EUP8202-4.2/8.4 Switch Mode Li-Ion/Polymer Battery Charger DESCRIPTION FEATURES The EUP8202 is a constant current, constant voltage Li-Ion battery charger controller that uses a current mode PWM step-down (buck) switching architecture. With a 500kHz switching frequency, the EUP8202 provides a small, simple and efficient solution to fast charge one (4.2V) or two (8.4V) cell lithium-ion batteries. z Wide Input Supply Voltage Range: z z z 4.7V to 20V – 4.2 Version 8.9V to 20V – 8.4 Version 500kHz Switching Frequency End-of-Charge Current Detection Output 3 Hour Charge Termination Timer z ±1% Charge Voltage Accuracy z ±10% Charge Current Accuracy z z z Low 10µA Reverse Battery Drain Current Automatic Battery Recharge Automatic Trickle Charging of Low Voltage Batteries Automatic Sleep Mode for Low Power Consumption Battery Temperature Sensing Stable with Ceramic Output Capacitor 8-Lead SOP and 10-Lead TDFN Packages RoHS Compliant and 100% Lead (Pb)-Free The EUP8202 charges the battery in three phases: conditioning, constant current, and constant voltage. An external sense resistor sets the charge current with ±10% accuracy. An internal resistor divider and precision reference set the final float voltage to 4.2V per cell with ± 1% accuracy. An internal comparator detects the near end-of-charge condition while an internal timer sets the total charge time and terminates the charge cycle. The EUP8202 automatically re-starts the charge if the battery voltage falls below an internal threshold, 4.05V per cell. The EUP8202 also automatically enters sleep mode when DC supplies are removed. The EUP8202 is available in the 8-lead SOP and 10-lead TDFN packages. z z z z z APPLICATIONS z z z Small Notebook Computer Portable DVD Handheld Instruments Typical Operating Performance Efficiency vs Input voltage Efficiency vs Input voltage 100 100 (Curves include input diode) 95 90 90 EFFICIENCY(%) EFFICIENCY(%) (Curves include input diode) 95 85 80 75 70 EUP8202-8.4 VBAT=7.0V VBAT=8.0V 65 85 80 75 70 EUP8202-4.2 VBAT=3.8V VBAT=4.0V 65 60 60 8 10 12 14 16 18 20 5 Input Voltage (V) DS8202 Ver 1.1 Nov.2007 10 15 Input Voltage (V) 1 20 EUP8202-4.2/8.4 Typical Application Circuit Figure 1. 2A Single/Dual Cells Li-Ion Battery Charger Figure 2. 1.5A Single/Dual Cells Li-Ion Battery Charger DS8202 Ver 1.1 Nov.2007 2 EUP8202-4.2/8.4 Block Diagram Figure 3. DS8202 Ver 1.1 Nov.2007 3 EUP8202-4.2/8.4 Pin Configurations Package Type Pin Configurations Package Type TDFN-10 Pin Configurations SOP-8 Pin Description PIN TDFN-10 SOP-8 DESCRIPTION Compensation, Soft-Start and Shutdown Control Pin. Charging begins when the COMP pin reaches 850mV. The recommended compensation components are a 2.2µF (or larger) capacitor and a 0.5k series resistor. A 100µA current into the compensation capacitor also sets the soft-start slew rate. Pulling the COMP pin below 280mV will shut down the charger. COMP 1 1 VCC 2 2 GATE 3 3 PGND 4 - SGND 5 - GND - 4 CHRG 6 5 BAT 7 6 SENSE 8 7 NTC 9 8 NC 10 - DS8202 Ver 1.1 Nov.2007 Positive Supply Voltage Input. Gate Drive Output. Driver Output for the external P-Channel MOSFET. The voltage at this pin is internally clamped to 8V below VCC, allowing a low voltage MOSFET with gate-to-source breakdown voltage of 8V or less to be used. IC Ground. Charge Status Output. Battery Sense Input. A bypass capacitor of 22µF is required to minimize ripple voltage. When VBAT is within 250mV of VCC, the EUP8202 is forced into sleep mode, dropping ICC to 10µA. Current Amplifier Sense Input. A sense resistor, RSENSE, must be connected between the SENSE and BAT pins. The maximum charge current is equal to 100mV/RSENSE. NTC (Negative Temperature Coefficient) Thermistor Input. With an external 10kΩ NTC thermistor to ground, this pin senses the temperature of the battery pack and stops the charger when the temperature is out of range. To disable the temperature qualification function, ground the NTC pin. No Connect. 4 EUP8202-4.2/8.4 Ordering Information Order Number Package Type EUP8202-42JIR1 TDFN-10 EUP8202-84JIR1 TDFN-10 EUP8202-42DIR1 SOP-8 EUP8202-84DIR1 SOP-8 Marking xxxxx P8202 1N xxxxx P8202 1P xxxxx P8202 1N xxxxx P8202 1P EUP8202- □□ □ □ □ □ Lead Free Code 1: Lead Free 0: Lead Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type J: TDFN D:SOP Output Voltage Option DS8202 Ver 1.1 Nov.2007 5 Operating Temperature range -40 °C to 85°C -40 °C to 85°C -40 °C to 85°C -40 °C to 85°C EUP8202-4.2/8.4 Absolute Maximum Ratings Supply Voltage (Vcc) ----------------------------------------------------------------------------------22V GATE ----------------------------------------------------------------------------------------- (Vcc-8V) to Vcc BAT, SENSE ------------------------------------------------------------------------------------- -0.3V to 14V CHRG ,NTC ----------------------------------------------------------------------------------------- Operating Temperature Range ---------------------------------------------------------------- -40℃ to 85℃ Storage Temperature Range ------------------------------------------------------------------ -65℃ to 125℃ Lead Temperature (Soldering, 10sec) -------------------------------------------------------------------- 260℃ -0.3V to 8V Electrical Characteristics (TA = 25℃, VCC = 10V, unless otherwise noted.) Symbol Parameter Conditions EUP8202-4.2 Min. Typ. Max. Unit DC Characteristics VCC ICC VCC Supply Voltage VCC Supply Current 4.7 20 V Current Mode 1.5 5 mA Shutdown Mode 1.5 5 mA Sleep Mode 10 20 µA 4.158 4.2 4.242 V VBAT(FLT) Battery Regulated Float Voltage 5V≦ VCC ≦ 20V 0℃≦ TA ≦85℃ VSNS(CHG) Constant Current Sense Voltage 3V≦ VBAT ≦ 4V 0℃≦ TA ≦85℃ 90 100 110 mV VSNS(TRKL) Trickle Current Sense Voltage Trickle Charge Threshold VTRKL Voltage VCC Undervoltage Lockout VUV Threshold Voltage VCC Undervoltage Lockout ∆VUV Hysteresis Voltage Manual shutdown Threshold VMSD Voltage Automatic shutdown Threshold VASD Voltage ICOMP COMP Pin Output Current VBAT = 1V 8 15 22 mV VBAT = Rising 2.75 2.9 3.05 V VCC = Rising 3.9 4.2 4.5 V ICHRG CHRG Pin Weak Pull-Down Current REOC CHRG Pin Output Low Voltage End-of-Charge Ratio tTIMER Charge time Accuracy VCHRG INTC 200 COMP Pin Falling 280 450 mV VCC - VBAT 250 mV VCOMP = 1.2V 100 µA VCHRG = 1V 15 ICHRG = 1mA VSNS(EOC) /VSNS(CHG) NTC Pin Output Current VNTC = 0.85V VNTC-HOT NTC Pin Thershold Voltage (Hot) VNTC = Falling VNTC-COLD NTC Pin Thershold Voltage (Cold) VNTC = Rising DS8202 Ver 1.1 Nov.2007 150 mV 10 25 35 µA 20 50 mV 25 32 % 10 % 0℃≦ TA ≦50℃ 75 85 95 µA -40℃≦ TA ≦85℃ 70 85 100 µA 340 360 380 mV Hysteresis 5 2.35 Hysteresis 2.4 100 6 mV 2.45 V mV EUP8202-4.2/8.4 Electrical Characteristics (TA = 25℃, VCC = 10V, unless otherwise noted.) Symbol Parameter Conditions Recharge Battery Voltage Offset VBAT(FULLCHARGD) –VRECHRG, VBAT ∆VRECHRG from Full Charged Battery Falling Voltage ILEAK CHRG Pin Leakage Current EUP8202-4.2 Unit Min. Typ. Max. 100 150 VCHRG= 8V, Charging Stops 200 mV 1 µA 550 kHz 100 % Oscillator fOSC Switching Frequency DC Maximum Duty Cycle 450 500 Gate Drive tr Rise Time CGATE =2000pF, 10% to 90% 20 ns tf Fall Time CGATE =2000pF, 10% to 90% 50 ns Output Clamp Voltage VCC -VGATE , VCC≧9V ∆VGATE -40℃≦ TA ≦85℃ ∆VGATEHI Output High Voltage ∆VGATEHI= VCC -VGATE , VCC≧7V ∆VGATELO Output Low Voltage ∆VGATELO= VCC -VGATE , VCC≧7V 8 V 0.3 V 4.5 V Electrical Characteristics (TA = 25℃, VCC = 12V, unless otherwise noted.) Symbol Parameter Conditions EUP8202-8.4 Min. Typ. Max. Unit DC Characteristics VCC ICC VCC Supply Voltage VCC Supply Current 8.9 1.5 5 mA Shutdown Mode 1.5 5 mA Sleep Mode 10 20 µA 8.316 8.4 8.484 V 90 100 110 mV 8 15 22 mV 4.7 5 5.3 V 7.5 8.5 V 6V≦ VBAT ≦ 8V 0℃≦ TA ≦85℃ VSNS(TRKL) Trickle Current Sense Voltage VBAT = 1V Trickle Charge Threshold VTRKL VBAT = Rising Voltage VCC Undervoltage Lockout VCC = Rising VUV Threshold Voltage VCC Undervoltage Lockout ∆VUV Hysteresis Voltage Manual shutdown Threshold VMSD COMP Pin Falling Voltage Automatic shutdown Threshold VASD VCC - VBAT Voltage ICOMP COMP Pin Output Current VCOMP = 1.2V ICHRG CHRG Pin Weak Pull-Down Current DS8202 Ver 1.1 Nov.2007 V Current Mode VBAT(FLT) Battery Regulated Float Voltage 9V≦ VCC ≦ 20V 0℃≦ TA ≦85℃ VSNS(CHG) Constant Current Sense Voltage 20 VCHRG = 1V 500 150 15 7 280 mV 450 mV 250 mV 100 µA 25 35 µA EUP8202-4.2/8.4 Electrical Characteristics (TA = 25℃, VCC = 12V, unless otherwise noted.) Symbol Parameter REOC CHRG Pin Output Low Voltage End-of-Charge Ratio tTIMER Charge time Accuracy VCHRG INTC Conditions ICHRG = 1mA VSNS(EOC) /VSNS(CHG) NTC Pin Output Current VNTC = 0.85V VNTC-HOT NTC Pin Thershold Voltage (Hot) VNTC = Falling VNTC-COLD NTC Pin Thershold Voltage (Cold) VNTC = Rising CHRG Pin Leakage Current 5 20 50 mV 15 25 % 10 % 0℃≦ TA ≦50℃ 75 85 95 µA -40℃≦ TA ≦85℃ 70 85 100 µA 340 360 380 mV Hysteresis 5 2.35 Hysteresis 2.4 mV 2.45 100 Recharge Battery Voltage Offset VBAT(FULLCHARGD) –VRECHRG, VBAT ∆VRECHRG from Full Charged Battery Falling Voltage ILEAK EUP8202-8.4 Unit Min. Typ. Max. 200 300 VCHRG= 8V, Charging Stops V mV 400 mV 1 µA 550 kHz 100 % Oscillator fOSC Switching Frequency DC Maximum Duty Cycle 450 500 Gate Drive tr Rise Time CGATE =2000pF, 10% to 90% 20 ns tf Fall Time CGATE =2000pF, 10% to 90% 50 ns Output Clamp Voltage VCC-VGATE , VCC≧9V ∆VGATE 40℃≦ TA ≦85℃ ∆VGATEHI Output High Voltage ∆VGATEHI= VCC -VGATE , VCC≧7V ∆VGATELO Output Low Voltage ∆VGATELO= VCC -VGATE , VCC≧7V DS8202 Ver 1.1 Nov.2007 8 4.5 8 V 0.3 V V EUP8202-4.2/8.4 Typical Operating Characteristics Oscillator Frequency vs Temperature Supply Current vs Vcc 2.0 (Current mode) 540 1.8 520 fosc(kHz) Icc(mA) 1.6 1.4 500 480 1.2 460 1.0 5 10 15 -40 20 -20 0 20 40 60 80 100 120 TEMPERATURE(°C) Vcc (V) Undervoltage Lockout Threshold vs Temperature Supply Current vs Temperature 4.0 9 3.5 8 3.0 7 Vuv(V) Icc(mA) 2.5 2.0 6 EUP8202-4.2 EUP8202-8.4 5 1.5 4 1.0 3 0.5 -40 -20 0 20 40 60 80 100 -40 120 Oscillator Frequency vs Vcc 540 fosc(kHz) 520 500 480 460 5 10 15 20 Vcc (V) DS8202 Ver 1.1 Nov.2007 -20 0 20 40 60 TEMPERATURE(°C) TEMPERATURE(°C) 9 80 100 120 EUP8202-4.2/8.4 Typical Operating Characteristics (continued) CHRG Pin Weak Pull-Down Current vs Vcc CHRG Pin Output Low Voltage vs Vcc 28 30 VCHRG=8V Iload=1mA 25 ICHRG(µV) VCHRG(mV) 26 20 24 15 22 10 5 10 15 5 20 10 20 Recharge Voltage Offset from Full Charged Voltage vs Vcc CHRG Pin Output Low Voltage vs Temperature 25 160 Iload=1mA EUP8202-4.2 20 155 VRECHARGE(mV) V CH R G (m V ) 15 Vcc (V) Vcc (V) 15 10 5 150 145 140 -40 -20 0 20 40 60 80 100 120 5 10 15 20 Vcc (V) TEMPERATURE(°C) Recharge Voltage Offset from Full Charged Voltage vs Vcc CHRG Pin Weak Pull-Down Current vs Temperature 32 320 VCHRG=8V EUP8202-8.4 315 30 VRECHARGE(mV) 310 ICHRG(µV) 28 26 24 305 300 295 290 285 22 280 -40 -20 0 20 40 60 80 100 120 5 DS8202 Ver 1.1 Nov.2007 10 15 Vcc (V) TEMPERATURE(°C) 10 20 EUP8202-4.2/8.4 Typical Operating Characteristics (continued) COMP Pin Output Current vs Vcc Current Mode Sense Voltage vs Vcc 104 102 VCOMP=1.2V VBAT=4.0V EUP8202-4.2 102 ICOMP(µV) VSNS(mV) 100 98 96 100 98 96 94 94 5 10 15 5 20 10 15 20 Vcc (V) Vcc (V) COMP Pin Output Current vs Temperature Current Mode Sense Voltage vs Vcc 120 106 VCOMP=1.2V VBAT=8V EUP8202-8.4 118 116 104 ICOMP(µA) VSNS(mV) 114 102 112 110 108 106 100 104 102 98 5 10 15 -40 20 Current Mode Sense Voltage vs Temperature 104 103 102 VSNS(mV) 101 100 99 98 97 96 -40 -20 0 20 40 60 80 100 120 TEMPERATURE(°C) DS8202 Ver 1.1 Nov.2007 -20 0 20 40 60 TEMPERATURE(°C) Vcc (V) 11 80 100 120 EUP8202-4.2/8.4 Typical Operating Characteristics (continued) Trickle Charge Voltage vs Vcc Trickle Charge Voltage vs Temperature 5.2 3.00 EUP8202-8.4 EUP8202-4.2 5.1 VTRKL(V) VTRKL(V) 2.95 2.90 5.0 4.9 2.85 4.8 2.80 -40 -20 0 20 40 60 80 100 5 120 10 15 20 Vcc (V) TEMPERATURE(°C) Trickle Charge Sense Voltage vs Temperature Trickle Charge Voltage vs Vcc 20 3.0 VBAT=2.5V EUP8202-4.2 EUP8202-4.2 18 VSNS(mV) VTRKL(V) 16 2.9 14 12 10 8 2.8 5 10 15 -40 20 0 20 40 60 80 100 120 Trickle Charge Sense Voltage vs Vcc Trickle Charge Voltage vs Temperature 25 5.2 VBAT=2.5V EUP8202-4.2V EUP8202-8.4 20 VSNS(mV) 5.1 VTRKL(V) -20 TEMPERATURE(°C) Vcc (V) 5.0 15 10 4.9 5 4.8 -40 -20 0 20 40 60 80 100 5 120 DS8202 Ver 1.1 Nov.2007 10 15 Vcc (V) TEMPERATURE(°C) 12 20 EUP8202-4.2/8.4 Typical Operating Characteristics (continued) End-of-Charge Ratio vs Temperature Trickle Charge Sense Voltage vs Temperature 22 20 EUP8202-8.4 VBAT=4V EUP8202-8.4 18 20 16 REOC(%) VSNS(mV) 18 14 16 12 14 10 12 8 -40 -20 0 20 40 60 80 100 -40 120 -20 0 20 40 60 80 100 120 TEMPERATURE(°C) TEMPERATURE(°C) End-of-Charge Ratio vs Vcc Trickle Charge Sense Voltage vs Vcc 25 EUP8202-4.2 VBAT=4V EUP8202-8.4V 28 20 REOC(%) VSNS(mV) 26 15 24 10 22 5 5 10 15 5 20 10 20 End-of-Charge Ratio vs Vcc End-of-Charge Ratio vs Temperature 22 30 EUP8202-8.4 EUP8202-4.2 28 20 REOC(%) 26 REOC(%) 15 Vcc (V) Vcc (V) 24 18 16 22 14 20 -40 -20 0 20 40 60 80 100 5 120 DS8202 Ver 1.1 Nov.2007 10 15 Vcc (V) TEMPERATURE(°C) 13 20 EUP8202-4.2/8.4 Typical Operating Characteristics (continued) NTC Pin Output Current vs Temperature NTC Pin Output Current vs Vcc 94 88 VNTC=0V VNTC=0V 92 88 INTC(µV) INTC(µV) 90 86 86 84 82 80 -40 -20 0 20 40 60 80 100 84 120 5 DS8202 Ver 1.1 Nov.2007 10 15 Vcc (V) TEMPERATURE(°C) 14 20 EUP8202-4.2/8.4 Application Information Figure 4. Operational Flow Chart DS8202 Ver 1.1 Nov.2007 15 EUP8202-4.2/8.4 OPERATION The EUP8202 is a constant current, constant voltage Li-Ion battery charger controller that uses a current mode PWM step-down (buck) switching architecture. The charge current is set by an external sense resistor (RSENSE) across the SENSE and BAT pins. The final battery float voltage is internally set to 4.2V per cell. For batteries like lithium-ion that require accurate final float voltage, the internal 2.4V reference, voltage amplifier and the resistor divider provide regulation with ±1% accuracy. and the CHRG pin is forced high impedance. To restart the charge cycle, remove and reapply the input voltage or momentarily shut the charger down. Also, a new charge cycle will begin if the battery voltage drops below the recharge threshold voltage of 4.05V per cell. When the input voltage is present, the charger can be shut down (ICC =1.5mA) by pulling the COMP pin low. When the input voltage is not present, the charger goes into sleep mode, dropping ICC to 10µA. This will greatly reduce the current drain on the battery and increase the standby time. A 10kΩ NTC (negative temperature coefficient) thermistor can be connected from the NTC pin to ground for battery temperature qualification. The charge cycle is suspended when the temperature is outside of the 0°C to 50°C window. APPLICATIONS INFORMATION Figure 5.Typical Charge Profile A charge cycle begins when the voltage at the VCC pin rises above the UVLO level and is 250mV or more greater than the battery voltage. At the beginning of the charge cycle, if the battery voltage is less than the trickle charge threshold, 2.9V for the 4.2 version and 5V for the 8.4 version, the charger goes into trickle charge mode. The trickle charge current is internally set to 15% of the full-scale current. If the battery voltage stays low for 30 minutes, the battery is considered faulty and the charge cycle is terminated. When the battery voltage exceeds the trickle charge threshold, the charger goes into the full-scale constant current charge mode. In constant current mode, the charge current is set by the external sense resistor RSENSE and an internal 100mV reference; VSNS(CHG) 100mV = R SENSE R SENSE When the battery voltage approaches the programmed float voltage, the charge current will start to decrease. When the current drops to 25% (4.2 version) or 15% (8.4 version) of the full-scale charge current, an internal comparator turns off the internal pull-down N-channel MOSFET at the CHRG pin, and connects a weak current source to ground to indicate a near end-of-charge condition. An internal 3 hour timer determines the total charge time. After a time out occurs, the charge cycle is terminated I CHG = DS8202 Ver 1.1 Nov.2007 16 Undervoltage Lockout (UVLO) An undervoltage lockout circuit monitors the input voltage and keeps the charger off until VCC rises above the UVLO threshold (4.2V for the 4.2 version, 7.5V for the 8.4 version) and at least 250mV above the battery voltage. To prevent oscillation around the threshold voltage, the UVLO circuit has 200mV per cell of built-in hysteresis. When specifying minimum input voltage requirements, the voltage drop across the input blocking diode must be added to the minimum VCC supply voltage specification. Trickle Charge and Defective Battery Detection At the beginning of a charge cycle, if the battery voltage is below the trickle charge threshold, the charger goes into trickle charge mode with the charge current reduced to 15% of the full-scale current. If the low-battery voltage persists for 30 minutes, the battery is considered defective, the charge cycle is terminated and the CHRG pin is forced high impedance. I TRKL = VSNS(TRKL) 15mV = R SENSE R SENSE Shutdown The EUP8202 can be shut down by pulling the COMP pin to ground which pulls the GATE pin high turning off the external P-channel MOSFET. When the COMP pin is released, the internal timer is reset and a new charge cycle starts. In shutdown, the output of the CHRG pin is high impedance and the quiescent current remains at 1.5mA. Removing the input power supply will put the charger into sleep mode. If the voltage at the VCC pin drops below (VBAT + 250mV) or below the UVLO level, the EUP8202 goes into a low current (ICC = 10µA) sleep mode, reducing the battery drain current. EUP8202-4.2/8.4 CHRG Status Output Pin When a charge cycle starts, the CHRG pin is pulled to ground by an internal N-channel MOSFET which is capable of driving an LED. When the charge current drops below the End-of-Charge threshold for more than 120µs, the N-channel MOSFET turns off and a weak 25µA current source to ground is connected to the CHRG pin. This weak 25µA pull-down remains until the timer ends the charge cycle, or the charger is in manual shutdown or sleep mode. Table1: CHRG Status Pin Summary CHARGE STATE CHRG Pin Trickle Charge in Process Strong On Constant Current Charge in Process Strong On Constant Voltage Charge in Process Strong On Charge Suspend (Temperature) Strong On (remains the same) Timer Fault Hi-Z Sleep / Shutdown Hi-Z End of Charge Weak On Battery Disconnected Weak On After a time out occurs (charge cycle ends), the pin will become high impedance. By using two different value resistors, a microprocessor can detect three states from this pin (charging, end-of-charge and charging stopped) see Figure 6. Figure 6. Microprocessor Interface To detect the charge mode, force the digital output pin, OUT, high and measure the voltage at the CHRG pin. The N-channel MOSFET will pull the pin low even with a 2k pull-up resistor. Once the charge current drops below the End-of-Charge threshold, the N-channel MOSFET is turned off and a 25µA current source is connected to the CHRG pin. The IN pin will then be pulled high by the 2k resistor connected to OUT. Now force the OUT pin into a high impedance state, the current source will pull the pin low through the 390k resistor. When the internal timer has expired, the CHRG DS8202 Ver 1.1 Nov.2007 17 pin changes to a high impedance state and the 390k resistor will then pull the pin high to indicate charging has stopped. Gate Drive The EUP8202gate driver can provide high transient currents to drive the external pass transistor. The rise and fall times are typically 20ns and 50ns respectively when driving a 2000pF load, which is typical for a P-channel MOSFET with RDS(ON) in the range of 50mΩ. A voltage clamp is added to limit the gate drive to 8V below VCC. For example, if VCC is 10V then the GATE output will pull down to 2V max. This allows low voltage P-channel MOSFETs with superior RDS(ON) to be used as the pass transistor thus increasing efficiency. Stability Both the current loop and the voltage loop share a common, high impedance, compensation node (COMP pin). A series capacitor and resistor on this pin compensates both loops. The resistor is included to provide a zero in the loop response and boost the phase margin. The compensation capacitor also provides a soft-start function for the charger. Upon start-up, then ramp at a rate set by the internal 100µA pullup current source and the external capacitor. Battery charge current starts ramping up when the COMP pin voltage reaches 0.85V and full current is achieved with the COMP pin at 1.3V. With a 2.2µF capacitor, time to reach full charge current is about 10ms. Capacitance can be increased if a longer start-up time is needed. Automatic Battery Recharge After the 3 hour charge cycle is completed and both the battery and the input power supply (wall adapter) are still connected, a new charge cycle will begin if the battery voltage drops below 4.05V per cell due to self-discharge or external loading. This will keep the battery capacity at more than 80% at all times without manually restarting the charge cycle. Battery Temperature Detection A negative temperature coefficient (NTC) thermistor located close to the battery pack can be used to monitor battery temperature and will not allow charging unless the battery temperature is within an acceptable range. Connect a 10kΩ thermistor from the NTC pin to ground. If the temperature rises to 50°C, the resistance of the NTC will be approximately 4.2kΩ. With the 85µA pull-up current source, the Hot temperature voltage threshold is 360mV. For Cold temperature, the voltage threshold is set at 2.4V which is equal to 0°C (RNTC ≅ 28kΩ) with 85µA of pull-up current. If the temperature is outside the window, the GATE pin will be pulled up to VCC and the timer frozen while the output status at the CHRG pin remains the same. The charge cycle begins or resumes once the temperature is within the acceptable EUP8202-4.2/8.4 range. Short the NTC pin to ground to disable the temperature qualification feature. However the user may modify these thresholds by adding two external resistor. See figure 8. for filtering and has the necessary RMS current rating. Switching ripple current splits between the battery and the output capacitor depending on the ESR of the output capacitor and the battery impedance. EMI considerations usually make it desirable to minimize ripple current in the battery leads. Ferrite beads or an inductor may be added to increase battery impedance at the 500kHz switching frequency. If the ESR of the output capacitor is 0.2Ω and the battery impedance is raised to 4Ω with a bead or inductor, only 5% of the current ripple will flow in the battery. Design Example As a design example, take a charger with the following specifications: For single cell charge, VIN = 5V to 20V, VBAT = 4V nominal, IBAT =1.5A, fOSC = 500kHz, IEOC=0.375A, see Figure 2. Figure 7. Temperature Sensing Configuration First, calculate the SENSE resistor : R SENSE = Choose the inductor for about 65% ripple current at the maximum VIN: 4V 4V L= = 6.56 µH 1 − (500 kHz )(0.65)(1.5A ) 20V Figure 8. Temperature Sensing Thresholds Input and Output Capacitors Since the input capacitor is assumed to absorb all input switching ripple current in the converter, it must have an adequate ripple current rating. Worst-case RMS ripple current is approximately one-half of output charge current. Actual capacitance value is not critical. Solid tantalum capacitors have a high ripple current rating in a relatively small surface mount package, but caution must be used when tantalum capacitors are used for input bypass. High input surge currents can be created when the adapter is hot-plugged to the charger and solid tantalum capacitors have a known failure mechanism when subjected to very high turn-on surge currents. Selecting the highest possible voltage rating on the capacitor will minimize problems. Consult with the manufacturer before use. The selection of output capacitor COUT is primarily determined by the ESR required to minimize ripple voltage and load step transients. The output ripple ∆VOUT is approximately bounded by: ∆VOUT ≤ ∆I L ESR + 1 8f OSC C OUT Since ∆IL increases with input voltage, the output ripple is highest at maximum input voltage. Typically, once the ESR requirement is satisfied, the capacitance is adequate DS8202 Ver 1.1 Nov.2007 100mV = 68mΩ 1.5A 18 Selecting a standard value of 6.8µH results in a maximum ripple current of : ∆I L = 4V = 941.2mA 1 − (500kHz )(6.8µH ) 20V I LPK = I 4V CHG + ∆I L = 1.5A + 941.2mA ≈ 1.975A 2 2 Next, choose the P-channel MOSFET. For example, a TSSOP-8 package with RDS(ON) = 42mΩ (nom), 55mΩ (max) offers a small solution. The maximum power dissipation with VIN = 5V and VBAT = 4V at 50℃ ambient temperature is: (1.5A )2 (55mΩ )(4V ) = 0.099 W P = D 5V TJ = 50℃ + (0.099W)(65℃/W) = 56.5℃ CIN is chosen for an RMS current rating of about 0.8A at 85℃. The output capacitor is chosen for an ESR similar to the battery impedance of about 100mΩ The ripple voltage on the BAT pin is: EUP8202-4.2/8.4 ∆I L(max ) (ESR ) VOUT ( RIPPLE ) = 2 = (0.94A )(0.1Ω ) = 47mV 2 For dual cells charge, VIN = 5V to 20V, VBAT = 8V nominal, IBAT =3A, fOSC = 500kHz, IEOC=0.45A, R SENSE = 100mV = 33mΩ 3A Choose the inductor for about 50% ripple current at the maximum VIN: L= 8V = 6 .4 µ H 1 − (500 kHz )(0.5)(3A ) 20V 8V Selecting a standard value of 6.8µH results in a maximum ripple current of : ∆I L = 8V = 1.441A 1 − (500kHz )(6.8µH ) 20V 8V ∆I L = 3A + 1.441A ≈ 3.720 A CHG 2 2 The maximum power dissipation with VIN = 9V and VBAT = 8V at 50℃ ambient temperature is: I LPK = I P = D + (3A )2 (55mΩ )(8V ) = 0.44 W 9V TJ = 50℃ + (0.44W)(65℃/W) = 78.6℃ VOUT ( RIPPLE ) = = ∆I L(max ) (ESR ) 2 (1.441A )(0.1Ω ) = 72mV 2 The Schottky diode D2 shown in Figure 2 conducts current when the pass transistor is off. In a low duty cycle case, the current rating should be the same or higher than the charge current. Also it should withstand reverse voltage as high as VIN. DS8202 Ver 1.1 Nov.2007 19 Board Layout Suggestions When laying out the printed circuit board, the following considerations should be taken to ensure proper operation of the EUP8202. GATE pin rise and fall times are 20ns and 50ns respectively (with CGATE = 2000pF). To minimize radiation, the catch diode, pass transistor and the input bypass capacitor traces should be kept as short as possible. The positive side of the input capacitor should be close to the source of the P-channel MOSFET; it provides the AC current to the pass transistor. The connection between the catch diode and the pass transistor should also be kept as short as possible. The SENSE and BAT pins should be connected directly to the sense resistor (Kelvin sensing) for best charge current accuracy. Avoid routing the NTC PC board trace near the MOSFET switch to minimize coupling switching noise into the NTC pin. The compensation capacitor connected at the COMP pin should return to the ground pin of the IC or as close to it as possible. This will prevent ground noise from disrupting the loop stability. The ground pin also works as a heat sink, therefore use a generous amount of copper around the ground pin. This is especially important for high VCC and/or high gate capacitance applications. EUP8202-4.2/8.4 Packaging Information TDFN-10 SYMBOLS A A1 D E1 E L b e D1 DS8202 Ver 1.1 Nov.2007 MILLIMETERS MIN. MAX. 0.70 0.80 0.00 0.05 2.90 3.10 1.70 2.90 3.10 0.30 0.50 0.18 0.30 0.50 2.40 20 INCHES MIN. 0.028 0.000 0.114 MAX. 0.031 0.002 0.122 0.067 0.114 0.012 0.007 0.122 0.020 0.012 0.020 0.094 EUP8202-4.2/8.4 SOP-8 SYMBOLS MILLIMETERS INCHES MIN. MAX. MIN. MAX. A 1.35 1.75 0.053 0.069 A1 0.10 0.25 0.004 0.010 D E 4.90 5.80 E1 6.20 0.228 3.90 0.244 0.153 L 0.40 1.27 0.016 0.050 b 0.31 0.51 0.012 0.020 e DS8202 Ver 1.1 Nov.2007 0.193 1.27 0.050 21