MP2612 2A,24V Input, 600kHz 2-3 Cells Switching Li-Ion Battery Charger The Future of Analog IC Technology DESCRIPTION FEATURES The MP2612 is a monolithic switching charger for 2-3 cells series Li-Ion cells battery with a built-in internal power MOSFET. It achieves up to 2A charge current with current mode control for fast loop response and easy compensation. The charge current can be programmed by sensing the current through an accurate sense resistor. MP2612 regulates the charge current and charge voltage using two control loops to realize high accuracy CC charge and CV charge. Fault condition protection includes cycle- bycycle current limiting and thermal shutdown. Other safety features include battery temperature monitoring, charge status indication and programmable timer to finish the charging cycle. The MP2612 requires a minimum number of readily available standard external components. The MP2612 is available in 16-pin 4mm x 4mm QFN package. Charges 2-3 Cells Series Li-Ion Battery Packs Wide Operating Input Range Up to 2 A Programmable Charging Current ±0.75% VBATT Accuracy 0.2Ω Internal Power MOSFET Switch Up to 90% Efficiency Fixed 600kHz Frequency Preconditioning for Fully Depleted Batteries Charging Operation Indicator Input Supply and Battery Fault Indicator Thermal Shutdown Cycle-by-Cycle Over Current Protection Battery Temperature Monitor and Protection APPLICATIONS Distributed Power Systems Chargers for 2-Cell or 3-Cell Li-Ion Batteries Pre-Regulator for Linear Regulators Smart Phones Net-book For MPS green status, please visit MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION Figure 1—Standalone Switching Charger MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 1 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER D1 VIN RS2 9V to 24V (9V min for 2-cell) VSYS 20m RG1 M2 RG2 C8 22uF RG1 RG2 MP8110 VCC NC SHDN OUT2 GND OUT1 M3 C1 4.7uF L VIN VREF33 SW VREF25 BST C3 1uF R1 R2 MP2612 ACOK CELLS 10k EN ON OFF 100m 2-3 cells battery C2 D2 CSP BATT R5 750 R4 2.5k COMPI COMPV NTC RNTC C7 0.1uF 22uF CHGOK R3 10k RS1 4.7uH GND TMR C6 C4 0.1uF 2.2nF C5 2.2nF Figure 2—Switching Charger with Power Path Management (1) Notes: 1) ACOK should be pulled up to VIN in the power path management application. MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 2 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER ORDERING INFORMATION Part Number* MP2612ER Package 4mm x 4mm QFN16 Top Marking 2612ER Free Air Temperature (TA) -20C to +85C *For Tape & Reel, add suffix –Z (eg. MP2612ER–Z); For RoHS compliant packaging, add suffix –LF (eg. MP MP2612ER–LF–Z) PACKAGE REFERENCE TOP VIEW VIN SW BST TMR PIN 1 ID 16 15 14 13 ACOK 2 11 CSP CHGOK 3 10 BATT VREF33 4 9 COMPI EXPOSED PAD ON BACKSIDE 5 6 7 8 COMPV GND CELLS 12 EN 1 VREF25 NTC ABSOLUTE MAXIMUM RATINGS (2) Thermal Resistance Supply Voltage VIN ....................................... 26V VSW ........................................ -0.3V to VIN + 0.3V VBST ...................................................... VSW + 6V VCSP, VBATT, ...................................-0.3V to +18V VACOK, VCHGOK, ..............................-0.3V to +26V All Other Pins ..................................-0.3V to +6V Continuous Power Dissipation (TA=+25C) (3) ............................................................. 2.7W Junction Temperature ...............................150C Lead Temperature ....................................260C Storage Temperature ............... -65C to +150C 4x4 QFN16 ............................. 46 ...... 10... C/W Recommended Operating Conditions (4) (5) θJA θJC Notes: 2) Exceeding these ratings may damage the device. 3) The maximum allowable power dissipation is a function of the maximum junction temperature TJ(MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD(MAX)=(TJ(MAX)TA)/ θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 4) The device is not guaranteed to function outside of its operating conditions. 5) Measured on JESD51-7 4-layer board. Supply Voltage VIN .............................. 9V to 24V Maximum Junction Temp. (TJ) ............. +125C MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 3 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER ELECTRICAL CHARACTERISTICS (6) VIN = 19V, TA = +25C, CELLS=0V, unless otherwise noted. Parameters Symbol Condition Terminal Battery Voltage VBATT CSP，BATT Current Min 8.337 8.4 8.463 CELLS= VREF33 12.505 12.6 12.695 RDS(ON) Switch Leakage CC Trickle CC current ICC Trickle charge current RS1=100mΩ 1.8 ITRICKLE Units V 1 µA 0.2 Ω 0 EN = 4V, VSW = 0V (6) Peak Current Limit Max CELLS=0V ICSP,IBATT Charging disabled Switch On Resistance Typ 10 μA 4.1 A 2 A 2.0 2.2 A 10% ICC Trickle charge voltage threshold 2.8 V/cell Trickle charge hysteresis 350 mV Termination current threshold IBF Oscillator Frequency fSW Fold-back Frequency 5% 15% kHz VBATT =0V 190 kHz 90 Sense Voltage Minimum On Time (6) Under Voltage Rising Lockout Threshold Under Voltage Hysteresis Lockout Threshold 170 VSENSE tON CELLS=0V, VBATT =5V 200 230 3.2 VDRAIN =0.3V Dead-battery indication Termination delay Time after CTMR=0.1μF 3.4 reached, VRECHG Recharge Hysteresis RNTC=NCP18XH103(0°C) V mV 5 IBF mV ns 200 Stay at trickle mode CTMR=0.1μF NTC Low Temp Rising Threshold % 100 3 Open-drain sink current Recharge threshold at VBATT ICC 600 Maximum Duty Cycle Maximum current (CSP to BATT) 10% CELLS=0V, VBATT =4.5V mA 30 min 1 min 4.0 V/cell 100 mV 73 %VREF33 NTC High Temp Falling Threshold RNTC=NCP18XH103(50°C) 30 %VREF33 VIN min head-room (reverse blocking) VIN-VBATT 180 mV 0.4 EN Input Low Voltage 1.8 EN Input High Voltage EN Input Current MP2612 Rev. 1.0 9/7/2011 V V EN =4V 4 EN =0V 0.2 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. μA 4 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER ELECTRICAL CHARACTERISTICS (continued) VIN = 19V, TA = +25C, CELLS=0V, unless otherwise noted. Parameters Symbol Condition Supply Current (Shutdown) Supply Current (Quiescent) Typ Max Units EN =4V 0.16 mA EN =4V, Consider VREF33 pin output current, R3=10k,RNTC=10k 0.32 mA 2.0 EN =0V, CELLS=0V (6) Thermal Shutdown VREF25 output voltage VREF33 output voltage VREF33 load regulation Min ILOAD =0 to 10mA 150 2.5 3.3 30 mA °C V V mV Notes: 6) Guaranteed by design. MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 5 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS VIN=19V, C1=4.7μF, C2=22μF, L=4.7μH, RS1=100mΩ, Real Battery Load, TA=25ºC, unless otherwise noted. 2 VBATT 8.2 8.1 1.5 8 7.9 1 7.8 IBATT 7.7 0.5 7.6 0 20 40 60 80 C HAR G E C UR R E NT (A) 8.3 CV Load 1. 5 1 VIN=12V 2 4 6 8 12.6 2 12.2 1.5 12 11.8 1 11.6 IBATT 11.4 0.5 11.2 11 10 VBATT 12.4 0 50 B AT T E R Y V OL T AG E (V ) 3 Cells Charge Current vs. Battery Voltage 0 150 100 T IME S (MIN) NTC Control Window CV Load 3 Low Temp Off 2.5 2 VIN=24V 1.5 2.5 1 2 Low Temp On 2 ICHG(A) VIN=19V VNTC(V) C HA R G E C U R R E NT(A ) VIN=19V VIN=24V 0. 5 T IME S (MIN) 2.5 2.5 12.8 2 0 0 0 100 120 3 Cells Battery Charge Curve B A T T E R Y C UR R E NT (A ) 8.4 7.5 2. 5 2.5 B A T T E R Y C UR R E NT (A ) B A T T E R Y V O L T A G E (V ) 8.5 2 Cells Charge Current vs. Battery Voltage B A T T E R Y V O L T A G E (V ) 2 Cells Battery Charge Curve 1.5 High Temp On 1.5 1 1 High Temp Off 0.5 0 0 0.5 0.5 2 4 6 8 10 12 B ATTER Y V OL TAGE(V ) MP2612 Rev. 1.0 9/7/2011 14 0 0 8 12 16 20 VIN(V) 24 28 0 0.5 1 1.5 2 2.5 ISYS(A) www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 6 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN=19V, C1=4.7μF, C2=22μF, L=4.7μH, RS1=100mΩ, Real Battery Load, TA=25ºC, unless otherwise noted. Efficiency vs. ICHG Efficiency vs. ICHG Efficiency vs. VIN 2 Cells, VBATT=8.4V 3 Cells, VBATT=12.6V 2 Cells, VBATT=7.4V 100 90 VIN=19V VIN=24V 80 VIN=15V VIN=15V EFFICIENCY (%) EFFICIENCY (%) VIN=12V 70 60 92 90 VIN=24V 80 70 0.4 0.8 1.2 1.6 2 89 86 83 80 60 0 0 0.4 0.8 ICHG(A) 1.2 1.6 5 2 2 Cells 8.4 8.4 2 8.2 8.1 VBATT (V) 2.2 VBATT (V) 8.5 8.3 8.3 8.2 18 23 28 8 -20 25 2 Cells, VBATT=7.4V 1.8 1.6 1.4 8.1 8 20 Charge Current vs. Temperature 8.5 13 15 VIN(V) BATT Float Voltage vs. Temperature 2 Cells 8 10 ICHG(A) BATT Float Voltage vs. VIN VBATT (V) 95 VIN=19V EFFICIENCY (%) 100 0 20 40 60 80 1.2 -20 0 20 40 60 80 VIN(V) MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 7 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN=19V, C1=4.7μF, C2=22μF, L=4.7μH, RS1=100mΩ, Real Battery Load, TA=25ºC, unless otherwise noted. VIN 10V/div. VBATT 5V/div. Steady State Waveform Steady State Waveform Steady State Waveform Trickle Charge 2 Cells, VBATT=5V CC Charge 2 Cells, VBATT=7.4V CV Charge 2 Cells, VBATT=8.4V VIN 10V/div. VBATT 5V/div. VIN 10V/div. VBATT 5V/div. VSW 10V/div. VSW 10V/div. VSW 10V/div. IBATT 500mA/div. IBATT 200mA/div. IBATT 1A/div. Power On Waveform Power Off Waveform EN On Waveform 2 Cells, ICHG=2A,VBATT=8V 2 Cells, ICHG=2A,VBATT=8V 2 Cells, ICHG=2A,VBATT=8V VEN 5V/div. VIN 10V/div. VIN 10V/div. VBATT 5V/div. VBATT 5V/div. VBATT 5V/div. VSW 10V/div. VSW 10V/div. VSW 10V/div. IBATT 2A/div. IBATT 2A/div. IBATT 2A/div. EN Off Waveform NTC Control, Timer Out 2 Cells, ICHG=2A,VBATT=8V VBATT=7.4V 2 Cells, VBATT=7.4V, CTMR=1nF VEN 5V/div. VNTC 2V/div. VBATT 5V/div. VBATT 5V/div. VBATT 5V/div. VSW 10V/div. VSW 10V/div. VTMR 500mV/div. IBATT 2A/div. IBATT 2A/div. MP2612 Rev. 1.0 9/7/2011 VIN 10V/div. IBATT 2A/div. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 8 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN=19V, C1=4.7μF, C2=22μF, L=4.7μH, RS1=110mΩ, RS2=20mΩ, Real Battery Load, TA=25ºC, unless otherwise noted. Power Path Management Current Sharing Power Path Management Steady State 2 Cells, ICHG=2A, VBATT=7.4V VIN 10V/div. VBATT 5V/div. ISYS 1A/div. IBATT 1A/div. 2 Cells, ICHG=2A, VBATT=8V, ISYS=0.8A VIN 10V/div. VSW 10V/div. ISYS 500mA/div. IBATT 1A/div. VIN 10V/div. VBATT 5V/div. IBATT 1A/div. VSYS 5V/div. VIN 10V/div. VBATT 5V/div. IBATT 1A/div. VSYS 5V/div. MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 9 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER PIN FUNCTIONS Pin # 1 2 3 4 5 6 Name Description Thermistor Input. Connect a resistor from this pin to the pin VREF33 and the Thermistor from this pin to ground. Valid Input Supply Indicator. A logic LOW on this pin indicates the presence of a valid input ACOK supply. Charging Completion Indicator. A logic LOW indicates charging operation. The pin will CHGOK become an open drain once the charging is complete. Internal linear regulator 3.3V reference output. Bypass to GND with a 1μF ceramic VREF33 capacitor. NTC VREF25 Internal linear 2.5V reference circuit. PLEASE KEEP THIS PIN FLOATING. EN On/Off Control Input. 8 Command Input for the number of Li-Ion Cells. Connect this pin to VREF33 for 3-cell operation or ground the pin for 2-cell operation. DO NOT LEAVE THIS PIN FLOAT. COMPV V-LOOP Compensation. Decouple this pin with a capacitor and a resistor. 9 COMPI I-LOOP Compensation. Decouple this pin with a capacitor and a resistor. 7 CELLS 10 BATT 11 CSP Positive Battery Terminal. Battery Current Sense Positive Input. Connect a resistor RSEN between CSP and BATT. The 200mV full charge current is: ICHG A . RS1mΩ 12 GND Ground. This pin is the voltage reference for the regulated output voltage. For this reason care must be taken in its layout. This node should be placed outside of the switching diode (D2) to the input ground path to prevent switching current spikes from inducing voltage noise into the part. 13 TMR Set time constant. 0.1uA current charges and discharges the external cap. 14 BST 15 SW 16 IN MP2612 Rev. 1.0 9/7/2011 Bootstrap. This capacitor is needed to drive the power switch’s gate above the supply voltage. It is connected between SW and BS pins to form a floating supply across the power switch driver. Switch Output. Supply Voltage. The MP2612 operates from a 9V to 24V unregulated input to charge 2~3 cell li-ion battery. Capacitor is needed to prevent large voltage spikes from appearing at the input. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 10 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER BLOCK DIAGRAM Figure 3—Function Block Diagram MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 11 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER OPERATION The MP2612 is a peak current mode controlled switching charger for use with Li-Ion batteries. Figure 3 shows the block diagram. At the beginning of a cycle, M1 is off. The COMP voltage is higher than the current sense result from amplifier A1’s output and the PWM comparator’s output is low. The rising edge of the 600 kHz CLK signal sets the RS Flip-Flop. Its output turns on M1 thus connecting the SW pin and inductor to the input supply. The increasing inductor current is sensed and amplified by the Current Sense Amplifier A1. Ramp compensation is summed to the output of A1 and compared to COMP by the PWM comparator. When the sum of A1’s output and the Slope Compensation signal exceeds the COMP voltage, the RS Flip-Flop is reset and M1 is turned off. The external switching diode D2 then conducts the inductor current. If the sum of A1’s output and the Slope Compensation signal does not exceed the COMP voltage, then the falling edge of the CLK resets the Flip-Flop. The MP2612 have two internal linear regulators power internal circuit, VREF33 and VREF25. The output of 3.3V reference voltage can also power external circuitry as long as the maximum current (50mA) is not exceeded. A 1μF bypass capacitor is required from VREF33 to GND to ensure stability. The output of 2.5V reference voltage can not carry any load. In typical application, VREF25 should be float and no capacitor is required. It can only connect to a capacitor which is smaller than 100pF. Charge Cycle (Mode change: Trickle CC CV) The battery current is sensed via RS1 (Figure 3) and amplified by A2. The charge will start in “trickle charging mode” (10% of the RSEN programmed current ICC) until the battery voltage reaches 2.8V/cell. If the charge stays in the “trickle charging mode” till “timer out” condition is triggered, the charge is terminated. Otherwise, the output of A2 is then regulated to the level set by RS1. The charger is operating at “constant MP2612 Rev. 1.0 9/7/2011 current charging mode.” The duty cycle of the switcher is determined by the COMPI voltage that is regulated by the amplifier GMI. When the battery voltage reaches the “constant voltage mode” threshold, the amplifier GMV will regulate the COMP pin, and then the duty cycle. The charger will then operate in “constant voltage mode.” Automatic Recharge A programmable time delay after the battery charging current drops below the termination threshold, the charger will cease charging and the CHGOK pin becomes an open drain. If for some reason, the battery voltage is lowered to 4.0V/Cell, recharge will automatically kick in. Termination Delay 1min C TMR 0.1uF Charger Status Indication MP2612 has two open-drain status outputs: CHGOK and ACOK . The ACOK pin pulls low when an input voltage is greater than battery voltage 300mV and over the under voltage lockout threshold. CHGOK is used to indicate the status of the charge cycle. Table 1 describes the status of the charge cycle based on the CHGOK and ACOK outputs. Table 1―Charging Status Indication ACOK low low CHGOK low high high high Charger status In charging End of charge, Vin<UVLO, timer out, thermal shutdown EN disable Timer Operation MP2612 uses internal timer to terminate the charge if the timer times out. The timer duration is programmed by an external capacitor at the TMR pin. The trickle mode charge time is: www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 12 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER TTICKLE_TMR 30mins CTMR 0.1uF The total charge time is: CTMR 0.1uF Coefficient TTOTAL_TMR 3hours Negative Thermal (NTC) Thermistor The MP2612 has a built-in NTC resistance window comparator, which allows MP2612 to sense the battery temperature via the thermistor packed internally in the battery pack to ensure a safe operating environment of the battery. A resistor with appropriate value should be connected from VREF33 to NTC pin and the thermistor is connected from NTC pin to GND. The voltage on NTC pin is determined by the resistor divider whose divide ratio depends on the battery temperature. When the voltage of pin NTC falls out of NTC window range, MP2612 will stop the charging. The charger will restart if the temperature goes back into NTC window range. MP2612 Rev. 1.0 9/7/2011 Power Path Management Using MP8110 together with MP2612 can implement a switching charger circuit with power path management function, which realizes the current sharing of the charger and system load (Figure 2). In another word, MP8110 senses the system current and feeds back to MP2612 and MP2612 reduces charge current according to the increase of the system current. However, after the charge current decrease to 0, the system current can only be limited by the adapter. The system current is satisfied first and always. It chooses the adapter as its power source when the adapter plugs in, and the battery is the backup power source when the adapter is removed. Figure 4 to 8 shows the charge profile, operation waveform and flow chart, respectively. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 13 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER CHARGE PROFILE AND POWER PATH MANAGEMENT FUNCTION Figure 4—Li-Ion Battery Charge Profile Figure 5 — Power Path Management Function- Current Sharing MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 14 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER OPERATION FLOW CHART Figure 6— Normal Charging Operation Flow Chart MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 15 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER OPERATION FLOW CHART (continued) Figure 7— Power Path Management Operation Flow Chart MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 16 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER OPERATION FLOW CHART (continued) Normal Operation Charge On, ACOK& CHGOK is low Charge Mode? VBATT=VBATT_FULL VBATT_TC<VBATT<VBATT_FULL VBATT<VBATT_TC C.V.C C.C.C T.C.C No No No Battery Full? ICHG<IBF VBATT>VBATT_FULL VBATT>VBATT_TC Yes Yes Yes Stop Charge. ACOK is low, CHGOK is high Yes No VBATT<VBATT_RECH? No No No o Timer Out ? NTC Fault? Tj>=150 C? Yes Yes Yes Charge Termination, ACOK& CHGOK are high Charge Suspend Charge Current Thermal Shutdown, ACOK& CHGOK are high No NTC OK? Tj<=130oC? Yes Yes Charger Recovery, Return to Normal Operation No Fault Protection Figure 8— Fault Protection Flow Chart MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 17 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER APPLICATION INFORMATION Setting the Charge Current 1. Standalone Switching Charger The charge current of MP2612 is set by the sense resistor RS1 (Figure1). The charge current programmable formula is as following: ICHG A 200mV RS1mΩ RS1 RGS1 RS2 RG1 RGS1/2 causes charge current sense error as it changes the sense gain of A2, which can be calculated from: (1) 2. Switching Charger with Power Path Management When MP2612 is applied together with MP8110, the charge current setting should be calibrated (Figure2). Figure 8 shows MP8110 sensing the system current and feeding back to the MP2612. (5) G A2 12.3 kΩ 2kΩ RGS kΩ (6) The charge current is set as: ICHG A 1230 G A2 RS1mΩ (7) Then the influence of RGS1 to the charge current is: ICHG A 2000 RGSΩ 10 RS1mΩ (8) To decrease the power loss of the sensing circuit, choose RS2 as small as possible, 20m is recommended. Too small RG1 results in too big current sense error of MP8110, 50Ω is at least. Substitute these two values into equation (5), then the calibrated charge current set formula in power path application is got from equation (8): ICHG A 2000 2.5 RS1mΩ 10 RS1mΩ (9) Following table is the calculated RS1 and RGS1 value for setting different charge current. Figure 8— System Current Sensing Circuit The gain of MP8110 is set as: Gain RGS1 RG1 (2) The voltage of OUT1 pin, VOUT1 can be calculated from: I RS2 RGS1 VOUT1 ISYS RS2 Gain SYS (3) RG1 Table2—ICHG Set in Power Path Application ICHG(A) 2 1.5 1 0.8 0.5 RGS(Ω) 280 402 665 909 2k RS1(mΩ) 110 160 260 360 800 If choose different RS2 and RG1, re-calculated from equation (5) and equation (8), then get the different equation (9) and the table. When the system current increased ΔISYS, to satisfy the charge current decreased ΔISYS accordingly, the relationship should be: ΔIBAT ΔVOUT1 ΔISYS RS2 RGS1 RS1 RS1 RG1 (4) BecauseΔISYS=ΔIBATT, we can get: MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 18 MP2612 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER Also, any relationship between ΔISYS and ΔIBATT can be realized by re-calculate equation (4),(5) and (8). Selecting the Inductor A 1µH to 10µH inductor is recommended for most applications. The inductance value can be derived from the following equation. L VOUT (VIN VOUT ) VIN IL fOSC According to equation (12) and equation (13), we can find that R3 = 9.63k and R6 = 505k. To be simple in project, making R3=10k and R6 no connect will approximately meet the specification. VREF33 (10) Where ΔIL is the inductor ripple current. VOUT is the 2/3 cell battery voltage. Choose inductor current to be approximately 30% if the maximum charge current, 2A. The maximum inductor peak current is: IL(MAX) ICHG IL 2 (11) Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. For optimized efficiency, the inductor DC resistance is recommended to be less than 200mΩ. NTC Function As Figure 9 shows, the low temperature threshold and high temperature threshold are preset internally via a resistive divider, which are 73%·VREF33 and 30%·VREF33. For a given NTC thermistor, we can select appropriate R3 and R6 to set the NTC window. In detail, for the thermistor (NCP18XH103) noted in above electrical characteristic, At 0ºC, RNTC_Cold = 27.445k; At 50ºC, RNTC_Hot = 4.1601k. Assume that the NTC window is between 0ºC and 50ºC, the following equations could be derived: R6//R NTC_Cold R3 R6//R NTC_Cold R6//R NTC_Hot R3 R6//R NTC_Hot MP2612 Rev. 1.0 9/7/2011 VTH_Low VREF33 VTH_High VREF33 73% (12) 30% (13) Low Temp Threshold R3 NTC R6 VTH_Low RNTC High Temp Threshold VTH_High Figure 9— NTC function block Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input and also the switching noise from the device. The input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current passing to the input. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 4.7µF capacitor is sufficient. Selecting the Output Capacitor The output capacitor keeps output voltage ripple small and ensures regulation loop stability. The output capacitor impedance should be low at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended. PC Board Layout The high frequency and high current paths (GND, IN and SW) should be placed to the device with short, direct and wide traces. The input capacitor needs to be as close as possible to the IN and GND pins. The external feedback resistors should be placed next to the FB pin. Keep the switching node SW short and away from the feedback network. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 19 MP2612 – 2A, 24V INPUT, 600kHz SWITCHING LI-ION BATTERY CHARGER MPS CONFIDENTIAL AND PROPRIETARY INFORMATION – INTERNAL USE ONLY PACKAGE INFORMATION QFN16 (4mm x 4mm) 3.90 4.10 2.15 2.45 0.50 0.70 PIN 1 ID MARKING 0.25 0.35 3.90 4.10 PIN 1 ID INDEX AREA 13 PIN 1 ID SEE DETAIL A 16 1 12 2.15 2.45 0.65 BSC 9 4 8 TOP VIEW 5 BOTTOM VIEW PIN 1 ID OPTION A 0.45x45º TYP. PIN 1 ID OPTION B R0.25 TYP. 0.80 1.00 0.20 REF 0.00 0.05 DETAIL A SIDE VIEW 3.80 2.30 NOTE: 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX. 4) JEDEC REFERENCE IS MO-220, VARIATION VGGC. 5) DRAWING IS NOT TO SCALE. 1.00 0.35 0.65 RECOMMENDED LAND PATTERN NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP2612 Rev. 1.0 9/7/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 20