MP2615 2A, 1- or 2- Cell Li-ion Battery Charger In 3mm x 3mm Package DESCRIPTION FEATURES The MP2615 is a high efficiency switch mode battery charger suitable for 1- or 2- cell lithiumion or lithium-Polymer applications. The MP2615 is capable of delivering 2A of charge current programmable via an accurate sense resistor over the entire input range. The MP2615 regulates the charge current and full battery voltage using two control loops to achieve high accuracy constant current (CC) charge and constant voltage (CV) charge. Constant-off-time (COT) mode control allows operation up to 99% duty cycle when the battery voltage is close to the input voltage and in order to keep charge current always at a relative high level. Battery temperature and charging status are always monitored during each charging cycle. Two status monitor output pins are provided to indicate the battery charging status and input power status. The MP2615 also features internal reverse blocking protection. 4.75V to 18V Operating Input Voltage Up to 99% Duty Cycle Operation Up to 2A Programmable Charging Current 0.75% Full Battery Voltage Accuracy 4.1V/Cell and 4.2V/Cell Selection for Full Battery Voltage Full Integrated Power Switches Internal Loop Compensation No External Reverse Blocking Diode Required Preconditioning for Fully Depleted Battery Charging Operation Indicator Programmable Safety Timer Thermal Shutdown Protection Cycle-by-Cycle Over Current Protection Battery Temperature Monitor and Protection APPLICATIONS Smart Phones Portable Hand-held Solutions Portable Media Players All MPS parts are lead-free and adhere to the RoHS directive. For MPS green status, please visit MPS website under Products, Quality Assurance page. The MP2615 is available in a 3mm x 3mm 16pin QFN package. "MPS" and "The Future of Analog IC Technology" are registered trademarks of Monolithic Power Systems, Inc. ADAM (Analog Digital Adaptive Modulation) and AAM (Advanced Asynchronous Mode) are trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION L 5V to 18V Input RS1 SW VIN R2 C4 BST CHGOK R1 ACOK C1 RNTC MP2615 CSP VCC BATT NTC TMR EN SEL R3 C3 ON OFF AGND MP2615 Rev. 1.0 1/16/2014 C2 PGND CELL 1- or 2Cell Battery CTMR www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 1 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER ORDERING INFORMATION Part Number* MP2615GQ Package QFN16 (3x3mm) Top Marking AEG * For Tape & Reel, add suffix -Z (e.g. MP2615GQ-Z); PGND BST TMR NTC ACOK PACKAGE REFERENCE 16 15 14 13 12 VIN 2 10 CSP VCC 3 9 BATT 5 6 7 8 AGND 4 N/C CHGOK EN 11 SEL 1 CELL SW ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VSW ............................................... -0.3V to 23V VIN, VACOK, VCHGOK............................................. -0.3V to 23V VBATT,VCSP.................................-0.3V to 12V VBST..................................................... VSW + 6V All Other Pins .................................. -0.3V to 6V Junction Temperature .............................. 150C Lead Temperature ................................... 260C (2) Continuous Power Dissipation (TA = +25C) ............................................................2.5W Operating Temperature............. -40C to +85C QFN16 (3x3mm) .................... 50 ...... 12 ... C/W Recommended Operating Conditions (3) VIN ................................................. 4.75V to 18V VBATT ................................................. 2V to 8.4V Operating Junction Temp. (TJ). -40C to +125C MP2615 Rev. 1.0 1/16/2014 (4) JA JC Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance JA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/JA. 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. 3) The device is not guaranteed to function outside of its operating conditions. 4) Measured on JESD51-7, 4-layer PCB. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 2 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER ELECTRICAL CHARACTERISTICS VIN = 12V, VCELL = 0V, VSEL = 0V, C1 = 22F, C2=22F, TA = 25C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units VCELL = 4V VCELL = 0V 4.5 8.75 5 12 18 18 V 3.55 3.75 3.95 V Input Voltage and Current Input Voltage VIN Under Voltage Threshold Rising Lockout VUVLO Under Voltage Lockout Threshold Hysteresis Supply Current 225 ISHDN EN = 4V, Shutdown Current 0.27 IQ EN = 0V, Quiescent Current 1.1 mV mA Power MOS High-side Resistance Low-side Resistance Switch On Switch On RH_DS(ON) Measured from VIN to SW 110 m RL_DS(ON) 110 m Switch Leakage 0 EN = 4V, VSW = 0V 1 A Frequency and Time Parameter Switching Frequency Fold-back Frequency (5) Minimum Off Time Charging Parameter Terminal Battery Voltage Battery Over Threshold Voltage Recharge Threshold at VBATT FSW TOFF VBATT_FULL VBOVP VRECH VBATT = 7.5V VBATT = 0V VBATT = 9V 760 160 200 VSEL = 0V VSEL = 4V 4.168 4.069 4.2 4.1 4.231 4.131 VCELL = 0V, VSEL=0V VCELL = 0V, VSEL=4V VCELL = 4V, VSEL=0V VCELL = 4V, VSEL=4V VSEL = 0V VSEL = 4V 8.34 8.14 4.17 4.07 8.71 8.51 4.36 4.26 4.0 3.9 150 9.08 8.88 4.54 4.44 Recharge Hysteresis Trickle Charge Threshold Voltage VTC VSEL = 0V VSEL = 4V CC Current ICC Trickle Charge Current ITC MP2615 Rev. 1.0 1/16/2014 CC Trickle RS1 = 50m V/Cell mV/Cell 3 2.91 225 Trickle Charge Hysteresis Peak Current Limit kHz kHz ns V/Cell mV/Cell 3.2 A 1.8 2.2 2 2.2 A 5% 10% 15% ICC www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 3 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER ELECTRICAL CHARACTERISTICS (continued) VIN = 12V, VCELL = 0V, VSEL = 0V, C1 = 22F, C2=22F, TA = 25C, unless otherwise noted. Parameter Symbol Condition Termination Current Threshold VIN minimum Head-room (reverse blocking) Maximum Current Sense Voltage (CSP to BATT) IBF Typ Max Units 5% 10% 15% ICC VIN - VBATT VSENSE VCC VCC 300 90 CSP, BATT Current ICSP, IBATT Charging disabled ACOK/CHGOK Open-drain VDRAIN = 0.3V Sink Current VCC Regulator Output VCC Output Voltage VCC Load Regulation EN Control Min 100 110 mV 3 A 5 4.35 mA 4.5 ILOAD=0 to 10mA EN Input Low Voltage 4.65 10 V mV 0.4 V 1.8 EN Input High Voltage IEN EN Input Current mV V EN = 4V 4 EN = 0V 0.2 A Timer Protection Trickle Charge Time tTrickle_tmr CTMR = 0.47F 30 CC/CV Charge Time NTC Protection tTotal_tmr 165 NTC Low Temp Threshold NTC Low Temp Threshold Hysteresis NTC High Temp Threshold NTC Low Temp Threshold Hysteresis Thermal Protection CTMR = 0.47F Rising 72 2 Falling 28 29.3 %VCC 30.6 RNTC=NCP18X103, 50C Falling (5) 74.6 RNTC=NCP18X103, 0C Rising Thermal Shutdown Thermal Shutdown (5) Hysteresis 73.3 Mins 2 TSHDN 150 C 20 C Reverse Leakage Blocking Battery Reverse Current Leakage ILEAKAGE VCELL = 0V VCELL = 4V 3 0.5 uA A Notes: 5) Guaranteed by design. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 4 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER PIN FUNCTIONS Package Pin # Name 1 2 SW VIN 3 VCC 4 CELL 5 SEL 6 EN N/C AGND BATT CSP 7 8 9 10 11 12 13 14 15 16 Description Switch Output Power Supply Voltage. Coarse Regulator Output. Internally generated 4.5V. Bypass with a 1F capacitor to AGND. Used to be low-side switch driver and pull-up bias voltage NTC resistive divider. Do not connect any external load at this pin. Command Input for the Number of Li-Ion Cells. Connect this pin to VCC for 1-cell application and short it to AGND or keep it floating for 2- Cell application. Input Pin for Setting Terminal Battery Voltage: SEL = Low-level or Float: VBATT = 4.2V/Cell. SEL = High-level: VBATT =4.1V/Cell. On/ Off Control Input. This pin is pulled to GND with a 1Meg internal resistor. NO CONNECT. Please leave this pin floating. Analog Ground. Positive Battery Terminal. Battery Current Sense Positive Input. Connect a resistor RS1 between CSP and BATT. Charging Completion Indicator. A logic Low indicates charging operation. The pin will CHGOK become an open drain once the charge is completed or suspended. Valid Input Supply Indicator. A logic Low on this pin indicates the presence of a valid input ACOK power supply. Thermistor Input. Connect a resistor from this pin to the pin VCC and the thermistor from NTC this pin to ground. Internal Safety Timer Control. Connect a capacitor from this node to AGND to set the timer. TMR And the timer can be disabled by connecting this pin to AGND directly. Bootstrap pin. A capacitor is needed to drive the power switch's gate above the supply BST voltage. It is connected between SW and BST pins to form a floating supply across the power switch driver. PGND Power Ground. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 5 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 5V/9V, C1=C2=22F, SEL=Float/High, CELL=Float/High, L=6.8H, RS1=50m, Battery Simulator, TA = 25C, unless otherwise noted. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 6 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V/9V, C1=C2=22F, SEL=Float/High, CELL=Float/High, L=6.8H, RS1=50m, Battery Simulator, TA = 25C, unless otherwise noted. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 7 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V/9V, C1=C2=22F, SEL=Float/High, CELL=Float/High, L=6.8H, RS1=50m, Battery Simulator, TA = 25C, unless otherwise noted. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 8 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V/9V, C1=C2=22F, SEL=Float/High, CELL=Float/High, L=6.8H, RS1=50m, Battery Simulator, TA = 25C, unless otherwise noted. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 9 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V/9V, C1=C2=22F, SEL=Float/High, CELL=Float/High, L=6.8H, RS1=50m, Battery Simulator, TA = 25C, unless otherwise noted. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 10 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER FUNCTIONAL BLOCK DIAGRAM VIN Current Sense IHS PRE_REGS EN A1 BST OSC Regulator CTRL VREF 5 bit trim M1 Current Limit Comparator S Q Drive R R M2 SW LDO COMP VCC PWM Comparator M3 Charge Current Sense BATT NTC FB cells COMPV GMV GMI COMPI 1.23V A2 0.123V or 1.23V L CSP BATT RS1 1- or 2cell battery OVP CTRL ICHG TMR SEL Timer TC/CC Charge Comparator OVP Comparator OVP 1.23V VIN ACOK Comparator Charge Control Logic Recharge Comparator CELLS FB 0.879V FB 1.171V BF Comparator VBATT+0.2V ACOK ICHG 0.123V CHGOK AGND PGND Figure 1: Functional Block Diagram MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 11 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER OPERATION The MP2615 is a peak current mode controlled switching charger for 1- or 2- cell lithium-ion and lithium-polymer battery. The MP2615 integrates both the high-side and low-side switches of the synchronous BUCK converter to provide high efficiency and save on PCB area. Charge Cycle (Mode change: TC CC CV) The MP2615 regulates the charge current (ICHG) and battery voltage (VBATT) using two control loops to achieve highly-accurate constant current (CC) charge and constant voltage (CV) charge. As shown in Figure 2, when the VBATT < VTC, the MP2615 stays in trickle-charge mode and the output of charge current loop COMPI dominates the control. The battery is charged by a tricklecharge current ITC until the battery voltage reaches VTC. If the charger stays in the tricklecharge mode till the trickle-charge timer is triggered, charging will be terminated. The MP2615 will enter constant-current charge mode once the battery voltage rises higher than VTC. In this mode the charge current will increase from ITC to ICC to fast charge the battery. When the battery voltage rises over full battery voltage VBATT_FULL, the charger enters into constant-voltage mode. In constant voltage mode, the battery voltage is regulated at VBATT_FULL precisely and the charge current will fall naturally due to the existing equivalent internal resistance of the battery. For the operation flow chart, please also refer to Figure 4. CV Charge Threshold Auto-recharge Threshold CC Charge Current ICHG VBATT CC Charge Threshold IBF Trickle Charge CC Charge CV Charge Charge Full TC Charge Current Autorecharge Figure 2: Li-ion Battery Charge Profile MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 12 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER Charge Full Termination and Auto-Recharge When the charge current drops below the termination threshold (IBF) during the CV charge phase, the charger will stop charging and the CHGOK pin becomes open drain. The timer will also be reset and turned off. Once the battery voltage decreases below the recharge threshold VRECH (4.0V/Cell while connect SEL-pin to AGND), recharging will automatically kick in and the timer restarts a new charge cycle. COT Charge Mode The MP2615 uses the floating ground method to drive the high-side MOSFET of the buck converter. During the off-time of the high-side MOSFET, the BST capacitor is recharged and the voltage across it is used as the HS-MOS gate drive. Thus a minimum off-time 200ns is required to maintain sufficient voltage at BST capacitor. When200ns minimum off-time is achieved due to large duty cycle, the MP2615 will enter COT (constant off-time) charge mode. In this mode of operation, switching frequency is slightly decreased in order to achieve 99% duty cycle. Charge Status Indication The MP2615 has two open-drain status outputs, CHGOK pin and ACOK pin. The ACOK pin goes low when the input voltage is 300mV larger than battery voltage and over the under voltage lockout threshold. Pin CHGOK is used to indicate the status of the charge cycle. Table 1 summarized the operation of both CHGOK and ACOK according to the status of charge. Table 1: Charging Status Indication ACOK Low Low High impedance MP2615 Rev. 1.0 1/16/2014 CHGOK Low High impedance High impedance Charger Status Safety Timer Operation The MP2615 has an internal safety timer to terminate charging during time out. The capacitor CTMR connected between the TMR pin and GND is used to set the internal oscillator period, TP (seconds) 0.46 CTMR (uF) (1) This timer limits the max trickle charge time to 8192 internal oscillating periods. If the charger stays in trickle charge mode for longer than the max oscillating periods, it will be terminated and the CHGOK becomes open drain to indicate the timer-out fault. If charge cycle successfully goes through trickle charge within the allowed time limit, it enters into the CC charge mode and the timer continues to count the oscillating periods. When the battery is charged full, the timer turns off and clears the counter, waiting for the autorecharge to restart. If the charge time during CC/CV mode exceeds 49152 oscillating periods and the battery full has not been qualified, the charger will be terminated and a timer-out fault is also indicated by floating the CHGOK . The charger can exit the timer-out fault state and the on-chip safety timer restarts counting when one of the following conditions occurs: The battery voltage falls below the autorecharge threshold VRECH. A power-on-reset (POR) event occurs; EN pin is toggled. The timer can be disabled by pulling TMR-pin to AGND. Thus, the trickle mode charge time is: t Trickle_tmr (minutes) 62.8 CTMR (uF) (2) In charging End of charge; NTC fault; Timer out: If connect a CTMR of 0.47uF, the trickle charge time is about 30 minutes. EN disable; The CC/CV mode charge time is: Thermal shutdown; VIN absent; VIN - VBATT < 0.3V t Total_tmr (hours) 6.28 CTMR (uF) (3) If connect a CTMR of 0.47uF, the CC/CV charge time is 2.95 hours. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 13 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER Negative Thermal Coefficient (NTC) Thermistor The NTC pin allows the MP2615 to sense the battery temperature using the Negative Thermal Coefficient (NTC) resistor available in the battery pack to ensure safe operating environment of the battery. . A resistor with appropriate value should be connected from VCC to NTC pin and the thermistor is connected from NTC pin to AGND. The voltage on the NTC-pin is determined by the resistor divider whose divide-ratio depends on the battery temperature. When the voltage at the NTC pin falls out of the NTC window range, the charging will pause until the battery temperature goes back to normal operating conditions. As a result the MP2615 will stop charging and report this condition to the status pins. Charging will automatically resume after the temperature falls back within safe range. Short Circuit Protection The MP2615 has an internal comparator to check for battery short circuit. Once VBATT falls below 2V, the device detects a battery-short status and the cycle-by-cycle peak current limit falls to about 2.2A to limit the current spike during the batteryshort transition. Furthermore, the switching frequency also folds back to minimize the power loss. Thermal Shutdown Protection To prevent the chip from overheating during charging, the MP2615 monitors the junction temperature, TJ, of the die. Once TJ reaches the thermal shutdown threshold (TSHTDWN) of 150C, the charger converter turns off. Once the TJ falls below 130C the charging will restart. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 14 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER INPUT POWER UP START UP TIMING FLOW Figure 3: Input Power Start-up Timing Diagram MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 15 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER OPERATION FLOW CHART Figure 4: Operation Flow Chart MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 16 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER APPLICATION INFORMATION COMPONENT SELECTION Charge Current Setting The constant charge current (ICC) of the MP2615 can be set by the sense resistor RS1 (see Typical Application). The equation to determine the programmable CC-charge current is expressed as following, ICC 100mV (A) RS1(m) (4) some tolerance. To optimize efficiency, chose an inductor with a DC resistance less than 50m. NTC Resistor Divider Selection Figure shows that an internal resistor divider is used to set the low temperature threshold and high temperature threshold at 73.3%*VCC and 29.3%*VCC, respectively. For a given NTC, thermistor, select appropriate RT1 and RT2 to set the NTC window. VCC To get 2A ICC, a RS1 of 50m should be selected. Accordingly, the trickle charge current (ITC) can be obtained by the following equation, ITC 10%ICC 10mV (A) RS1(m) VTH_Low NTC (5) Inductor Selection To select the right inductor, a trade off should be made between cost, size, and efficiency. An inductor of lower inductance value corresponds with smaller size, but it results in higher ripple currents, higher magnetic hysteretic losses, and higher output capacitances. Conversely, higher inductance value is beneficial to getting a lower ripple current and smaller output filter capacitors, but resulting in higher inductor DC resistance (DCR) loss. Based on practical experience, the inductor ripple current should not exceed 30% of the maximum charge current under worst cases. For the MP2615 with a typical 12V input voltage to charge a 2-cell battery, the maximum inductor current ripple occurs at the corner point between trickle charge and CC charge (VBATT = 6V). Inductance estimations are as follow: V -V V L IN BATT BATT I L_MAX VIN fS Low Temp Threshold RT1 RT2 RNTC High Temp Threshold VTH_High Figure 5: NTC Function Block The thermistor (NCP18XH103) noted above has the following electrical characteristic: At 0C, RNTC_Cold = 27.445k; At 50C, RNTC_Hot = 4.1601k. The following equations are derived assuming that the NTC window is between 0C and 50C: R T2 //R NTC_Cold VTH_Low (8) = = 73.3% R T1 + R T2 //R NTC_Cold VREF33 RT2//R NTC_Hot (6) Where VIN, VBATT, and fS are the typical input voltage, the CC charge threshold, and the switching frequency, respectively. And I L_MAX is RT1 + RT2//R NTC_Hot = VTH_High VREF33 = 29.3% (9) According to Equation (8) (9), and the required battery temperature range to calculate RT1 and RT2. the maximum inductor ripple current, which is usually 30% of the CC charge current. I L_MAX 30%ICC (7) Based on the condition where ICC = 2A, VIN = 12V, VBATT = 6V and fs = 760kHz the calculated inductance is 6.6H. The inductor saturation current must exceed 2.6A at least and have MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 17 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER Input Capacitor Selection The input capacitors C1 from the typical application circuit absorbs the maximum ripple current from the buck converter, which is given by: IRMS_MAX ICC VTC (VIN_MAX VTC ) VIN_MAX (10) For a given ICC = 2A, VTC = 6V, VIN_MAX = 18V, the maximum ripple current is 1A. Select the input capacitors so that the temperature rise due to the ripple current does not exceed 10C. Use ceramic capacitors with X5R or X7R dielectrics because of their low ESR and small temperature coefficients. For most applications, use a 22F capacitor. Output Capacitor Selection The output capacitor C2 (see the typical application circuit) is in parallel with the battery. C2 absorbs the high-frequency switching ripple current and smoothes the output voltage. Its impedance must be much less than that of the battery to ensure it absorbs the ripple current. Use a ceramic capacitor because it has lower ESR and smaller size.. The output voltage ripple is given by, VO VO VIN r O 2 VO 8CO fS L 1- (11) In order to guarantee 0.5% full battery voltage accuracy, the maximum output voltage ripple must not exceed 0.5% (e.g., 0.1%). The maximum output voltage ripple occurs at the minimum battery voltage of the CC charge and the maximum input voltage. MP2615 Rev. 1.0 1/16/2014 For VIN_MAX = 18V, VCC_MIN = VTC =6V, L = 6.8H, fS = 760kHz, rO_MAX = 0.1%, the output capacitor can be calculated as, 1CO VTC VIN_MAX 8fs2LrO_MAX 21.3F (12) We can then approximate this value and choose a 22F ceramic capacitor. PCB Layout Guide PCB layout is important to meet specified noise, efficiency and stability requirements. The following design considerations can improve circuit performance, 1) Route the power stage adjacent to the grounds. Aim to minimize the high-side switching node (SW, inductor), trace lengths in the high-current paths and the current-sense resistor trace. Keep the switching node short and away from the feedback network. 2) Connect the charge current sense resistor to CSP (pin 10), BATT (pin 9). Minimize the length and area of this circuit loop. 3) Place the input capacitor as close as possible to the VIN and PGND pins. Place the output inductor close to the IC as and connect the output capacitor between the inductor and PGND of the IC. This minimizes the current path loop area from the SW pin through the LC filter and back to the PGND pin. 4) Connect AGND and PGND at a single point. 5) Figure 6 is a PCB layout reference design. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 18 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER PGND BST TMR NTC ACOK BATT GND GND VIN CHGOK CSP BATT CELL SEL EN NC AGND SW VIN VCC Figure 6: MP2615 PCB Guild Design MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 19 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER TYPICAL APPLICATION CIRCUITS L VIN 1k SW VIN R2 BST CHGOK 1k R1 ACOK C1 22uF RNTC C3 MP2615 RS1 6.8uH C4 50m 100nF CSP VCC BATT NTC TMR EN SEL C2 22uF R3 10k 10k 1uF ON OFF AGND PGND CELL 1uF 2 Cell Battery CTMR Figure 7: Typical Application Circuit to Charge a 2 Cell Battery with 12VIN. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 20 MP2615 - 2A, 1- CELL OR 2- CELL LI-ION BATTERY CHARGER PACKAGE INFORMATION QFN16 3X3 PACKAGE OUTLINE DRAWING FOR 16L FCQFN (3X3MM) MF-PO-D-0157 revision 0.0 PIN 1 ID MARKING PIN 1 ID 0.10x45 TYP. PIN 1 ID INDEX AREA BOTTOM VIEW TOP VIEW SIDE VIEW NOTE: 0.10x45 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETERS MAX. 4) JEDEC REFERENCE IS MO-220. 5) DRAWING IS NOT TO SCALE. 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. MP2615 Rev. 1.0 1/16/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2014 MPS. All Rights Reserved. 21 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Monolithic Power Systems (MPS): MP2615GQ-P MP2615GQ-Z