LTC4160EPDCPBF

FEATURES n LTC4160/LTC4160-1 Switching Power Manager with USB On-The-Go And Overvoltage Protection DESCRIPTION The LTC®4160/LTC4160-1 are high efficiency power management and Li-Ion/Polymer battery charger ICs. They each include a bidirectional switching PowerPath™ controller with automatic load prioritization, a battery charger, and an ideal diode. The LTC4160/LTC4160-1’s bidirectional switching regulator transfers nearly all of the power available from the USB port to the load with minimal loss and heat which eases thermal constraints in small spaces. These devices feature a precision input current limit for USB compatibility and Bat-Track output control for efficient charging. In addition, the ICs can also generate 5V at 500mA for USB On-TheGo applications. An overvoltage circuit protects the LTC4160/LTC4160-1 from high voltage damage on the USB/wall adapter inputs with an external N-channel MOSFET and a resistor. The LTC4160/LTC4160-1 are available in the ultra-thin (0.55 mm) 20-pin 3mm × 4mm UTQFN surface mount package. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. PowerPath and Bat-Track are a trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 6522118, 6404251. Other patents pending. n n n n n n n n n n Bidirectional Switching Regulator Makes Optimal Use of Limited Power Available from USB Port and also Provides a 5V Output for USB On-The-Go Overvoltage Protection Guards Against Damage 180mΩ Internal Ideal Diode Plus Optional External Ideal Diode Controller Seamlessly Provides Low Loss PowerPath When Input Power is Limited or Unavailable Instant-On Operation with Discharged Battery Full Featured Li-Ion/Polymer Battery Charger Bat-Track™ Adaptive Output Control For Efficient Charging 1.2A Max Input Current Limit 1.2A Max Charge Current with Thermal Limiting Battery Float Voltage: 4.2V (LTC4160), 4.1V (LTC4160-1) Low Battery Powered Quiescent Current (8μA) Ultra-Thin (0.55mm) 20-pin 3mm × 4mm QFN Package APPLICATIONS n n Media Players and Personal Navigation Devices Digital Cameras, PDAs, Smart Phones TYPICAL APPLICATION USB OTG VBUS Voltage vs VBUS Current 5.5 VOUT = BAT = 3.8V USB VBUS = 4.75V VBUS (V) 4.5 IVBUS = 500mA USB 2.0 SPECIFICATIONS REQUIRE THAT HIGH POWER DEVICES NOT OPERATE IN THIS REGION 6.2k OPTIONAL OVERVOLTAGE PROTECTION 10μF High Efficiency Power Manager/Battery Charger with USB On-The-Go and Overvoltage Protection USB ON-THE-GO VBUS LTC4160/ LTC4160-1 OVGATE OVSENS CLPROG BAT PROG SW VOUT CURRENT (mA) 10μF 3.3μH SYSTEM LOAD 750 Battery and VBUS Currents vs Load Current VBUS CURRENT 5.0 500 250 BATTERY CURRENT (CHARGING) 0 VBUS = 5V BAT = 3.8V 5x MODE BATTERY CURRENT (DISCHARGING) –500 0 200 600 800 400 LOAD CURRENT (mA) 1000 41601 TA01c 4.0 + Li-Ion 3.5 0.1μF 3.01k 1k 41601 TA01a –250 3.0 0 100 200 300 400 500 VBUS CURRENT (mA) 600 700 41601 TA01b 41601f 1 LTC4160/LTC4160-1 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2, 3) PIN CONFIGURATION TOP VIEW NTCBIAS CLPROG 16 ILIM1 15 ILIM0 21 14 SW 13 VBUS 12 VOUT 11 BAT 7 ENCHARGER 8 PROG 9 10 IDGATE CHRG LDO3V3 NTC OVGATE 1 OVSENS 2 VBUSGD 3 FAULT 4 ID 5 ENOTG 6 VBUS (Transient) t < 1ms, Duty Cycle < 1% .. –0.3V to 7V VBUS (Static), BAT, VOUT, NTC, ENOTG, ID, ENCHARGER, VBUSGD, FAULT, CHRG......... –0.3V to 6V ILIM0, IILIM1 ........ –0.3V to Max(VBUS, VOUT, BAT) + 0.3V IOVSENS...................................................................10mA ICLPROG ....................................................................3mA ICHRG, IVBUSGD, IFAULT.............................................50mA IPROG ........................................................................2mA ILDO3V3 ...................................................................30mA ISW, IBAT, IVOUT, IVBUS..................................................2A Operating Temperature Range.................. –40°C to 85°C Maximum 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 LTC4160EPDC#PBF LTC4160EPDC-1#PBF TAPE AND REEL LTC4160EPDC#TRPBF LTC4160EPDC-1#TRPBF PART MARKING FDRT FDST 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. Consult LTC Marketing for information on non-standard lead based finish parts. 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/ ELECTRICAL CHARACTERISTICS SYMBOL VBUS IBUS(LIM) PARAMETER Input Supply Voltage Total Input Current PowerPath Switching Regulator – Step-Down Mode 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. CONDITIONS MIN 4.35 1x Mode 5x Mode 10x Mode Suspend Mode 1x Mode 5x, 10x Modes Suspend Mode 1x Mode 5x Mode 10x Mode Suspend Mode l l l l TYP MAX 5.5 UNITS V mA mA mA mA mA mA mA mA/mA mA/mA mA/mA mA/mA 41601f 82 440 900 0.32 90 480 955 0.43 7 20 0.050 211 1170 2377 9.6 100 500 1000 0.5 IVBUSQ (Note 4) Input Quiescent Current hCLPROG (Note 4) Ratio of Measured VBUS Current to CLPROG Program Current 2 LTC4160/LTC4160-1 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER IVOUT(POWERPATH) VOUT Current Available Before Discharging Battery 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. CONDITIONS 1x Mode, BAT = 3.3V 5x Mode, BAT = 3.3V 10x Mode, BAT = 3.3V Suspend Mode Switching Modes Suspend Mode Rising Threshold Falling Threshold Rising Threshold Falling Threshold 1x, 5x, 10x Modes, 0V < BAT ≤ 4.2V, IVOUT = 0mA, Battery Charger Off USB Suspend Mode, IVOUT = 250μA 3.5 4.5 1.8 3.95 MIN TYP 121 667 1217 0.34 1.183 100 4.3 4 200 50 BAT + 0.3 4.6 2.25 0.18 0.3 1x Mode (Note 5) 5x Mode (Note 5) 10x Mode (Note 5) Closed Loop 0 ≤ IVBUS ≤ 500mA, VOUT > 3.2V l MAX UNITS mA mA mA mA V mV 0.26 0.43 VCLPROG VUVLO VDUVLO VOUT CLPROG Servo Voltage in Current Limit VBUS Undervoltage Lockout VBUS To BAT Differential Undervoltage Lockout VOUT Voltage 4.35 V V mV mV 4.7 4.7 2.7 V V MHz Ω Ω A A A Ω fOSC Switching Frequency RPMOS_POWERPATH PMOS On-Resistance RNMOS_POWERPATH NMOS On-Resistance IPEAK_POWERPATH Peak Inductor Current Clamp 1 1.6 3 10 4.75 2.9 550 680 1.8 1.6 1.15 2.5 2.6 2.8 7.2 6.1 6.42 1.88 • VOVSENS 0 1.25 4.179 4.165 4.079 4.065 1120 185 4.2 4.2 4.1 4.1 1219 206 3.8 8 4.221 4.235 4.121 4.135 1320 223 6 12 6.7 12 2.9 5.25 4.2 RSUSP VBUS VOUT IVBUS IPEAK IOTGQ VCLPROG VOUTUVLO tSCFAULT VOVCUTOFF VOVGATE tRISE Battery Charger VFLOAT Suspend LDO Output Resistance Output Voltage Input Voltage Output Current Limit Peak Inductor Current Limit VOUT Quiescent Current Output Current Limit Servo Voltage VOUT UVLO – VOUT Falling VOUT UVLO – VOUT Rising Short Circuit Fault Delay Overvoltage Protection Threshold OVGATE Output Voltage OVGATE Time To Reach Regulation BAT Regulated Output Voltage PowerPath Switching Regulator – Step-Up Mode (USB On-The-Go) V V mA A mA V V V ms V V V ms V V V V mA mA μA μA 41601f (Note 5) VOUT = 3.8V, IVBUS = 0mA (Note 6) PMOS Switch Off With 6.2k Series Resistor VOVSENS < VOVCUTOFF VOVSENS > VOVCUTOFF OVGATE CLOAD = 1nF LTC4160 LTC4160-1 Overvoltage Protection l l ICHG IBAT Constant Current Mode Charger Current Battery Drain Current RPROG = 845Ω, 10x Mode RCLPROG ≤ 2.49k RPROG = 5k, 5x or 10x Mode VBUS > VUVLO, Suspend Mode, IVOUT = 0μA VBUS = 0V, IVOUT = 0μA (Ideal Diode Mode) 3 LTC4160/LTC4160-1 ELECTRICAL CHARACTERISTICS SYMBOL VPROG VPROG_TRKL VC/10 hPROG ITRKL VTRKL ΔVTRKL ΔVRECHRG tTERM tBADBAT hC/10 RON_CHG TLIM NTC VCOLD VHOT VDIS INTC Ideal Diode VFWD RDROPOUT IMAX_DIODE VLDO3V3 RCL_LDO3V3 ROL_LDO3V3 VIL VIH IPD1 IPU1 VVBUSGD VCHRG, VFAULT ICHRG, IVBUSGD, IFAULT Forward Voltage Detection Internal Diode On-Resistance, Dropout Diode Current Limit Regulated Output Voltage Closed-Loop Output Resistance Dropout Output Resistance Logic Low Input Voltage Logic High Input Voltage ILIM0, ILIM1, ENOTG, ENCHARGER Pull-Down Current ID Pull-Up Current Output Low Voltage Output Low Voltage Leakage Current IVBUSGD = 5mA, VBUS = 5V ICHRG = IFAULT = 5mA, VOUT = 3.8V VCHRG = VVBUSGD = VFAULT = 5V 1.2 1.8 2.5 65 100 100 150 1 0mA < ILDO3V3 < 20mA VBUS = 0V, IVOUT = 10mA IVOUT = 10mA IVOUT = 200mA 2 3.1 3.3 2.7 23 0.4 3.5 2 15 0.18 mV mV Ω A V Ω Ω V V μA μA mV mV μA Cold Temperature Fault Threshold Voltage Rising Threshold Hysteresis 75 33.4 0.7 –50 76.5 1.5 34.9 1.8 1.7 50 78 36.4 2.7 50 %NTCBIAS %NTCBIAS %NTCBIAS %NTCBIAS %NTCBIAS mV nA PARAMETER PROG Pin Servo Voltage PROG Pin Servo Voltage in Trickle Charge BAT < VTRKL C/10 Threshold Voltage at PROG Ratio of IBAT to PROG Pin Current Trickle Charge Current Trickle Charge Threshold Voltage Trickle Charge Hysteresis Voltage Recharge Battery Threshold Voltage Safety Timer Termination Period Bad Battery Termination Time End of Charge Current Ratio Battery Charger Power FET On-Resistance (Between VOUT and BAT) Junction Temperature in Constant Temperature Mode Threshold Voltage Relative to VFLOAT Timer Starts when VBAT = VFLOAT BAT < VTRKL (Note 7) –75 3.9 0.4 0.085 BAT < VTRKL BAT Rising 2.7 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. CONDITIONS MIN TYP 1 0.1 100 1030 100 2.85 135 –100 4.3 0.5 0.1 0.18 110 –125 5.4 0.6 0.115 3 MAX UNITS V V mV mA/mA mA V mV mV Hour Hour mA/mA Ω °C Hot Temperature Fault Threshold Voltage Falling Threshold Hysteresis NTC Disable Threshold Voltage NTC Leakage Current Falling Threshold Hysteresis NTC = NTCBIAS = 5V Always On 3.3V LDO Supply Logic (ILIM0, ILIM1, ID, ENOTG, ENCHARGER) Status Outputs (CHRG, VBUSGD, FAULT) 41601f 4 LTC4160/LTC4160-1 ELECTRICAL CHARACTERISTICS 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 LTC4160E/LTC4160E-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 LTC4160E/LTC4160E-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: The current limit features of this part are intended to protect the IC from short term or intermittent fault conditions. Continuous operation above the maximum specified pin current rating may result in device degradation or failure. Note 6: The bidirectional switcher’s supply current is bootstrapped to VBUS and in the application will reflect back to VOUT by (VBUS/VOUT) • 1/efficiency. Total quiescent current is the sum of the current into the VOUT pin plus the reflected current. Note 7: hC/10 is expressed as a fraction of the measured full charge current with indicated PROG resistor. TYPICAL PERFORMANCE CHARACTERISTICS USB Limited Load Current vs Battery Voltage (Battery Charger Disabled) 900 800 700 LOAD CURRENT (mA) 600 500 400 300 200 100 0 2.7 3.0 3.9 3.6 3.3 BATTERY VOLTAGE (V) 4.2 41601 G01 TA = 25°C, unless otherwise noted. Battery and VBUS Currents vs Load Current 750 VBUS CURRENT USB Limited Load Current vs Battery Voltage (Battery Charger Disabled) 160 140 LOAD CURRENT (mA) 120 100 80 60 40 –250 20 0 2.7 3.0 3.6 3.3 3.9 BATTERY VOLTAGE (V) 4.2 41601 G02 VBUS = 5V 5x MODE VBUS = 5V 1x MODE 500 CURRENT (mA) 250 BATTERY CURRENT (CHARGING) 0 VBUS = 5V BAT = 3.8V 5x MODE RCLPROG = 3.01k BATTERY CURRENT RPROG = 1k (DISCHARGING) 0 200 600 800 400 LOAD CURRENT (mA) 1000 41601 G03 –500 USB Limited Battery Charge Current vs Battery Voltage 700 600 CHARGE CURRENT (mA) 500 400 300 200 100 0 2.7 3.0 3.9 3.6 3.3 BATTERY VOLTAGE (V) 4.2 41601 G04 USB Limited Battery Charge Current vs Battery Voltage 140 120 CHARGE CURRENT (mA) 100 80 60 40 20 0 VBUS = 5V 1x MODE RPROG = 1k 2.7 3.0 3.9 3.6 3.3 BATTERY VOLTAGE (V) 4.2 41601 G05 Battery and VBUS Currents vs Load Current 1000 VBUS CURRENT 750 CURRENT (mA) 500 250 0 VBUS = 5V BAT = 3.8V 10x MODE RCLPROG = 3.01k RPROG = 2k BATTERY CURRENT (CHARGING) VBUS = 5V 5x MODE RPROG = 1k –250 –500 BATTERY CURRENT (DISCHARGING) 1500 0 250 750 1000 1250 500 LOAD CURRENT (mA) 41601 G06 41601f 5 LTC4160/LTC4160-1 TYPICAL PERFORMANCE CHARACTERISTICS Ideal Diode V-I Characteristics 1.0 INTERNAL IDEAL DIODE WITH SUPPLEMENTAL EXTERNAL VISHAY Si2333 PMOS RESISTANCE (Ω) 0.25 TA = 25°C, unless otherwise noted. VOUT Voltage vs Load Current (Battery Charger Disabled) 4.50 4.25 BAT = 4V BAT = 3.4V VOUT (V) 3.75 3.50 3.25 3.00 2.75 4.2 41601 G08 Ideal Diode Resistance vs Battery Voltage 0.8 CURRENT (A) 0.20 INTERNAL IDEAL DIODE 0.15 4.00 0.6 INTERNAL IDEAL DIODE ONLY 0.4 BAT = 2.8V 0.10 INTERNAL IDEAL DIODE WITH SUPPLEMENTAL EXTERNAL VISHAY Si2333 PMOS 0.2 VBUS = 5V 0 0.04 0.12 0.16 0.08 FORWARD VOLTAGE (V) 0.20 41601 G07 0.05 0 0 2.7 3.0 3.6 3.9 3.3 BATTERY VOLTAGE (V) 2.50 VBUS = 5V RCLPROG = 3.01k RPROG = 2k 0 200 600 800 400 LOAD CURRENT (mA) 1000 41601 G09 Battery Charge Current vs VOUT Voltage 600 500 BATTERY CURRENT (mA) 400 VOUT (V) 300 200 100 0 3.40 3.45 3.50 3.55 3.60 3.65 3.70 3.75 3.80 VOUT (V) 41601 G10 VOUT Voltage vs Battery Voltage (Charger Overprogrammed) 4.7 4.5 4.3 4.1 5x MODE VOUT (V) 3.9 3.7 3.5 3.3 3.1 2.9 2.7 2.7 3.0 1x MODE VBUS = 5V IVOUT = 0μA RCLPROG = 3.01k RPROG = 1k 4.50 4.25 4.00 3.75 3.50 3.25 3.00 BATTERY VOLTAGE 2.75 4.2 41601 G11 VOUT Voltage vs Load Current (Battery Charger Enabled) RCLPROG = 3.01k RPROG = 2k 5x MODE BAT = 4V BAT = 3.4V BAT = 2.8V VBUS = 5V RCLPROG = 3.01k RPROG = 2k 0 200 600 800 400 LOAD CURRENT (mA) 1000 41601 G12 3.6 3.9 3.3 BATTERY VOLTAGE (V) 2.50 PowerPath Switching Regulator Transient Response 100 VOUT 50mV/DIV AC-COUPLED EFFICIENCY (%) 90 PowerPath Switching Regulator Efficiency vs Load Current 95 90 1x MODE 80 5x, 10x MODE 70 60 50 EFFICIENCY (%) 85 80 75 70 65 Battery Charging Efficiency vs Battery Voltage with No External Load (PBAT/PVBUS) RCLPROG = 3.01k RPROG = 1k 1x MODE IVOUT 500mA/DIV 0mA VBUS = 5V VOUT = 3.65V CHARGER OFF 10x MODE 20μs/DIV 41601 G13 5x MODE 60 55 10 100 LOAD CURRENT (mA) 1000 41601 G14 40 30 50 2.7 3.0 3.9 3.6 3.3 BATTERY VOLTAGE (V) 4.2 41601 G15 41601f 6 LTC4160/LTC4160-1 TYPICAL PERFORMANCE CHARACTERISTICS VBUS Quiescent Current vs VBUS Voltage (Suspend) 60 50 QUIESCENT CURRENT (μA) 40 30 20 10 0 0 1 2 3 4 BUS VOLTAGE (V) 5 6 41601 G16 TA = 25°C, unless otherwise noted. VBUS Current vs Load Current in Suspend 0.5 VBUS = 5V BAT = 3.3V RCLPROG = 3.01k VOUT Voltage vs Load Current in Suspend 5.0 BAT = 3.8V 4.5 VBUS CURRENT (mA) VBUS = 5V BAT = 3.3V RCLPROG = 3.01k 0 0.1 0.3 0.4 0.2 LOAD CURRENT (mA) 0.5 41601 G17 0.4 VOUT (V) 4.0 0.3 3.5 0.2 3.0 0.1 2.5 0 0 0.1 0.3 0.4 0.2 LOAD CURRENT (mA) 0.5 41601 G18 Battery Drain Current vs Battery Voltage 9 8 BATTERY CURRENT (μA) CHARGE CURRENT (mA) 7 6 5 4 3 2 1 0 2.7 3.0 3.3 3.6 3.9 4.2 41601 G19 Battery Charge Current vs Temperature 600 500 RPROG = 2k NORMALIZED FLOAT VOLTAGE 1.001 Normalized Battery Charger Float Voltage vs Temperature IVOUT = 0mA VBUS = 0V 1.000 400 THERMAL REGULATION 300 200 100 0 –40 –20 0.999 0.998 VBUS = 5V (SUSPEND MODE) 0.997 0 BATTERY VOLTAGE (V) 20 40 60 80 TEMPERATURE (°C) 100 120 41601 G20 0.996 –40 –15 35 10 TEMPERATURE (°C) 60 85 41601 G21 VBUS Quiescent Current vs Temperature 25 VBUS = 5V 60 QUIESCENT CURRENT (mA) QUIESCENT CURRENT (μA) 20 5x MODE 15 50 40 30 20 10 0 –40 70 VBUS Quiescent Current in Suspend vs Temperature VBUS = 5V 12 10 BATTERY CURRENT (μA) 8 6 4 2 Battery Drain Current vs Temperature 10 1x MODE 5 –15 35 10 TEMPERATURE (°C) 60 85 41601 G22 0 –40 –15 10 35 TEMPERATURE (°C) 60 85 41601 G23 0 –40 BAT = 3.8V VBUS = 0V –15 10 35 60 85 41601 G24 TEMPERATURE (°C) 41601f 7 LTC4160/LTC4160-1 TYPICAL PERFORMANCE CHARACTERISTICS OTG Boost Quiescent Current vs Battery Voltage 3.0 VOUT = BAT 5.5 5.0 EFFICIENCY (%) 4.5 VBUS (V) 2.0 4.0 3.5 1.0 3.0 2.5 3.0 3.9 3.6 3.3 BATTERY VOLTAGE (V) 4.2 41601 G25 TA = 25°C, unless otherwise noted. OTG Boost Efficiency vs Load Current 100 90 OTG Boost VBUS Voltage vs Load Current QUIESCENT CURRENT (mA) 2.5 VBUS = 4.75V 80 70 60 50 40 30 600 700 1 IVBUS = 500mA 1.5 VOUT = BAT = 4.2V VOUT = BAT = 3.8V VOUT = BAT = 3.4V VOUT = BAT = 3V 0 100 200 300 400 500 LOAD CURRENT (mA) 0.5 2.7 VOUT = BAT = 4.2V VOUT = BAT = 3.8V VOUT = BAT = 3.4V VOUT = BAT = 3V 10 100 LOAD CURRENT (mA) 1000 41601 G27 41601 G26 OTG Boost Efficiency vs Battery Voltage 100 95 EFFICIENCY (%) 90 85 80 100mA LOAD 75 70 2.7 500mA LOAD TIME (ms) 2.1 2.0 1.9 1.8 1.7 3.0 3.9 3.6 3.3 BATTERY VOLTAGE (V) 4.2 41601 G28 OTG Boost Start-Up Time into Current Source Load vs Battery Voltage VOUT = BAT 2.4 2.3 2.2 22μF ON VBUS, 22μF AND LOAD THROUGH OVP LOAD CURRENT (mA) 100 90 80 70 60 50 40 30 20 10 4.2 41601 G29 OTG Boost Burst Mode Current Threshold vs Battery Voltage VOUT = BAT 22μF ON VBUS, NO OVP 22μF ON VBUS, LOAD THROUGH OVP VOUT = BAT ILOAD = 500mA 3.0 3.9 3.6 3.3 BATTERY VOLTAGE (V) 1.6 2.7 0 2.7 3.0 3.9 3.6 3.3 BATTERY VOLTAGE (V) 4.2 41601 G30 OTG Boost Transient Response VBUS 50mV/DIV AC COUPLED OTG Boost Start-Up into Current Source Load VBUS 50mV/DIV AC COUPLED IVBUS 200mA/DIV 0mA VSW 1V/DIV OTG Boost Burst Mode Operation IVBUS 200mA/DIV 0mA VOUT = 3.8V 20μs/DIV 41601 G31 VBUS 2V/DIV 0V VOUT = 3.8V ILOAD = 500mA 200μs/DIV 41601 G32 0V VOUT = 3.8V ILOAD = 10mA 50μs/DIV 41601 G33 41601f 8 LTC4160/LTC4160-1 TYPICAL PERFORMANCE CHARACTERISTICS 3.3V LDO Output Voltage vs Load Current, VBUS = 0V 3.4 BAT = 3.9V, 4.2V BAT = 3.4V BAT = 3.5V BAT = 3.6V ILDO3V3 5mA/DIV 0mA 3.0 VLDO3V3 20mV/DIV AC COUPLED 41601 G35 TA = 25°C, unless otherwise noted. Oscillator Frequency vs Temperature 2.30 3.3V LDO Step Response (5mA to 15mA) OUTPUT VOLTAGE (V) 3.2 2.25 FREQUENCY (MHz) 2.20 2.15 VOUT = 5V VOUT = 4.2V VOUT = 3.6V VOUT = 3V VOUT = 2.7V –15 35 10 TEMPERATURE (°C) 60 85 41601 G36 2.8 BAT = 3V BAT = 3.1V BAT = 3.2V BAT = 3.3V 2.6 5 15 0 20 10 LOAD CURRENT (mA) BAT = 3.8V 20μs/DIV 2.10 25 41601 G34 2.05 –40 OVP Connect Waveform OVGATE 2V/DIV VBUS OVGATE 5V/DIV OVP INPUT VOLTAGE 5V TO 10V STEP 5V/DIV 250μs/DIV 41601 G37 OVP Disconnect Waveform 6.47 VBUS 5V/DIV OVP THRESHOLD (V) Rising OVP Threshold vs Temperature 6.46 6.45 0V 6.44 500μs/DIV 41601 G38 6.43 6.42 –40 –15 35 10 TEMPERATURE (°C) 60 85 41601 G39 OVGATE vs OVSENS 12 OVSENS CONNECTED TO INPUT THROUGH 10 6.2k RESISTOR QUIESCENT CURRENT (μA) 8 OVGATE (V) 6 4 2 0 0 2 4 6 INPUT VOLTAGE (V) 8 41601 G40 OVSENS Quiescent Current vs Temperature VBUSGD, CHRG, FAULT PIN CURRENT (mA) 48 45 42 39 36 33 30 –40 VOVSENS = 5V 120 100 VBUSGD, CHRG, FAULT Pin Current vs Voltage (Pull-Down State) VBUS = 5V BAT = 3.8V VBUSGD 80 60 40 20 0 FAULT, CHRG –15 35 10 TEMPERATURE (°C) 60 85 41601 G41 0 1 3 4 5 2 VBUSGD, CHRG, FAULT PIN VOLTAGE (V) 41601 G42 41601f 9 LTC4160/LTC4160-1 PIN FUNCTIONS OVGATE (Pin 1): Overvoltage Protection Gate Output. Connect OVGATE to the gate pin of an external N-channel MOSFET. The source of the transistor should be connected to VBUS and the drain should be connected to the product’s DC input connector. In the absence of an overvoltage condition, this pin is connected to an internal charge pump capable of creating sufficient overdrive to fully enhance the MOSFET. If an overvoltage condition is detected, OVGATE is brought rapidly to GND to prevent damage to the LTC4160/LTC4160-1. OVGATE works in conjunction with OVSENS to provide this protection. OVSENS (Pin 2): Overvoltage Protection Sense Input. OVSENS should be connected through a 6.2k resistor to the input power connector and the drain of an external N-channel MOSFET. When the voltage on this pin exceeds VOVCUTOFF, the OVGATE pin will be pulled to GND to disable the MOSFET and protect the LTC4160/LTC4160-1. The OVSENS pin shunts current during an overvoltage transient in order to keep the pin voltage at 6V. VBUSGD (Pin 3): Logic Output. This is an open-drain output which indicates that VBUS is above VUVLO and VDUVLO. VBUSGD requires a pull-up resistor and/or LED to provide indication. FAULT (Pin 4): Logic Output. This in an open-drain output which indicates a bad battery fault when the charger is enabled or a short circuit condition on VBUS when the bidirectional PowerPath switching regulator is in step-up mode (On-The-Go). FAULT requires a pull-up resistor and/or LED to provide indication. ID (Pin 5): Logic Input. This pin independently enables the bidirectional switching regulator to step-up the voltage on VOUT and provide a 5V output on the VBUS pin for USB On-The-Go applications. If the host does not power down VBUS then connect this pin directly to the ID pin of a USB micro-AB receptacle. Active low. Has an internal 2.5μA pull-up current source. ENOTG (Pin 6): Logic Input. This pin independently enables the bidirectional switching regulator to step-up the voltage on VOUT and provide a 5V output on the VBUS pin for USB On-The-Go applications. Active high. Has an internal 1.8μA pull-down current source. ENCHARGER (Pin 7): Logic Input. This pin enables the battery charger. Active low. Has an internal 1.8μA pulldown current source. PROG (Pin 8): 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 9): Logic Output. This is an open-drain output that indicates whether the battery is charging or not charging. CHRG requires a pull-up resistor and/or LED to provide indication. IDGATE (Pin 10): Ideal Diode Amplifier Output. This pin controls the gate of an optional external P-channel MOSFET used as an ideal diode between VOUT and BAT. The external ideal diode operates in parallel with the internal ideal diode. The source of the P-channel MOSFET should be connected to VOUT and the drain should be connected to BAT. If the external ideal diode MOSFET is not used, IDGATE should be left floating. BAT (Pin 11): Single Cell Li-Ion Battery Pin. Depending on available VBUS power, a Li-Ion battery on BAT will either deliver power to VOUT through the ideal diode or be charged from VOUT via the battery charger. VOUT (Pin 12): Output Voltage of the Bidirectional PowerPath Switching Regulator in Step-Down Mode and Input Voltage of the Battery Charger. The majority of the portable product should be powered from VOUT. The LTC4160/ LTC4160-1 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. In On-The-Go mode, this pin delivers power to VBUS via the SW pin. VOUT should be bypassed with a 41601f 10 LTC4160/LTC4160-1 PIN FUNCTIONS low impedance multilayer ceramic capacitor. VBUS (Pin 13): Power Pin. This pin delivers power to VOUT via the SW pin by drawing controlled current from a DC source such as a USB port or DC output wall adapter. In On-The-Go mode this pin provides power to external loads. Bypass VBUS with a low impedance multilayer ceramic capacitor. SW (Pin 14): The SW pin transfers power between VBUS to VOUT via the bidirectional switching regulator. See the Applications Information section for a discussion of inductance value and current rating. ILIM0, ILIM1 (Pins 15, 16): ILIM0 and ILIM1 control the VBUS input current limit of the bidirectional PowerPath switching regulator in step-down mode. See Table 1. Each has an internal 1.8μA pull-down current source. CLPROG (Pin 17): USB Current Limit Program and Monitor Pin. A 1% resistor from CLPROG to ground determines the upper limit of the current drawn or sourced from the VBUS pin. A precise fraction, hCLPROG, of the VBUS current is sent to the CLPROG pin when the PMOS switch of the bidirectional PowerPath switching regulator is on. The switching regulator delivers power until the CLPROG pin reaches 1.18V in step-down mode and 1.15V in step-up mode. When the switching regulator is in step-down mode, CLPROG is used to regulate the average input current. Several VBUS current limit settings are available via user input which will typically correspond to the 500mA and 100mA USB specifications. When the switching regulator is in step-up mode (USB On-The-Go), CLPROG is used to limit the average output current to 680mA. A multilayer ceramic averaging capacitor or R-C network is required at CLPROG for filtering. LDO3V3 (Pin 18): 3.3V LDO Output Pin. This pin provides a regulated always-on 3.3V supply voltage. LDO3V3 gets its power from VOUT. It may be used for light loads such as a watch dog microprocessor or real time clock. A 1μF capacitor is required from LDO3V3 to ground. If the LDO3V3 output is not used it should be disabled by connecting it to VOUT. NTCBIAS (Pin 19): 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 20): Input to the Thermistor Monitoring Circuits. The NTC pin connects to a negative temperature coefficient thermistor, which is typically co-packaged with the battery, 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 it 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. To disable NTC operation, connect NTC to GND and leave NTCBIAS open. Exposed Pad (Pin 21): Ground. The Exposed Pad should be connected to a continuous ground plane on the second layer of the printed circuit board by several vias directly under the LTC4160/LTC4160-1. 41601f 11 BLOCK DIAGRAM LTC4160/LTC4160-1 ILDO/M SUSPEND LDO 4.6V VFLOAT OmV VCLPROG VBUS VOLTAGE CONTROLLER VOUT VOLTAGE CONTROLLER 0.3V 3.6V IBAT/1000 0.2V 4 CONTROL LOGIC BAD CELL OTG SHORT CIRCUIT FAULT FAULT NTC FAULT 1 6V 2 OVGATE OVERVOLTAGE PROTECTION + – ILIM1 16 NTC ENABLE 2 ILIM0 15 6 ENOTG 5 ID 7 ENCHARGER GND 21 OVSENS + – OVERTEMP + – – + RECHRG – + –+ –+ + – 3 VBUSGD 4.3V BAT 4HRS LOW BAT 2.9V NTCBIAS VRECHRG VOUT UNDERTEMP 19 VBUSGD + + – + – + – 17 AVERAGE VBUS CURRENT LIMIT CONTROLLER 5.1V +– 100mV – + + – CLPROG 15mV + – + – – + 12 3V3 LDO PWM AND GATE DRIVE 18 14 SW TO SYSTEM LOAD OPTIONAL EXTERNAL OVERVOLTAGE PROTECTION N-CHANNEL MOSFET TO USB OR WALL ADAPTER 13 VBUS –+ 3.3V VOUT 12 BATTERY CHARGER 1V IDEAL DIODE LDO3V3 OPTIONAL EXTERNAL OVERVOLTAGE PROTECTION RESISTOR ISWITCH/N 100mV + – –+ + – 10 IDGATE OPTIONAL EXTERNAL IDEAL DIODE P-CHANNEL MOSFET 11 BAT 8 PROG + SINGLE CELL Li-Ion CHRG 9 NTC 20 NTC T + – 0.1V 41601 BD 41601f LTC4160/LTC4160-1 OPERATION Introduction The LTC4160/LTC4160-1 are high efficiency bidirectional switching power managers and Li-Ion/Polymer battery chargers designed to make optimal use of the power available while minimizing power dissipation and easing thermal budgeting constraints. The innovative PowerPath architecture ensures that the end product application is powered immediately after external voltage is applied, even with a completely dead battery, by prioritizing power to the end product. When acting as a step-down converter, the LTC4160/ LTC4160-1’s bidirectional switching regulator takes power from USB, wall adapters, or other 5V sources and provides power to the end product application and efficiently charges the battery using Bat-Track. Because power is conserved, the LTC4160/LTC4160-1 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. For USB compatibility, the switching regulator includes a precision average input current limit. The bidirectional switching regulator and battery charger communicate to ensure that the average input current never exceeds the USB specifications. In addition, the bidirectional switching regulator can also operate as a 5V synchronous step-up converter, taking power from VOUT and delivering up to 500mA to VBUS without the need for any additional external components. This enables systems with USB dual-role transceivers to function as USB On-The-Go dual-role devices. True output disconnect and average output current limit features are included for short circuit protection. The LTC4160/LTC4160-1 contain both an internal 180mΩ ideal diode as well as an ideal diode controller for use with an external P-channel MOSFET. 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. An always-on LDO provides a regulated 3.3V from available power at VOUT. Drawing very little quiescent current, this LDO will be on at all times and can be used to supply up to 20mA. The LTC4160/LTC4160-1 also feature an overvoltage protection circuit which is designed to work with an external N-channel MOSFET to prevent damage to their inputs caused by accidental application of high voltage. Finally, to prevent battery drain when a device is connected to a suspended USB port, an LDO from VBUS to VOUT provides low power USB suspend current to the end product application. Bidirectional PowerPath Switching Regulator – Step-Down Mode The power delivered from VBUS to VOUT is controlled by a 2.25MHz constant frequency bidirectional switching regulator in step-down mode. VOUT drives the combination of the external load and the battery charger. To meet the maximum USB 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. If the combined load does not cause the switching regulator 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 flow in step-down mode. If the combined external load plus battery charge current is large enough to cause the switching regulator 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 diode(s) even when the battery charger is enabled. The current out of 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 41601f 13 LTC4160/LTC4160-1 OPERATION the programmed limit, CLPROG reaches 1.18V and power delivered by the switching regulator is held constant. The input current limit is programmed by the ILIM0 and ILIM1 pins. The input current limit has four possible settings ranging from the USB suspend limit of 500μA up to 1A for wall adapter applications. Two of these settings are specifically intended for use in the 100mA and 500mA USB application. Refer to Table 1 for current limit settings using ILIM0 and ILIM1. Table 1. USB Current Limit Settings Using ILIM0 and ILIM1 ILIM1 0 0 1 1 ILIM0 0 1 0 1 USB SETTING 1x Mode (USB 100mA Limit) 10x Mode (Wall 1A Limit) Low Power Suspend (USB 500μA Limit) 5x Mode (USB 500mA Limit) where IVBUSQ is the quiescent current of the LTC4160/ LTC4160-1, 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 100mA or 500mA mode will not be violated, provided that RCLPROG is 3.01k or greater. 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 slightly below the battery voltage, indicated by the shaded region of Figure 2. When the switching regulator is activated, the average input current will be limited by the CLPROG programming resistor according to the following expression: IVBUS = IVBUSQ + VCLPROG • hCLPROG + 1 RCLPROG ( ) TO USB OR WALL ADAPTER 13 VBUS PWM AND GATE DRIVE VBUS VOLTAGE CONTROLLER ISWITCH/N 5V 14 SW 3.5V TO (BAT + 0.3V) TO SYSTEM LOAD VOUT 12 BATTERY CHARGER CLPROG 17 1.18V 15mV IBAT/1000 1 OVGATE 2 OVSENS 2 + – 0.3V 3.6V 6V +– OVERVOLTAGE PROTECTION VOUT VOLTAGE CONTROLLER PROG Figure 1. Power Path Block Diagram – Power Available from USB/Wall Adapter 41601f 14 + – AVERAGE VBUS INPUT CURRENT LIMIT CONTROLLER + – + + – + – –+ + – 1V IDEAL DIODE VFLOAT OmV + – 10 IDGATE + – 11 BAT 8 + SINGLE CELL Li-Ion 41601 F01 USB INPUT BATTERY POWER LTC4160/LTC4160-1 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. See Over Programming the Battery Charger in the Applications Information section. The voltage regulation loop compensation is controlled by the capacitance on VOUT. A multilayer ceramic 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 4.30V and is about 200mV above the battery voltage. When both conditions are met, VBUSGD goes low and the switching regulator turns on. Hysteresis on the UVLO forces VBUSGD high and turns off the switching regulator if VBUS falls below 4.00V or to within 50mV of the battery voltage. When this happens, system power at VOUT will be drawn from the battery via the ideal diode(s). 4.5 4.2 3.9 VOUT (V) NO LOAD 3.6 300mV 3.3 3.0 2.7 2.4 2.4 comes from the battery via the ideal diode(s). As a step-up converter, the bidirectional switching regulator produces 5V on VBUS and is capable of delivering at least 500mA. USB On-The-Go can be enabled by either of the external control pins, ENOTG or ID. Figure 3 shows the power flow in step-up mode. An undervoltage lockout circuit monitors VOUT and prevents step-up conversion until VOUT rises above 2.8V. To prevent backdriving of VBUS when input power is available, the VBUS undervoltage lockout circuit prevents step-up conversion if VBUS is already greater than 4.3V at the time step-up mode is enabled. The switching regulator is also designed to allow true output disconnect by eliminating body diode conduction of the internal PMOS switch. This allows VBUS to go to zero volts during a short-circuit condition or while shutdown, drawing zero current from VOUT. The voltage regulation loop is compensated by the capacitance on VBUS. A 4.7μF multilayer ceramic capacitor is required for loop stability. Additional capacitance beyond this value will improve transient response. The VBUS voltage has approximately 3% load regulation up to an output current of 500mA. At light loads, the switching regulator goes into Burst Mode® operation. The regulator will deliver power to VBUS until it reaches 5.1V after which the NMOS and PMOS switches shut off. The regulator delivers power again to VBUS once it falls below 5.1V. The switching regulator features both peak inductor and average output current limit. The peak current-mode architecture limits peak inductor current on a cycle-bycycle basis. The peak current limit is equal to VBUS/2Ω to a maximum of 1.8A so that in the event of a sudden short circuit, the current limit will fold back to a lower value. In step-up mode, the voltage on CLPROG represents the average output current of the switching regulator when a programming resistor and an averaging capacitor are connected from CLPROG to GND. With a 3.01k resistor on CLPROG, the bidirectional switching regulator has an output current limit of 680mA. As the output current approaches this limit, CLPROG servos to 1.15V and VBUS falls rapidly to VOUT. When VBUS is close to VOUT there may not be sufficient negative slope on the inductor current when the PMOS switch is on to balance the rise in the inductor Burst Mode is a registered trademark of Linear Technology Corporation. 41601f 2.7 3.0 3.6 3.3 BAT (V) 3.9 4.2 41601 F02 Figure 2. VOUT vs BAT Bidirectional PowerPath Switching Regulator – Step-Up Mode For USB On-The-Go applications, the bidirectional PowerPath switching regulator acts as a step-up converter to deliver power from VOUT to VBUS. The power from VOUT 15 LTC4160/LTC4160-1 OPERATION TO USB OR WALL ADAPTER 13 VBUS PWM AND GATE DRIVE VBUS VOLTAGE CONTROLLER ISWITCH/N 5.1V VOUT 12 BATTERY CHARGER 14 SW 3.5V TO (BAT + 0.3V) TO SYSTEM LOAD CLPROG 17 1.18V 15mV IBAT/1000 1 OVGATE 2 OVSENS 2 + – 0.3V 3.6V 6V +– OVERVOLTAGE PROTECTION VOUT VOLTAGE CONTROLLER PROG Figure 3. PowerPath Block Diagram – USB On-The-Go current when the NMOS switch is on. This will cause the inductor current to run away and the voltage on CLPROG to rise. When CLPROG reaches 1.2V the switching of the synchronous PMOS is terminated and VOUT is applied statically to its gate. This ensures that the inductor current will have sufficient negative slope during the time current is flowing out of the VBUS pin. The PMOS will resume switching when CLPROG drops down to 1.15V. The PMOS switch is enabled when VBUS rises above VOUT + 180mV and is disabled when it falls below VOUT + 70mV to prevent the inductor current from running away when not in current limit. If the PMOS switch is disabled for more than 7.2ms then the switcher will shut off, the FAULT pin will go low and a short circuit fault will be declared. To re-enable step-up mode, the ENOTG pin, with ID high, must be cycled low and then high or the ID pin, with ENOTG grounded, must be cycled high and then low. Ideal Diode(s) from BAT to VOUT The LTC4160/LTC4160-1 each 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 bidirectional switching regulator, additional power will be pulled from the battery via the ideal diode(s). Furthermore, if power to VBUS (USB or wall adapter) is removed, then all of the application power will be provided by the battery via the ideal diode(s). The ideal diode(s) will prevent VOUT from drooping with only the storage capacitance required for the bidirectional switching regulator. The internal ideal diode consists of a precision amplifier that activates a large on-chip P-channel MOSFET whenever 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) 41601 F04 VISHAY Si2333 OPTIONAL EXTERNAL IDEAL DIODE LTC4160/ LTC4160-1 IDEAL DIODE Figure 4. Ideal Diode V-I Characteristics 41601f 16 + – AVERAGE VBUS OUTPUT CURRENT LIMIT CONTROLLER + – + + – + – –+ + – 1V IDEAL DIODE VFLOAT OmV + – 10 IDGATE + – 11 BAT 8 + SINGLE CELL Li-Ion 41601 F03 BATTERY POWER ON SEMICONDUCTOR MBRM120LT3 LTC4160/LTC4160-1 OPERATION 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 MOSFET will be in full conduction. To supplement the internal ideal diode, an external Pchannel MOSFET may be added from BAT to VOUT. The IDGATE pin of the LTC4160/LTC4160-1 drives the gate of the external P-channel MOSFET 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 having an on-resistance of 30mΩ or lower. Suspend LDO If the LTC4160/LTC4160-1 is configured for USB suspend mode, the bidirectional switching regulator is disabled and the suspend LDO provides power to the VOUT pin (presuming there is power available at VBUS). 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 bidirectional switching regulator is disabled (suspended). The suspend LDO sends a scaled copy of the VBUS current to the CLPROG pin, which will servo to approximately 100mV in this mode. In accordance with the USB specification, the input to the LDO is current limited so that it will not exceed the low power suspend specification. If the load on VOUT exceeds the suspend current limit, the additional current will come from the battery via the ideal diode(s). 3.3V Always-On LDO Supply The LTC4160/LTC4160-1 include a low quiescent current low dropout regulator that is always powered. This LDO can be used to provide power to a system pushbutton controller, standby microcontroller or real time clock. Designed to deliver up to 20mA, the always-on LDO requires at least a 1μF multilayer ceramic bypass capacitor for compensation. The LDO is powered from VOUT, and therefore will enter dropout at loads less than 20mA as VOUT falls near 3.3V. If the LDO3V3 output is not used, it should be disabled by connecting it to VOUT. Battery Charger The LTC4160/LTC4160-1 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. The charger can be disabled using the ENCHARGER pin. Battery Preconditioning 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 a 1/2 hour, the battery charger automatically terminates and indicates via the CHRG and FAULT pins that the battery was unresponsive. Once the battery voltage is above 2.85V, the charger begins charging in full power constant-current mode. The current delivered to the battery will try to reach 1030/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. Likewise, 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. Charge Termination The battery charger has a built-in safety timer. When the voltage on the battery reaches the pre-programmed float voltage, the battery charger will regulate the battery voltage and the charge current will decrease naturally. Once the battery charger detects that the battery has reached the float voltage, the four 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 After 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, 41601f 17 LTC4160/LTC4160-1 OPERATION 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 the recharge threshold which is typically 100mV less than the charger’s float voltage. In the event that the safety timer is running when the battery voltage falls below the recharge threshold, it will reset back to zero. To prevent brief excursions below the recharge threshold from resetting the safety timer, the battery voltage must be below the recharge threshold for more than 1ms. 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 battery charger is cycled on and off by the ENCHARGER pin. Charge Current The charge current is programmed using a single resistor from PROG to ground. 1/1030th of the battery charge current is sent 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 equation: V ICHG = PROG • 1030 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. Therefore, the actual charge current can be determined at any time by monitoring the PROG pin voltage and using the following equation: IBAT = VPROG •1030 RPROG Charge Status Indication The CHRG and FAULT pins can be used to indicate the status of the battery charger. Two possible states are represented by CHRG: charging and not charging. 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. When charging begins, CHRG is pulled low and remains low for the duration of a normal charge cycle. When charging is complete, i.e., the BAT pin reaches the float and the charge current has dropped to one tenth of the programmed value, the CHRG pin goes high. The CHRG pin does not respond to the C/10 threshold if the LTC4160/LTC4160-1 is in VBUS input current limit. This prevents false end-ofcharge indications due to insufficient power available to the battery charger. Table 2 illustrates the possible states of the CHRG and FAULT pins when the battery charger is active. Table 2. Charge Status Readings Using the CHRG and FAULT Pins STATUS Charging/NTC Fault Not Charging Bad Battery CHRG Low High High FAULT High High Low An NTC fault pauses charging while the battery temperature is out of range but is not indicated using the CHRG or FAULT pins. 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 goes high and the FAULT pin goes low to indicate a bad battery fault. Note that the LTC4160/LTC4160-1 are 3-terminal PowerPath products where 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 trickle charge threshold voltage within the bad battery timeout period. In this case, the battery charger will falsely indicate a bad battery. System software may then reduce the load and reset the battery charger to try again. The FAULT pin is also used to indicate whether there is a short circuit condition on VBUS when the bidirectional 41601f In many cases, the actual battery charge current, IBAT, will be lower than ICHG due to limited input power available and prioritization with the system load drawn from VOUT. The Battery Charger Flow Chart on the next page illustrates the battery charger’s algorithm. 18 LTC4160/LTC4160-1 OPERATION Battery Charger Flow Chart POWER ON/ ENABLE CHARGER CLEAR EVENT TIMER ASSERT CHRG LOW NTC OUT OF RANGE YES NO 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) INHIBIT CHARGING RUN EVENT TIMER PAUSE EVENT TIMER RUN EVENT TIMER PAUSE EVENT TIMER NO TIMER > 30 MINUTES TIMER > 4 HOURS NO YES YES NO INHIBIT CHARGING STOP CHARGING IBAT < C/10 YES INDICATE BATTERY FAULT AT FAULT BAT RISING THROUGH VRECHRG YES CHRG Hi-Z CHRG Hi-Z NO NO BAT > 2.85V BAT FALLING THROUGH VRECHRG YES NO BAT < VRECHRG YES NO YES 41601 FLOW 41601f 19 LTC4160/LTC4160-1 OPERATION switching regulator is in On-The-Go mode. When a short circuit condition is detected, FAULT will go low-Z. The ENOTG or VBUSGD pins can be used to determine which fault has occurred. If ENOTG or VBUSGD is low when FAULT went low, then a bad battery fault has occurred. If either pin is high, then a short circuit on VBUS has occurred. NTC Thermistor The battery temperature is measured by placing a negative temperature coefficient (NTC) thermistor close to the battery pack. 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% 200ppm resistor with a value equal to the value of the chosen NTC thermistor at 25°C (R25). The LTC4160/LTC4160-1 will pause charging when the resistance of the NTC thermistor drops to 0.54 times the value of R25 or approximately 54k for a 100k thermistor. For a Vishay Curve 1 thermistor, this corresponds to approximately 40°C. If the battery charger is in constantvoltage (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 LTC4160/LTC4160-1 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 100k 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. Thermal Regulation To prevent thermal damage to the LTC4160/LTC4160-1 or surrounding components, an internal thermal feedback loop will automatically decrease the programmed charge current if the die temperature rises to 105°C. This thermal regulation technique protects the LTC4160/LTC4160-1 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. The benefit of the LTC4160/ LTC4160-1 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. Overvoltage Protection The LTC4160/LTC4160-1 can protect themselves from the inadvertent application of excessive voltage to VBUS with just two external components: an N-channel MOSFET and a 6.2k resistor. The maximum safe overvoltage magnitude will be determined by the choice of the external MOSFET and its associated drain breakdown voltage. The overvoltage protection circuit 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 the external MOSFET. When OVSENS is below 6V, an internal charge pump will drive OVGATE to approximately 1.88 • OVSENS. This will enhance the N-channel MOSFET and provide a low impedance connection to VBUS which will, in turn, power the LTC4160/LTC4160-1. If OVSENS should rise above 6V due to a fault or the use of an incorrect wall adapter, OVGATE will be pulled to GND. This disables the external MOSFET and protects downstream circuitry. When the voltage drops below 6V again, the external MOSFET will be re-enabled. 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 resistor power dissipation rating calculations, a table of recommended components, and reverse-voltage protection. Shutdown Mode The USB switching regulator is enabled whenever VBUS is above VUVLO and the LTC4160/LTC4160-1 are not in USB suspend mode. The ideal diode(s) are enabled at all times and cannot be disabled. 41601f 20 LTC4160/LTC4160-1 APPLICATIONS INFORMATION Bidirectional PowerPath Switching Regulator CLPROG Resistor and Capacitor Selection As described in the Bidirectional PowerPath Switching Regulator – Step-Down Mode section, the resistor on the CLPROG pin determines the average VBUS input current limit. In step-down mode the switching regulator’s VBUS input current limit can be set to either the 1x mode (USB 100mA), the 5x mode (USB 500mA) or the 10x mode. The VBUS 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. Recall that: IVBUS = IVBUSQ + VCLPROG/RCLPPROG • (hCLPROG +1). 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. Bidirectional PowerPath Switching Regulator Inductor Selection Because the VBUS voltage range and VOUT voltage range of the PowerPath switching regulator are both fairly narrow, the LTC4160/LTC4160-1 were designed for a specific inductance value of 3.3μH. Some inductors which may be suitable for this application are listed in Table 3. Table 3. Recommended PowerPath Inductors for the LTC4160/LTC4160-1 INDUCTOR L MAX IDC MAX DCR SIZE IN mm TYPE (μH) (A) (Ω) (L x W x H) MANUFACTURER LPS4018 3.3 2.2 0.08 3.9 x 3.9 x 1.7 Coilcraft www.coilcraft.com D53LC 3.3 2.26 0.034 5 x 5 x 3 Toko DB318C 3.3 1.55 0.070 3.8 x 3.8 x 1.8 www.toko.com WE-TPC 3.3 1.95 0.065 4.8 x 4.8 x 1.8 Wurth Electronik Type M1 www.we-online.com CDRH6D12 3.3 2.2 0.063 6.7 x 6.7 x 1.5 Sumida CDRH6D38 3.3 3.5 0.020 7 x 7 x 4 www.sumida.com Bidirectional PowerPath Switching Regulator VBUS and VOUT Bypass Capacitor Selection The type and value of capacitors used with the LTC4160/ LTC4160-1 determine several important parameters such as regulator control-loop stability and input voltage ripple. Because the LTC4160/LTC4160-1 use a bidirectional switching regulator between VBUS and VOUT, the VBUS current waveform contains high frequency components. It is strongly recommended that a low equivalent series resistance (ESR) multilayer ceramic capacitor (MLCC) 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 inrush current limit specification for USB devices is calculated in terms of the total number of Coulombs needed to charge the VBUS bypass capacitor to 5V. The maximum inrush charge for USB On-The-Go devices is 33μC. This places a limit of 6.5μF of capacitance on VBUS assuming a linear capacitor. However, most ceramic capacitors have a capacitance that varies with bias voltage. The average capacitance needs to be less than 6.5μF over a 0V to 5V bias voltage range to meet the inrush current-limit specification. A 10μF capacitor in a 0805 package, such as the Murata GRM21BR71A106KE51L would be a suitable VBUS bypass capacitor. If more capacitance is required for better noise performance and stability, it should be connected directly to the VBUS pin when using the overvoltage protection circuit. This extra capacitance will be soft-connected over a couple of milliseconds to limit inrush current and avoid excessive transient voltage drops on VBUS. To prevent large VOUT voltage steps during transient load conditions, it is also recommended that an MLCC 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. MLCCs 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. 41601f 21 LTC4160/LTC4160-1 APPLICATIONS INFORMATION There are MLCCs available with several types of dielectrics each having considerably different characteristics. For example, X7R MLCCs have the best voltage and temperature stability. X5R MLCCs have apparently higher packing density but poorer performance over their rated voltage and temperature ranges. Y5V MLCCs 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. Overvoltage Protection VBUS can be protected from overvoltage damage with two additional components, a resistor R1 and an N-channel MOSFET MN1, as shown in Figure 5. Suitable choices for MN1 are listed in Table 4. Table 4. Recommended N-Channel MOSFETs for the Overvoltage Protection Circuit PART # Si1472DH Si2302ADS Si2306BDS Si2316DS IRLML2502 FDN372S NTLJS4114N BVDSS 30V 20V 30V 30V 20V 30V 30V RON 57mΩ 60mΩ 47mΩ 50mΩ 50mΩ 50mΩ 35mΩ PACKAGE SC70-6 SOT-23 SOT-23 SOT-23 SOT-23 SOT-23 WDFN6 VBUS POSITIVE PROTECTION UP TO BVDSS OF MN1 VBUS NEGATIVE PROTECTION UP TO BVDSS OF MP1 R1 is a 6.2k resistor and must be rated for the power dissipated during maximum overvoltage. In an overvoltage condition the OVSENS pin will be clamped at 6V. R1 must be sized appropriately to dissipate the resultant power. For example, a 1/10W 6.2k resistor can have at most √(PMAX • 6.2kΩ) = 25V applied across its terminals. With the 6V at OVSENS, the maximum overvoltage magnitude that this resistor can withstand is 31V. A 1/4W 6.2k resistor raises this value to 45V. OVSENS’s absolute maximum current rating of 10mA imposes an upper limit of 68V protection. Reverse Voltage Protection The LTC4160/LTC4160-1 can also be easily protected against the application of reverse voltages, as shown in Figure 6. 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 6 offers forward voltage protection up to MN1’s BVDSS and reverse voltage protection up to MP1’s BVDSS. USB/WALL ADAPTER MP1 D1 MN1 VBUS C1 LTC4160/ LTC4160-1 R1 R2 OVGATE OVSENS 41601 F06 Figure 6. Dual Polarity Voltage Protection Battery Charger Over Programming The USB high power specification allows for up to 2.5W to be drawn from the USB port. The LTC4160/LTC4160-1’s bidirectional switching regulator in step-down mode converts the voltage at VBUS to a voltage just above BAT on VOUT, 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, the charge current will be reduced until the system load on VOUT is satisfied and the VBUS current limit is satisfied. Programming the charger for more 41601f USB/WALL ADAPTER MN1 VBUS C1 R1 LTC4160/ LTC4160-1 OVGATE OVSENS 41601 F05 Figure 5. Overvoltage Protection 22 LTC4160/LTC4160-1 APPLICATIONS INFORMATION 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 dissipation within the charger. Battery Charger Stability Considerations The LTC4160/LTC4160-1’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 MLCCs reduce the constant-voltage loop phase margin, possibly resulting in instability. Up to 22μF may be used in parallel with a battery, but larger capacitors should be decoupled with 0.2Ω to 1Ω of series resistance. Furthermore, a 100μF capacitor in series with a 0.3Ω resistor 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 are connected to NTC. By using a bias resistor whose value is equal to the room temperature resistance of the thermistor (R25) the upper and lower temperatures are pre-programmed 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 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 the thermistor at the cold trip point RNTC|HOT = Value of the 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 7) R1 = Optional temperature range adjustment resistor (see Figure 8) The trip points for the LTC4160/LTC4160-1’s temperature qualification are internally programmed at 0.349 • NTCBIAS for the hot threshold and 0.765 • NTCBIAS for the cold threshold. 41601f Alternate NTC Thermistors and Biasing The LTC4160/LTC4160-1 provide temperature qualified charging if a grounded thermistor and a bias resistor 23 LTC4160/LTC4160-1 APPLICATIONS INFORMATION Therefore, the hot trip point is set when: RNTCHOT RNOM + RNTCHOT • NTCBIAS = 0.349 • NTCBIAS be set to 46.4k. With this value of RNOM, rCOLD is 1.436 and 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, R1, as shown in Figure 8. The following formulas can be used to compute the values of RNOM and R1: rCOLD – rHOT • R25 2.714 R1 = 0.536 • RNOM – rHOT • R25 RNOM = 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 And the cold trip point is set when: RNTC COLD RNOM + RNTC COLD • NTCBIAS = 0.765 • NTCBIAS 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 above 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 non-linear behavior of the thermistor. The following equations can be used to calculate a new value for the bias resistor: r RNOM = HOT • R25 0.536 r RNOM = COLD • R25 3.25 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. From the Vishay Curve 1 R-T characteristics, rHOT is 0.2488 at 60°C. Using the above equation, RNOM should the nearest 1% value is 105k: R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k the nearest 1% value is 12.7k. The final solution is shown in Figure 8 and results in an upper trip point of 45°C and a lower trip point of 0°C. NTCBIAS 3 LTC4160/LTC4160-1 NTC BLOCK 0.765 • NTCBIAS RNOM 100k NTC 4 – TOO_COLD + T RNTC 100k 0.349 • NTCBIAS – TOO_HOT + + NTC_ENABLE 0.1V – 41601 F07 Figure 7. Standard NTC Configuration 41601f 24 LTC4160/LTC4160-1 APPLICATIONS INFORMATION NTCBIAS 3 LTC4160/LTC4160-1 NTC BLOCK 0.765 • NTCBIAS RNOM 105k NTC R1 12.7k T RNTC 100k 4 – TOO_COLD + switching and VBUS will be held at the regulation voltage of the external supply. If the external supply has a lower regulation voltage and is capable of only sourcing current, then VBUS will be regulated to 5.1V. The external supply will not source current to VBUS. For a supply that can also sink current and has a regulation voltage less than 5.1V, the bidirectional switching regulator will source current into the external supply in an attempt to bring VBUS up to 5.1V. As long as the external supply holds VBUS to more than VOUT + 70mV, the bidirectional switching regulator will source up to 680mA into the supply. If VBUS is held to a voltage that is less than VOUT + 70mV then the short circuit timer will shut off the switching regulator after 7.2ms. The FAULT pin will then go low to indicate a short circuit current fault. VBUS Bypass Capacitance and USB On-The-Go Session Request Protocol When two On-The-Go devices are connected, one will be the A device and the other will be the B device depending on whether the device is connected to a micro-A or microB plug. The A device provides power to the B device and starts as the host. To prolong battery life, the A device can power down VBUS when the BUS is not being used. If the A device has powered down VBUS, the B device can request the A device to power up VBUS and start a new session using the session request protocol (SRP). The SRP consists of data-line pulsing and VBUS pulsing. The B device must first pulse the D+ or D– data lines. The B device must then pulse VBUS only if the A device does not respond to the data-line pulse. The A device is required to respond to only one of the pulsing methods. USB A devices that never power down VBUS are not required to respond to the SRP . For VBUS pulsing, the limit on the VBUS capacitance on the A device allows a B device to differentiate between a powered down On-The-Go device and a powered down standard host. The B device will send out a pulse of current that will raise VBUS to a voltage between 2.1 and 5.25V if connected to an On-The-Go A device which must have no more than 6.5μF An On-The-Go A device must drive VBUS . as soon as the current pulse raises VBUS above 2.1V if the device is capable of responding to VBUS pulsing. 41601f – TOO_HOT 0.349 • NTCBIAS + + NTC_ENABLE 0.1V – 41601 F08 Figure 8. Modified NTC Configuration Hot Plugging and USB Inrush Current Limiting The overvoltage protection circuit provides inrush current limiting due to the long time it takes for OVGATE to fully enhance the N-channel MOSFET. This prevents the current from building up in the cable too quickly and dampens out any resonant overshoot on VBUS. It is possible to observe voltage overshoot on VBUS when connecting the LTC4160/LTC4160-1 to a lab supply if the overvoltage protection circuit is not used. This overshoot is caused by the inductance of the long leads from the supply to VBUS. Twisting the wires together from the supply to VBUS can greatly reduce the parasitic inductance of these long leads and keep VBUS at a safe level. USB cables are generally manufactured with the power leads in close proximity and thus have fairly low parasitic inductance. Hot Plugging and USB On-The-Go If there is more than 4.3V on VBUS when On-The-Go is enabled, the bidirectional switching regulator will not try to drive VBUS. If USB On-The-Go is enabled and an external supply is then connected to VBUS, one of three things will happen depending on the properties of the external supply. If the external supply has a regulation voltage higher than 5.1V, the bidirectional switching regulator will stop 25 LTC4160/LTC4160-1 APPLICATIONS INFORMATION This same current pulse must not raise VBUS any higher than 2V when connected to a standard host which must have at least 96μF The 96μF for a standard host represents . the minimum capacitance with VBUS between 4.75V and 5.25V. Since the SRP pulse must not drive VBUS greater than 2V, the capacitance seen at these voltage levels can be greater than 96μF especially if MLCCs are used. Therefore, , the 96μF represents a lower bound on the standard host bypass capacitance for determining the amplitude and duration of the current pulse. More capacitance will only decrease the maximum level that VBUS will rise to for a given current pulse. Figure 9 shows an On-The-Go device using the LTC4160/ LTC4160-1 acting as the A device. Additional capacitance can be placed on the VBUS pin of the LTC4160/LTC41601 when using the overvoltage protection circuit. The B device may not be able to distinguish between a powered down LTC4160/LTC4160-1 with overvoltage protection and a powered down standard host because of this extra capacitance. In addition, if the SRP pulse raises VBUS above its UVLO threshold of 4.3V the LTC4160/LTC4160-1 will assume input power is available and will not attempt to drive VBUS. Therefore, it is recommended that an OnThe-Go device using the LTC4160/LTC4160-1 respond to data-line pulsing. When an On-The-Go device using the LTC4160/LTC4160-1 becomes the B device, as in Figure 10, it must send out a data line pulse followed by a VBUS pulse to request a session from the A device. The On-The-Go device designer can choose how much capacitance will be placed on the VBUS pin of the LTC4160/LTC4160-1 and then generate a VBUS pulse that can distinguish between a powered down On-The-Go A device and a powered down standard host. A suitable pulse can be generated because of the disparity in the bypass capacitances of an On-The-Go A device and a standard host even if there is somewhat more than 6.5μF capacitance connected to the VBUS pin of the LTC4160/LTC4160-1. Board Layout Considerations The Exposed Pad on the backside of the LTC4160/ LTC4160-1 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 N-channel MOSFET switch. Furthermore, due to its high frequency switching circuitry, it is imperative that the input capacitor, inductor, and output capacitor be as close to the LTC4160/LTC4160-1 as possible and that there be an unbroken ground plane under the LTC4160/LTC4160-1 and all of its external high frequency components. High frequency current, such as the VBUS current tends to find its 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 11). 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). OVP (OPTIONAL) OVSENS LTC4160/ LTC4160-1 ENOTG OVGATE VBUS CA