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| FEATURES LTC4090/LTC4090-5 USB Power Manager with 2A High Voltage Bat-Track Buck Regulator DESCRIPTION The LTC(R)4090/LTC4090-5 are USB power managers plus high voltage Li-Ion/Polymer battery chargers. The devices control the total current used by the USB peripheral for operation and battery charging. Battery charge current is automatically reduced such that the sum of the load current and the charge current does not exceed the programmed input current limit. The LTC4090/LTC4090-5 also accommodate high voltage power supplies, such as 12V AC/DC wall adapters, FireWire, or automotive power. The LTC4090 provides a Bat-Track adaptive output that tracks the battery voltage for high efficiency charging from the high voltage input. The LTC4090-5 provides a fixed 5V output from the high voltage input to charge single cell Li-Ion bateries. The charge current is programmable and an end-of-charge status output (CHRG) indicates full charge. Also featured are programmable total charge time, an NTC thermistor input used to monitor battery temperature while charging and automatic recharging of the battery. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Bat-Track is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Seamless Transition Between Power Sources: LiIon Battery, USB, and 6V to 36V Supply (60V Max) 2A Output High Voltage Buck Regulator with BatTrackTM Adaptive Output Control (LTC4090) Internal 215m Ideal Diode Plus Optional External Ideal Diode Controller Provides Low Loss Power Path When External Supply / USB Not Present Load Dependent Charging from USB Input Guarantees Current Compliance Full Featured Li-Ion Battery Charger 1.5A Maximum Charge Current with Thermal Limiting NTC Thermistor Input for Temperature Qualified Charging Tiny (3mm x 6mm x 0.75mm) 22-Pin DFN Package APPLICATIONS HDD-Based Media Players Personal Navigation Devices Other USB-Based Handheld Products Automotive Accessories TYPICAL APPLICATION 0.47F HIGH (6V-36V) VOLTAGE INPUT 5V WALL ADAPTER IN USB 4.7F VC TIMER RT 0.1F 40.2k CLPROG 2k GND LTC4090 OUT 4.7F BAT PROG 100k HVIN 1F HVOUT HVPR 1k BOOST SW 22F 6.8H LTC4090/LTC4090-5 High Voltage Battery Charger Efficiency 90 FIGURE 12 SCHEMATIC WITH RPROG = 52k 80 NO OUTPUT LOAD LTC4090 EFFICIENCY (%) LOAD 70 LTC4090-5 60 50 40 30 HVIN = 8V HVIN = 12V HVIN = 24V HVIN = 36V 2.5 3.5 3.0 VBAT (V) 4.0 4.5 4090 TA01b 59k 270pF + Li-Ion BATTERY VOUT (TYP) VBAT + 0.3V 5V 5V VBAT AVAILABLE INPUT HV INPUT (LTC4090) HV INPUT (LTC4090-5) USB ONLY BAT ONLY 20 2.0 4090 TAO1 4090fa 1 LTC4090/LTC4090-5 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2, 3, 4) PIN CONFIGURATION TOP VIEW SYNC PG RT VC NTC VNTC HVPR CHRG PROG 1 2 3 4 5 6 7 8 9 23 22 HVEN 21 HVIN 20 SW 19 BOOST 18 HVOUT 17 TIMER 16 SUSP 15 HPWR 14 CLPROG 13 OUT 12 IN HVIN, HVEN (Note 9) ................................................60V BOOST ......................................................................56V BOOST above SW .....................................................30V PG, SYNC ..................................................................30V IN, OUT, HVOUT t < 1ms and Duty Cycle < 1% .................. -0.3V to 7V Steady State............................................. -0.3V to 6V BAT, HPWR, SUSP, VC, CHRG, HVPR ........... -0.3V to 6V NTC, TIMER, PROG, CLPROG ..........-0.3V to VCC + 0.3V IIN, IOUT, IBAT (Note 5) ..............................................2.5A Operating Temperature Range ..................... -40 to 85C Junction Temperature ........................................... 110C Storage Temperature Range....................... -65 to 125C GATE 10 BAT 11 DJC PACKAGE 22-LEAD (6mm x 3mm) PLASTIC DFN TJMAX = 110C, JA = 47C/W EXPOSED PAD (PIN 23) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH LTC4090EDJC#PBF LTC4090EDJC-5#PBF TAPE AND REEL LTC4090EDJC#TRPBF LTC4090EDJC-5#TRPBF PART MARKING 4090 40905 PACKAGE DESCRIPTION 22-Lead (6mm x 3mm) Plastic DFN 22-Lead (6mm x 3mm) Plastic DFN TEMPERATURE RANGE -40C to 85C -40C to 85C 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 VIN IIN ILIM IIN(MAX) RON VCLPROG ISS PARAMETER USB Input Supply Voltage Input Bias Current Current Limit Maximum Input Current Limit On-Resistance VIN to VOUT CLPROG Servo Voltage in Current Limit Soft-Start Inrush Current USB Input Current Limit The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V, RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted. CONDITIONS MIN 4.35 TYP MAX 5.5 UNITS V mA A mA mA A IBAT = 0 (Note 6) Suspend Mode; SUSP = 5V HPWR = 5V HPWR = 0V (Note 7) IOUT = 80mA RCLPROG = 2k RCLPROG = 1k 0.5 50 475 90 500 100 2.4 0.215 1 100 525 110 0.98 0.98 1.00 1.00 10 1.02 1.02 V V mA/s 4090fa 2 LTC4090/LTC4090-5 ELECTRICAL CHARACTERISTICS SYMBOL VCLEN VUVLO VUVLO VHVIN VOVLO IHVIN VOUT VOUT fSW PARAMETER Input Current Limit Enable Threshold Voltage (VIN - VOUT) Input Undervoltage Lockout Input Undervoltage Lockout Hysteresis HVIN Supply Voltage HVIN Overvoltage Lockout Threshold HVIN Bias Current Output Voltage with HVIN Present Output Voltage with HVIN Present Switching Frequency Shutdown; HVEN = 0.2V Not Switching, HVOUT = 3.6V Assumes HVOUT to OUT Connection, 0 VBAT 4.2V (LTC4090) Assumes HVOUT to OUT Connection (LTC4090-5) RT = 8.66k RT = 29.4k RT = 187k The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V, RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted. CONDITIONS (VIN - VOUT) Rising (VIN - VOUT) Falling VIN Rising VIN Rising - VIN Falling MIN 20 -80 3.6 TYP 50 -50 3.8 130 MAX 80 -20 4 UNITS mV mV V mV High Voltage Regulator 6 36 41.5 0.01 130 3.45 4.85 2.1 0.9 160 3.0 VBAT + 0.3 5 2.4 1.0 200 60 3.5 500 0.02 60 45 0.5 200 4.6 5.15 2.7 1.15 240 150 4.0 2 2.1 35 27 35 100 4.235 4.242 535 1080 1.02 1.02 0.11 60 3.0 V V A A V V MHz MHz kHz ns A mV A V mA A A A V V mA mA A V V mA/mA mA V mV mV tOFF ISW(MAX) VSAT IR VB(MIN) IBST IBAT Minimum Switch Off-Time Switch Current Limit Switch VCESAT Boost Schottky Reverse Leakage Minimum Boost Voltage (Note 8) BOOST Pin Current Battery Drain Current ISW = 1A VBAT = 4.3V, Charging Stopped Suspend Mode, SUSP = 5V VIN = 0V, BAT Powers OUT, No Load IBAT = 2mA IBAT = 2mA; 0 TA 85C Duty Cycle = 5% ISW = 2A SW = 10V, HVOUT = 0V 1.5 22 Battery Management 15 22 60 4.165 4.158 4.200 4.200 500 1000 1.5 1.00 1.00 0.1 50 2.9 55 80 VFLOAT ICHG ICHG(MAX) VPROG kEOC ITRKL VTRKL VCEN VRECHRG VBAT Regulated Output Voltage Constant-Current Mode Charge Current, RPROG = 100k No Load RPROG = 50k, 0 TA 85C Maximum Charge Current PROG Pin Servo Voltage Ratio of End-of-Charge Indication Current to Charge Current Trickle Charge Current Trickle Charge Threshold Voltage Charge Enable Threshold Voltage Recharge Battery Threshold Voltage RPROG = 100k RPROG = 50k VBAT = VFLOAT (4.2V) BAT = 2V BAT Rising (VOUT - VBAT) Falling; VBAT = 4V (VOUT - VBAT) Rising; VBAT = 4V Threshold Voltage Relative to VFLOAT 465 900 0.98 0.98 0.085 35 2.75 -65 -100 -135 mV 4090fa 3 LTC4090/LTC4090-5 ELECTRICAL CHARACTERISTICS SYMBOL tTIMER PARAMETER TIMER Accuracy Recharge Time Low Battery Trickle Charge Time TLIM Junction Temperature in Constant Temperature Mode Incremental Resistance, VON Regulation IOUT = 100mA On-Resistance VBAT to VOUT Voltage Forward Drop (VBAT - VOUT) IOUT = 600mA IOUT = 5mA IOUT = 100mA IOUT = 600mA The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V, RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted. CONDITIONS VBAT = 4.3V Percent of Total Charge Time Percent of Total Charge Time, VBAT <2.9V MIN -10 50 25 105 TYP MAX 10 UNITS % % % C Internal Ideal Diode RFWD RDIO, ON VFWD 125 215 10 30 55 160 2.7 550 2.2 20 m m 50 mV mV mV V mA A mV 0.4 V A 0.4 0.4 V V V V 0.3 V A 10 A V mV 1 A A V 0.8 V A VOFF IFWD ID(MAX) VFWD, EXT VCHG, SD ICHG, SD VOL VIH VIL VHVEN, H VHVEN, L IPULLDN IHVEN VPG VPG IPGLK IPG VSYNC, L VSYNC, H ISYNC Diode Disable Battery Voltage Load Current Limit for VON Regulation Diode Current Limit External Diode Forward Voltage Charger Shutdown Threshold Voltage on TIMER Charger Shutdown Pull-Up Current on TIMER Output Low Voltage Input High Voltage Input Low Voltage HVEN High Threshold HVEN Low Threshold Logic Input Pull-Down Current HVEN Pin Bias Current PG Threshold PG Hysteresis PG Leakage PG Sink Current SYNC Low Threshold SYNC High Threshold SYNC Pin Bias Current VSYNC = 0V PG = 5V PG = 0.4V External Ideal Diode Logic (CHRG, HVPR, TIMER, SUSP, HPWR, HVEN, PG, SYNC) 0.14 5 14 0.1 1.2 2.3 SUSP, HPWR HVEN = 2.5V HVOUT Rising 2 5 2.8 35 0.1 100 0.5 0.1 900 VTIMER = 0V (CHRG, HVPR); ISINK = 5mA SUSP, HPWR SUSP, HPWR 4090fa 4 LTC4090/LTC4090-5 ELECTRICAL CHARACTERISTICS SYMBOL NTC IVNTC VVNTC INTC VCOLD VHOT VDIS VNTC Pin Current VNTC Bias Voltage NTC Input Leakage Current Cold Temperature Fault Threshold Voltage Hot Temperature Fault Threshold Voltage NTC Disable Threshold Voltage VNTC = 2.5V IVNTC = 500A NTC = 1V Rising NTC Voltage Hysteresis Falling NTC Voltage Hysteresis Falling NTC Voltage Hysteresis The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V, RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted. PARAMETER CONDITIONS MIN 1.4 4.4 TYP 2.5 4.85 0 0.738 * VNTC 0.02 * VNTC 0.29 * VNTC 0.01 * VNTC 75 100 35 125 1 MAX 3.5 UNITS mA V A V V V V mV mV 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 LTC4090/LTC4090-5 are guaranteed to meet performance specifications from 0C to 85C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperatures will exceed 110C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may result in device degradation or failure. Note 4: VCC is the greater of VIN, VOUT, and VBAT Note 5: Guaranteed by long term current density limitations. Note 6: Total input current is equal to this specification plus 1.002 * IBAT where IBAT is the charge current. Note 7: Accuracy of programmed current may degrade for currents greater than 1.5A. Note 8: This is the minimum voltage across the boost capacitor needed to guarantee full saturation of the switch. Note 9: Absolute Maximum Voltage at HVIN and HVEN pins is for nonrepetative 1 second transients; 40V for continuous operation. TYPICAL PERFORMANCE CHARACTERISTICS VFLOAT Load Regulation 4.30 4.25 4.20 VFLOAT (V) VFLOAT (V) 4.15 4.10 4.05 4.00 0 200 400 600 IBAT (mA) 800 1000 4090 G01 Battery Regulation (Float) Voltage vs Temperature 4.220 4.215 4.210 4.205 4.200 4.195 4.190 4.185 4.180 -50 -25 50 25 TEMPERATURE (C) 0 75 100 4090 G02 Battery Current and Voltage vs Time (LTC4090) 5 1500 RPROG = 34k VIN = 5V IBAT = 2mA VBAT, VOUT, VCHRGB (V) 4 3 VBAT VOUT VCHRGB IBAT 1200 900 IBAT (mA) 2 1250mAh CELL HVIN = 12V RPROG = 50k 0 50 100 TIME (MIN) C/10 600 1 TERMINATION 300 0 150 0 200 4090 G03 4090fa 5 LTC4090/LTC4090-5 TYPICAL PERFORMANCE CHARACTERISTICS Charging from USB, IBAT vs VBAT 600 VIN = 5V VOUT = NO LOAD 500 RPROG = 100k RCLPROG = 2k 600 HPWR = 5V 500 400 IBAT (mA) IOUT (mA) 300 200 HPWR = 0V RPROG = 2.1k 100 VIN = 5V VBAT = 3.5V JA = 40C/W 0 50 25 75 -50 -25 0 TEMPERATURE (C) Charge Current vs Temperature (Thermal Regulation) 1000 Ideal Diode Current vs Forward Voltage and Temperature (No External Device) VBAT = 3.7V 900 VIN = 0V 800 700 600 500 400 300 200 100 0 -50C 0C 50C 100C 0 50 100 VFWD (mV) 150 200 4090 G06 400 IBAT (mA) 300 200 100 0 0 0.5 1 1.5 2 2.5 VBAT (V) 3 3.5 4 4.5 100 125 4090 G04 4090 G05 Ideal Diode Current vs Forward Voltage and Temperature with External Device 5000 VBAT = 3.7V 4500 VIN = 0V Si2333 PFET 4000 EFFICIENCY (%) 3500 IOUT (mA) 3000 2500 2000 1500 1000 500 0 0 20 60 40 VFWD (mV) 80 -50C 0C 50C 100C 100 4090 G07 LTC4090 High Voltage Regulator Efficiency vs Output Load 100 FIGURE 12 SCHEMATIC 95 VBAT = 4.21V (IBAT = 0) 90 85 80 75 70 65 60 55 50 0 0.2 0.6 0.4 IOUT (A) HVIN = 8V HVIN = 12V HVIN = 24V HVIN = 36V 0.8 1.0 4090 G08 LTC4090-5 High Voltage Regulator Efficiency vs Output Load 100 FIGURE 12 SCHEMATIC 95 VBAT = 4.21V (IBAT = 0) 90 EFFICIENCY (%) 85 80 75 70 65 60 55 50 0 0.2 0.6 0.4 IOUT (A) HVIN = 8V HVIN = 12V HVIN = 24V HVIN = 36V 0.8 1.0 4090 G29 High Voltage Regulator Maximum Load Current 3.0 2.8 TYPICAL 2.6 IOUT (A) 2.4 2.2 2.0 1.8 MINIMUM SWITCH ON TIME (ns) FIGURE 12 SCHEMATIC VBAT = 4.21V (IBAT = 0) 140 120 100 80 60 40 20 High Voltage Regulator Minimum Switch On-Time vs Temperature 700 600 VOLTAGE DROP (mV) 0 25 50 75 100 125 150 TEMPERATURE (C) 4090 G10 High Voltage Regulator Switch Voltage Drop 500 400 300 200 100 0 0 500 1500 1000 2000 SWITCH CURRENT (mA) 2500 4090 G11 MINIMUM 5 10 15 20 25 HVIN (V) 30 35 4090 G09 0 -50 -25 4090fa 6 LTC4090/LTC4090-5 TYPICAL PERFORMANCE CHARACTERISTICS High Voltage Regulator Switch Frequency 1100 1000 FREQUENCY (kHz) 900 800 700 600 500 -50 -25 1000 900 SWITCHING FREQUENCY (kHz) SWITCH CURRENT LIMIT (A) 0 1 2 3 HVOUT (V) 4 4090 G13 High Voltage Regulator Frequency Foldback 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 High Voltage Regulator Soft-Start 800 700 600 500 400 300 200 100 0 0 25 50 75 100 125 150 TEMPERATURE (C) 4090 G12 0 0.5 1 2 2.5 1.5 RUN/SS PIN VOLTAGE (V) 3 3.5 4090 G14 High Voltage Regulator Switch Current Limit 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0 20 60 40 DUTY CYCLE (%) 80 100 4090 G15 High Voltage Regulator Switch Current Limit 4.5 4.0 DUTY CYCLE = 10 % 7.0 6.5 6.0 5.5 DUTY CYCLE = 90 % HVIN (V) 5.0 4.5 4.0 3.5 3.0 0 25 50 75 100 125 150 TEMPERATURE (C) 4090 G16 High Voltage Regulator Minimum Input Voltage SWITCH CURRENT LIMIT(A) SWITCH CURRENT LIMIT (A) TO START 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -50 -25 TO RUN 1 10 100 LOAD CURRENT (mA) 1000 4090 G17 High Voltage Regulator Boost Diode VF vs IF 1.4 1.2 2.00 BOOST DIODE Vf (V) 1.0 VC VOLTAGE (V) 1.50 0.8 0.6 0.4 0.50 0.2 0 0 0.5 1.0 1.5 BOOST DIODE CURRENT (A) 2.0 4090 G18 High Voltage Regulator VC Voltages 2.50 HVOUT THRESHOLD VOLTAGE (V) 2.90 High Voltage Regulator Power Good Threshold 2.85 2.80 CURRENT LIMIT CLAMP 1.00 2.75 SWITCHING THRESHOLD 2.70 0 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 4090 G19 2.65 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 4090 G20 4090fa 7 LTC4090/LTC4090-5 TYPICAL PERFORMANCE CHARACTERISTICS LTC4090 Input Connect Waveforms VIN 5V/DIV VOUT 5V/DIV IIN 0.5A/DIV IBAT 0.5A/DIV 1ms/DIV VBAT = 3.85V IOUT = 100mA VIN 5V/DIV VOUT 5V/DIV IIN 0.5A/DIV IBAT 0.5A/DIV 1ms/DIV VBAT = 3.85V IOUT = 100mA LTC4090 Input Disconnect Waveforms SUSP 5V/DIV VOUT 5V/DIV IIN 0.5A/DIV IBAT 0.5A/DIV LTC4090 Response to Suspend 4090 G21 4090 G22 1ms/DIV VBAT = 3.85V IOUT = 50mA 4090 G23 LTC4090 High Voltage Input Connect Waveforms VHVIN 10V/DIV VOUT 5V/DIV IHVIN 1A/DIV IBAT 1A/DIV 2ms/DIV VBAT = 3.85V IOUT = 100mA VHVIN 5V/DIV VOUT 5V/DIV IHVIN 1A/DIV IBAT 1A/DIV LTC4090 High Voltage Input Disconnect Waveforms HPWR LTC4090 Response to HPWR 5V/DIV IIN 0.5A/DIV IBAT 0.5A/DIV 4090 G24 2ms/DIV VBAT = 3.85V IOUT = 100mA 4090 G25 100s/DIV VBAT = 3.85V IOUT = 50mA 4090 G26 LTC4090 High Voltage Regulator Load Transient LTC4090 High Voltage Regulator Load Transient HVOUT 50mV/DIV HVOUT 50mV/DIV IOUT 1A/DIV IL 1A/DIV 25s/DIV ILOAD = 500mA 4090 G27 ILOAD = 500mA 25s/DIV 4090 G28 4090fa 8 LTC4090/LTC4090-5 PIN FUNCTIONS SYNC (Pin 1): External Clock Synchronization Input. See synchronizing section in the Applications Information section. Ground pin when not used. PG (Pin 2): The PG pin is the open collector output of an internal comparator. PG remains low until the HVOUT pin is above 2.8V. PG output is valid when HVIN is above 3.6V and HVEN is high. RT (Pin 3): Oscillator Resistor Input. Connecting a resistor to ground from this pin sets the switching frequency. VC (Pin 4): High Voltage Buck Regulator Control Pin. The voltage on this pin controls the peak switch current in the high voltage regulator. Tie an RC network from this pin to ground to compensate the control loop. 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 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 VNTC to NTC and a thermistor is required from NTC to ground. If the NTC function is not desired, the NTC pin should be grounded. VNTC (Pin 6): Output Bias Voltage for NTC. A resistor from this pin to the NTC pin will bias the NTC thermistor. HVPR (Pin 7): High Voltage Present Output (Active Low). A low on this pin indicates that the high voltage regulator has sufficient voltage to charge the battery. This feature is enabled if power is present on HVIN, IN, or BAT (i.e., above UVLO thresholds). CHRG (Pin 8): Open-Drain Charge Status Output. When the battery is being charged, the CHRG pin is pulled low by an internal N-channel MOSFET. When the timer runs out or the charge current drops below 10% of the programmed charge current or the input supply is removed, the CHRG pin is forced to a high impedance state. PROG (Pin 9): Charge Current Program Pin. Connecting a resistor from PROG to ground programs the charge current: ICHG( A) = 50, 000 V RPROG GATE (Pin 10): External Ideal Diode Gate Connection. This pin controls the gate of an optional external P-channel MOSFET transistor used to supplement the internal ideal diode. The source of the P-channel MOSFET should be connected to OUT and the drain should be connected to BAT. When not in use, this pin should be left floating. It is important to maintain high impedance on this pin and minimize all leakage paths. BAT (Pin 11): Single-Cell Li-Ion Battery. This pin is used as an output when charging the battery and as an input when supplying power to OUT. When the OUT pin potential drops below the BAT pin potential, an ideal diode function connects BAT to OUT and prevents OUT from dropping more than 100mV below BAT. A precision internal resistor divider sets the final float (charging) potential on this pin. The internal resistor divider is disconnected when IN and HVIN are in undervoltage lockout. IN (Pin 12): Input Supply. Connect to USB supply, VBUS. Input current to this pin is limited to either 20% or 100% of the current programmed by the CLPROG pin as determined by the state of the HPWR pin. Charge current (to the BAT pin) supplied through the input is set to the current programmed by the PROG pin but will be limited by the input current limit if charge current is set greater than the input current limit or if the sum of charge current plus load current is greater than the input current limit. OUT (Pin 13): Voltage Output. This pin is used to provide controlled power to a USB device from either USB VBUS (IN), an external high voltage supply (HVIN), or the battery (BAT) when no other supply is present. The high voltage supply is prioritized over the USB VBUS input. OUT should be bypassed with at least 4.7F to GND. 4090fa 9 LTC4090/LTC4090-5 PIN FUNCTIONS CLPROG (Pin 14): Current Limit Program and Input Current Monitor. Connecting a resistor, RCLPROG, to ground programs the input to output current limit. The current limit is programmed as follows: 1000 V ICL ( A) = RCLPROG In USB applications, the resistor RCLPROG should be set to no less than 2.1k. The voltage on the CLPROG pin is always proportional to the current flowing through the IN to OUT power path. This current can be calculated as follows: IIN( A) = VCLPROG * 1000 RCLPROG Charge time is increased if charge current is reduced due to load current, thermal regulation and current limit selection (HPWR low). Shorting the TIMER pin to GND disables the battery charging functions. HVOUT (Pin 18): Voltage Output of the High Voltage Regulator. When sufficient voltage is present at HVOUT, the low voltage power path from IN to OUT will be disconnected and the HVPR pin will be pulled low to indicate that a high voltage wall adapter has been detected. The LTC4090 high voltage regulator will maintain just enough differential voltage between HVOUT and BAT to keep the battery charger MOSFET out of dropout (typically 300mV from OUT to BAT). The LTC4090-5 high voltage regulator will provide a 5V output to the battery charger MOSFET. HVOUT should be bypassed with at least 22F to GND. BOOST (Pin 19): This pin is used to provide drive voltage, higher than the input voltage, to the internal bipolar NPN power switch. SW (Pin 20): The SW pin is the output of the internal high voltage power switch. Connect this pin to the inductor, catch diode and boost capacitor. HVIN (Pin 21): High Voltage Regulator Input. The HVIN pin supplies current to the internal high voltage regulation and to the internal high voltage power switch. The presence of a high voltage input takes priority over the USB VBUS input (i.e., when a high voltage input supply is detected, the USB IN to OUT path is disconnected). This pin must be locally bypassed. HVEN (Pin 22): High Voltage Regulator Enable Input. The HVEN pin is used to disable the high voltage input path. Tie to ground to disable the high voltage input or tie to at least 2.3V to enable the high voltage path. If this feature is not used, tie HVEN to the HVIN pin. This pin can also be used to soft-start the high voltage regulator; see the Applications Information section for more information. Exposed Pad (Pin 23): Ground. The exposed package pad is ground and must be soldered to the PC board for proper functionality and for maximum heat transfer (use several vias directly under the LTC4090/LTC4090-5). 4090fa HPWR (Pin 15): High Power Select. This logic input is used to control the input current limit. A voltage greater than 1.2V on the pin will set the input current limit to 100% of the current programmed by the CLPROG pin. A voltage less than 0.4V on the pin will set the input current limit to 20% of the current programmed by the CLPROG pin. A 2A pull-down current is internally connected to this pin to ensure it is low at power up when the pin is not being driven externally. SUSP (Pin 16): Suspend Mode Input. Pulling this pin above 1.2V will disable the power path from IN to OUT. The supply current from IN will be reduced to comply with the USB specification for suspend mode. Both the ability to charge the battery from HVIN and the ideal diode function (from BAT to OUT) will remain active. Suspend mode will reset the charge timer if OUT is less than BAT while in suspend mode. If OUT is kept greater than BAT, such as when the high voltage input is present, the charge timer will not be reset when the part is put in suspend. A 2A pull-down current is internally connected to this pin to ensure it is low at power up when the pin is not being driven externally. TIMER (Pin 17): Timer Capacitor. Placing a capacitor, CTIMER, to GND sets the timer period. The timer period is: tTIMER (hours) = CTIMER * RPROG * 3hours 0.1F * 100k 10 LTC4090/LTC4090-5 BLOCK DIAGRAM C2 BOOST 10 HVIN Q1 INTERNAL REFERENCE SW L1 D1 + IL 10 HVEN SOFT-START + - R S Q Q DRIVER - OSCILLATOR 200kHz - 2.4MHz 10 RT SYNC RT1 10 10 VC - GM VC CLAMP HVOUT VSET 3.6V (LTC4090) 5V (LTC4090-5) C1 RC CC CF + + 10 PG + - 2.8V 4.25V (RISING) 3.15V (FALLING) CURRENT LIMIT 1V IN ILIM CNTL ENABLE OUT OUT 21 10 IN - 105C 30mV IDEAL DIODE 2A - TA + IN OUT BAT BAT CHARGE CONTROL ICHG SOFT-START2 + - + - 0.25V 2.9V BATTERY UVLO + CHG 1V - 23 PROG RPROG VOLTAGE DETECT VNTC UVLO BAT UV RECHRG NTCERR OSCILLATOR CONTROL LOGIC HOLD 10k T TOO HOT RESET CLK COUNTER STOP + - 15 4.1V RECHARGE 14 0.1V - 16 + NTC + - 10k TOO COLD + NTC ENABLE 2A C/10 EOC GND 11 SUSP 4090 BD + 13 HPWR 500mA/100mA - RCLPROG DIE TEMP + - 22 - CC/CV REGULATOR CHARGER ENABLE + - IIN 1000 CLPROG + CL CURRENT CONTROL SOFT-START ILIM + + HVPR 19 + - 350mV (LTC4090) + - 75mV (RISING) 25mV (FALLING) - 20mV GATE EDA 21 BAT 21 TIMER 21 CHRG CTIMER 18 - 4090fa 11 LTC4090/LTC4090-5 OPERATION Introduction The LTC4090/LTC4090-5 are complete PowerPathTM controllers for battery powered USB applications. The LTC4090/LTC4090-5 are designed to receive power from a low voltage source (e.g., USB or 5V wall adapter), a high voltage source (e.g., FireWire/IEEE1394, automotive battery, 12V wall adapter, etc.), and a single-cell Li-Ion battery. They can then deliver power to an application connected to the OUT pin and a battery connected to the BAT pin (assuming that an external supply other than the battery is present). Power supplies that have limited current resources (such as USB VBUS supplies) should be connected to the IN pin which has a programmable current limit. Battery charge current will be adjusted to ensure that the sum of the charge current and load current does not exceed the programmed input current limit (see Figure 1). An ideal diode function provides power from the battery when output / load current exceeds the input current limit or when input power is removed. Powering the load through HVIN Q1 the ideal diode instead of connecting the load directly to the battery allows a fully charged battery to remain fully charged until external power is removed. Once external power is removed the output drops until the ideal diode is forward biased. The forward biased ideal diode will then provide the output power to the load from the battery. The LTC4090/LTC4090-5 also include a high voltage switching regulator which has the ability to receive power from a high voltage input. This input takes priority over the USB VBUS input (i.e., if both HVIN and IN are present, load current and charge current will be delivered via the high voltage path). When enabled, the high voltage regulator regulates the HVOUT voltage using a constant frequency, current mode regulator. An external PFET between HVOUT (drain) and OUT (source) is turned on via the HVPR pin allowing OUT to charge the battery and/or supply power to the application. The LTC4090's Bat-Track maintains approximately 300mV between the OUT pin and the BAT pin, while the LTC4090-5 provides a fixed 5V output. PowerPath is a trademark of Linear Technology Corporation SW L1 HIGH VOLTAGE BUCK REGULATOR D1 HVOUT C1 + 4.25V (RISING) 3.15V (FALLING) - HVPR 19 + - IN ENABLE USB CURRENT LIMIT + - 75mV (RISING) 25mV (FALLING) OUT 21 OUT LOAD 30mV CC/CV REGULATOR CHARGER IDEAL DIODE BAT Figure 1. Simplified PowerPath Block Diagram 4090fa 12 + - + - 30mV + EDA 21 GATE - 21 4090 F01 BAT + Li-Ion LTC4090/LTC4090-5 OPERATION USB Input Current Limit The input current limit and charge control circuits of the LTC4090/LTC4090-5 are designed to limit input current as well as control battery charge current as a function of IOUT. OUT drives the external load and the battery charger. If the combined load at OUT does not exceed the programmed input current limit, OUT will be connected to IN through an internal 215m P-channel MOSFET. If the combined load at OUT exceeds the programmed input current limit, the battery charger will reduce its charge current by the amount necessary to enable the external load to be satisfied while maintaining the programmed input current. Even if the battery charge current is set to exceed the allowable USB current, a correctly programmed input current limit will ensure that the USB specification is never violated. Furthermore, load current at OUT will always be prioritized and only excess available current will be used to charge the battery. The input current limit, ICL, can be programmed using the following formula: 1000 1000 V ICL = * VCLPROG = RCLPROG RCLPROG where VCLPROG is the CLPROG pin voltage (typically 1V) and RCLPROG is the total resistance from the CLPROG pin to ground. For best stability over temperature and time, 1% metal film resistors are recommended. The programmed battery charge current, ICHG, is defined as: 50, 000 50, 000 V ICHG = * VPROG = RPROG RPROG Input current, IIN, is equal to the sum of the BAT pin output current and the OUT pin output current. VCLPROG will track the input current according to the following equation: IIN = IOUT + IBAT = VCLPROG * 1000 RCLPROG and quiescent currents. A 2.1k CLPROG resistor will give a typical current limit of 476mA in high power mode (when HPWR is high) or 95mA in low power mode (when HPWR is low). When SUSP is driven to a logic high, the input power path is disabled and the ideal diode from BAT to OUT will supply power to the application. High Voltage Step Down Regulator The power delivered from HVIN to HVOUT is controlled by a constant frequency, current mode step down regulator. An external P-channel MOSFET directs this power to OUT and prevents reverse conduction from OUT to HVOUT (and ultimately HVIN). An oscillator, with frequency set by RT, enables an RS flipflop, turning on the internal power switch. An amplifier and comparator monitor the current flowing between HVIN and SW pins, turning the switch off when this current reaches a level determined by the voltage at VC. An error amplifier servos the VC node to maintain approximately 300mV between OUT and BAT (LTC4090). By keeping the voltage across the battery charger low, efficiency is optimized because power lost to the battery charger is minimized and power available to the external load is maximized. If the BAT pin voltage is less than approximately 3.3V, then the error amplifier will servo the VC node to provide a constant HVOUT output voltage of about 3.6V (LTC4090). An active clamp on the VC node provides current limit. The VC node is also clamped to the voltage on the HVEN pin; soft-start is implemented by generating a voltage ramp at the HVEN pin using an external resistor and capacitor. The switch driver operates from either the high voltage input or from the BOOST pin. An external capacitor and internal diode are used to generate a voltage at the BOOST pin that is higher than the input supply. This allows the driver to fully saturate the internal bipolar NPN power switch for efficient operation. To further optimize efficiency, the high voltage buck regulator automatically switches to Burst Mode(R) operation in light load situations. Between bursts, all circuitry associated with controlling the output switch is shut down reducing the input supply current. 4090fa In USB applications, the maximum value for RCLPROG should be 2.1k. This will prevent the input current from exceeding 500mA due to LTC4090/LTC4090-5 tolerances 13 LTC4090/LTC4090-5 OPERATION 500 IIN 100 IIN 500 IIN 400 CURRENT (mA) CURRENT (mA) ILOAD 300 80 CURRENT (mA) ILOAD 60 400 ILOAD IBAT = ICHG 300 200 40 200 IBAT = ICL = IOUT 100 100 IBAT (CHARGING) 20 IBAT (CHARGING) IBAT (CHARGING) 0 0 4090 F02c 0 0 4090 F02a 0 100 200 500 IBAT ILOAD(mA) (IDEAL DIODE) 300 400 0 4090 F02b 20 40 100 IBAT ILOAD(mA) (IDEAL DIODE) 60 80 100 200 300 400 500 IBAT ILOAD (mA) (IDEAL DIODE) (a) High Power Mode/Full Charge RPROG = 100k and RCLPROG = 2k (a) Low Power Mode/Full Charge RPROG = 100k and RCLPROG = 2k (a) High Power Mode with ICL = 500mA and ICHG = 250mA RPROG = 100k and RCLPROG = 2k Figure 2. Input and Battery Currents as a Function of Load Current The oscillator reduces the switch regulator's operating frequency when the voltage at the HVOUT pin is low (below 2.95V). This frequency foldback helps to control the output current during start-up and overload. The high voltage regulator contains a power good comparator which trips when the HVOUT pin is at 2.8V. The PG output is an open-collector transistor that is off when the output is in regulation, allowing an external resistor to pull the PG pin high. Power good is valid when the switching regulator is enabled and HVIN is above 3.6V. Ideal Diode From BAT to OUT The LTC4090/LTC4090-5 have an internal ideal diode as well as a controller for an optional external ideal diode. If a battery is the only power supply available, or if the load current exceeds the programmed input current limit, then the battery will automatically deliver power to the load via an ideal diode circuit between the BAT and OUT pins. The ideal diode circuit (along with the recommended 4.7F capacitor on the OUT pin) allows the LTC4090/LTC4090-5 to handle large transient loads and wall adapter or USB VBUS connect/disconnect scenarios without the need for large bulk capacitors. The ideal diode responds within a few microseconds and prevents the OUT pin voltage from dropping significantly below the BAT pin voltage. A comparison of the I-V curve of the ideal diode and a Schottky diode can be seen in Figure 3. If the desired input current increases beyond the programmed input current limit additional current will be drawn from the battery via the internal ideal diode. Furthermore, if power to IN (USB VBUS) or HVIN (high voltage input) is removed, then all of the application power will be provided by the battery via the ideal diode. A 4.7F capacitor at OUT is sufficient to keep a transition from input power to battery power from causing significant output voltage droop. The ideal diode consists of a precision amplifier that enables a large P-channel MOSFET transistor whenever the voltage at OUT is approximately 20mV (VFWD) below the voltage at BAT. The resistance of the internal ideal diode is approximately 215m. If this is sufficient for the application then no external components are necessary. However if more conductance is needed, an external P-channel MOSFET can be added from BAT to OUT. The GATE pin of the LTC4090/LTC4090-5 drives the gate of the external PFET for automatic ideal diode control. The source of the external MOSFET should be connected to OUT and the drain should be connected to BAT. In order to help protect the external MOSFET in overcurrent situations, it should be placed in close thermal contact to the LTC4090/LTC4090-5. Burst Mode is a registered trademark of Linear Technology Corporation 4090fa 14 LTC4090/LTC4090-5 OPERATION Suspend Mode When SUSP is pulled above VIH the LTC4090/LTC4090-5 enter suspend mode to comply with the USB specification. In this mode, the power path between IN and OUT is put in a high impedance state to reduce the IN input current to 50A. If no other power source is available to drive HVIN, the system load connected to OUT is supplied through the ideal diodes connected to BAT. Battery Charger The battery charger circuits of the LTC4090/LTC4090-5 are designed for charging single cell lithium-ion batteries. Featuring an internal P-channel power MOSFET, the charger uses a constant current / constant voltage charge algorithm with programmable charge current and a programmable timer for charge termination. Charge current can be programmed up to 1.5A. The final float voltage accuracy is 0.8% typical. No blocking diode or sense resistor is required when powering either the IN or the HVIN pins. The CHRG open-drain status output provides information regarding the charging status of the LTC4090/LTC4090-5 at all times. An NTC input provides the option of charge qualification using battery temperature. The charge cycle begins when the voltage at the OUT pin rises above the battery voltage and the battery voltage is below the recharge threshold. No charge current actually flows until the OUT voltage is 100mV above the BAT voltage. At the beginning of the charge cycle, if the battery voltage is below 2.9V, the charger goes into LTC4090/LTC4090-5 IMAX CONSTANT I0N trickle charge mode to bring the cell voltage up to a safe level for charging. The charger goes into the fast charge constant current mode once the voltage on the BAT pin rises above 2.9V. In constant current mode, the charge current is set by RPROG. When the battery approaches the final float voltage, the charge current begins to decrease as the LTC4090/LTC4090-5 switch to constant voltage mode. When the charge current drops below 10% of the programmed value while in constant voltage mode the CHRG pin assumes a high impedance state. An external capacitor on the TIMER pin sets the total minimum charge time. When this time elapses, the charge cycle terminates and the CHRG pin assumes a high impedance state, if it has not already done so. While charging in constant current mode, if the charge current is decreased by thermal regulation or in order to maintain the programmed input current limit, the charge time is automatically increased. In other words, the charge time is extended inversely proportional to the actual charge current delivered to the battery. For Li-Ion and similar batteries that require accurate final float potential, the internal bandgap reference, voltage amplifier and the resistor divider provide regulation with 0.8% accuracy. Trickle Charge and Defective Battery Detection At the beginning of a charge cycle, if the battery voltage is below 2.9V, the charger goes into trickle charge reducing the charge current to 10% of the full-scale current. If the low battery voltage persists for one quarter of the programmed total charge time, the battery is assumed to be defective, the charge cycle is terminated and the CHRG pin output assumes a high impedance state. If for any reason the battery voltage rises above ~2.9V the charge cycle will be restarted. To restart the charge cycle (i.e., when the dead battery is replaced with a discharged battery), simply remove the input voltage and reapply it or cycle the TIMER pin to 0V. Programming Charge Current The formula for the battery charge current is: VPROG * 50, 000 RPROG 4090fa CURRENT (A) SLOPE: 1/RDIO(ON) CONSTANT R0N IFWD SCHOTTKY DIODE SLOPE: 1/RFWD CONSTANT V0N 0 FORWARD VOLTAGE (V) VFWD 4090 F03 ICHG = IPROG * 50, 000 = Figure 3. LTC4090/LTC4090-5 Versus Schottky Diode Forward Voltage Drop 15 LTC4090/LTC4090-5 OPERATION where VPROG is the PROG pin voltage and RPROG is the total resistance from the PROG pin to ground. Keep in mind that when the LTC4090/LTC4090-5 are powered from the IN pin, the programmed input current limit takes precedence over the charge current. In such a scenario, the charge current cannot exceed the programmed input current limit. For example, if typical 500mA charge current is required, calculate: RPROG = 1V * 50, 000 = 100k 500mA As the LTC4090/LTC4090-5 approach constant voltage mode the charge current begins to drop. This change in charge current is due to normal charging operation and does not affect the timer duration. Consider, for example, a USB charge condition where RCLPROG = 2k, RPROG = 100k and CTIMER = 0.1F. This corresponds to a three hour charge cycle. However, if the HPWR input is set to a logic low, then the input current limit will be reduced from 500mA to 100mA. With no additional system load, this means the charge current will be reduced to 100mA. Therefore, the termination timer will automatically slow down by a factor of five until the charger reaches constant voltage mode (i.e. VBAT approaches 4.2V) or HPWR is returned to a logic high. The charge cycle is automatically lengthened to account for the reduced charge current. The exact time of the charge cycle will depend on how long the charger remains in constant current mode and/or how long the HPWR pin remains logic low. Once a time-out occurs and the voltage on the battery is greater than the recharge threshold, the charge current stops, and the CHRG output assumes a high impedance state if it has not already done so. Connecting the TIMER pin to ground disables the battery charger. CHRG Status Output Pin When the charge cycle starts, the CHRG pin is pulled to ground by an internal N-channel MOSFET capable of driving an LED. When the charge current drops below 10% of the programmed full charge current while in constant voltage mode, the pin assumes a high impedance state, but charge current continues to flow until the charge time elapses. If this state is not reached before the end of the programmable charge time, the pin will assume a high impedance state when a time-out occurs. The CHRG current detection threshold can be calculated by the following equation: IDETECT = 0.1V 5000 V * 50, 000 = RPROG RPROG For best stability over temperature and time, 1% metal film resistors are recommended. Under trickle charge conditions, this current is reduced to 10% of the fullscale value. The Charge Timer The programmable charge timer is used to terminate the charge cycle. The timer duration is programmed by an external capacitor at the TIMER pin. The charge time is typically: tTIMER (hours) = CTIMER * RPROG * 3hours 0.1F * 100k The timer starts when an input voltage greater than the undervoltage lockout threshold level is applied or when leaving shutdown and the voltage on the battery is less than the recharge threshold. At power-up or exiting shutdown with the battery voltage less than the recharge threshold, the charge time is a full cycle. If the battery is greater than the recharge threshold the timer will not start and charging is prevented. If after power-up the battery voltage drops below the recharge threshold, or if after a charge cycle the battery voltage is still below the recharge threshold, the charge time is set to one-half of a full cycle. The LTC4090/LTC4090-5 have a feature that extends charge time automatically. Charge time is extended if the charge current in constant current mode is reduced due to load current or thermal regulation. This change in charge time is inversely proportional to the change in charge current. 4090fa 16 LTC4090/LTC4090-5 OPERATION For example, if the full charge current is programmed to 500mA with a 100k PROG resistor the CHRG pin will change state at a battery charge current of 50mA. Note: The end-of-charge (EOC) comparator that monitors the charge current latches its decision. Therefore, the first time the charge current drops below 10% of the programmed full charge current while in constant voltage mode, it will toggle CHRG to a high impedance state. If, for some reason the charge current rises back above the threshold, the CHRG pin will not resume the strong pull-down state. The EOC latch can be reset by a recharge cycle (i.e., VBAT drops below the recharge threshold) or toggling the input power to the part. Automatic Recharge After the battery charger terminates, it will remain off drawing only microamperes of current from the battery. If the 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). To prevent brief excursions below VRECHRG from resetting the safety timer, the battery voltage must be below VRECHRG for more than a few milliseconds. The charge cycle and safety timer will also restart if the IN UVLO cycles low and then high (e.g. IN, is removed and then replaced). Thermal Regulation To prevent thermal damage to the IC or surrounding components, an internal thermal feedback loop will automatically decrease the programmed charge current if the die temperature rises to approximately 105C. Thermal regulation protects the LTC4090/LTC4090-5 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 LTC4090/LTC4090-5 or external components. The benefit of the LTC4090/LTC4090-5 thermal regulation loop is that charge current can be set according to actual conditions rather than worst-case conditions with the assurance that the battery charger will automatically reduce the current in worst-case conditions. Undervoltage Lockout An internal undervoltage lockout circuit monitors the input voltage (IN) and the output voltage (OUT) and disables either the input current limit or the battery charger circuits or both. The input current limit circuitry is disabled until VIN rises above the undervoltage lockout threshold and VIN exceeds VOUT by 50mV. The battery charger circuits are disabled until VOUT exceeds VBAT by 50mV. Both undervoltage lockout comparators have built-in hysteresis. 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 VNTC to NTC. RNOM should be a 1% resistor with a value equal to the value of the chosen NTC thermistor at 25C (denoted R25C). The LTC4090/LTC4090-5 will pause charging when the resistance of the NTC thermistor drops to 0.41 times the value of R25C or approximately 4.1k (for a Vishay "Curve 2" thermistor, this corresponds to approximately 50C). 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 LTC4090/ LTC4090-5 are also designed to pause charging (and timer) when the value of the NTC thermistor increases to 2.82 times the value of R25C. For a Vishay "Curve 2" thermistor this resistance, 28.2k, corresponds to approximately 0C. The hot and cold comparators each have approximately 3C of hysteresis to prevent oscillation about the trip point. Grounding the NTC pin disables all NTC functionality. 4090fa 17 LTC4090/LTC4090-5 APPLICATIONS INFORMATION USB and 5V Wall Adapter Power Although the LTC4090/LTC4090-5 are designed to draw power from a USB port, a higher power 5V wall adapter can also be used to power the application and charge the battery (higher voltage wall adapters can be connected directly to HVIN). Figure 4 shows an example of combining a 5V wall adapter and a USB power input. With its gate grounded by 1k, P-channel MOSFET MP1 provides USB power to the LTC4090/LTC4090-5 when 5V wall power is not available. When 5V wall power is available, diode D1 supplies power to the LTC4090/LTC4090-5, pulls the gate of MN1 high to increase the charge current (by increasing the input current limit), and pulls the gate of MP1 high to disable it and prevent conduction back to the USB port. Setting the Switching Frequency The high voltage switching regulator uses a constant frequency PWM architecture that can be programmed to switch from 200kHz to 2.4MHz by using a resistor tied from the RT pin to ground. A table showing the necessary RT value for a desired switching frequency is in Table 1. Table 1. Switching Frequency vs RT Value SWITCHING FREQUENCY (MHz) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 RT VALUE (k) 187 121 88.7 68.1 56.2 46.4 40.2 34.0 29.4 23.7 19.1 16.2 13.3 11.5 9.76 8.66 5V WALL ADAPTER 850mA ICHG D1 LTC4090 USB POWER 500mA ICHG IN MP1 PROG CLPROG 2.87k ICHG BAT + Li-Ion BATTERY 1k MN1 2k 59k 4090 F04 Figure 4. USB or 5V Wall Adapter Power Operating Frequency Tradeoffs Selection of the operating frequency for the high voltage buck regulator is a tradeoff between efficiency, component size, minimum dropout voltage, and maximum input voltage. The advantage of high frequency operation is that smaller inductor and capacitor values may be used. The disadvantages are lower efficiency, lower maximum input voltage, and higher dropout voltage. The highest acceptable switching frequency (fSW(MAX)) for a given application can be calculated as follows: fSW(MAX ) = VD + VHVOUT tON(MIN) * ( VD + VHVIN - VSW ) where VHVIN is the typical high voltage input voltage, VHVOUT is the output voltage of the switching regulator, VD is the catch diode drop (~0.5V), and VSW is the internal switch drop (~0.5V at max load). This equation shows that slower switching frequency is necessary to safely accommodate high VHVIN/VHVOUT ratio. Also, as shown in the next section, lower frequency allows a lower dropout voltage. The reason input voltage range depends on the switching frequency is because the high voltage switch has finite minimum on and off times. The switch can turn on for a minimum of ~150ns and turn off for a minimum of ~150ns. This means that the minimum and maximum duty cycles are: DCMIN = fSW * tON(MIN) DCMAX = 1 - fSW * tOFF(MIN) where fSW is the switching frequency, tON(MIN) is the minimum switch-on time (~150ns), and tOFF(MIN) is the 4090fa 18 LTC4090/LTC4090-5 APPLICATIONS INFORMATION minimum switch-off time (~150ns). These equations show that duty cycle range increases when switching frequency is decreased. A good choice of switching frequency should allow adequate input voltage range (see next section) and keep the inductor and capacitor values small. HVIN Input Voltage Range The maximum input voltage range for the LTC4090/ LTC4090-5 applications depends on the switching frequency, the Absolute Maximum Ratings of the VHVIN and BOOST pins, and the operating mode. The high voltage switching regulator can operate from input voltages up to 36V, and safely withstand input voltages up to 60V. Note that while VHVIN > 41.5V (typical), the LTC4090/LTC4090-5 will stop switching, allowing the output to fall out of regulation. While the high voltage regulator output is in start-up, short-circuit, or other overload conditions, the switching frequency should be chosen according to the following discussion. For safe operation at inputs up to 60V the switching frequency must be low enough to satisfy VHVIN(MAX) 45V according to the following equation. If lower VHVIN(MAX) is desired, this equation can be used directly. VHVIN(MAX ) = VHVOUT + VD -V +V fSW * tON(MIN) D SW may enter pulse skipping operation where some switching pulses are skipped to maintain output regulation. In this mode the output voltage ripple and inductor current ripple will be higher than in normal operation. Above 41.5V, switching will stop. The minimum input voltage is determined by either the high voltage regulator's minimum operating voltage of ~6V or by its maximum duty cycle (see equation in previous section). The minimum input voltage due to duty cycle is: VHVIN(MIN) = VHVOUT + VD -V +V 1- fSW tOFF(MIN) D SW where VHVIN(MIN) is the minimum input voltage, and tOFF(MIN) is the minimum switch off time (150ns). Note that higher switching frequency will increase the minimum input voltage. If a lower dropout voltage is desired, a lower switching frequency should be used. Inductor Selection and Maximum Output Current A good choice for the inductor value is L = 6.8H (assuming a 800kHz operating frequency). With this value the maximum load current will be ~2.4A. The RMS current rating of the inductor must be greater than the maximum load current and its saturation current should be about 30% higher. Note that the maximum load current will be programmed charge current plus the largest expected application load current. For robust operation in fault conditions, the saturation current should be ~3.5A. To keep efficiency high, the series resistance (DCR) should be less than 0.1. Table 2 lists several vendors and types that are suitable. Table 2. Inductor Vendors VENDOR URL Murata TDK Toko www.murata.com www.componenttdk.com www.toko.com PART SERIES LQH55D SLF7045 SLF10145 D62CB D63CB D75C D75F CR54 CDRH74 CDRH6D38 CR75 TYPE Open Shielded Shielded Shielded Shielded Shielded Open Open Shielded Shielded Open 4090fa where VHVIN(MAX) is the maximum operating input voltage, VHVOUT is the high voltage regulator output voltage, VD is the catch diode drop (~0.5V), VSW is the internal switch drop (~0.5V at max load), fSW is the switching frequency (set by RT), and tON(MIN) is the minimum switch-on time (~150ns). Note that a higher switching frequency will depress the maximum operating input voltage. Conversely, a lower switching frequency will be necessary to achieve safe operation at high input voltages. If the output is in regulation and no short-circuit, startup, or overload events are expected, then input voltage transients of up to 60V are acceptable regardless of the switching frequency. In this mode, the LTC4090/LTC4090-5 Sumida www.sumida.com 19 LTC4090/LTC4090-5 APPLICATIONS INFORMATION Catch Diode The catch diode conducts current only during switch-off time. Average forward current in normal operation can be calculated from: ID( AVG) = IHVOUT * COUT = 100 VOUT fSW ( VHVIN - VHVOUT ) VHVIN where IHVOUT is the output load current. The only reason to consider a diode with a larger current rating than necessary for nominal operation is for the worst-case condition of shorted output. The diode current will then increase to the typical peak switch current. Peak reverse voltage is equal to the regulator input voltage. Use a Schottky diode with a reverse voltage rating greater than the input voltage. The overvoltage protection feature in the high voltage regulator will keep the switch off when VHVIN > 45V which allows the use of 45V rated Schottky even when VHVIN ranges up to 60V. Table 3 lists several Schottky diodes and their manufacturers. Table 3. Diode Vendors PART NUMBER On Semiconductor MBRM120E MBRM140 Diodes Inc. B130 B220 B230 B360 DFLS240L International Rectifier 10BQ030 20BQ030 VR (V) 20 40 30 20 30 60 40 30 30 IAVE (A) 1 1 1 2 2 3 2 1 2 VF AT 1A (MV) 530 550 500 500 500 500 550 500 470 470 VF AT 2A (MV) 595 where fSW is in MHz, and COUT is the recommended output capacitance in F. Use X5R or X7R types. This choice will provide low output ripple and good transient response. Transient performance can be improved with a higher value capacitor if the compensation network is also adjusted to maintain the loop bandwidth. A lower value of output capacitor can be used to save space and cost but transient performance will suffer. See the High Voltage Regulator Frequency Compensation section to choose an appropriate compensation network. When choosing a capacitor, look carefully through the data sheet to find out what the actual capacitance is under operating conditions (applied voltage and temperature). A physically larger capacitor, or one with a higher voltage rating, may be required. High performance tantalum or electrolytic capacitors can be used for the output capacitor. Low ESR is important, so choose one that is intended for use in switching regulators. The ESR should be specified by the supplier, and should be 0.05 or less. Such a capacitor will be larger than a ceramic capacitor and will have a larger capacitance, because the capacitor must be large to achieve low ESR. Ceramic Capacitors Ceramic capacitors are small, robust and have very low ESR. However, ceramic capacitors can cause problems when used with the high voltage switching regulator due to their piezoelectric nature. When in Burst Mode operation, the LTC4090/LTC4090-5's switching frequency depends on the load current, and at very light loads the LTC4090/LTC4090-5 can excite the ceramic capacitor at audio frequencies, generating audible noise. Since the LTC4090/LTC4090-5 operate at a lower current limit during Burst Mode operation, the noise is typically very quiet to a casual ear. If this is unacceptable, use a high performance tantalum or electrolytic capacitor at the output. High Voltage Regulator Frequency Compensation The LTC4090/LTC4090-5 high voltage regulator uses current mode control to regulate the output. This simplifies loop compensation. In particular, the high voltage 4090fa 420 High Voltage Regulator Output Capacitor Selection The high voltage regulator output capacitor has two essential functions. Along with the inductor, it filters the square wave generated at the switch pin to produce the DC output. In this role it determines the output ripple, and low impedance at the switching frequency is important. The second function is to store energy in order to satisfy transient loads and stabilize the LTC4090/LTC4090-5's control loop. Ceramic capacitors have very low equivalent series resistance (ESR) and provide the best ripple performance. A good starting value is: 20 LTC4090/LTC4090-5 APPLICATIONS INFORMATION regulator does not require the ESR of the output capacitor for stability, so you are free to use ceramic capacitors to achieve low output ripple and small circuit size. Frequency compensation is provided by the components tied to the VC pin, as shown in Figure 1. Generally a capacitor (CC) and a resistor (RC) in series to ground are used. In addition, there may be a lower value capacitor in parallel. This capacitor (CF) is not part of the loop compensation but is used to filter noise at the switching frequency, and is required only if a phase-lead capacitor is used or if the output capacitor has high ESR. Loop compensation determines the stability and transient performance. Designing the compensation network is a bit complicated and the best values depend on the application and in particular the type of output capacitor. A practical approach is to start with the front page schematic and tune the compensation network to optimize performance. Stability should then be checked across all operating conditions, including load current, input voltage and temperature. The LTC1375 datasheet contains a more thorough discussion of loop compensation and describes how to test the stability using a transient load. Figure 5 shows the transient response when the load current is stepped from 500mA to 1500mA and back to 500mA. Low Ripple Burst Mode Operation and Pulse-Skip Mode The LTC4090/LTC4090-5 are capable of operating in either low ripple Burst Mode operation or pulse-skip mode which are selected using the SYNC pin. Tie the SYNC pin below VSYNC,L (typically 0.5V) for low ripple Burst Mode operation or above VSYNC,H (typically 0.8V) for pulse-skip mode. FIGURE 12 SCHEMATIC HVOUT 50mV/DIV VSW 5V/DIV To enhance efficiency at light loads, the LTC4090/LTC4090-5 can be operated in low ripple Burst Mode operation which keeps the output capacitor charged to the proper voltage while minimizing the input quiescent current. During Burst Mode operation, the LTC4090/LTC4090-5 deliver single cycle bursts of current to the output capacitor followed by sleep periods where the output power is delivered to the load by the output capacitor. Because the LTC4090/ LTC4090-5 deliver power to output with single, low current pulses, the output ripple is kept below 15mV for a typical application. As the load current decreases towards a no load condition, the percentage of time that the high voltage regulator operates in sleep mode increases and the average input current is greatly reduced resulting in high efficiency even at very low loads. See Figure 6. At higher output loads (above 70mA for the front page application) the LTC4090/LTC4090-5 will be running at the frequency programmed by the RT resistor, and will be operating in standard PWM mode. The transition between PWM and low ripple Burst Mode operation is seamless, and will not disturb the output voltage. If low quiescent current is not required, the LTC4090/ LTC4090-5 can operate in pulse-skip mode. The benefit of this mode is that the LTC4090/LTC4090-5 will enter full frequency standard PWM operation at a lower output load current than when in Burst Mode operation. The front page application circuit will switch at full frequency at output loads higher than about 60mA. VIN = 12V; FIGURE 12 SCHEMATIC ILOAD = 10mA IL 0.5A/DIV IL 1A/DIV VOUT 10mV/DIV 5s/DIV 25s/DIV 4090 F05 4090 F06 Figure 6. High Voltage Regulator Burst Mode Operation Figure 5. Transient Load Response of the LTC4090 High Voltage Regulator Front Page Application as the Load Current is Stepped from 500mA to 1500mA. 4090fa 21 LTC4090/LTC4090-5 APPLICATIONS INFORMATION Boost Pin Considerations Capacitor C2 (see Block Diagram) and an internal diode are used to generate a boost voltage that is higher than the input voltage. In most cases, a 0.47F capacitor will work well. The BOOST pin must be at least 2.3V above the SW pin for proper operation. High Voltage Regulator Soft-Start The HVEN pin can be used to soft-start the high voltage regulator of the LTC4090/LTC4090-5, reducing maximum input current during start-up. The HVEN pin is driven through an external RC filter to create a voltage ramp at this pin. Figure 7 shows the start-up and shutdown waveforms with the soft-start circuit. By choosing a large RC time constant, the peak start-up current can be reduced to the current that is required to regulate the output, with no overshoot. Choose the value of the resistor so that it can supply 20A when the HVEN pin reaches 2.3V. lower than the external synchronization frequency to ensure adequate slope compensation. While synchronized, the high voltage regulator will turn on the power switch on positive going edges of the clock. When the power good (PG) output is low, such as during start-up, short-circuit, and overload conditions, the LTC4090/LTC4090-5 will disable the synchronization feature. The SYNC pin should be grounded when synchronization is not required. Alternate NTC Thermistors and Biasing The LTC4090/LTC4090-5 provide temperature qualified charging if a grounded thermistor and a bias resistor are connected to NTC (see Figure 8). By using a bias resistor whose value is equal to the room temperature resistance of the thermistor (R25C) the upper and lower temperatures are pre-programmed to approximately 50C and 0C, respectively (assuming a Vishay "Curve 2" 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 NTHS0603N02N1002J, used in the following examples, has a nominal value of 10k and follows the Vishay "Curve 2" resistance-temperature characteristic. The LTC4090/LTC4090-5's trip points are designed to work with thermistors whose resistance-temperature characteristics follow Vishay Dale's "R-T Curve 2." The Vishay NTHS0603N02N1002J is an example of such a thermistor. However, Vishay Dale has many thermistor products that follow the "R-T Curve 2" characteristic in a variety of sizes. Furthermore, any thermistor whose ratio of RCOLD to RHOT is about 7.0 will also work (Vishay Dale R-T Curve 2 shows a ratio of 2.815/0.409 = 6.89). 4090fa RUN 15k HVEN 0.22F GND IL 1A/DIV VRUN/SS 2V/DIV VOUT 2V/DIV 2ms/DIV 4090 F07 Figure 7. To Soft-Start the High Voltage Regulator, Add a Resistor and Capacitor to the HVEN Pin Synchronization and Mode The SYNC pin allows the high voltage regulator to be synchronized to an external clock. Synchronizing the LTC4090/LTC4090-5 internal oscillator to an external frequency can be done by connecting a square wave (with 20% to 80% duty cycle) to the SYNC pin. The square wave amplitude should be such that the valleys are below 0.3V and the peaks are above 0.8V (up to 6V). The high voltage regulator may be synchronized over a 300kHz to 2MHz range. The RT resistor should be chosen such that the LTC4090/LTC4090-5 oscillate 25% 22 LTC4090/LTC4090-5 APPLICATIONS INFORMATION In the explanation below, the following notation is used. R25C = Value of the Thermistor at 25C RNTC|COLD = Value of Thermistor at the Cold Trip Point RNTC|HOT = Value of the Thermistor at the Hot Trip Point rcold = Ratio of RNTC|COLD to R25C rHOT= Ratio of RNTC|HOT to R25C RNOM = Primary Thermistor Bias Resistor (see Figure 8) R1 = Optional Temperature Range Adjustment resistor (see Figure 9) The trip points for the LTC4090/LTC4090-5's temperature qualification are internally programmed at 0.29 * VNTC for the hot threshold and 0.74 * VNTC for the cold threshold. Therefore, the hot trip point is set when: RNTCHOT | RNOM + RNTCHOT | * VNTC = 0.29 * VNTC Solving these equations for RNTC|COLD and RNTC|HOT results in the following: RNTC|HOT = 0.409 * RNOM and RNTC|COLD = 2.815 * RNOM By setting RNOM equal to R25C, the above equations result in rHOT = 0.409 and rCOLD = 2.815. Referencing these ratios to the Vishay Resistance-Temperature Curve 2 chart gives a hot trip point of about 50C and a cold trip point of about 0C. The difference between the hot and cold trip points is approximately 50C. By using a bias resistor, RNOM, different in value from R25C, 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 easily calculate a new value for the bias resistor: rHOT *R 0.409 25C r RNOM = COLD * R25C 2.815 RNOM = and the cold trip point is set when: RNTC|COLD RNOM + RNTC|COLD VNTC 6 RNOM 10k NTC 5 0.738 * VNTC * VNTC = 0.74 * VNTC NTC BLCOK VNTC 6 NTC BLCOK - TOO_COLD RNOM 13.2k NTC 5 0.738 * VNTC - TOO_COLD + + RNTC 10k 0.29 * VNTC - TOO_HOT R1 1.97k 0.29 * VNTC RNTC 10k - TOO_HOT + + + NTC_ENABLE 0.1V + NTC_ENABLE 0.1V - 4090 F08 - 4090 F09 Figure 8. Typical NTC Thermistor Circuit Figure 9. NTC Thermistor Circuit with Additional Bias Resistor 4090fa 23 LTC4090/LTC4090-5 APPLICATIONS INFORMATION 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 40C hot trip point is desired. From the Vishay Curve 2 R-T characteristics, rHOT is 0.5758 at 40C. Using the above equation, RNOM should be set to 14.0k. With this value of RNOM, the cold trip point is about -7C. Notice that the span is now 47C rather than the previous 50C. This is due to the increase in "temperature gain" of the thermistor as absolute temperature decreases. The upper and lower temperature trip points can be independently programmed by using an additional bias resistor as shown in Figure 9. The following formulas can be used to compute the values of RNOM and R1: rCOLD - rHOT * R25C 2.815 R1= 0.409 * RNOM - rHOT * R25C RNOM = For example, to set the trip points to -5C and 55C with a Vishay Curve 2 thermistor choose RNOM = 3.532 - 0.3467 * 10k = 13.2k 2.815 - 0.409 In general, if the LTC4090/LTC4090-5 is being powered from IN the power dissipation can be calculated as follows: PD = (VIN - VBAT) * IBAT + (VIN - VOUT) * IOUT where PD is the power dissipated, IBAT is the battery charge current, and IOUT is the application load current. For a typical application, an example of this calculation would be: PD = (5V - 3.7V) * 0.4A + (5V - 4.75V) * 0.1A = 545mW This examples assumes VIN = 5V, VOUT = 4.75V, VBAT = 3.7V, IBAT = 400mA, and IOUT = 100mA resulting in slightly more than 0.5W total dissipation. If the LTC4090 is being powered from HVIN, the power dissipation can be estimated by calculating the regulator power loss from an efficiency measurement, and subtracting the catch diode loss. PD = (1- ) * VHVOUT *(IBAT + IOUT ) V - VD * 1- HVOUT * (IBAT + IOUT ) + 0.3V * IBAT ) VHVIN where is the efficiency of the high voltage regulator and VD is the forward voltage of the catch diode at I = IBAT + IOUT. The first term corresponds to the power lost in converting VHVIN to VHVOUT, the second term subtracts the catch diode loss, and the third term is the power dissipated in the battery charger. For a typical application, an example of this calculation would be: PD = (1- 0.87) * [ 4V *(1A + 0.6 A)] 4V -0.4V * 1- * (1A + 0.6 A ) + 0.3V * 1A = 0.7 W 12V This example assumes 87% efficiency, VHVIN = 12V, VBAT = 3.7V (VHVOUT is about 4V), IBAT = 1A, IOUT = 600mA resulting in about 0.7W total dissipation. If the LTC4090-5 is being powered from HVIN, the power dissipation can be estimated by calculating the regulator power loss from an efficiency measurement, and subtracting the catch diode loss. the nearest 1% value is 13.3k. R1 = 0.409 * 13.3k - 0.3467 * 10k = 1.97k the nearest 1% value is 1.96k. The final solution is shown in Figure 9 and results in an upper trip point of 55C and a lower trip point of -5C. Power Dissipation and High Temperature Considerations The die temperature of the LTC4090/LTC4090-5 must be lower than the maximum rating of 110C. This is generally not a concern unless the ambient temperature is above 85C. The total power dissipated inside the LTC4090/ LTC4090-5 depend on many factors, including input voltage (IN or HVIN), battery voltage, programmed charge current, programmed input current limit, and load current. 4090fa 24 LTC4090/LTC4090-5 APPLICATIONS INFORMATION PD = 1 - * 5V * IBAT + IOUT )( ( )) (IBAT + IOUT ) + (5V - VBAT ) * IBAT ( 5V - VD * 1 - * VHVIN thermal resistance from die (i.e., junction) to ambient can be reduced to JA = 40C/W. Board Layout Considerations As discussed in the previous section, it is critical that the exposed metal pad on the backside of the LTC4090/ LTC4090-5 package be soldered to the PC board ground. Furthermore, proper operation and minimum EMI requires a careful printed circuit board (PCB) layout. Note that large, switched currents flow in the power switch (between the HVIN and SW pins), the catch diode and the HVIN input capacitor. These components, along with the inductor and output capacitor, should be placed on the same side of the circuit board, and their connections should be made on that layer. Place a local, unbroken ground plane below these components. The loop formed by these components should be as small as possible. Additionally, the SW and BOOST nodes should be kept as small as possible. Figure 10 shows the recommended component placement with trace and via locations. High frequency currents, such as the high voltage input current of the LTC4090/LTC4090-5, tend to find their way along the ground plane on 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. The difference between this equation and that for the LTC4090 is the last term, which represents the power dissipation in the battery charger. For a typical application, an example of this calculation would be: 5V PD = 1 - 0.87 * 5V * 1A + 0.6 A - 0.4V * 1 - * 12V )( ( )) (1A + 0.6A ) + (5V - 3.7V ) * 1A = 1.97W ( Like the LTC4090 example, this examples assumes 87% efficiency, VHVIN = 12V, VBAT = 3.7V, IBAT = 1A and IOUT = 600mA resulting in about 2W total power dissipation. It is important to solder the exposed backside of the package to a ground plane. This ground should be tied to other copper layers below with thermal vias; these layers will spread the heat dissipated by the LTC4090/LTC4090-5. Additional vias should be placed near the catch diode. Adding more copper to the top and bottom layers and tying this copper to the internal planes with vias can reduce thermal resistance further. With these steps, the C1 AND D1 GND PADS SIDE-BY-SIDE AND SEPERATED WITH C3 GND PAD MINIMIZE D1, L1, C3, U1, SW PIN LOOP U1 THERMAL PAD SOLDERED TO PCB. VIAS CONNECTED TO ALL GND PLANES WITHOUT THERMAL RELIEF 4090 F11 MINIMIZE TRACE LENGTH 4090 F10 Figure 10. Suggested Board Layout Figure 11. Ground Currents Follow Their Incident Path at High Speed. Slices in the Ground Plane Cause High Voltage and Increased Emissions. 4090fa 25 LTC4090/LTC4090-5 APPLICATIONS INFORMATION IN and HVIN Bypass Capacitor Many types of capacitors can be used for input bypassing; however, caution must be exercised when using multilayer ceramic capacitors. Because of the self-resonant and high Q characteristics of some types of ceramic capacitors, high voltage transients can be generated under some start-up conditions, such as from connecting the charger input to a hot power source. For more information, refer to Application Note 88. Battery Charger Stability Considerations The constant-voltage mode feedback 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 1F from BAT to GND. Furthermore, a 4.7F capacitor with a 0.2 to 1 series resistor to GND is recommended at the BAT pin to keep ripple voltage low when the battery is disconnected. TYPICAL APPLICATIONS HIGH (6V TO 36V) VOLTAGE INPUT C1 1F 50V 1206 HVIN HVEN IN 4.7F 6.3V 680 59k 1% HPWR VC 270pF 0.1F 2.1k 1% 71.5k 1% 40.2k 1% SUSP TIMER OUT CLPROG GATE PROG BAT RT PG SYNC VNTC 10k 1% NTC T 10k 680 CHRG 4090 F12 BOOST SW 0.47F 16V D1 L1 6.8H C3 22F 6.3V 1206 USB LTC4090 HVOUT HVPR 1k Q1 LOAD 4.7F 6.3V Q2 + Li-Ion BATTERY D: DIODES INC. B360A L: SUMIDA CDR6D28MN-GR5 Q1, Q2: SILICONIX Si2333DS Figure 12. 800kHz Switching Frequency 0.47F HIGH (6V TO 36V) TRANSIENT TO 60V* BOOST HVIN 1F HVOUT USB 4.7F VC RT TIMER CLPROG 2.1k GND IN LTC4090 HVPR 1k OUT BAT PROG 71.5k 4.7F LOAD VC RT TIMER Li-Ion BATTERY 30k 330pF L: SUMIDA CDRH4D22/HP-2R2 4090 TAO3 4090 TAO4 L 10H 4.7F HIGH (6V TO 16V) VOLTAGE INPUT BOOST SW HVIN 1F 0.47F SW L 2.2H 22F HVOUT Q1 USB 4.7F IN LTC4090 HVPR 1k OUT BAT PROG 71.5k LOAD 4.7F Q1 35k 330pF 88.7k + CLPROG 2.1k GND 11.5k 0.1F 0.1F + Li-Ion BATTERY L: SUMIDA CDRH8D28/HP-100 * USE SCHOTTKY DIODE RATED AT VR > 45V Figure 13. 400kHz Switching Frequency Figure 14. 2MHz Switching Frequency 4090fa 26 LTC4090/LTC4090-5 PACKAGE DESCRIPTION DJC Package 22-Lead Plastic DFN (6mm x 3mm) (Reference LTC DWG # 05-08-1714) 0.889 0.70 0.05 R = 0.10 0.889 PACKAGE OUTLINE 3.60 0.05 1.65 0.05 2.20 0.05 (2 SIDES) 0.25 0.05 0.50 BSC 5.35 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3. DRAWING IS NOT TO SCALE 6.00 0.10 (2 SIDES) R = 0.10 TYP R = 0.115 TYP 22 0.40 0.05 0.889 12 3.00 0.10 (2 SIDES) PIN 1 TOP MARK (NOTE 6) 1.65 0.10 (2 SIDES) 0.889 11 0.200 REF 0.75 0.05 5.35 0.10 (2 SIDES) 1 0.25 0.05 0.50 BSC (DJC) DFN 0605 PIN #1 NOTCH R0.30 TYP OR 0.25mm x 45 CHAMFER 0.00 - 0.05 NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WXXX) IN JEDEC PACKAGE OUTLINE M0-229 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 TOP AND BOTTOM OF PACKAGE BOTTOM VIEW--EXPOSED PAD 4090fa 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. 27 LTC4090/LTC4090-5 RELATED PARTS PART NUMBER Battery Chargers LTC1733 LTC1734 LTC4002 LTC4053 LTC4054 Monolithic Lithium-Ion Linear Battery Charger Lithium-Ion Linear Battery Charger in ThinSOTTM Switch Mode Lithium-Ion Battery Charger USB Compatible Monolithic Li-Ion Battery Charger Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOT Lithium-Ion Linear Battery Charger Standalone Charger with Programmable Timer, Up to 1.5A Charge Current Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed Standalone, 4.7V VIN 24V, 500kHz Frequency, 3 Hour Charge Termination Standalone Charger with Programmable Timer, Up to 1.25A Charge Current Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA Charge Current Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package DESCRIPTION COMMENTS LTC4057 LTC4058 LTC4059 Standalone 950mA Lithium-Ion Charger C/10 Charge Termination, Battery Kelvin Sensing, 7% Charge Accuracy in DFN 900mA Linear Lithium-Ion Battery Charger 2mm 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output 4.2V, 0.6% Float Voltage, Up to 750mA Charge Current, 2mm 2mm DFN, "A" Version has ACPR Function. 950mA Charge Current, Timer Termination + C/10 Detection Output, 4.2V, 0.6% Accurate Float Voltage, 4 CHRG Pin Indicator States 95% Efficiency, VIN = 2.5V to 5.5V, VOUT = 0.6V, IQ = 20A, ISD < 1A, ThinSOT Package 95% Efficiency, VIN = 2.5V to 5.5V, VOUT = 0.8V, IQ = 60A, ISD < 1A, MS10 Package 95% Efficiency, VIN = 2.5V to 5.5V, VOUT = 2.5V, IQ = 25A, ISD < 1A, MS Package Seamless Transition Between Power Sources: USB, Wall Adapter and Battery; 95% Efficient DC/DC Conversion 88% Efficiency, VIN = 3.6V to 36V (40V Maximum), VOUT = 0.8V, ISD < 2A, 2mm 3mm DFN Package Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation, 200m Ideal Diode, 4mm 4mm QFN16 Package LTC4065/LTC4065A Standalone Li-Ion Battery Chargers in 2mm 2mm DFN LTC4095 Power Management LTC3406/LTC3406A 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter LTC3411 LTC3440 LTC3455 LT3493 LTC4055 LTC4066 LTC4067 LTC4085 LTC4089/ LTC4089-5 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger 1.2A, 750kHz Step-Down Switching Regulator USB Power Controller and Battery Charger Standalone USB Lithium-Ion/Polymer Battery Charger in in 2mm 2mm DFN USB Power Controller and Li-Ion Battery Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation, 50m Charger with Low-Loss Ideal Diode Ideal Diode, 4mm 4mm QFN24 Package USB Power Controller with OVP, Ideal Diode and Li-Ion Battery Charger USB Power Manager with Ideal Diode Controller and Li-Ion Charger USB Power Manager with Ideal Diode Controller and High Efficiency Li-Ion Battery Charger Low Loss PowerPath Controller in ThinSOT High Voltage Power Path Controllers in ThinSOT 13V Overvoltage Transient Protection, Thermal Regulation, 200m Ideal Diode with <50m Option, 4mm x 3mm DFN-14 Package Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation, 200m Ideal Diode with <50m Option, 4mm 3mm DFN14 Package High Efficiency 1.2A Charger from 6V to 36V (40V Max) Input Charges Single-Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation, 200m Ideal Diode with <50m Option, Bat-Track Adaptive Output Control (LTC4089), Fixed 5V Output (LTC4089-5), 6mm x 3mm DFN-22 Package Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diode VIN = 3V to 36V, More Efficient than Diode ORing, Automatic Switching Between DC Sources, Simplified Load Sharing, ThinSOT Package. LTC4411/LTC4412 LTC4412HV ThinSOT is a trademark of Linear Technology Corporation. 4090fa 28 Linear Technology Corporation (408) 432-1900 FAX: (408) 434-0507 LT 0208 REV A * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 www.linear.com (c) LINEAR TECHNOLOGY CORPORATION 2007 |
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