EVALUATION KIT AVAILABLE MAX1870A General Description The MAX1870A step-up/step-down multichemistry battery charger charges with battery voltages above and below the adapter voltage. This highly integrated charger requires a minimum number of external components. The MAX1870A uses a proprietary step-up/ step-down control scheme that provides efficient charging. Analog inputs control charge current and voltage, and can be programmed by the host or hardwired. The MAX1870A accurately charges two to four lithiumion (Li+) series cells at greater than 4A. A programmable input current limit is included, which avoids overloading the AC adapter when supplying the load and the battery charger simultaneously. This reduces the maximum adapter current, which reduces cost. The MAX1870A provides analog outputs to monitor the current drawn from the AC adapter and charge current. A digital output indicates the presence of an AC adapter. When the adapter is removed, the MAX1870A consumes less than 1A from the battery. The MAX1870A is available in a 32-pin thin QFN (5mm x 5mm) package and is specified over the -40C to +85C extended temperature range. The MAX1870A evaluation kit (MAX1870AEVKIT) is available to help reduce design time. Applications Notebook and Subnotebook Computers Handheld Terminals Step-Up/Step-Down Li+ Battery Charger Benefits and Features Highly Flexible Input Voltage Range Works with Affordable AC Adapters * Step-Up/Step-Down Control Scheme * Input Voltage from 8V to 28V * Analog Output Indicates Adapter Current Accurately Charge Li+ or NiCd/NiMH Batteries * Battery Voltage from 0V to 17.6V * 0.5% Charge-Voltage Accuracy * 9% Charge-Current Accuracy * 8% Input Current-Limit Accuracy Tune Design to Increase Safety and Efficiency * Programmable Maximum Battery Charge Current * Analog Inputs Control-Charge Current, Charge Voltage, and Input-Current Limit 32-Pin Thin QFN (5mm x 5mm) Package Saves Space while Supporting Step-Up and Step-Down Operation Typical Operating Circuit FROM WALL ADAPTER SYSTEM LOAD CSSS DCIN VHP CSSP CSSN MAX1870A VHN DHI CELLS N ASNS IINP DBST CSIP CSIN REFIN SHDN BATT BLKP ICTL VCTL LDO PGND DLOV Ordering Information appears at end of data sheet. 19-3243; Rev 3; 8/15 P REF CLS GND MAX1870A Step-Up/Step-Down Li+ Battery Charger Absolute Maximum Ratings DCIN, CSSP, CSSS, CSSN, VHP, VHN, DHI to GND......................................-0.3V to +30V VHP, DHI to VHN ....................................................-0.3V to +6V BATT, CSIP, CSIN, BLKP to GND..........................-0.3V to +20V CSIP to CSIN, CSSP to CSSN, CSSP to CSSS, PGND to GND........................-0.3V to +0.3V CCI, CCS, CCV, REF, IINP to GND........ -0.3V to (VLDO + 0.3V) DBST to GND........................................ -0.3V to (VDLOV + 0.3V) DLOV, VCTL, ICTL, REFIN, CELLS, CLS, LDO, ASNS, SHDN to GND........................-0.3V to +6V LDO Current........................................................................50mA Continuous Power Dissipation (TA = +70C) 32-Pin Thin QFN 5mm x 5mm (derate 21mW/C above +70C)......................................1.7W Operating Temperature Range MAX1870AETJ................................................ -40C to +85C Storage Temperature Range............................. -60C to +150C Lead Temperature (soldering, 10s)................................. +300C Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Package Information 32 TQFN Package Code T3255+4 Outline Number 21-0140 Land Pattern Number 90-0012 For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. Electrical Characteristics (Circuit of Figure 2, VDCIN = VCSSP = VCSSN = VCSSS = VVHP = 18V, VBATT = VCSIP = VCSIN = VBLKP = 12V, VREFIN = 3.0V, VICTL = 0.75 x VREFIN, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, VDLOV = 5.4V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 0 3.6 V VVCTL = VLDO (2 cells) -0.5 +0.5 VVCTL = VLDO (3 cells) -0.5 +0.5 VVCTL = VLDO (4 cells) -0.5 +0.5 VVCTL = VREFIN (2 cells) -0.8 +0.8 VVCTL = VREFIN (3 cells) -0.8 +0.8 VVCTL = VREFIN (4 cells) -0.8 +0.8 VVCTL = VREFIN / 20 (2 cells) -1.2 +1.2 VVCTL = VREFIN / 20 (3 cells) -1.2 +1.2 VVCTL = VREFIN / 20 (4 cells) -1.2 +1.2 VCTL rising 4.0 0 < VVCTL < VREFIN -1 +1 DCIN = 0, VREFIN = VVCTL = 3.6V -1 +1 VCTL = DCIN = 0, VREFIN = 3.6V -1 +1 CHARGE-VOLTAGE REGULATION VCTL Range Battery Regulation Voltage Accuracy VCTL Default Threshold VCTL Input Bias Current www.maximintegrated.com 4.1 4.2 % V A Maxim Integrated 2 MAX1870A Step-Up/Step-Down Li+ Battery Charger Electrical Characteristics (continued) (Circuit of Figure 2, VDCIN = VCSSP = VCSSN = VCSSS = VVHP = 18V, VBATT = VCSIP = VCSIN = VBLKP = 12V, VREFIN = 3.0V, VICTL = 0.75 x VREFIN, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, VDLOV = 5.4V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 3.6 V CHARGE-CURRENT REGULATION ICTL Range Quick-Charge-Current Accuracy Trickle-Charge-Current Accuracy 0 VICTL = VREFIN 67 73 79 VICTL = VREFIN x 0.8 54 59 64 VICTL = VREFIN x 0.583 39 43 47 VICTL = VREFIN x 0.0625 3.0 4.5 6.0 mV 19 V BATT/CSIP/CSIN Input Voltage Range CSIP Input Current CSIN Input Current 0 DCIN = 0 0.1 2 ICTL = 0 0.1 2 ICTL = REFIN 350 600 DCIN = 0 0.1 2 ICTL = 0 0.1 2 ICTL = REFIN 0.1 2 REFIN / 55 REFIN / 32 ICTL Power-Down-Mode Threshold Voltage ICTL Input Bias Current REFIN / 100 0 < VICTL < VREFIN -1 +1 ICTL = DCIN = 0, VREFIN = 3.6V -1 +1 mV A A V A INPUT-CURRENT REGULATION Charger-Input Current-Limit Accuracy (VCSSP - VCSSN) CSSS = CSSP System-Input Current-Limit Accuracy (VCSSP - VCSSS) CSSN = CSSP CLS = REF 97 105 113 CLS = REF x 0.845 81 88 95 CLS = REF 97 105 113 CLS = REF x 0.845 81 88 95 CSSP/CSSS/CSSN Input Voltage Range CSSP Input Current CSSS/CSSN Input Current 8 VCSSP = VCSSN = VCSSS = VDCIN = 6V -1 VCSSP = VCSSN = VCSSS = VDCIN = 8V, 28V -1 +1 -1 +1 VREF / 2 VREF CLS = REF -1 IINP Transconductance VCSSP - VCSSS = 102mV, CSSN = CSSP 2.5 VCSSP - VCSSN = 200mV, VIINP = 0V 350 VCSSP - VCSSS = 200mV, VIINP = 0V 350 VCSSP - VCSSN = 200mV, IINP float 3.5 VCSSP - VCSSS = 200mV, IINP float 3.5 www.maximintegrated.com 1200 VCSSP = VCSSN = VCSSS = VDCIN = 8V, 28V CLS Input Bias Current IINP Output Voltage +1 700 VCSSP = VCSSN = VCSSS = VDCIN = 6V CLS Input Range IINP Output Current 28 2.8 mV mV V A A V +1 A 3.1 A/mV A V Maxim Integrated 3 MAX1870A Step-Up/Step-Down Li+ Battery Charger Electrical Characteristics (continued) (Circuit of Figure 2, VDCIN = VCSSP = VCSSN = VCSSS = VVHP = 18V, VBATT = VCSIP = VCSIN = VBLKP = 12V, VREFIN = 3.0V, VICTL = 0.75 x VREFIN, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, VDLOV = 5.4V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 28 V SUPPLY AND LINEAR REGULATOR DCIN Input Voltage Range DCIN Undervoltage Lockout DCIN Quiescent Current 8 DCIN falling 6.2 V 6.3 7.85 8.0V < VDCIN < 28V 3.5 6 mA 19 V BATT Input Voltage Range BATT Input Bias Current 4 DCIN rising 0 DCIN = 0 0.1 1 VBATT = 2V to 19V 300 500 5.4 5.5 V 70 150 mV 4.00 5.0 5.25 V 4.076 4.096 4.116 V 5 10 mV 3.1 3.9 V 3.6 V 2.2 V LDO Output Voltage No load LDO Load Regulation 0 < ILDO < 10mA LDO Undervoltage Lockout VDCIN = 8V, LDO rising 5.3 A REFERENCE REF Output Voltage IREF = 0A REF Load Regulation 0 < IREF < 500A REF Undervoltage-Lockout Trip Point VREF falling REFIN Input Range 2.5 REFIN UVLO Rising 1.9 REFIN UVLO Hysteresis REFIN Input Bias Current 50 VDCIN = 18V DCIN = 0, VREFIN = 3.6V 50 -1 mV 100 +1 A SWITCHING REGULATOR Cycle-by-Cycle Step-Up Maximum Current-Limit Sense Voltage VDCIN = 12V, VBATT = 16.8V 135 150 165 mV Cycle-by-Cycle Step-Down Maximum Current-Limit Sense Voltage VDCIN = 19V, VBATT = 16.8V 135 150 165 mV Step-Down On-Time VDCIN = 18V, VBATT = 16.8V 2.2 2.4 2.6 s Minimum Step-Down Off-Time VDCIN = 18V, VBATT = 16.8V 0.15 0.4 0.50 s Step-Up Off-Time VDCIN = 12V, VBATT = 16.8V 1.6 1.8 2.0 s Minimum Step-Up On-Time VDCIN = 12V, VBATT = 16.8V 0.15 0.3 0.40 s www.maximintegrated.com Maxim Integrated 4 MAX1870A Step-Up/Step-Down Li+ Battery Charger Electrical Characteristics (continued) (Circuit of Figure 2, VDCIN = VCSSP = VCSSN = VCSSS = VVHP = 18V, VBATT = VCSIP = VCSIN = VBLKP = 12V, VREFIN = 3.0V, VICTL = 0.75 x VREFIN, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, VDLOV = 5.4V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 4.5 5 5.5 V MOSFET DRIVERS VHP - VHN Output Voltage 8V < VVHP < 28V, no load VHN Load Regulation 0 < IVHN < 10mA 70 150 mV DHI On-Resistance High ISOURCE = 10mA 2 5 DHI On-Resistance Low ISINK = 10mA 1 3 DCIN = 0 0.1 1 A VDCIN = 18V 1.3 2 mA VHP Input Bias Current BLKP Input Bias Current ICTL = 0 0.1 2 VICTL = VREFIN = 3.3V 100 400 A DLOV Supply Current DBST low 5 10 A DBST On-Resistance High ISOURCE = 10mA 2 5 DBST On-Resistance Low ISINK = 10mA 1 3 ERROR AMPLIFIERS GMV Amplifier Loop Transconductance VCTL = REFIN, VBATT = 16.8V 0.05 0.1 0.20 A/mV GMI Amplifier Loop Transconductance ICTL = REFIN, VCSIP - VCSIN = 72mV 1.8 2.4 3.0 A/mV VCLS = REF, VCSSP - VCSSN = 102mV, VCSSP = VCSSS 1.2 1.7 2.2 VCLS = REF, VCSSP - VCSSS = 102mV, VCSSP = VCSSN 1.2 1.7 2.2 VCTL = REFIN, VBATT = 15.8V 50 GMS Amplifier Loop Transconductance CCV Output Current CCI Output Current CCS Output Current CCI/CCS/CCV Clamp Voltage www.maximintegrated.com A/mV VCTL = REFIN, VBATT = 17.8V ICTL = REFIN, VCSIP - VCSIN = 0mV -50 150 ICTL = REFIN, VCSIP - VCSIN = 150mV CLS = REF, VCSSP = VCSSN, VCSSP = VCSSS -150 A 100 CLS = REF, VCSSP - VCSSN = 200mV, VCSSP - VCSSS = 200mV 1.1V < VCCV < 3.5V, 1.1V < VCCS < 3.5V, 1.1V < VCCI < 3.5V A -100 100 300 500 A mV Maxim Integrated 5 MAX1870A Step-Up/Step-Down Li+ Battery Charger Electrical Characteristics (continued) (Circuit of Figure 2, VDCIN = VCSSP = VCSSN = VCSSS = VVHP = 18V, VBATT = VCSIP = VCSIN = VBLKP = 12V, VREFIN = 3.0V, VICTL = 0.75 x VREFIN, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, VDLOV = 5.4V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER CONDITIONS MIN TYP MAX UNITS LOGIC LEVELS ASNS Output-Voltage Low VIINP = GND, ISINK = 1mA ASNS Output-Voltage High VIINP = 4V, ISOURCE = 1mA ASNS Current Detect SHDN Input Bias Current SHDN Threshold VIINP rising 0.4 LDO - 0.5 1.1 Hysteresis V 1.15 -1 +1 DCIN = 0, VREFIN = 5V, VSHDN = 0 to VREFIN -1 +1 SHDN falling, VREFIN = 2.8V to 3.6V 22 23.5 40 50 CELLS = 0 to REFIN -2 A % of REFIN % of REFIN 0.75 V 60 % of REFIN REFIN 0.75V CELLS Input High Voltage www.maximintegrated.com 25 1 CELLS Float Voltage V mV VSHDN = 0 to VREFIN CELLS Input Low Voltage CELLS Input Bias Current 1.2 50 SHDN Hysteresis V V +2 A Maxim Integrated 6 MAX1870A Step-Up/Step-Down Li+ Battery Charger Electrical Characteristics (Circuit of Figure 2, VDCIN = VCSSP = VCSSN = VCSSS = VVHP = 18V, VBATT = VCSIP = VCSIN = VBLKP = 12V, VREFIN = 3.0V, VICTL = 0.75 x VREFIN, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, VDLOV = 5.4V, TA = -40C to +85C.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS 0 3.6 V VVCTL = VLDO (2 cells) -0.8 +0.8 VVCTL = VLDO (3 cells) -0.8 +0.8 VVCTL = VLDO (4 cells) -0.8 +0.8 VVCTL = VREFIN (2 cells) -1.2 +1.2 VVCTL = VREFIN (3 cells) -1.2 +1.2 VVCTL = VREFIN (4 cells) -1.2 +1.2 VVCTL = VREFIN / 20 (2 cells) -1.4 +1.4 VVCTL = VREFIN / 20 (3 cells) -1.4 +1.4 VVCTL = VREFIN / 20 (4 cells) -1.4 +1.4 VCTL rising 4.0 4.2 V 0 3.6 V VICTL = VREFIN 66 80 VICTL = VREFIN x 0.8 53 65 VICTL = VREFIN x 0.583 38 48 0 19 V 600 A REFIN / 100 REFIN / 32 V CLS = REF 95 115 CLS = REF x 0.845 79 97 CLS = REF 95 115 CLS = REF x 0.845 79 97 8 28 V 1200 A CHARGE-VOLTAGE REGULATION VCTL Range Battery Regulation Voltage Accuracy VCTL Default Threshold % CHARGE-CURRENT REGULATION ICTL Range Quick-Charge-Current Accuracy BATT/CSIP/CSIN Input Voltage Range CSIP Input Current ICTL = REFIN ICTL Power-Down-Mode Threshold Voltage mV INPUT-CURRENT REGULATION Charger-Input Current-Limit Accuracy (VCSSP - VCSSN) CSSS = CSSP System-Input Current-Limit Accuracy (VCSSP - VCSSS) CSSN = CSSP CSSP/CSSS/CSSN Input Voltage Range CSSP Input Current VCSSP = VCSSN = VCSSS = VDCIN = 8V, 28V CLS Input Range IINP Transconductance IINP Output Current IINP Output Voltage www.maximintegrated.com mV mV VREF / 2 VREF V VCSSP - VCSSS = 102mV, CSSN = CSSP 2.5 3.1 A/mV VCSSP - VCSSN = 200mV, VIINP = 0V 350 VCSSP - VCSSS = 200mV, VIINP = 0V 350 VCSSP - VCSSN = 200mV, IINP float 3.5 VCSSP - VCSSS = 200mV, IINP float 3.5 A V Maxim Integrated 7 MAX1870A Step-Up/Step-Down Li+ Battery Charger Electrical Characteristics (continued) (Circuit of Figure 2, VDCIN = VCSSP = VCSSN = VCSSS = VVHP = 18V, VBATT = VCSIP = VCSIN = VBLKP = 12V, VREFIN = 3.0V, VICTL = 0.75 x VREFIN, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, VDLOV = 5.4V, TA = -40C to +85C.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS 28 V SUPPLY AND LINEAR REGULATOR DCIN Input Voltage Range DCIN Undervoltage Lockout DCIN Quiescent Current 8 DCIN falling 4 DCIN rising 7.85 8.0V < VDCIN < 28V BATT Input Voltage Range 0 V 6 mA 19 V BATT Input Bias Current VBATT = 2V to 19V 500 A LDO Output Voltage No load 5.3 5.5 V LDO Undervoltage Lockout VDCIN = 8V, LDO rising 4.00 5.25 V REF Output Voltage IREF = 0A 4.060 4.132 V REF Load Regulation 0 < IREF < 500A 10 mV REF Undervoltage-Lockout Trip Point VREF falling 3.9 V 3.6 V 2.2 V 100 A REFERENCE REFIN Input Range 2.5 REFIN UVLO Rising REFIN Input Bias Current VDCIN = 18V SWITCHING REGULATOR Cycle-by-Cycle Step-Up Maximum Current-Limit Sense Voltage VDCIN = 12V, VBATT = 16.8V 130 170 mV Cycle-by-Cycle Step-Down Maximum Current-Limit Sense Voltage VDCIN = 19V, VBATT = 16.8V 130 170 mV Step-Down On-Time VDCIN = 18V, VBATT = 16.8V 2.2 2.6 s Minimum Step-Down Off-Time VDCIN = 18V, VBATT = 16.8V 0.15 0.50 s Step-Up Off-Time VDCIN = 12V, VBATT = 16.8V 1.6 2.0 s Minimum Step-Up On-Time VDCIN = 12V, VBATT = 16.8V 0.15 0.40 s VHP - VHN Output Voltage 8V < VVHP < 28V, no load 4.5 5.5 V VHN Load Regulation 0 < IVHN < 10mA 150 mV DHI On-Resistance High ISOURCE = 10mA 5 DHI On-Resistance Low ISINK = 10mA 3 VHP Input Bias Current VDCIN = 18V 2 mA BLKP Input Bias Current VICTL = VREFIN = 3.3V 400 A DLOV Supply Current DBST low 10 A DBST On-Resistance High ISOURCE = 10mA 5 DBST On-Resistance Low ISINK = 10mA 3 MOSFET DRIVERS www.maximintegrated.com Maxim Integrated 8 MAX1870A Step-Up/Step-Down Li+ Battery Charger Electrical Characteristics (continued) (Circuit of Figure 2, VDCIN = VCSSP = VCSSN = VCSSS = VVHP = 18V, VBATT = VCSIP = VCSIN = VBLKP = 12V, VREFIN = 3.0V, VICTL = 0.75 x VREFIN, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, VDLOV = 5.4V, TA = -40C to +85C.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS ERROR AMPLIFIERS GMV Amplifier Loop Transconductance VCTL = REFIN, VBATT = 16.8V 0.05 0.20 A/mV GMI Amplifier Loop Transconductance ICTL = REFIN, VCSIP - VCSIN = 72mV 1.8 3.0 A/mV VCLS = REF, VCSSP - VCSSN = 102mV, VCSSP = VCSSS 1.2 2.2 VCLS = REF, VCSSP - VCSSS = 102mV, VCSSP = VCSSN 1.2 2.2 VCTL = REFIN, VBATT = 15.8V 50 GMS Amplifier Loop Transconductance CCV Output Current CCI Output Current CCS Output Current CCI/CCS/CCV Clamp Voltage VCTL = REFIN, VBATT = 17.8V ICTL = REFIN, VCSIP - VCSIN = 0mV -50 150 ICTL = REFIN, VCSIP - VCSIN = 150mV CLS = REF, VCSSP = VCSSN, VCSSP = VCSSS -150 A A 100 CLS = REF, VCSSP - VCSSN = 200mV, VCSSP - VCSSS = 200mV 1.1V < VCCV < 3.5V, 1.1V < VCCS < 3.5V, 1.1V < VCCI < 3.5V A/mV -100 100 A 500 mV 0.4 V LOGIC LEVELS ASNS Output-Voltage Low VIINP = GND, ISINK = 1mA ASNS Output-Voltage High VIINP = 4V, ISOURCE = 1mA ASNS Current Detect VIINP rising 1.1 SHDN Threshold SHDN falling, VREFIN = 2.8V to 3.6V 22 LDO 0.5 CELLS Input Low Voltage CELLS Float Voltage CELLS Input High Voltage 40 REFIN -0.75V V 1.15 1.2 V 25 % of REFIN 0.75 V 60 % of REFIN V Note 1: Specifications to -40C are guaranteed by design, not production tested. www.maximintegrated.com Maxim Integrated 9 MAX1870A Step-Up/Step-Down Li+ Battery Charger Typical Operating Characteristics (Circuit of Figure 1, VDCIN = 16V, CELLS = REFIN, VCLS = VREF, VICTL = VREFIN = 3.3V, TA = +25C, unless otherwise noted.) BATTERY INSERTION AND REMOVAL ICHARGE 5A/div 0 CCV CCI CCI 4V CCI AND CCV 2V CCV 0 2.00ms/div MAX1870Atoc03 SYSTEM LOAD-TRANSIENT RESPONSE STEP-DOWN MODE 200s STEP-DOWN MODE MAX1870Atoc05 CHARGE-CURRENT STEP RESPONSE 5A SYSTEM LOAD 0A 4A RCV = 10k, COUT = 22F 20V RCV = 10k, COUT = 44F 19V VBATT 18V RCV = 20k, COUT = 44F 17V 16V 10.0s/div SYSTEM LOAD-TRANSIENT RESPONSE HYBRID MODE 5A SYSTEM LOAD 0A 4A 2A INDUCTOR CURRENT 0A 5A INPUT CURRENT 0A 5A INPUT CURRENT 0A 2A BATTERY CURRENT 0A 2A BATTERY CURRENT 0A 5V VICTL 0V 2A INDUCTOR CURRENT 0A 100s CHARGE-CURRENT STEP RESPONSE HYBRID MODE 2A BATTERY CURRENT 0A www.maximintegrated.com 21V 2A INDUCTOR CURRENT 0A 1V CCI 0V 400s MAX1870Atoc02 18V VBATT 16V MAX1870Atoc04 20V MAX1870Atoc06 BATTERY REMOVAL MAX1870Atoc01 BATTERY INSERTION BATTERY-REMOVAL RESPONSE 5V VICTL 0V 2A INDUCTOR CURRENT 0A 1V CCI 0V 2A BATTERY CURRENT 0A 400s Maxim Integrated 10 MAX1870A Step-Up/Step-Down Li+ Battery Charger Typical Operating Characteristics (continued) (Circuit of Figure 1, VDCIN = 16V, CELLS = REFIN, VCLS = VREF, VICTL = VREFIN = 3.3V, TA = +25C, unless otherwise noted.) VIN = 16V 80 75 70 VBATT = 8.4V 80 75 70 65 65 60 60 2 4 6 8 10 12 14 16 18 0.1 VBATT = 8.4V 0 VBATT = 16.8V -0.1 -0.2 -0.3 -0.4 0 0.5 1.0 1.5 2.0 -0.5 2.5 0 0.5 1.0 1.5 2.0 CHARGE-CURRENT ERROR vs. ICTL CHARGE-CURRENT ERROR vs. BATTERY VOLTAGE MAX1870Atoc11 10 0 -10 -20 -30 -40 -50 -60 15 CHARGE-CURRENT ERROR (%) 0.05 CHARGE-CURRENT ERROR (mA) 0.10 20 1.00 0 3.00 0 0.50 1.00 1.50 2.00 2.50 ICHG = 2.4A 5 0 ICHG = 1.4A -10 -15 3.00 ICHG = 1.9A -5 5 0 10 15 VICTL (V) VBATT (V) IINP ERROR vs. SYSTEM LOAD INPUT CURRENT-LIMIT ERROR vs. SYSTEM CURRENT INPUT CURRENT-LIMIT ERROR vs. CLS 1 0 -1 -2 -3 -4 0.5 1.0 1.5 2.0 2.5 SYSTEM LOAD (A) www.maximintegrated.com 3.0 3.5 4.0 VBATT = 10V 6 4 2 VBATT = 8V VBATT = 6V VBATT = 14V 0 -2 -4 VBATT = 16V -6 VBATT = 12V -8 -10 0 0.5 1.0 1.5 2.0 2.5 SYSTEM CURRENT (A) 3.0 3.5 200 20 MAX1870A toc15 8 INPUT CURRENT-LIMIT ERROR (mA) 2 INPUT CURRENT-LIMIT ERROR (%) 3 10 MAX1870A toc14 VCTL (V) 4 0 -80 4.00 MAX1870Atoc13 5 2.00 ICHG = 0.15A 10 2.5 MAX1870Atoc12 BATTERY VOLTAGE ERROR vs. VCTL -70 IINP ERROR (mV) 0.2 CHARGE CURRENT (A) 0.15 -5 0.3 CHARGE CURRENT (A) 0.20 0 VBATT = 12.6V 0.4 BATTERY VOLTAGE (V) MAX1870Atoc10 0.25 BATTERY VOLTAGE ERROR (%) VBATT = 12.6V 85 BATTERY VOLTAGE ERROR IN CV MODE MAX1870A toc09 90 0.5 BATTERY VOLTAGE ERROR (%) 85 VBATT = 16.8V 95 EFFICIENCY (%) EFFICIENCY (%) MAX1870A toc07 VIN = 12V 90 EFFICIENCY vs. CHARGE CURRENT 100 MAX1870A toc08 EFFICIENCY vs. BATTERY VOLTAGE 95 150 100 50 0 -50 -100 -150 -200 -250 -300 0 1.00 2.00 3.00 4.00 5.00 VCLS (V) Maxim Integrated 11 MAX1870A Step-Up/Step-Down Li+ Battery Charger Typical Operating Characteristics (continued) (Circuit of Figure 1, VDCIN = 16V, CELLS = REFIN, VCLS = VREF, VICTL = VREFIN = 3.3V, TA = +25C, unless otherwise noted.) 4.07 4.06 4.05 4.04 500 1000 1500 2000 0.30 0.25 0.20 0.15 0 -40 -20 0 VIN = 9V 20 40 60 80 5.24 100 0 10 20 TEMPERATURE (C) 0.6 0.4 0.2 0 -0.2 30 40 50 LOAD (mA) OUTPUT VOLTAGE RIPPLE vs. BATTERY VOLTAGE LDO vs. TEMPERATURE MAX1870A toc19 LDO VOLTAGE ERROR (%) VIN = 16V 5.30 5.26 LOAD CURRENT (A) 0.8 5.32 5.28 0.10 2500 VIN = 28V 5.34 0.05 0 MAX1870A toc18 5.36 180 MAX1870Atoc20 4.03 LDO LOAD REGULATION 5.38 VLDO (V) 4.08 0.35 160 RMS OUTPUT RIPPLE (mV) VREF (V) 4.09 REFERENCE ERROR vs. TEMPERATURE 0.40 REFERENCE ERROR (%) MAX1870A toc16 4.10 0.45 MAX1870Atoc17 REF LOAD REGULATION 4.11 140 120 100 80 60 40 20 -0.4 -40 -20 0 20 40 60 TEMPERATURE (C) www.maximintegrated.com 80 100 0 0 5 10 15 20 VBATT (V) Maxim Integrated 12 MAX1870A Step-Up/Step-Down Li+ Battery Charger Typical Operating Characteristics (continued) (Circuit of Figure 1, VDCIN = 16V, CELLS = REFIN, VCLS = VREF, VICTL = VREFIN = 3.3V, TA = +25C, unless otherwise noted.) 2.00s MAX1870Atoc23 STEP-UP SWITCHING WAVEFORM VIN = 12V VBATT = 16V 10V D4 CATHODE 0V MAX1870Atoc22 VIN = 16V VBATT = 16V 20V STEP-DOWN SWITCHING WAVEFORM VIN = 16V VBATT = 12V 4A INDUCTOR CURRENT 2A 4A INDUCTOR CURRENT 2A VBATT (AC-COUPLED) 200mV/div VBATT (AC-COUPLED) 10mV/div 20V 10V D4 CATHODE 0V 4A INDUCTOR CURRENT 2A www.maximintegrated.com 10V D4 CATHODE 0V 10V D3 ANODE 0V 2.00s STEP-UP/STEP-DOWN LIGHT LOAD VIN = 16V VBATT = 16V 10V D3 ANODE 0V 2.00s 20V 10V D3 ANODE 0V MAX1870Atoc24 MAX1870Atoc21 STEP-UP/STEP-DOWN SWITCHING WAVEFORM VBATT (AC-COUPLED) 50mV/div 20V 10V D4 CATHODE 0V 10V D3 ANODE 0V CHARGE CURRENT = 300mA 2.00s 4A INDUCTOR CURRENT 2A VBATT (AC-COUPLED) 50mV/div Maxim Integrated 13 MAX1870A Step-Up/Step-Down Li+ Battery Charger Pin Configuration I.C. PGND DBST I.C. I.C. BLKP CSIP CSIN 24 23 22 21 20 19 18 17 TOP VIEW DLOV 25 16 BATT VHN 26 15 SHDN DHI 27 14 IINP VHP 28 13 CELLS CSSN 29 12 ICTL CSSS 30 11 VCTL CSSP 31 10 ASNS DCIN 32 9 REFIN 1 2 3 4 5 6 7 8 LDO REF CLS GND CCV CCI CCS GND + MAX1870A 32 TQFN (5mm x 5mm) Pin Description PIN NAME 1 LDO Device Power Supply. Output of the 5.4V linear regulator supplied from DCIN. Bypass LDO to GND with a 1F or greater ceramic capacitor. 2 REF 4.096V Voltage Reference. Bypass REF to GND with a 1F or greater ceramic capacitor. 3 CLS Source Current-Limit Input. Voltage input for setting the current limit of the input source. See the Setting the Input Current Limit section. 4, 8 GND Analog Ground 5 CCV Voltage Regulation Loop Compensation Point. Connect a 10k resistor in series with a 0.01F capacitor to GND. 6 CCI Charge-Current Regulation Loop Compensation Point. Connect a 0.01F capacitor to GND. 7 CCS Input-Current Regulation Loop Compensation Point. Connect a 0.01F capacitor to GND. 9 REFIN Reference Input. ICTL and VCTL are ratiometric with respect to REFIN for increased accuracy. 10 ASNS Adapter Sense Output. Logic output is high when input current is greater than 1.5A (using 30m sense resistors and a 10k resistor from IINP to GND). 11 VCTL Charge-Voltage Control Input. Drive VCTL from 0 to VREFIN to adjust the charge voltage from 4V to 4.4V per cell. See the Setting the Charge Voltage section. 12 ICTL Charge-Current Control Input. Drive ICTL from VREFIN / 32 to VREFIN to adjust the charge current. See the Setting the Charge Current section. Drive ICTL to GND to disable charging. www.maximintegrated.com FUNCTION Maxim Integrated 14 MAX1870A Step-Up/Step-Down Li+ Battery Charger Pin Description (continued) PIN NAME FUNCTION 13 CELLS 14 IINP 15 SHDN Shutdown Comparator Input. Pull SHDN low to stop charging. Optionally connect a thermistor to stop charging when the battery temperature is too hot. 16 BATT Battery-Voltage Feedback Input 17 CSIN Charge Current-Sense Negative Input 18 CSIP Charge Current-Sense Positive Input. Connect a current-sense resistor from CSIP to CSIN. Connect a 2.2F capacitor from CSIP to GND. 19 BLKP Power Connection for Current-Sense Amplifier. Connect BLKP to BATT. 20, 21 I.C. 22 DBST Step-Up Power MOSFET (NMOS) Gate-Driver Output 23 PGND Power Ground Cell-Count Selection Input. Connect CELLS to GND for two Li+ cells. Float CELLS for three Li+ cells, or connect CELLS to REFIN for four Li+ cells. Input-Current Monitor Output. IINP is a replica of the input current sensed by the MAX1870. It represents the sum of the current consumed by the charger and the current consumed by the system. IINP has a transconductance of 2.8A/mV. Internally Connected. Do not connect this pin. 24 I.C. 25 DLOV 26 VHN Power Connection for the High-Side MOSFET Driver. Bypass VHP to VHN with a 1F or greater ceramic capacitor. 27 DHI High-Side Power MOSFET (PMOS) Driver Output. Connect to the gate of the high-side step-down MOSFET. 28 VHP Power Connection for the High-Side MOSFET Driver. Bypass VHP to VHN with a 1F or greater ceramic capacitor. 29 CSSN Negative Terminal for Current-Sense Resistor for Charger Current. Connect a 2.2F capacitor from CSSN to GND. 30 CSSS Negative Terminal for Current-Sense Resistor for System Load Current 31 CSSP Positive Terminal for Input Current-Sense Resistors. Connect a current-sense resistor from CSSP to CSSN. Connect an equivalent sense resistor from CSSP to CSSS. 32 DCIN DC Supply Voltage Input. Bypass DCIN with a 1F or greater ceramic capacitor to power ground. -- Paddle www.maximintegrated.com Internally Connected. Do not connect this pin. Low-Side Driver Supply. Bypass DLOV with a 1F capacitor to GND. Paddle. Connect to GND. Maxim Integrated 15 MAX1870A Step-Up/Step-Down Li+ Battery Charger OPTIONAL REVERSEADAPTER PROTECTION D2 + AC ADAPTER C8 22F D1 - 30 32 C5 1F C7 1F 28 VHP CSSS VHN DCIN CSSP 26 RS1a 30m 31 2 C1 1F REF R3 DHI 3 6 7 C3 0.01F HOST 12 D/A OUTPUT 13 HI-IMPEDANCE OUTPUT 15 LOGIC OUTPUT 14 A/D INPUT R7 10k L1 10H D4 CCV DBST M2 22 N D3 CCI CCS CSIP 18 RS2 30m 11 D/A OUTPUT P 2.2F 10 DIGITAL INPUT GND C4 0.01F 9 VDD M1 27 MAX1870A 5 R5 10k 29 CLS R4 C2 0.01F CSSN SYSTEM LOAD RS1b 30m 2.2F C6 0.01F CSIN REFIN ASNS BATT VCTL BLKP ICTL 17 16 C9 44F 19 CELLS SHDN DLOV IINP LDO GND 4 PGND 23 25 1 R6 33 C11 1F C12 1F Figure 1. C-Controlled Typical Application Circuit www.maximintegrated.com Maxim Integrated 16 MAX1870A Step-Up/Step-Down Li+ Battery Charger OPTIONAL REVERSEADAPTER PROTECTION OPTIONAL D2 + AC ADAPTER C8 22F D1 32 C5 1F CSSS VHP DCIN VHN CSSP 13 2 C1 1F 28 30 R3 SHORT 3 26 C7 1F RS1a 30m 31 2.2F CELLS REF CSSN CLS DHI 29 M1 27 R4 OPEN 9 R9 OPEN R1 SHORT 15 11 12 LDO R10 OPEN DBST VCTL CSIP ICTL CSIN ASNS BATT 14 R7 10k C6 0.01F 5 IINP BLKP CCV DLOV R5 10k C2 0.01F L1 10H REFIN LDO C3 0.01F CCI 6 CCS 7 C4 0.01F GND 4 PGND 23 M2 22 N D3 18 2.2F R12 OPEN 10 P D4 MAX1870A SHDN SYSTEM LOAD RS1b 30m RS2 30m 17 16 C9 44F 19 25 1 R6 33 C11 1F C12 1F Figure 2. Stand-Alone Typical Application Circuit www.maximintegrated.com Maxim Integrated 17 MAX1870A Detailed Description The MAX1870A includes all of the functions necessary to charge Li+, NiMH, and NiCd batteries. A high-efficiency H-bridge topology DC-DC converter controls charge voltage and current. A proprietary control scheme offers improved efficiency and smaller inductor size compared to conventional H-bridge controllers and operates from input voltages above and below the battery voltage. The MAX1870A includes analog control inputs to limit the AC adapter current, charge current, and battery voltage. An analog output (IINP) delivers a current proportional to the source current. The Typical Application Circuit shown in Figure 1 uses a microcontroller (C) to control the charge current or voltage, while Figure 2 shows a typical application with the charge voltage and current fixed to specific values for the application. The voltage at ICTL and the value of RS2 set the charge current. The voltage at VCTL and the CELLS inputs set the battery regulation voltage for the charger. The voltage at CLS and the value of R3 and R4 set the source current limit. The MAX1870A features a voltage-regulation loop (CCV) and two current-regulation loops (CCI and CCS). CCV is the compensation point for the battery voltage regulation loop. CCI and CCS are the compensation points for the battery charge current and supply current loops, respectively. The MAX1870A regulates the adapter current by reducing battery charge current according to system load demands. Setting the Charge Voltage The MAX1870A provides high-accuracy regulation of the charge voltage. Apply a voltage to VCTL to adjust the battery-cell voltage limit. Set VCTL to a voltage between 0 and VREFIN for a 10% adjustment of the battery cell voltage, or connect VCTL to LDO for a default setting of 4.2V per cell. The limited adjustment range reduces the sensitivity of the charge voltage to external resistor tolerances. The overall accuracy of the charge voltage is better than 1% when using 1% resistors to divide down the reference to establish VCTL. The per-cell batterytermination voltage is a function of the battery chemistry and construction. Consult the battery manufacturer to determine this voltage. Calculate battery voltage using the following equation: V VBATT NCELLS x 4V + 0.4V x VCTL = VREFIN where NCELLS is the cell count selected by CELLS. VCTL is ratiometric with respect to REFIN to improve accuracy when using resistive voltage-dividers. Connect CELLS as www.maximintegrated.com Step-Up/Step-Down Li+ Battery Charger Table 1. Cell Connections CELLS CELL COUNT GND 2 Float 3 REFIN 4 shown in Table 1 to charge two, three, or four cells. The cell count can either be hard-wired or software controlled. The internal error amplifier (GMV) maintains voltage regulation (see Figure 3 for the Functional Diagram). Connect a 10k resistor in series with a 0.01F capacitor from CCV to GND to compensate the battery voltage loop. See the Voltage Loop Compensation section for more information. Setting the Charge Current Set the maximum charge current using ICTL and the current-sense resistor RS2 connected between CSIP and CSIN. The current threshold is set by the ratio of VICTL / VREFIN. Use the following equation to program the battery charge current: ICHG = VCSIT VICTL x RS2 VREFIN where VCSIT is the full-scale charge current-sense threshold, 73mV (typ). The input range for ICTL is VREFIN / 32 to VREFIN. To shut down the MAX1870A, force ICTL below VREFIN / 100. The internal error amplifier (GMI) maintains chargecurrent regulation (see Figure 3 for the Functional Diagram). Connect a 0.01F capacitor from CCI to GND to compensate the charge-current loop. See the Charge-Current and Wall-Adapter-Current Loop Compensation section for more information. Setting the Input-Current Limit The total input current, from a wall adapter or other DC source, is a function of the system supply current and the battery charge current. The MAX1870A limits the wall adapter current by reducing the charge current when the input current exceeds the input current-limit set point. As the system supply current rises, the available charge current decreases linearly to zero in proportion to the system current. After the charge current has fallen to zero, the MAX1870A cannot further limit the wall adapter current if the system current continues to increase. Maxim Integrated 18 MAX1870A Step-Up/Step-Down Li+ Battery Charger IINP ASNS INPUT-CURRENT BLOCK CSSN CSS A = 18V/V Gm IMAX1 CURRENTSENSE AMPLIFIERS CSSP 3.6V (6.7A FOR 30m) 0.81mV (1.5A FOR 30m) A = 18V/V CSSS GMS CLS MAX1870A CCS LVC CCI 0.15V x 50mV REFIN ICTL CSIP GMI A = 18V/V CSIN CSI LVC 22.5mV (42mA ON 30m) IZX HIGHSIDE DRIVER IMAX1 STEP-UP/DOWN CURRENT-MODE STATE MACHINE CHARGE-CURRENT BLOCK (6.7A FOR 30m) 3.6V VHP IMIN VHN LEVEL SHIFT DLOV LOWSIDE DRIVER IMAX2 CHG 23% OF REFIN CCV x 400mV + 4.0V REFIN VCTL DHI DBST PGND SHDN SHUTDOWN LOGIC 4.2V ICTL GMV RDY REF BATT CELLS GND CELLSELECT LOGIC 4.096V REFERENCE 5.4V LINEAR REGULATOR 1/55 BATTERY-VOLTAGE BLOCK DCIN LDO REF REFIN Figure 3. Functional Diagram www.maximintegrated.com Maxim Integrated 19 MAX1870A The input source current is the sum of the MAX1870A quiescent current, the charger input current, and the system load current. The MAX1870A's 6mA maximum quiescent current is minimal compared to the charge and load currents. The actual wall adapter current is determined as follows: I x VBATT = IADAPTER ISYS_LOAD + CHARGE VIN x where is the efficiency of the DC-DC converter (85% to 95% typ), ISYS_LOAD is the system load current, IADAPTER is the adapter current, and ICHARGE is the charge current. Step-Up/Step-Down Li+ Battery Charger In the Typical Application Circuit, the duty cycle and AC load current affect the accuracy of VIINP (see the Typical Operating Characteristics). LDO Regulator LDO provides a 5.4V supply derived from DCIN. The lowside MOSFET driver is powered by DLOV, which must be connected to LDO as shown in Figure 1. LDO also supplies the 4.096V reference (REF) and most of the internal control circuitry. Bypass LDO to GND with a 1F or greater ceramic capacitor. Bypass DLOV to PGND with a 1F or greater ceramic capacitor. AC-Adapter Detection By controlling the input current, the current requirements of the AC wall adapter are reduced, minimizing system size and cost. Since charge current is reduced to control input current, priority is given to system loads. The MAX1870A includes a logic output, ASNS, which indicates AC adapter presence. When the system load draws more than 1.5A (for 30m sense resistors and R7 is 10k), the ASNS logic output pulls high. An internal amplifier compares the sum of (VCSSP VCSSN) and (VCSSP - VCSSS) to a scaled voltage set by the CLS input. Drive VCLS directly or set with a resistive voltage-divider between REF and GND. Connect CLS to REF for the maximum input current limit of 105mV. Sense resistors RS1a and RS1b set the maximum-allowable wall adapter current. Use the same values for RS1a, RS1b, and RS2. Calculate the maximum wall adapter current as follows: When the AC adapter is removed, the MAX1870A shuts down to a low-power state, and typically consumes less than 1A from the battery through the combined load of the CSIP, CSIN, BLKP, and BATT inputs. The charger enters this low-power state when DCIN falls below the undervoltage-lockout (UVLO) threshold of 7.5V. V V IADAPTER_MAX = CLS x CSST VREF RS1_ where VCSST is the full-scale source current-sense voltage threshold, and is 105mV (typ). The internal error amplifier (GMS) maintains input-current regulation (see Figure 3 for the Functional Diagram). Typically, connect a 0.01F capacitor from CCS to GND to compensate the source current loop (GMS). See the Charge-Current and Wall-Adapter-Current Loop Compensation section for more information. Input-Current Measurement The MAX1870A includes an input-current monitor output, IINP. IINP is a scaled-down replica of the system load current plus the input-referred charge current. The output voltage range for IINP is 0 to 3.5V. The voltage of IINP is proportional to the output current by the following equation: VIINP = IADAPTER x RS1_ x GIINP x R7 where IADAPTER is the DC current supplied by the AC adapter, GIINP is the transconductance of IINP (2.8A/mV typ), and R7 is the resistor connected between IINP and ground. www.maximintegrated.com Shutdown Alternatively, drive SHDN below 23.5% of VREFIN or drive ICTL below VREFIN / 100 to inhibit charge. This suspends switching and pulls CCI, CCS, and CCV to ground. The LDO, input current monitor, and control logic all remain active in this state. Step-Up/Step-Down DC-DC Controller The MAX1870A is a step-up/step-down DC-DC controller. The MAX1870A controls a low-side n-channel MOSFET and a high-side p-channel MOSFET to a constant output voltage with input voltage variation above, near, and below the output. The MAX1870A implements a control scheme that delivers higher efficiency with smaller components and less output ripple when compared with other step-up/step-down control algorithms. This occurs because the MAX1870A operates with lower inductor currents, as shown in Figure 4. The MAX1870A proprietary algorithm offers the following benefits: Inductor current requirements are minimized. Low inductor-saturation current requirements allow the use of physically smaller inductors. Low inductor current improves efficiency by reducing I2R losses in the MOSFETs, inductor, and sense resistors. Maxim Integrated 20 MAX1870A Step-Up/Step-Down Li+ Battery Charger Continuous output current for VIN > 1.4 x VOUT reduces output ripple. The MAX1870A uses the state machine shown in Figure 5. The controller switches between the states A, B, and C, depending on VIN and VBATT. State D provides PFM operation during light loads. Under moderate and heavy loads the MAX1870A operates in PWM. Step-Down Operation (VIN > 1.4 x VBATT) During medium and heavy loads when VIN > 1.4 x VBATT, the MAX1870A alternates between state A and state B, keeping MOSFET M2 off (Figure 5). Figure 6 shows the inductor current in step-down operation. During this mode, the MAX1870A regulates the step-down off-time. Initially, DHI switches M1 off (state A) and the inductor current ramps down with a dI/dt of VBATT / L until a target current is reached (determined by the error integrator). After the target current is reached, DHI switches M1 on (state B), and the inductor current ramps up with a dI/dt of (VIN - VBATT) / L. M1 remains on until a step-down on-time timer expires. This on-time is calculated based on the input and output voltage to maintain pseudofixed-frequency 400kHz operation. At the end of state B, another step-down off-time (state A) is initiated and the cycle repeats. The off-time is valley regulated according to the error signal. The error signal is set by the charge current or source current if either is at its limit, or the battery voltage if both charge current and source current are below their respective current limits. During light loads, when the inductor current falls to zero during state A, the controller switches to state D to reduce power consumption and avoid shuttling current in and out of the output. Step-Up Operation (VIN < 0.9 x VBATT) When VIN < 0.9 x VBATT, the MAX1870A alternates between state B and state C, keeping MOSFET M1 on. In this mode, the controller looks like a simple step-up controller. Figure 7 shows the inductor current in step-up Table 2. MAX1870A H-Bridge Controller Advantages MAX1870A H-BRIDGE CONTROLLER * * TRADITIONAL H-BRIDGE CONTROLLER * * Only 1 MOSFET switched per cycle Continuous output current in step-down mode A) CONVENTIONAL ALGORITHM 2 MOSFETs switched per cycle Always discontinuous output current (requires higher inductor currents) 2 x ICHARGE B) MAX1870A ALGORITHM SHADED REGIONS REPRESENT CHARGE DELIVERED TIME Figure 4. Inductor Current for VIN = VBATT www.maximintegrated.com Maxim Integrated 21 MAX1870A Step-Up/Step-Down Li+ Battery Charger operation. During this mode, the MAX1870A regulates the step-up on-time. Initially DBST switches M2 on (state C) and the inductor current ramps up with a dI/dt of VIN / L. After the inductor current crosses the target current (set by the error integrators), DBST switches M2 off (state B) and the inductor current ramps down with a dI/dt of (VBATT - VIN) / L. M2 remains off until a step-up off-time timer expires. This off-time is calculated based on the input and output voltage to maintain 400kHz pseudo-fixedfrequency operation. The step-up on-time is regulated by the error signal, set according to the charge current or source current if either is at its limit, or the battery voltage if both charge current and source current are below their respective current limits. Step-Up/Step-Down Operation (0.9 x VBATT < VIN < 1.4 x VBATT) The MAX1870A features a step-up/step-down mode that eliminates dropout. Figure 8 shows the inductor current in step-up/step-down operation. When VIN is within 10% of VBATT, the MAX1870A alternates through states A, B, STATE A and C, following the order A, B, C, B, A, B, C, etc., with the majority of the time spent in state B. Since more time is spent in state B, the inductor ripple current is reduced, improving efficiency. The time in state C is peak-current regulated, and the remaining time is spent in state B (Figure 8A). During this operating mode, the average inductor current is approximately 20% higher than the load current. The time in state A is valley current and the remaining time is spent in state B (Figure 8B). During this mode, the average inductor current is approximately 10% higher than the load current. Alternative algorithms require inductor currents twice as high, resulting in four times larger I2R losses and inductors typically four times larger in volume. IMIN, IMAX, CCMP, and ZCMP The MAX1870A state machine utilizes five comparators to decide which state to be in and when to switch states (Figure 3). The MAX1870A generates an error signal STATE B STEP-DOWN ON STEP-DOWN OFF VIN STATE C VIN VOUT D3 M1 STEP-DOWN PWM M2 D4 D3 M1 M2 D4 STEP-UP OFF VOUT VIN VOUT STEP-UP PWM M1 + - D3 M2 D4 STEP-UP ON STEP-DOWN PFM VIN VOUT D3 M1 M2 D2 IDLE STATE D Figure 5. MAX1870A State Machine www.maximintegrated.com Maxim Integrated 22 MAX1870A Step-Up/Step-Down Li+ Battery Charger dl VIN - VOUT = L dt dl VOUT = L dt STATE B STATE A VALLEY REGULATED OFF-TIME PRECALCULATED STEP-DOWN ON-TIME VIN > 1.4 x VBATT DUTY = VIN / VOUT Figure 6. MAX1870A Step-Down Inductor Current Waveform dl VIN - VOUT = L dt STATE B STATE C VIN > 0.9 x VBATT dl VOUT = L dt PEAK REGULATED ON-TIME PRECALCULATED OFF-TIME DUTY = 1 - VIN / VOUT Figure 7. Step-Up Inductor-Current Waveform based on the integrated error of the input current, charge current, and battery voltage. The error signal, determined by the lowest voltage clamp (LVC), sets the threshold for current-mode regulation. The following comparators are used for regulation: IMIN: The MAX1870A operates in discontinuous conduction if LVC is below 0.15V, and does not initiate another step-down on-time. In discontinuous step-up www.maximintegrated.com conduction, the peak current is set by IMIN. The peak inductor current in discontinuous step-up mode: IPK > VIMIN ACSI x RS2 where VIMIN is the IMIN comparator threshold, 0.15V, and ACSI is the charge current-sense amplifier gain, 18V/V. Maxim Integrated 23 MAX1870A Step-Up/Step-Down Li+ Battery Charger CCMP: CCMP compares the current-mode control point, LVC, to the inductor current. In step-down mode, the off-time (state A) is terminated when the inductor current falls below the current threshold set by LVC. In step-up mode, the on-time (state C) is terminated when the inductor current rises above the current threshold set by LVC. step-up mode) to the internally fixed cycle-by-cycle current limit. The current-sense voltage limit is 200mV. With RS1_ = RS2 = 30m, which corresponds to 6.7A. If the inductor current-sense voltage is greater than VIMAX (200mV), a step-up on-time is terminated or a step-down on-time is not permitted. ZCMP: The ZCMP comparator detects when the inductor current crosses zero. If the ZCMP output goes high during a step-down off-time, the MAX1870A switches to the idle state (state D) to conserve power. IMAX: The IMAX comparators provide a cycle-bycycle inductor current limit. This circuit compares the inductor current (CSI in step-down mode or CSS in MINIMUM STEP-DOWN OFF-TIME PEAK REGULATED STEP-UP ON-TIME STATE B A) STATE A STATE B STATE C MINIMUM STEP-UP ON-TIME PRECALCULATED STEP-DOWN ON-TIME PRECALCULATED STEP-UP OFF-TIME STATE B dl VBATT - VIN = L dt STATE A B) STATE C dl VIN = L dt dl VBATT = L dt STATE B VALLEY REGULATED STEP-DOWN OFF-TIME PRECALCULATED STEP-DOWN ON-TIME Figure 8. MAX1870A Step-Up/Step-Down Inductor-Current Waveform www.maximintegrated.com Maxim Integrated 24 MAX1870A Step-Up/Step-Down Li+ Battery Charger Switching Frequency The MAX1870A includes input and output-voltage feedforward to maintain pseudo-fixed-frequency (400kHz) operation. The time in state B is set according to the input voltage, output voltage, and a time constant. In step-up/ step-down mode the switching frequency is effectively cut in half to allow for both the step-up cycle and the stepdown cycle. The switching frequency is typically between 350kHz and 405kHz for VIN between 8V and 28V. See the Typical Operating Characteristics. Compensation Each of the three regulation loops (the battery voltage, the charge current, and the input current limit) are compensated separately using the CCV, CCI, and CCS pins, respectively. Compensate the voltage regulation loop with a 10k resistor in series with a 0.01F capacitor from CCV to GND. Compensate the charge current loop and source current loop with 0.01F capacitors from CCI to GND and from CCS to GND, respectively. Voltage Loop Compensation When regulating the charge voltage, the MAX1870A behaves as a current-mode step-down or step-up power supply. Since a current-mode controller regulates its output current as a function of the error signal, the duty-cycle modulator can be modeled as a GM stage (Figure 9). Results are similar in step-down, step-up, or step-up/down, with the exception of a load-dependent right-half-plane zero that occurs in step-up mode. The required compensation network is a pole-zero pair formed with CCV and RCV. CCV is chosen to be large enough that its impedance is relatively small compared to RCV at frequencies near crossover. RCV sets the gain of the error amplifier near crossover. RCV and COUT determine the crossover frequency and, therefore, the closedloop response of the system and the response time upon battery removal. RESR is the equivalent series resistance (ESR) of the charger's output capacitor (COUT). RL is the equivalent charger output load, RL = VBATT / ICHG = RBATT. The equivalent output impedance of the GMV amplifier, ROGMV, is greater than 10M. The voltage loop transconductance (GMV = ICCV / VBATT) scales inversely with the number of cells. GMV = 0.1A/mV for four cells, 0.133A/mV for three cells, and 0.2A/mV for two cells. The DC-DC converter's transconductance depends upon the charge current-sense resistor RS2: GMPWM = 1 ACSI x RS2 where ACSI = 18, and RS2 = 30m in Figure 1 and 2 so GMPWM = 1.85A/V. www.maximintegrated.com Use the following equation to calculate the loop transfer function (LTF): R x (1 + sCCV RCV ) LTF = GMPWM x OGMV x (1 + sCCV x ROGMV ) RL x GMV x (1 + sCOUT x RESR ) (1 + sCOUT x RL ) The poles and zeros of the voltage-loop transfer function are listed from lowest frequency to highest frequency in Table 3. Near crossover, CCV has much lower impedance than ROGMV. Since CCV is in parallel with ROGMV, CCV dominates the parallel impedance near crossover. Additionally, RCV has a much higher impedance than CCV and dominates the series combination of RCV and CCV, so: ROGMV x (1 + sCCV x RCV ) RCV,near crossover (1 + sCCV x ROGMV ) COUT also has a much lower impedance than RL near crossover, so the parallel impedance is mostly capacitive and: RL (1 + sCOUT x RL ) 1 sCOUT If RESR is small enough, its associated output zero has a negligible effect near crossover and the loop transfer function can be simplified as follows: BATT GMOUT RESR RL COUT CCV RCV GMV RO REF CCV Figure 9. CCV Simplified Loop Diagram Maxim Integrated 25 MAX1870A Step-Up/Step-Down Li+ Battery Charger LTF = GMPWM x RCV GMV sCOUT RCV = 2 x COUT x fCO_CV = 10k GMV x GMPWM Setting the LTF = 1 to solve for the unity-gain frequency yields: To ensure that the compensation zero adequately cancels the output pole, select fZ_CV fP_OUT. RCV fCO_CV = GMPWM x GMV 2 x COUT CCV (RL / RCV) x COUT CCV 440pF For stability, choose a crossover frequency lower than 1/10th of the switching frequency. The crossover frequency must also be below the RHP zero, calculated at maximum charge current, minimum input voltage, and maximum battery voltage. Choosing a crossover frequency of 13kHz and solving for RCV using the component values listed in Figure 1 yields: MODE = VCC (4 cells) COUT = 22F GMV = 0.1A/mV VBATT = 16.8V fCO_CV = 13kHz RL = 0.2 fOSC = 400kHz GMPWM = 1.85A/V Figure 10 shows the Bode Plot of the voltage-loop frequency response using the values calculated above. Charge-Current and Wall-Adapter-Current Loop Compensation When the MAX1870A regulates the charge current or the wall adapter current, the system stability does not depend on the output capacitance. The simplified schematic in Figure 11 describes the operation of the MAX1870A when the charge-current loop (CCI) is in control. The simplified schematic in Figure 12 describes the operation of the MAX1870A when the source-current loop (CCS) is in control. Since the output capacitor's impedance has little Table 3. Constant Voltage Loop Poles and Zeros NO. NAME 1 CCV Pole CALCULATION fP_CV = 1 2 x ROGMV CCV 1 2 x RCV CCV 2 CCV Zero fZ_CV = 3 Output Pole fP_OUT = 4 Output Zero fZ_OUT = 1 2 x RL COUT 1 2 x RESR COUT VIN 2 x L IL VIN2 = 2 x L IOUT VOUT fRHPZ = 5 RHP Zero www.maximintegrated.com DESCRIPTION Lowest Frequency Pole created by CCV and GMV's finite output resistance. Since ROGMV is very large (ROGMV > 10M), this is a low-frequency pole. Voltage-Loop Compensation Zero. If this zero is lower than the output pole, fP_OUT, then the loop transfer function approximates a single-pole response near the crossover frequency. Choose CCV to place this zero at least 1 decade below crossover to ensure adequate phase margin. Output Pole Formed with the Effective Load Resistance RL and the Output Capacitance COUT. RL influences the DC gain but does not affect the stability of the system or the crossover frequency. Output ESR Zero. This zero can keep the loop from crossing unity gain if fZ_OUT is less than the desired crossover frequency. Therefore, choose a capacitor with an ESR zero greater than the crossover frequency. Step-Up Mode RHP Zero. This zero occurs because of the initial opposing response of a step-up converter. Efforts to increase the inductor current result in an immediate decrease in current delivered, although eventually result in an increase in current delivered. This zero is dependent on charge current and may cause the system to go unstable at high currents when in step-up mode. A right-half-plane zero is detrimental to both phase and gain. To ensure stability under maximum load in step-up mode, the crossover frequency must be lower than half of fRHPZ. Maxim Integrated 26 MAX1870A Step-Up/Step-Down Li+ Battery Charger effect on the response of the current loop, only a single pole is required to compensate this loop. ACSI and ACSS are the internal gains of the current-sense amplifiers. RS2 is the charge current-sense resistor. RS1a and RS1b are the adapter current-sense resistors. ROGMI and ROGMS are the equivalent output impedance of the GMI and GMS amplifiers, which are greater than 10M. GMI is the charge-current amplifier transconductance (2.4A/mV). GMS is the adapter-current amplifier transconductance (1.7A/mV.) GMPWM is the DC-DC converter transconductance (1.85A/V). Use the following equation to calculate the loop transfer function: LTF = GMPWM x ACS _ x RS_ x GM_ ROGM_ 1 + sROGM_ x CC_ which describes a single-pole system. Since GMPWM = 1 ACS_ x RS_ This zero is inversely proportional to charge current and might cause the system to go unstable at high currents when in step-up mode. A right-half-plane zero is detrimental to both phase and gain. To also ensure stability under maximum load in step-up mode, the CCI crossover frequency must also be lower than fRHPZ. The right-halfplane zero does not affect CCS. Choosing a crossover frequency of 30kHz and using the component values listed in Figure 1 yields CCI and CCS_ > 10nF. Values for CCI / CCS greater than ten times the minimum value may slow down the current loop response excessively. Figure 13 shows the Bode Plot of the inputcurrent frequency response using the values calculated above. DHI and DBST are optimized for driving moderately-sized power MOSFETs. Use low-inductance and low-resistance traces from driver outputs to MOSFET gates. ROGM_ 1 + sROGM_ x CC_ Use the following equations to calculate the crossover frequency: = fCO_CI VIN_MIN VIN_MIN 2 = 2 x L IL 2 L IOUTMAX VOUTMAX fRHPZ_WorstCase = MOSFET Drivers the loop-transfer function simplifies to: LTF = GM_ 1/10th of the switching frequency and lower than half of the RHP zero. CCI = 10 GMI / (2 x fOSC), CCS = 10 GMS / (2 x fOSC) GMI GMS = , fCO_CS 2 CCI 2 CCS DHI typically sources 1.6A and sinks 0.8A to or from the gate of the p-channel MOSFET. DHI swings from VHP to VHN. VHN is a negative LDO that regulates with respect to VHP to provide high-side gate drive. Connect VHP to DCIN. Bypass VHN with a 1F capacitor to VHP. For stability, choose a crossover frequency lower than 80 CCV LOOP RESPONSE 0 MAGNITUDE (dB) 60 MAG 40 20 -45 PHASE ACSI -90 0 CSI CCI GMI -20 -40 RS2 GMPWM -135 1.E-01 1.E+001.E+011.E+021.E+031.E+041.E+051.E+06 CCI ROGMI REF FREQUENCY (Hz) Figure 10. CCV Loop Response www.maximintegrated.com Figure 11. CCI Simplified Loop Diagram Maxim Integrated 27 MAX1870A Step-Up/Step-Down Li+ Battery Charger LDO provides a 5.4V supply derived from DCIN and delivers over 10mA. The n-channel MOSFET driver DBST is powered by DLOV and can source 2.5A and sink 5A. Since LDO provides power to the internal analog circuitry, use an RC filter from LDO to DLOV as shown in Figure 1 to minimize noise at LDO. LDO also supplies the 4.096V reference (REF) and most of the internal control circuitry. Bypass LDO with a 1F or greater capacitor to GND. CSSP CSS CLS ACSS RS1_ CSSN/ CSSS GMS GMPWM CCS CCS Applications Information Component Selection Table 4 lists the recommended components and refers to the circuit of Figure 1. The following sections describe how to select these components. MOSFETs The MAX1870A requires one p-channel MOSFET and one n-channel MOSFET. Component substitutions are permissible as long as the on-resistance and gate charge are equal or lower and the voltage, current, and powerdissipation ratings are high enough. If using a lowerpower application, scale down the MOSFETs with lower gate charge and the MOSFET's on-resistance can be scaled up. For example, in a system designed to deliver half as much current, MOSFETs selected with twice the on-resistance and half as much gate charge ensure equal or better efficiency, and reduce size and cost. If resistive losses dominate, it can be possible to reduce the gate charge at the cost of on-resistance and still achieve a similar efficiency. Make sure that the linear regulators can drive the selected MOSFETs. The average current required to drive a given MOSFET is: ROGMS ILDO = QgM2 x fswitch IVHN = QgM1 x fswitch where fswitch is 400kHz (typ). Figure 12. CCS Simplified Loop Diagram CCI LOOP RESPONSE 100 0 0 80 60 MAG 40 -45 20 0 PHASE -20 0.1 10 MAGNITUDE (dB) MAGNITUDE (dB) 80 -40 CCS LOOP RESPONSE 100 60 MAG 40 -45 20 0 PHASE -20 1k FREQUENCY (Hz) 100k -90 -40 0.1 10 1k 100k 10M -90 FREQUENCY (Hz) Figure 13. CCI and CCS Loop Response www.maximintegrated.com Maxim Integrated 28 MAX1870A Step-Up/Step-Down Li+ Battery Charger MOSFET Power Dissipation Table 5 shows the resistive losses and switching losses in each of the MOSFETs during either step-up or stepdown operation. Table 5 provides a first-order estimate, but does not consider second-order effects such as ripple current or nonlinear gate drive. For typical applications where VBATT / 2 < VIN < 2 x VBATT, the resistive losses are primarily dissipated in M1 since M2 operates at a lower duty cycle. Switching losses are dissipated in M1 when in step-down mode and in M2 when in step-up mode. Ratio the MOSFETs so that resistive losses roughly equal switching losses when at maximum load and typical input/output conditions. The resistive loss equations are a good approximation in hybrid mode (VIN near VBATT). Both M1 and M2 switching losses apply in hybrid mode. Switching losses can become a heat problem when the maximum AC-adapter voltage is applied in step-down operation or minimum AC-adapter voltage is applied with a maximum battery voltage. This behavior occurs because of the squared term in the CV2 f switching-loss equation. Table 5 provides only an estimate and is not a substitute for breadboard evaluation. Inductor Selection Select the inductor to minimize power dissipation in the MOSFETs, inductor, and sense resistors. To optimize resistive losses and RMS inductor current, set the LIR (inductor current ripple) to 0.3. Because the maximum resistive power loss occurs at the step-up boundary of hybrid mode, select LIR for operating in this mode. Select the inductance according to the following equation: L= 2 x VIN x tmin LIR ICHG Larger inductance values can be used; however, they contribute extra resistance that can reduce efficiency. Smaller inductance values increase RMS currents and can also reduce efficiency. Saturation-Current Rating The inductor must have a saturation current rating high enough so it does not saturate at full charge, maximum output voltage, and minimum input voltage. In step-up operation, the inductor carries a higher current than in step-down operation with the same load. Calculate the inductor saturation current rating by the following equation: ISAT VOUT_MAX x ICHG_MAX + VIN_MIN VIN_MIN T x VIN_MIN x 1 - VOUT_MAX 2xL Input-Capacitor Selection The input capacitor must meet the ripple current requirement (IRMS) imposed by the switching currents. Nontantalum chemistries (ceramic, aluminum, or Table 4. Component List DESIGNATION PART SPECIFICATIONS INDUCTORS L1 Sumida CDRH104R-100 Sumida CDRH104R-7R0 Sumida CDRH104R-5R2 Sumida CDRH104R-3R8 10H, 4.4A, 35m power inductor 7H, 4.8A, 27m power inductor 5.2H, 5.5A, 22m power inductor 3.8H, 6A, 13m power inductor P-CHANNEL MOSFETs M1 Siliconix Si4435DY Fairchild FDC602P Fairchild FDS4435A Fairchild FDW256P P-FET 35m, QG = 17nC, VDSMAX = 30V, 8-pin SO P-FET 35m, QG = 14nC, VDSMAX = 20V, 6-pin SuperSOT P-FET 25m, QG = 21nC, VDSMAX = 30V, 8-pin SO P-FET 20m, QG = 28nC, VDSMAX = 30V, 8-pin TSSOP N/P-CHANNEL MOSFET PAIRS M1/M2 Fairchild FDW2520C (8-pin TSSOP) N-FET 18m, QG = 14nC, VDSMAX = 20V, P-FET 35m, QG = 14nC, VDSMAX = 20V N-CHANNEL MOSFETs M2 IRF7811W www.maximintegrated.com N-FET, 9m, QG = 18nC, VDSMAX = 30V, 8-pin SO Maxim Integrated 29 MAX1870A Step-Up/Step-Down Li+ Battery Charger Table 5. MOSFET Resistive and Switching Losses DESIGNATION STEP-DOWN MODE STEP-UP MODE DC LOSSES M1 VBATT V x ICHG 2 x RDS ( ON ) DCIN VBATT 2 x ICHG x RDS ( ON ) V DCIN D4 VBATT 1 - V x ICHG VDiode DCIN 0 M2 0 VDCIN VBATT 2 x ICHG x RDS ( ON ) 1 - V x V BATT DCIN D3 ICHG x VDIODE ICHG x VDIODE SWITCHING LOSSES M1 VDCIN( MAX ) 2 x CLX x fSW ICHG IGATE 0 D4 0 0 M2 0 VBATT ( MAX ) 3 x CLX x fSW ICHG IGATE x VDCIN( MAX ) D3 0 0 Note: CLX is the total parasitic capacitance at the drain terminals of M1 and M2. IGATE is the peak gate-drive source/sink current of M1 or M2. OS-CON) are preferred due to their resilience to powerup surge currents. The input capacitors should be sized so that the temperature rise due to ripple current in continuous conduction does not exceed approximately 10C. Choose a capacitor with a ripple current rating higher than 0.5 x ICHG. Output-Capacitor Selection The output capacitor absorbs the inductor ripple current in step-down mode, or a peak-to-peak ripple current equal to the inductor current when in step-up or hybrid mode. As such, both capacitance and ESR are important parameters in specifying the output capacitor. The actual amplitude of the ripple is the combination of the two. Ceramic devices are preferable because of their resilience to surge currents. The worst-case output ripple occurs during hybrid mode when the input voltage is at its minimum. See the Typical Operating Characteristics. Select a capacitor that can handle 0.5 x ICHG x VBATT / VIN while keeping the rise in capacitor temperature less than 10C. Also, select the output capacitor to tolerate the surge current delivered from the battery when it is initially plugged into the charger. www.maximintegrated.com Battery-Removal Response Upon battery removal, the MAX1870A continues to regulate a constant inductor current until the battery voltage, VBATT, exceeds the regulation threshold. The MAX1870A's response time depends on the bandwidth of the CCV loop, fCO (see the Voltage Loop Compensation section). For applications where battery overshoot is critical, either increase COUT or increase fCO by increasing RCV. See Battery Insertion and Removal in the Typical Operating Characteristics. System Load Transient The MAX1870A battery charger features a very fast response time to system load transients. Since the input current loop is configured as a single-pole system, the MAX1870A responds quickly to system load transients (see the System Load-Transient Response graph in the Typical Operating Characteristics). This reduces the risk of tripping the overcurrent threshold of the wall adapter and minimizes requirements for adapter oversizing. Maxim Integrated 30 MAX1870A Layout and Bypassing Bypass DCIN with a 1F to ground (Figure 1). Optional diodes D1 and D2 protect the MAX1870A when the DC power-source input is reversed. A signal diode for D1 is adequate because DCIN only powers the LDO and the internal reference. Good PC board layout is required to achieve specified noise, efficiency, and stable performance. The PC board layout artist must be given explicit instructions--preferably, a pencil sketch showing the placement of the power-switching components and high-current routing. Refer to the PC board layout in the MAX1870A evaluation kit for examples. A ground plane is essential for optimum performance. In most applications, the circuit is located on a multilayer board, and full use of the four or more copper layers is recommended. Use the top layer for high-current connections (PGND, DHI, VHP, VHN, BLKP, and DLOV), the bottom layer for quiet connections (CSSP, CSSN, CSSS, CSIP, CSIN, REF, CCV, CCI, CCS, DCIN, LDO and GND), and the inner layers for an uninterrupted ground plane. Use the following stepby-step guide: 1) Place the high-power connections first, with their grounds adjacent: Minimize the current-sense resistor trace lengths, and ensure accurate current sensing with Kelvin connections. Use independent branches for CSSP, CSSS, CSSN, CSIP, and CSIN. Minimize ground trace lengths in the high-current paths. Step-Up/Step-Down Li+ Battery Charger Ideally, surface-mount power components are flush against one another with their ground terminals almost touching. These high-current grounds are then connected to each other with a wide, filled zone of top-layer copper, so they do not go through vias. Other high-current paths should also be minimized, but focus primarily on short ground and current-sense connections to eliminate about 90% of all PC board layout problems. 2) Place the IC and signal components. Keep the main switching nodes (inductor connections) away from sensitive analog components (current-sense traces and REF capacitor). Important: the IC must be no further than 10mm from the current-sense resistors. Keep the gate-drive traces (DHI and DBST) shorter than 20mm, and route them away from the current-sense lines and REF. Place ceramic bypass capacitors close to the IC. The bulk capacitors can be placed further away. Bypass CSSP, CSSN, CSIN, and CSIP to analog GND to reduce switching noise and maintain input-current and charger-current accuracy. Place the current-sense input filter capacitors under the part, connected directly to GND. 3) Use a single-point star ground placed directly below the part. Connect the input ground trace, power ground (subground plane), and normal ground to this node. Figure 14 shows a partial layout of the power path and components. Refer to the EV kit data sheet for more information. Minimize other trace lengths in the high-current paths. Use > 5mm wide traces for high-current paths. www.maximintegrated.com Maxim Integrated 31 MAX1870A Step-Up/Step-Down Li+ Battery Charger BATT C9 PGND RS2 L1 D3 D4 N P M1 M2 C8 IN RS1b RS1a LOAD Figure 14. Recommended Layout for the MAX1870A Ordering Information PART Chip Information TEMP RANGE PIN-PACKAGE MAX1870AETJ -40C to +85C 32 Thin QFN MAX1870AETJ+ -40C to +85C 32 Thin QFN TRANSISTOR COUNT: 6484 PROCESS: BiCMOS +Denotes a lead(Pb)-free/RoHS-compliant package. www.maximintegrated.com Maxim Integrated 32 MAX1870A Step-Up/Step-Down Li+ Battery Charger Revision History REVISION NUMBER REVISION DATE 1 5/15 Updated Benefits and Features section 2 8/15 Updated Figures 1 and 2 DESCRIPTION PAGES CHANGED 1 14, 15 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. (c) 2015 Maxim Integrated Products, Inc. 33 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX1870AETJ+ MAX1870AETJ+T