulator’s Bat-Track feature will set VOUT to approximately 300mV above the voltage at BAT. However, if the voltage at BAT is below 3.3V, and the load requirement does not cause the switching regulator to exceed its current limit, VOUT will regulate at a fixed 3.6V, as shown in Figure 2. This instant-on operation will allow a portable product to run immediately when power is applied without waiting for the battery to charge. If the load does exceed the current limit at VBUS, VOUT will range between the no-load voltage and slighly below the battery voltage, indicated by the shaded region of Figure 2. 4.5 4.2 3.9 VOUT (V) NO LOAD 3.6 300mV 3.3 3.0 2.7 2.4 2.4 where IVBUSQ is the quiescent current of the LTC4098/ LTC4098-1, VCLPROG is the CLPROG servo voltage in current limit, RCLPROG is the value of the programming resistor and hCLPROG is the ratio of the measured current at VBUS to the sample current delivered to CLPROG. Refer to the Electrical Characteristics table for values of hCLPROG, VCLPROG and IVBUSQ. Given worst-case circuit tolerances, the USB specification for the average input current in 1x or 5x mode will not be violated, provided that RCLPROG is 3.01k or greater. Table 1 shows the available settings for the D0, D1 and D2 pins. Table 1. Controlled Input Current Limit D2 0 0 0 0 1 1 1 1 D1 0 0 1 1 0 0 1 1 D0 0 1 0 1 0 1 0 1 CHARGER STATUS IBUS(LIM) On 100mA (1x) On 1A (10x) On 500mA (5x) Off 500μA (Susp Low) Off 100mA (1x) Off 1A (10x) Off 500mA (5x) Off 2.5mA (Susp High) 2.7 3.0 3.6 3.3 BAT (V) 3.9 4.2 40981 F02 Figure 2. VOUT vs BAT 40981fb 14 LTC4098/LTC4098-1 OPERATION For very low battery voltages, the battery charger acts like a load and, due to limited input power, its current will tend to pull VOUT below the 3.6V instant-on voltage. To prevent VOUT from falling below this level, an undervoltage circuit automatically detects that VOUT is falling and reduces the battery charge current as needed. This reduction ensures that load current and voltage are always prioritized while allowing as much battery charge current as possible. Refer to Overprogramming the Battery Charger in the Applications Information section. The voltage regulation loop compensation is controlled by the capacitance on VOUT. An MLCC capacitor of 10μF is required for loop stability. Additional capacitance beyond this value will improve transient response. An internal undervoltage lockout circuit monitors VBUS and keeps the switching regulator off until VBUS rises above the rising UVLO threshold (4.3V). If VBUS falls below the falling UVLO threshold (4V), system power at VOUT will be drawn from the battery via the ideal diodes. The voltage at VBUS must also be higher than the voltage at BAT by approximately 170mV for the switching regulator to operate. Bat-Track High Voltage External Switching Regulator Control The WALL, ACPR and VC pins can be used in conjunction with an external high voltage step-down switching regulator such as the LT3653 or LT3480 to minimize heat production when operating from higher voltage sources, as shown in Figures 3 and 4. Bat-Track control circuitry regulates the external switching regulator’s output voltage to the larger of BAT + 300mV or 3.6V. This maximizes battery charger efficiency while still allowing instant-on operation when the battery is deeply discharged. When using the LT3480, the feedback network should be set to generate an output voltage between 4.5V and 5.5V. When high voltage is applied to the external regulator, WALL will rise toward this programmed output voltage. When WALL exceeds approximately 4.3V, ACPR is brought low and the Bat-Track control of the LTC4098/LTC4098-1 overdrives the local VC control of the external high voltage step-down switching regulator. Therefore, once the Bat-Track control is enabled, the output voltage is set independent of the switching regulator feedback network. Bat-Track control provides a significant efficiency advantage over the simple use of a 5V switching regulator output to drive the battery charger. With a 5V output driving VOUT, battery charger efficiency is approximately: ηTOTAL = ηBUCK • VBAT 5V where ηBUCK is the efficiency of the high voltage switching regulator and 5V is the output voltage of the switching regulator. With a typical switching regulator efficiency of 87% and a typical battery voltage of 3.8V, the total battery charger efficiency is approximately 66%. Assuming a 1A charge current, nearly 2W of power is dissipated just to charge the battery! SW LT3653 ISENSE VOUT VC LT3480 SW FB VC HVOK VC WALL LTC4098/ LTC4098-1 ACPR VOUT 40981 F03 VC SYSTEM LOAD WALL LTC4098/ LTC4098-1 ACPR VOUT 40981 F04 SYSTEM LOAD Figure 3. LT3653 Typical Interface Figure 4. LT3480 Typical Interface 40981fb 15 LTC4098/LTC4098-1 OPERATION With Bat-Track, battery charger efficiency is approximately: ηTOTAL = ηBUCK • BAT BAT + 0.3V In an overvoltage condition, the OVSENS pin will be clamped at 6V. The external 6.04k resistor must be sized appropriately to dissipate the resultant power. For example, a 1/10W 6.04k resistor can have at most √PMAX • 6.04kΩ = 24V applied across its terminals. With the 6V at OVSENS, the maximum overvoltage magnitude that this resistor can withstand is 30V. A 1/4W 6.04k resistor raises this value to 44V. WALL’s absolute maximum current rating of 10mA imposes an upper protection limit of 66V. The charge pump output on OVGATE has limited output drive capability. Care must be taken to avoid leakage on this pin, as it may adversely affect operation. See the Applications Information section for examples of multiple input protection, reverse input protection, and a table of recommended components. Ideal Diode from BAT to VOUT The LTC4098/LTC4098-1 have an internal ideal diode as well as a controller for an external ideal diode. Both the internal and the external ideal diodes are always on and will respond quickly whenever VOUT drops below BAT. If the load current increases beyond the power allowed from the switching regulator, additional power will be pulled from the battery via the ideal diodes. Furthermore, if power to VBUS (USB or wall power) is removed, then all of the application power will be provided by the battery via the ideal diodes. The ideal diodes will be fast enough to keep VOUT from drooping with only the storage capacitance required for the switching regulator. The internal ideal diode consists of a precision amplifier that activates a large on-chip MOSFET transistor whenever the voltage at VOUT is approximately 15mV (VFWD) below the voltage at BAT. Within the amplifier’s linear range, the small-signal resistance of the ideal diode will be quite low, keeping the forward drop near 15mV. At higher current levels, the With the same assumptions as above, the total battery charger efficiency is approximately 81%. This example works out to less than 1W of power dissipation, or almost 60% less heat. See the Typical Applications section for complete circuits using the LT3653 and LT3480 with Bat-Track control. Overvoltage Protection The LTC4098/LTC4098-1 can protect itself from the inadvertent application of excessive voltage to VBUS or WALL with just two external components: an N-channel FET and a 6.04k resistor. The maximum safe overvoltage magnitude will be determined by the choice of the external NMOS and its associated drain breakdown voltage. The overvoltage protection module consists of two pins. The first, OVSENS, is used to measure the externally applied voltage through an external resistor. The second, OVGATE, is an output used to drive the gate pin of an external FET. The voltage at OVSENS will be lower than the OVP input voltage by (IOVSENS • 6.04k) due to the OVP circuit’s quiescent current. The OVP input will be 200mV to 400mV higher than OVSENS under normal operating conditions. When OVSENS is below 6V, an internal charge pump will drive OVGATE to approximately 1.88 • OVSENS. This will enhance the N-channel FET and provide a low impedance connection to VBUS or WALL which will, in turn, power the LTC4098/LTC4098-1. If OVSENS should rise above 6V (6.35V OVP input) due to a fault or use of an incorrect wall adapter, OVGATE will be pulled to GND, disabling the external FET to protect downstream circuitry. When the voltage drops below 6V again, the external FET will be reenabled. 40981fb 16 LTC4098/LTC4098-1 OPERATION MOSFET will be in full conduction. If additional conductance is needed, an external P-channel MOSFET transistor may be added from BAT to VOUT. The IDGATE pin of the LTC4098/LTC4098-1 drives the gate of the external P-channel MOSFET transistor for automatic ideal diode control. The source of the external P-channel MOSFET should be connected to VOUT and the drain should be connected to BAT. Capable of driving a 1nF load, the IDGATE pin can control an external P-channel MOSFET transistor having an on-resistance of 30mΩ or lower. Figure 5 shows the decreased forward voltage compared to a conventional Schottky diode. Suspend LDO The LTC4098/LTC4098-1 provide a small amount of power to VOUT in suspend mode by including an LDO from VBUS to VOUT. This LDO will prevent the battery from running down when the portable product has access to a suspended USB port. Regulating at 4.6V, this LDO only becomes active when the switching converter is disabled. In accordance with the USB specification, the input to the LDO is current limited so 2200 2000 1800 1600 CURRENT (mA) 1400 1200 1000 800 600 400 200 0 0 60 120 180 240 300 360 420 480 FORWARD VOLTAGE (mV) (BAT – VOUT) 40981 F05 that it will not exceed the low power or high power suspend specification. If the load on VOUT exceeds the suspend current limit, the additional current will come from the battery via the ideal diodes. The suspend LDO sends a scaled copy of the VBUS current to the CLPROG pin, which will servo to approximately 100mV in this mode. Thus, the high power and low power suspend settings are related to the levels programmed by the same resistor for 1x and 5x modes. Battery Charger The LTC4098/LTC4098-1 include a constant-current/constant-voltage battery charger with automatic recharge, automatic termination by safety timer, low voltage trickle charging, bad cell detection and thermistor sensor input for out-of-temperature charge pausing. When a battery charge cycle begins, the battery charger first determines if the battery is deeply discharged. If the battery voltage is below VTRKL, typically 2.85V, an automatic trickle charge feature sets the battery charge current to 10% of the programmed value. If the low voltage persists for more than 1/2 hour, the battery charger automatically terminates and indicates, via the CHRG pin, that the battery was unresponsive. Once the battery voltage is above VTRKL, the charger begins charging in full power constant-current mode. The current delivered to the battery will try to reach 1030V/RPROG. Depending on available input power and external load conditions, the battery charger may or may not be able to charge at the full programmed rate. The external load will always be prioritized over the battery charge current. The USB current limit programming will always be observed and only additional power will be available to charge the battery. When system loads are light, battery charge current will be maximized. VISHAY Si2333 EXTERNAL IDEAL DIODE LTC4098/ LTC4098-1 IDEAL DIODE ON SEMICONDUCTOR MBRM120LT3 Figure 5. Ideal Diode V-I Characteristics 40981fb 17 LTC4098/LTC4098-1 OPERATION Charge Termination The battery charger has a built-in safety timer. Once the voltage on the battery reaches the preprogrammed float voltage of 4.200V for the LTC4098 or 4.100V for the LTC4098-1, the charger will regulate the battery voltage there and the charge current will decrease naturally. Once the charger detects that the battery has reached 4.200V or 4.100V respectively, the 4-hour safety timer is started. After the safety timer expires, charging of the battery will discontinue and no more current will be delivered. Automatic Recharge Once the battery charger terminates, it will remain off drawing only microamperes of current from the battery. If the portable product remains in this state long enough, the battery will eventually self discharge. To ensure that the battery is always topped off, a charge cycle will automatically begin when the battery voltage falls below VRECHRG (typically 4.1V for the LTC4098 and 4.0V for the LTC4098-1). In the event that the safety timer is running when the battery voltage falls below VRECHRG, it will reset back to zero. To prevent brief excursions below VRECHRG from resetting the safety timer, the battery voltage must be below VRECHRG for more than 1.5ms. The charge cycle and safety timer will also restart if the VBUS UVLO cycles low and then high (e.g., VBUS is removed and then replaced) or if the charger is momentarily disabled using the D2 pin. Charge Current The charge current is programmed using a single resistor from PROG to ground. 1/1030th of the battery charge current is delivered to PROG, which will attempt to servo to 1.000V. Thus, the battery charge current will try to reach 1030 times the current in the PROG pin. The program resistor and the charge current are calculated using the following equations: RPROG = 1030 V 1030 V , ICHG = ICHG RPROG In either the constant-current or constant-voltage charging modes, the voltage at the PROG pin will be proportional to the actual charge current delivered to the battery. The charge current can be determined at any time by monitoring the PROG pin voltage and using the following equation: IBAT = VPROG • 1030 RPROG In many cases, the actual battery charge current, IBAT, will be lower than the programmed current, ICHG, due to limited input power available and prioritization to the system load drawn from VOUT. Charge Status Indication The CHRG pin indicates the status of the battery charger. Four possible states are represented by CHRG which include charging, not charging (or float charge current less than programmed end of charge indication current), unresponsive battery and battery temperature out of range. The signal at the CHRG pin can be easily recognized as one of the above four states by either a human or a microprocessor. An open-drain output, the CHRG pin can drive an indicator LED through a current limiting resistor for human interfacing or simply a pull-up resistor for microprocessor interfacing. 40981fb 18 LTC4098/LTC4098-1 OPERATION To make the CHRG pin easily recognized by both humans and microprocessors, the pin is either a DC signal of ON for charging, OFF for not charging or it is switched at high frequency (35kHz) to indicate the two possible faults. While switching at 35kHz, its duty cycle is modulated at a slow rate that can be recognized by a human. When charging begins, CHRG is pulled low and remains low for the duration of a normal charge cycle. When charge current drops to 1/10th the value programmed by RPROG, the CHRG pin is released (Hi-Z). The CHRG pin does not respond to the C/10 threshold if the LTC4098/LTC4098-1 are in VBUS current limit. This prevents false end-of-charge indications due to insufficient power available to the battery charger. If a fault occurs while charging, the pin is switched at 35kHz. While switching, its duty cycle is modulated between a high and low value at a very low frequency. The low and high duty cycles are disparate enough to make an LED appear to be on or off thus giving the appearance of “blinking”. Each of the two faults has its own unique “blink” rate for human recognition as well as two unique duty cycles for machine recognition. Table 2 illustrates the four possible states of the CHRG pin when the battery charger is active. Table 2. CHRG Signal STATUS Charging IBAT < C/10 NTC Fault Bad Battery FREQUENCY 0Hz 0Hz 35kHz 35kHz MODULATION (BLINK) FREQUENCY 0Hz (Low Z) 0Hz (Hi-Z) 1.5Hz at 50% 6.1Hz at 50% DUTY CYCLES 100% 0% 6.25% or 93.75% 12.5% or 87.5% Notice that an NTC fault is represented by a 35kHz pulse train whose duty cycle toggles between 6.25% and 93.75% at a 1.5Hz rate. A human will easily recognize the 1.5Hz rate as a “slow” blinking which indicates the out of range battery temperature while a microprocessor will be able to decode either the 6.25% or 93.75% duty cycles as an NTC fault. If a battery is found to be unresponsive to charging (i.e., its voltage remains below 2.85V for 1/2 hour), the CHRG pin gives the battery fault indication. For this fault, a human would easily recognize the frantic 6.1Hz “fast” blink of the LED while a microprocessor would be able to decode either the 12.5% or 87.5% duty cycles as a bad cell fault. Because the LTC4098/LTC4098-1 are 3-terminal PowerPath products, system load is always prioritized over battery charging. Due to excessive system load, there may not be sufficient power to charge the battery beyond the bad-cell threshold voltage within the bad-cell timeout period. In this case the battery charger will falsely indicate a bad cell. System software may then reduce the load and reset the battery charger to try again. Although very improbable, it is possible that a duty cycle reading could be taken at the bright-dim transition (low duty cycle to high duty cycle). When this happens the duty cycle reading will be precisely 50%. If the duty cycle reading is 50%, system software should disqualify it and take a new duty cycle reading. 40981fb 19 LTC4098/LTC4098-1 OPERATION 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 the Block Diagram. To use this feature, connect the NTC thermistor, RNTC, between the NTC pin and ground and a bias resistor, RNOM, from NTCBIAS to NTC. RNOM should be a 1% resistor with a value equal to the value of the chosen NTC thermistor at 25°C (R25). The LTC4098/LTC4098-1 will pause charging when the resistance of the NTC thermistor drops to 0.54 times the value of R25 or approximately 54k (for a Vishay curve 1 thermistor, this corresponds to approximately 40°C). If the battery charger is in constant-voltage (float) mode, the safety timer also pauses until the thermistor indicates a return to a valid temperature. As the temperature drops, the resistance of the NTC thermistor rises. The LTC4098/ LTC4098-1 are also designed to pause charging when the value of the NTC thermistor increases to 3.25 times the value of R25. For a Vishay curve 1 thermistor, this resistance, 325k, corresponds to approximately 0°C. The hot and cold comparators each have approximately 3°C of hysteresis to prevent oscillation about the trip point. Grounding the NTC pin disables all NTC functionality. Figure 6 is a flow chart representation of the battery charger algorithm employed by the LTC4098/LTC4098-1. Thermal Regulation To prevent thermal damage to the LTC4098/LTC4098-1 or surrounding components, an internal thermal feedback loop will automatically decrease the programmed charge current if the die temperature rises to approximately 110°C. Thermal regulation protects the LTC4098/LTC4098-1 from excessive temperature due to high power operation or high ambient thermal conditions, and allows the user to push the limits of the power handling capability with a given circuit board design without risk of damaging the LTC4098/LTC4098-1 or external components. The benefit of the LTC4098/LTC4098-1 thermal regulation loop is that charge current can be set according to actual conditions rather than worst-case conditions for a given application with the assurance that the charger will automatically reduce the current in worst-case conditions. Shutdown Mode The USB switching regulator is enabled whenever VBUS is above the UVLO voltage and the LTC4098/LTC4098-1 are not in one of the two USB suspend modes (500μA or 2.5mA). When power is available from both the USB and high voltage inputs, the high voltage regulator is prioritized and the USB switching regulator is disabled. The ideal diode is enabled at all times and cannot be disabled. 40981fb 20 LTC4098/LTC4098-1 OPERATION POWER ON/ ENABLE CHARGER CLEAR EVENT TIMER ASSERT CHRG LOW NTC OUT OF RANGE YES INHIBIT CHARGING NO PAUSE EVENT TIMER BAT < 2.85V BATTERY STATE BAT > VFLOAT – 2.85V < BAT < VFLOAT – CHARGE AT 100V/RPROG (C/10 RATE) CHARGE AT 1030V/RPROG RATE CHARGE WITH FIXED VOLTAGE (VFLOAT) CHRG CURRENTLY Hi-Z YES NO RUN EVENT TIMER PAUSE EVENT TIMER RUN EVENT TIMER INDICATE NTC FAULT AT CHRG NO TIMER > 30 MINUTES TIMER > 4 HOURS NO YES YES NO INHIBIT CHARGING STOP CHARGING IBAT < C/10 YES INDICATE BATTERY FAULT AT CHRG BAT RISING THROUGH VRECHRG YES CHRG HIGH-Z CHRG Hi-Z NO NO BAT > 2.85V BAT FALLING THROUGH VRECHRG YES NO BAT < VRECHRG YES NO YES 40981 F06 Figure 6. Battery Charger State Diagram 40981fb 21 LTC4098/LTC4098-1 APPLICATIONS INFORMATION CLPROG Resistor and Capacitor As described in the Bat-Track Input Current Limited Step Down Switching Regulator section, the resistor on the CLPROG pin determines the average input current limit in each of the six current limit modes. The input current will be comprised of two components, the current that is used to drive VOUT and the quiescent current of the switching regulator. To ensure that the total average input current remains below the USB specification, both components of input current should be considered. The Electrical Characteristics table gives the typical values for quiescent currents in all settings as well as current limit programming accuracy. To get as close to the 500mA or 100mA specifications as possible, a precision resistor should be used. An averaging capacitor is required in parallel with the resistor so that the switching regulator can determine the average input current. This capacitor also provides the dominant pole for the feedback loop when current limit is reached. To ensure stability, the capacitor on CLPROG should be 0.1μF or larger. Choosing the Inductor Because the input voltage range and output voltage range of the PowerPath switching regulator are both fairly narrow, the LTC4098/LTC4098-1 were designed for a specific inductance value of 3.3μH. Some inductors which may be suitable for this application are listed in Table 3. VBUS and VOUT Bypass Capacitors The style and value of capacitors used with the LTC4098/ LTC4098-1 determine several important parameters such as regulator control loop stability and input voltage ripple. Because the LTC4098/LTC4098-1 use a step-down switching power supply from VBUS to VOUT, its input current waveform contains high frequency components. It is strongly recommended that a low equivalent series resistance (ESR) multilayer ceramic capacitor be used to bypass VBUS. Tantalum and aluminum capacitors are not recommended because of their high ESR. The value of the capacitor on VBUS directly controls the amount of input ripple for a given load current. Increasing the size of this capacitor will reduce the input ripple. The USB specification allows a maximum of 10μF to be connected directly across the USB power bus. If additional capacitance is required for noise performance, it may be connected directly to the VBUS pin when using the OVP feature of the LTC4098/LTC4098-1. This extra capacitance will be soft-connected over several milliseconds to limit inrush current and avoid excessive transient voltage drops on the bus. To prevent large VOUT voltage steps during transient load conditions, it is also recommended that a ceramic capacitor be used to bypass VOUT. The output capacitor is used in the compensation of the switching regulator. At least 10μF with low ESR are required on VOUT. Additional capacitance will improve load transient performance and stability. Table 3. Recommended Inductors for the LTC4098/LTC4098-1 INDUCTOR TYPE LPS4018 D53LC DB318C WE-TPC Type M1 CDRH6D12 CDRH6D38 L (μH) 3.3 3.3 3.3 3.3 3.3 3.3 MAX IDC MAX DCR (A) (Ω) 2.2 2.26 1.55 1.95 2.2 3.5 0.08 0.034 0.070 0.065 0.0625 0.020 SIZE IN mm (L × W × H) 3.9 × 3.9 × 1.7 5×5×3 3.8 × 3.8 × 1.8 4.8 × 4.8 × 1.8 6.7 × 6.7 × 1.5 7×7×4 MANUFACTURER Coilcraft www.coilcraft.com Toko www.toko.com Würth Elektronik www.we-online.com Sumida www.sumida.com 40981fb 22 LTC4098/LTC4098-1 APPLICATIONS INFORMATION Multilayer ceramic chip capacitors typically have exceptional ESR performance. MLCCs combined with a tight board layout and an unbroken ground plane will yield very good performance and low EMI emissions. There are several types of ceramic capacitors available each having considerably different characteristics. For example, X7R ceramic capacitors have the best voltage and temperature stability. X5R ceramic capacitors have apparently higher packing density but poorer performance over their rated voltage and temperature ranges. Y5V ceramic capacitors have the highest packing density, but must be used with caution, because of their extreme nonlinear characteristic of capacitance versus voltage. The actual in-circuit capacitance of a ceramic capacitor should be measured with a small AC signal and DC bias as is expected in-circuit. Many vendors specify the capacitance versus voltage with a 1VRMS AC test signal and, as a result, over state the capacitance that the capacitor will present in the application. Using similar operating conditions as the application, the user must measure or request from the vendor the actual capacitance to determine if the selected capacitor meets the minimum capacitance that the application requires. Overprogramming the Battery Charger The USB high power specification allows for up to 2.5W to be drawn from the USB port. The switching regulator transforms the voltage at VBUS to just above the voltage at BAT with high efficiency, while limiting power to less than the amount programmed at CLPROG. The charger should be programmed (with the PROG pin) to deliver the maximum safe charging current without regard to the USB specifications. If there is insufficient current available to charge the battery at the programmed rate, it will reduce charge current until the system load on VOUT is satisfied and the VBUS current limit is satisfied. Programming the charger for more current than is available will not cause the average input current limit to be violated. It will merely allow the battery charger to make use of all available power to charge the battery as quickly as possible, and with minimal power dissipation within the charger. Overvoltage Protection It is possible to protect both VBUS and WALL from overvoltage damage with several additional components, as shown in Figure 7. Schottky diodes D1 and D2 pass the larger of V1 and V2 to R1 and OVSENS. If either V1 or V2 MN1 V1 WALL V2 D2 D1 MN2 C1 OVGATE LTC4098/ LTC4098-1 VBUS R1 OVSENS 40981 F07 Figure 7. Dual Input Overvoltage Protection 40981fb 23 LTC4098/LTC4098-1 APPLICATIONS INFORMATION exceeds 6V plus VF(SCHOTTKY), OVGATE will be pulled to GND and both the WALL and USB inputs will be protected. Each input is protected up to the drain-source breakdown, BVDSS, of MN1 and MN2. R1 must also be rated for the power dissipated during maximum overvoltage. See the Operations section for an explanation of this calculation. Table 4 shows some N-channel MOSFETs that may be suitable for overvoltage protection. Table 4. Recommended OVP FETs N-CHANNEL MOSFET Si2302ADS IRLML2502 Si1472DH NTLJS4114N FDN372S BVDSS 20V 20V 30V 30V 30V RON 70mΩ 35mΩ 65mΩ 20mΩ 45mΩ PACKAGE SOT-23 SOT-23 SC70-6 2mm × 2mm DFN SOT-23 USB/WALL ADAPTER MP1 D1 MN1 VBUS C1 LTC4098/ LTC4098-1 R1 R2 OVGATE OVSENS 40981 F08 VBUS POSITIVE PROTECTION UP TO BVDSS OF MN1 VBUS NEGATIVE PROTECTION UP TO BVDSS OF MP1 Figure 8. Dual-Polarity Voltage Protection Alternate NTC Thermistors and Biasing The LTC4098/LTC4098-1 provide temperature-qualified charging if a grounded thermistor and a bias resistor are connected to NTC and NTCBIAS. By using a bias resistor whose value is equal to the room temperature resistance of the thermistor (R25) the upper and lower temperatures are preprogrammed to approximately 40°C and 0°C, respectively (assuming a Vishay curve 1 thermistor). The upper and lower temperature thresholds can be adjusted by either a modification of the bias resistor value or by adding a second adjustment resistor to the circuit. If only the bias resistor is adjusted, then either the upper or the lower threshold can be modified but not both. The other trip point will be determined by the characteristics of the thermistor. Using the bias resistor in addition to an Reverse Voltage Protection The LTC4098/LTC4098-1 can also be easily protected against the application of reverse voltage, as shown in Figure 8. D1 and R1 are necessary to limit the maximum VGS seen by MP1 during positive overvoltage events. D1’s breakdown voltage must be safely below MP1’s BVGS. The circuit shown in Figure 8 offers forward voltage protection up to MN1’s BVDSS and reverse voltage protection up to MP1’s BVDSS. 40981fb 24 LTC4098/LTC4098-1 APPLICATIONS INFORMATION adjustment resistor, both the upper and the lower temperature trip points can be independently programmed with the constraint that the difference between the upper and lower temperature thresholds cannot decrease. Examples of each technique are given below. NTC thermistors have temperature characteristics which are indicated on-resistance temperature conversion tables. The Vishay-Dale thermistor NTHS0603N011-N1003F used , in the following examples, has a nominal value of 100k and follows the Vishay curve 1 resistance-temperature characteristic. In the explanation below, the following notation is used. R25 = Value of the thermistor at 25°C RNTC|COLD = Value of thermistor at the cold trip point RNTC|HOT = Value of thermistor at the hot trip point rCOLD = Ratio of RNTC|COLD to R25 rHOT = Ratio of RNTC|HOT to R25 RNOM = Primary thermistor bias resistor (see Figure 9a) R1 = Optional temperature range adjustment resistor (see Figure 9b) The trip points for the LTC4098/LTC4098-1’s temperature qualification are internally programmed at 0.349 • NTCBIAS for the hot threshold and 0.765 • NTCBIAS for the cold threshold. Therefore, the hot trip point is set when: RNTCHOT | RNOM + RNTCHOT | • NTCBIAS = 0.349 • NTCBIAS and the cold trip point is set when: RNTC|COLD RNOM + RNTC|COLD • NTCBIAS = 0.765 • NTCBIAS NTCBIAS 4 RNOM 100k NTC 5 RNTC 100k 0.349 • NTCBIAS 0.765 • NTCBIAS LTC4098/LTC4098-1 NTC BLOCK NTCBIAS 4 RNOM 105k TOO_COLD NTC 5 0.765 • NTCBIAS LTC4098/LTC4098-1 NTC BLOCK – + – TOO_COLD + T – TOO_HOT R1 12.7k 0.349 • NTCBIAS T RNTC 100k – TOO_HOT + + + NTC_ENABLE 0.1V + NTC_ENABLE 0.1V – 40981 F09a – 40981 F09b (9a) Figure 9. NTC Circuits (9b) 40981fb 25 LTC4098/LTC4098-1 APPLICATIONS INFORMATION Solving these equations for RNTC|COLD and RNTC|HOT results in the following: RNTC|HOT = 0.536 • RNOM and RNTC|COLD = 3.25 • RNOM By setting RNOM equal to R25, the previous equations result in rHOT = 0.536 and rCOLD = 3.25. Referencing these ratios to the Vishay Resistance-Temperature Curve 1 chart gives a hot trip point of about 40°C and a cold trip point of about 0°C. The difference between the hot and cold trip points is approximately 40°C. By using a bias resistor, RNOM, different in value from R25, the hot and cold trip points can be moved in either direction. The temperature span will change somewhat due to the nonlinear behavior of the thermistor. The following equations can be used to easily calculate a new value for the bias resistor: RNOM = RNOM = rHOT • R25 0.536 rCOLD • R25 3.25 From the Vishay curve 1 R-T characteristics, rHOT is 0.2488 at 60°C. Using the previous equation, RNOM should be set to 46.4k. With this value of RNOM, the cold trip point is about 16°C. Notice that the span is now 44°C rather than the previous 40°C. This is due to the decrease in temperature gain of the thermistor as absolute temperature increases. The upper and lower temperature trip points can be independently programmed by using an additional bias resistor as shown in Figure 9b. The following formulas can be used to compute the values of RNOM and R1: r –r RNOM = COLD HOT • R25 2.714 R1 = 0.536 • RNOM – rHOT • R25 For example, to set the trip points to 0°C and 45°C with a Vishay Curve 1 thermistor choose: RNOM = 3.266 – 0.4368 • 100k = 104.2k 2.714 the nearest 1% value is 105k: R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k the nearest 1% value is 12.7k. The final circuit is shown in Figure 9b and results in an upper trip point of 45°C and a lower trip point of 0°C. where rHOT and rCOLD are the resistance ratios at the desired hot and cold trip points. Note that these equations are linked. Therefore, only one of the two trip points can be chosen, the other is determined by the default ratios designed in the IC. Consider an example where a 60°C hot trip point is desired. 40981fb 26 LTC4098/LTC4098-1 APPLICATIONS INFORMATION USB Inrush Limiting The USB specification allows at most 10μF of downstream capacitance to be hot-plugged into a USB hub. In most LTC4098/LTC4098-1 applications, 10μF should be enough to provide adequate filtering on VBUS. If more capacitance is required, the OVP circuit will provide adequate soft-connect time to prevent excessive inrush currents. An additional 22μF on the VBUS pin will generally contribute less than 100mA to the hot-plug inrush current. Voltage overshoot on VBUS may sometimes be observed when connecting the LTC4098/LTC4098-1 to a lab power supply. This overshoot is caused by long leads from the power supply to VBUS. Twisting the wires together from the supply to VBUS can greatly reduce the parasitic inductance of these long leads, and keep the voltage at VBUS to safe levels. USB cables are generally manufactured with the power leads in close proximity, and thus fairly low parasitic inductance. Board Layout Considerations The Exposed Pad on the backside of the LTC4098/ LTC4098-1 package must be securely soldered to the PC board ground. This is the primary ground pin in the package, and it serves as the return path for both the control circuitry and the synchronous rectifier. Furthermore, due to its high frequency switching circuitry, it is imperative that the input capacitor, inductor, and output capacitor be as close to the LTC4098/LTC4098-1 as possible and that there be an unbroken ground plane under the LTC4098/LTC4098-1 and all of its external high frequency components. High frequency currents, such as the input current on the LTC4098/LTC4098-1, tend to find their way on the ground plane along a mirror path directly beneath the incident path on the top of the board. If there are slits or cuts in the ground plane due to other traces on that layer, the current will be forced to go around the slits. If high frequency currents are not allowed to flow back through their natural least-area path, excessive voltage will build up and radiated emissions will occur (see Figure 10). There should be a group of vias directly under the grounded backside leading directly down to an internal ground plane. To minimize parasitic inductance, the ground plane should be as close as possible to the top plane of the PC board (layer 2). The IDGATE pin for the external ideal diode controller has extremely limited drive current. Care must be taken to minimize leakage to adjacent PC board traces. 100nA of leakage from this pin will introduce an additional offset to the ideal diode of approximately 10mV. To minimize leakage, the trace can be guarded on the PC board by surrounding it with VOUT connected metal, which should generally be less than one volt higher than IDGATE. 40981 F10 Figure 10. Ground Currents Follow Their Incident Path at High Speed. Slices in the Ground Plane Cause High Voltage and Increased Emissions 40981fb 27 LTC4098/LTC4098-1 APPLICATIONS INFORMATION Battery Charger Stability Considerations The LTC4098/LTC4098-1’s battery charger contains both a constant-voltage and a constant-current control loop. The constant-voltage loop is stable without any compensation when a battery is connected with low impedance leads. Excessive lead length, however, may add enough series inductance to require a bypass capacitor of at least 1μF from BAT to GND. High value, low ESR multilayer ceramic chip capacitors reduce the constant-voltage loop phase margin, possibly resulting in instability. Ceramic capacitors up to 22μF may be used in parallel with a battery, but larger ceramics should be decoupled with 0.2Ω to 1Ω of series resistance. Furthermore, a 100μF MLCC in series with a 0.3Ω resistor or a 100μF OS-CON capacitor from BAT to GND is required to prevent oscillation when the battery is disconnected. In constant-current mode, the PROG pin is in the feedback loop rather than the battery voltage. Because of the additional pole created by any PROG pin capacitance, capacitance on this pin must be kept to a minimum. With no additional capacitance on the PROG pin, the charger is stable with program resistor values as high as 25k. However, additional capacitance on this node reduces the maximum allowed program resistor. The pole frequency at the PROG pin should be kept above 100kHz. Therefore, if the PROG pin has a parasitic capacitance, CPROG, the following equation should be used to calculate the maximum resistance value for RPROG: RPROG ≤ 1 2π • 100kHz • CPROG 40981fb 28 LTC4098/LTC4098-1 TYPICAL APPLICATIONS High Efficiency USB/2A Automotive Battery Charger with Overvoltage Protection and Low Battery Start-Up 2 AUTOMOTIVE, FIREWIRE, ETC. 4 C1 C7 4.7μF 68nF R10 40.2k R11 150k 5 10 VIN BOOST SW RUN/SS RT PG 7 VC 9 LT3480 FB SYNC 6 8 3 D3 C6 0.47μF L2 10μH R9 R8 499k 100k C4 22μF GND 11 BD 1 M1 L1 3.3μH USB M3 20 13 C2 10μF 0805 2 1 3 15-17 8 4 M1, M2: VISHAY-SILICONIX Si2333DS M3: ON SEMICONDUCTOR NTLJS4114N R5: VISHAY-DALE NTHS0603N011-N1003F R4 100k VBUS 18 19 14 VC WALL ACPR SW 12 10 11 M2 SYSTEM LOAD R3 6.04k TO μC TO μC OVGATE OVSENS D0-D2 CHRG NTCBIAS LTC4098/LTC4098-1 VOUT IDGATE BAT C5 10μF 0805 PROG GND BATSENS 7 R7 1k 9, 21 6 Li-Ion 5 NTC CLPROG 3 R6 3.01k T R5 100k C3 0.1μF 0603 + 40981 TA02 USB/Wall Adapter Battery Charger with Dual Overvoltage Protection, Reverse-Voltage Protection and Low Battery Start-Up M1 5V WALL ADAPTER R1 R2 D4 USB M2 D1 D2 M4 R3 6.04k 3 13 C2 10μF 0805 1 15-17 8 4 M1, M2, M5, M6: VISHAY-SILICONIX Si2333DS M3, M4: FAIRCHILD SEMI FDN372S R5: VISHAY-DALE NTHS0603N011-N1003F D1, D2: NXP BAT54C D3, D4: ON SEMICONDUCTOR MNBZ5232BLT1G R4 100k VBUS 2 OVGATE 18 WALL 19 D3 M3 C1 10μF 0805 L1 3.3μH 14 ACPR SW 12 10 11 M6 M5 SYSTEM LOAD VOUT OVSENSE D0-D2 CHRG NTCBIAS LTC4098/LTC4098-1 IDGATE BAT TO μC TO μC C4 10μF 0805 PROG GND BATSENS 7 R7 1k 9, 21 6 Li-Ion 5 NTC CLPROG 3 R6 3.01k T R5 100k C3 0.1μF 0603 + 40981 TA03 40981fb 29 LTC4098/LTC4098-1 TYPICAL APPLICATIONS USB/Automotive Switching Battery Charger with Automatic Current Limiting on Both Inputs 7 AUTOMOTIVE, FIREWIRE, ETC. 1 C1 4.7μF 4 R1 27.4k VIN BOOST SW ILIM GND 9 VC 3 20 13 C3 10μF 0805 2 1 3 15-17 8 4 M1: ON SEMICONDUCTOR NTLJS4114N R3: VISHAY-DALE NTHS0603N011-N1003F R2 100k VBUS VC LT3653 ISENSE 5 VOUT L2 3.3μH 19 14 C5 10μF 0805 12 10 11 SYSTEM LOAD 6 8 C2 0.1μF 10V D1 L1 4.7μH HVOK 2 18 USB WALL ADAPTER R6 6.04k TO μC TO μC M1 WALL ACPR SW OVGATE OVSENS D0-D2 CHRG NTCBIAS LTC4098/LTC4098-1 VOUT IDGATE BAT 5 NTC CLPROG PROG GND BATSENS 7 R5 1k 9, 21 6 3 R4 3.01k R3 T 100k C4 0.1μF 0603 + 40981 TA04 Li-Ion Low Component Count USB and Automotive High Efficiency Power Manager 7 AUTOMOTIVE, FIREWIRE, ETC. 1 C1 4.7μF 4 R1 27.4k VIN BOOST SW ILIM GND 9 VC 3 20 USB WALL ADAPTER 13 C3 10μF 0805 2 1 3 15-17 8 4 5 VBUS OVGATE OVSENS LTC4098/LTC4098-1 VC LT3653 ISENSE 5 VOUT L2 3.3μH 19 14 6 8 C2 0.1μF 10V D1 L1 4.7μH HVOK 2 18 SYSTEM LOAD WALL ACPR SW VOUT IDGATE BAT 12 10 11 TO μC TO μC D0-D2 CHRG NTCBIAS NTC CLPROG C4 0.1μF 0603 3 R2 3.01k PROG 7 R3 1k GND BATSENS 9, 21 6 C5 10μF 0805 + Li-Ion 40981 TA05 40981fb 30 LTC4098/LTC4098-1 PACKAGE DESCRIPTION PDC Package 20-Lead Plastic UTQFN (3mm × 4mm) (Reference LTC DWG # 05-08-1752 Rev Ø) 0.70 0.05 3.50 0.05 2.10 0.05 1.50 REF 1.65 2.65 0.05 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.50 REF 3.10 4.50 0.05 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 0.55 3.00 0.10 0.05 R = 0.05 TYP 1.50 REF 19 PIN 1 NOTCH R = 0.20 OR 0.25 45 CHAMFER 20 0.40 0.10 PIN 1 TOP MARK (NOTE 6) 2.65 4.00 0.10 2.50 REF 1.65 0.10 0.10 1 2 (PDC20) UTQFN 0407 REV Ø 0.127 REF 0.00 – 0.05 R = 0.115 TYP 0.25 0.05 0.50 BSC BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 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 40981fb 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. 31 LTC4098/LTC4098-1 TYPICAL APPLICATION High Efficiency USB Automotive Battery Charger with Overvoltage Protection and Low Battery Start-Up AUTOMOTIVE, FIREWIRE, ETC. 1 C1 4.7μF 50V R2 27.4k VIN BOOST SW 4 ILIM GND 9 M2 13 C3 10μF 0805 2 1 3 15-17 8 4 M1: VISHAY-SILICONIX Si2333DS M2: ON SEMICONDUCTOR NTLJS4114N R6: VISHAY-DALE NTHS0603N011-N1003F R5 100k VC 3 20 VBUS VC LT3653 6 ISENSE 5 VOUT 7 8 C2 0.1μF 10V , D2 L1 4.7μH HVOK 2 18 L2 3.3μH 19 14 SYSTEM LOAD USB WALL ACPR SW R4 6.04k TO μC TO μC OVGATE OVSENS D0-D2 CHRG NTCBIAS LTC4098/LTC4098-1 VOUT IDGATE BAT 12 10 11 M1 5 C5 10μF 0805 PROG 7 R8 1k GND BATSENS 9, 21 6 3 R7 3.01k NTC CLPROG C4 0.1μF 0603 R6 T 100k + Li-Ion 40981 TA06 RELATED PARTS PART NUMBER LTC3555/ LTC3555-1/ LTC3555-3 LTC3576/ LTC3576-1 DESCRIPTION Switching USB Power Manager with Li-Ion/Polymer Charger, Triple Synchronous Buck Converter Plus LDO Switching Power Manager with USB On-The-Go Plus Triple Step-Down DC/DCs COMMENTS Complete Multifunction PMIC: Switchmode Power Manager and Three Buck Regulators Plus LDO Charge Current Programmable Up to 1.5A from Wall Adapter Input, Synchronous Buck Converters Efficiency >95%, ADJ Outputs: 0.8V to 3.6V at 400mA/400mA/1A Bat-Track Adaptive Output Control, 200mΩ Ideal Diode, 4mm × 5mm QFN-28 Package Complete Multifunction PMIC: Bidirectional Switching Power Manager Plus Three Buck Regulators Plus LDO, ADJ Output Down to 0.8V at 400mA/400mA/1A, Overvoltage Protection, USB On-The-Go, Charge Current Programmable Up to 1.5A from Wall Adapter Input, Thermal Regulation, I2C, High Voltage Bat-Track Buck Interface, 180mΩ Ideal Diode; 4mm × 6mm QFN-38 Package Maximizes Available Power from USB Port, Bat-Track, Instant-On Operation, 1.5A Max Charge Current, 180mΩ Ideal Diode with