19-2764; Rev 4; 7/05 KIT ATION EVALU E L B AVAILA Low-Cost Multichemistry Battery Chargers The MAX1908/MAX8724/MAX8765 highly integrated, multichemistry battery-charger control ICs simplify the construction of accurate and efficient chargers. These devices use analog inputs to control charge current and voltage, and can be programmed by the host or hardwired. The MAX1908/MAX8724/MAX8765 achieve high efficiency using a buck topology with synchronous rectification. The MAX1908/MAX8724/MAX8765 feature input current limiting. This feature reduces battery charge current when the input current limit is reached to avoid overloading the AC adapter when supplying the load and the battery charger simultaneously. The MAX1908/MAX8724/ MAX8765 provide outputs to monitor current drawn from the AC adapter (DC input source), battery-charging current, and the presence of an AC adapter. The MAX1908’s conditioning charge feature provides 300mA to safely charge deeply discharged lithium-ion (Li+) battery packs. The MAX1908 includes a conditioning charge feature while the MAX8724/MAX8765 do not. The MAX1908/MAX8724/MAX8765 charge two to four series Li+ cells, providing more than 5A, and are available in a space-saving, 28-pin, thin QFN package (5mm × 5mm). An evaluation kit is available to speed designs. Features ♦ ±0.5% Output Voltage Accuracy Using Internal Reference (0°C to +85°C) ♦ ±4% Accurate Input Current Limiting ♦ ±5% Accurate Charge Current ♦ Analog Inputs Control Charge Current and Charge Voltage ♦ Outputs for Monitoring Current Drawn from AC Adapter Charging Current AC Adapter Presence ♦ Up to 17.6V Battery-Voltage Set Point ♦ Maximum 28V Input Voltage ♦ > 95% Efficiency ♦ Shutdown Control Input ♦ Charge Any Battery Chemistry Li+, NiCd, NiMH, Lead Acid, etc. Ordering Information Applications Notebook and Subnotebook Computers PART TEMP RANGE PINPACKAGE PKG CODE Personal Digital Assistants MAX1908ETI -40°C to +85°C 28 Thin QFN T2855-6 Handheld Terminals MAX8724ETI -40°C to +85°C 28 Thin QFN T2855-6 MAX8765ETI -40°C to +85°C 28 Thin QFN T2855-6 Minimum Operating Circuit TO EXTERNAL LOAD CSSN ACOK FROM HOST μP MAX1908 MAX8724 MAX8765 DHI BATT VCTL 20 19 18 17 16 15 DLOV 22 14 GND LX 23 13 ICTL 12 REFIN SHDN LX BST 24 ICHG DLO DHI 25 CSSN 26 CSSP IINP MAX1908 MAX8724 MAX8765 11 ACOK 10 ACIN 27 9 ICHG 28 8 SHDN CCV CSIP 0.015Ω CCI CSIN BATT CCS REF CLS GND BATT+ 1 2 LDO PGND DCIN 10μH IINP 3 4 5 6 7 CCV ACIN 21 CCI DLOV REF BST ICTL CCS VCTL CELLS REFIN LDO CSIN LDO CSIP TOP VIEW CELLS PGND CSSP DCIN Pin Configuration CLS 0.01Ω DLO AC ADAPTER INPUT THIN QFN ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX1908/MAX8724/MAX8765 General Description MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers ABSOLUTE MAXIMUM RATINGS DCIN, CSSP, CSSN, ACOK to GND.......................-0.3V to +30V BST to GND ............................................................-0.3V to +36V BST to LX..................................................................-0.3V to +6V DHI to LX ...................................................-0.3V to (VBST + 0.3V) LX to GND .................................................................-6V to +30V BATT, CSIP, CSIN to GND .....................................-0.3V to +20V CSIP to CSIN or CSSP to CSSN or PGND to GND ....................................................-0.3V to +0.3V CCI, CCS, CCV, DLO, ICHG, IINP, ACIN, REF to GND.......................-0.3V to (VLDO + 0.3V) DLOV, VCTL, ICTL, REFIN, CELLS, CLS, LDO, SHDN to GND .............................................-0.3V to +6V DLOV to LDO.........................................................-0.3V to +0.3V DLO to PGND .........................................-0.3V to (VDLOV + 0.3V) LDO Short-Circuit Current...................................................50mA Continuous Power Dissipation (TA = +70°C) 28-Pin Thin QFN (5mm × 5mm) (derate 20.8mW/°C above +70°C) .........................1666.7mW Operating Temperature Range ..........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-60°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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. ELECTRICAL CHARACTERISTICS (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CHARGE-VOLTAGE REGULATION VVCTL = VREFIN (2, 3, or 4 cells) -0.5 +0.5 VVCTL = VREFIN / 20 (2, 3, or 4 cells) -0.5 +0.5 VVCTL = VLDO (2, 3, or 4 cells) -0.5 +0.5 VCTL Default Threshold VVCTL rising 4.0 REFIN Range (Note 1) 2.5 REFIN Undervoltage Lockout VREFIN falling Battery-Regulation Voltage Accuracy % 4.1 4.2 V 3.6 V 1.20 1.92 V 75 78.75 mV CHARGE-CURRENT REGULATION CSIP-to-CSIN Full-Scale CurrentSense Voltage Charging-Current Accuracy VICTL = VREFIN 71.25 VICTL = VREFIN -5 +5 VICTL = VREFIN x 0.6 -5 +5 VICTL = VLDO -6 +6 MAX8765 only; VICTL = VREFIN x 0.036 -45 +45 MAX8724 only; VICTL = VREFIN x 0.058 % -33 +33 Charge-Current Gain Error (MAX8765 Only) -2 +2 % Charge-Current Offset (MAX8765 Only) -2 +2 mV 4.2 V 19 V 1 650 µA ICTL Default Threshold VICTL rising BATT/CSIP/CSIN Input Voltage Range CSIP/CSIN Input Current 2 4.0 4.1 0 VDCIN = 0 or VICTL = 0 or SHDN = 0 Charging 400 _______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL Cycle-by-Cycle Maximum Current Limit IMAX ICTL Power-Down Mode Threshold Voltage (MAX1908/MAX8724 Only) CONDITIONS RS2 = 0.015Ω REFIN Input Bias Current TYP MAX UNITS 6.0 6.8 7.5 A REFIN / 33 V REFIN / REFIN / 55 100 VICTL rising ICTL, VCTL Input Bias Current MIN VVCTL = VICTL = 0 or 3V -1 +1 VDCIN = 0, VVCTL = VICTL = VREFIN = 5V -1 +1 VDCIN = 5V, VREFIN = 3V -1 +1 VREFIN = 5V -1 +1 µA µA ICHG Transconductance (MAX1908/MAX8724 Only) GICHG VCSIP - VCSIN = 45mV 2.7 3 3.3 µA/mV ICHG Transconductance (MAX8765 Only) GICHG VCSIP - VCSIN = 45mV 2.85 3 3.15 µA/mV ICHG Transconductance Error (MAX8765 Only) -5 +5 % ICHG Transconductance Offset (MAX8765 Only) -5 +5 µA VCSIP - VCSIN = 75mV -6 +6 VCSIP - VCSIN = 45mV -5 +5 +40 ICHG Accuracy % VCSIP - VCSIN = 5mV -40 ICHG Output Current VCSIP - VCSIN = 150mV, VICHG = 0 350 µA ICHG Output Voltage VCSIP - VCSIN = 150mV, ICHG = float 3.5 V INPUT-CURRENT REGULATION CSSP-to-CSSN Full-Scale Current-Sense Voltage 72 VCLS = VREF 75 78 mV -4 +4 VCLS = VREF / 2 -7.5 +7.5 VCLS = 1.1V (MAX8765 only) -10 +10 Input Current-Limit Gain Error (MAX8765 Only) -2 +2 % Input Current-Limit Offset (MAX8765 Only) -2 +2 mV CSSP, CSSN Input Voltage Range 8 28 V Input Current-Limit Accuracy CSSP, CSSN Input Current (MAX1908/MAX8724 Only) CSSP Input Current (MAX8765 Only) VDCIN = 0 0.1 1 VCSSP = VCSSN = VDCIN > 8V 350 600 VDCIN = 0V 0.1 1 VDCIN = 28V 400 650 VCSSP = VCSSN = 28V % µA µA _______________________________________________________________________________________ 3 MAX1908/MAX8724/MAX8765 ELECTRICAL CHARACTERISTICS (continued) MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers ELECTRICAL CHARACTERISTICS (continued) (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CSSN Input Current (MAX8765 Only) CONDITIONS VCSSP = VCSSN = 28V MIN TYP MAX VDCIN = 0 0.1 1 VDCIN = 28V 0.1 1 UNITS µA CLS Input Range (MAX1908/MAX8724 Only) 1.6 REF V CLS Input Range (MAX8765 Only) 1.1 REF V VCLS = 2V -1 +1 µA VCSSP - VCSSN = 75mV 2.7 3.3 µA/mV CLS Input Bias Current IINP Transconductance (MAX1908/MAX8724 Only) GIINP VCSSP - VCSSN = 75mV IINP Accuracy IINP Transconductance (MAX8765 Only) GIINP 3 -5 +5 VCSSP - VCSSN = 37.5mV -7.5 +7.5 VCSSP - VCCSN = 75mV 2.82 3 % 3.18 µA/mV IINP Transconductance Error (MAX8765 Only) -6 +6 % IINP Transconductance Offset (MAX8765 Only) -10 +10 µA IINP Output Current VCSSP - VCSSN = 150mV, VIINP = 0 350 µA IINP Output Voltage VCSSP - VCSSN = 150mV, VIINP = float 3.5 V SUPPLY AND LDO REGULATOR DCIN Input Voltage Range VDCIN DCIN Quiescent Current BATT Input Current 8 VDCIN falling DCIN Undervoltage-Lockout Trip Point IDCIN IBATT 7 28 7.4 VDCIN rising 7.5 7.85 8.0V < VDCIN < 28V 3.2 6 VBATT = 19V, VDCIN = 0 1 VBATT = 2V to 19V, VDCIN = 19.3V 5.25 V V mA µA 200 500 5.4 5.55 V 34 100 mV LDO Output Voltage 8V < VDCIN < 28V, no load LDO Load Regulation 0 < ILDO < 10mA LDO Undervoltage-Lockout Trip Point VDCIN = 8V 3.20 4 5.15 V REF Output Voltage 0 < IREF < 500µA 4.072 4.096 4.120 V REF Undervoltage-Lockout Trip Point VREF falling 3.1 3.9 V REFERENCE 4 _______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 50 100 150 UNITS TRIP POINTS VDCIN falling, referred to VCSIN (MAX1908/MAX8724 only) BATT Power-Fail Threshold mV VCSSP falling, referred to VCSIN (MAX8765 only) 50 BATT Power-Fail Threshold Hysteresis 100 150 200 ACIN Threshold mV ACIN rising (MAX8765 only) 2.028 2.048 2.068 ACIN rising (MAX1908/MAX8724 only) 2.007 2.048 2.089 ACIN Threshold Hysteresis 0.5% of REF ACIN Input Bias Current VACIN = 2.048V 20 -1 V V mV +1 µA SWITCHING REGULATOR DHI Off-Time VBATT = 16V, VDCIN = 19V, VCELLS = VREFIN 0.36 0.4 0.44 µs DHI Minimum Off-Time VBATT = 16V, VDCIN = 17V, VCELLS = VREFIN 0.24 0.28 0.33 µs 2.5 5 7.5 ms DHI Maximum On-Time DLOV Supply Current BST Supply Current IDLOV DLO low 5 10 µA IBST DHI high 6 15 µA BST Input Quiescent Current VDCIN = 0, VBST = 24.5V, VBATT = VLX = 20V 0.3 1 µA LX Input Bias Current VDCIN = 28V, VBATT = VLX = 20V 150 500 µA LX Input Quiescent Current VDCIN = 0, VBATT = VLX = 20V 0.3 1 µA DHI Maximum Duty Cycle 99 Minimum Discontinuous-Mode Ripple Current Battery Undervoltage Charge Current Battery Undervoltage Current Threshold VBATT = 3V per cell (RS2 = 15mΩ), MAX1908 only, VBATT rising 99.9 % 0.5 A 150 300 450 CELLS = GND, MAX1908 only, VBATT rising 6.1 6.2 6.3 CELLS = float, MAX1908 only, VBATT rising 9.15 9.3 9.45 CELLS = VREFIN, MAX1908 only, VBATT rising 12.2 12.4 12.6 mA V DHI On-Resistance High VBST - VLX = 4.5V, IDHI = +100mA 4 7 Ω DHI On-Resistance Low VBST - VLX = 4.5V, IDHI = -100mA 1 3.5 Ω DLO On-Resistance High VDLOV = 4.5V, IDLO = +100mA 4 7 Ω DLO On-Resistance Low VDLOV = 4.5V, IDLO = -100mA 1 3.5 Ω _______________________________________________________________________________________ 5 MAX1908/MAX8724/MAX8765 ELECTRICAL CHARACTERISTICS (continued) MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers ELECTRICAL CHARACTERISTICS (continued) (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.0625 0.125 0.2500 µA/mV ERROR AMPLIFIERS GMV VVCTL = VLDO, VBATT = 16.8V, CELLS = VREFIN GMI Amplifier Transconductance GMI VICTL = VREFIN, VCSIP - VCSIN = 75mV 0.5 1 2.0 µA/mV GMS Amplifier Transconductance GMS VCLS = VREF, VCSSP - VCSSN = 75mV 0.5 1 2.0 µA/mV 0.25V < VCCV,CCS,CCI < 2V 150 300 600 mV 0.4 V (VREFIN / 2) + 0.2V V GMV Amplifier Transconductance CCI, CCS, CCV Clamp Voltage LOGIC LEVELS CELLS Input Low Voltage CELLS Input Float Voltage CELLS = float VREFIN /2 VREFIN - 0.4V CELLS Input High Voltage CELLS Input Bias Current (VREFIN / 2) 0.2V CELLS = 0 or VREFIN V -2 +2 µA 0 28 V ACOK AND SHDN ACOK Input Voltage Range ACOK Sink Current V ACOK = 0.4V, VACIN = 3V ACOK Leakage Current V ACOK = 28V, VACIN = 0 SHDN Threshold SHDN Threshold Hysteresis 6 mA 1 µA 0 LDO V V SHDN = 0 or VLDO -1 +1 VDCIN = 0, V SHDN = 5V -1 +1 V SHDN falling 22 SHDN Input Voltage Range SHDN Input Bias Current 1 23.5 1 _______________________________________________________________________________________ 25 µA % of VREFIN % of VREFIN Low-Cost Multichemistry Battery Chargers (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = FLOAT, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CHARGE-VOLTAGE REGULATION VVCTL = VREFIN (2, 3, or 4 cells) -0.6 +0.6 VVCTL = VREFIN / 20 (2, 3, or 4 cells) -0.6 +0.6 VVCTL = VLDO (2, 3, or 4 cells) -0.6 +0.6 REFIN Range (Note 1) 2.5 3.6 V REFIN Undervoltage Lockout VREFIN falling 1.92 V 79.5 mV Battery Regulation Voltage Accuracy % CHARGE CURRENT REGULATION CSIP-to-CSIN Full-Scale CurrentSense Voltage VICTL = VREFIN VICTL = VREFIN 70.5 -6 +6 VICTL = VREFIN x 0.6 -7.5 +7.5 VICTL = VLDO -7.5 +7.5 MAX8765 only; VICTL = VREFIN x 0.036 -50 +50 MAX8724 only; VICTL = VREFIN x 0.058 -33 +33 Charge-Current Gain Error (MAX8765 Only) -2 +2 % Charge-Current Offset (MAX8765 Only) -2 +2 mV BATT/CSIP/CSIN Input Voltage Range 0 19 V Charging-Current Accuracy VDCIN = 0 or VICTL = 0 or SHDN = 0 CSIP/CSIN Input Current Cycle-by-Cycle Maximum Current Limit 1 Charging IMAX ICTL Power-Down Mode Threshold Voltage (MAX1908/MAX8724 Only) RS2 = 0.015Ω VICTL rising 650 % µA 6.0 7.5 A REFIN / 100 REFIN / 33 V ICHG Transconductance (MAX1908/MAX8724 Only) GICHG VCSIP - VCSIN = 45mV 2.7 3.3 µA/mV ICHG Transconductance (MAX8765 Only) GICHG VCSIP - VCSIN = 45mV 2.785 3.225 µA/mV ICHG Transconductance Error (MAX8765 Only) -7.5 +7.5 % ICHG Transconductance Offset (MAX8765 Only) -6.5 +6.5 µA _______________________________________________________________________________________ 7 MAX1908/MAX8724/MAX8765 ELECTRICAL CHARACTERISTICS MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers ELECTRICAL CHARACTERISTICS (continued) (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = FLOAT, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS VCSIP - VCSIN = 75mV -7.5 +7.5 VCSIP - VCSIN = 45mV -7.5 +7.5 VCSIP - VCSIN = 5mV -40 +40 71.25 78.75 -5 +5 VCLS = VREF / 2 -7.5 +7.5 VCLS = 1.1V (MAX8765 only) -10 +10 Input Current-Limit Gain Error (MAX8765 Only) -2 +2 % Input Current-Limit Offset (MAX8765 Only) -2 +2 mV CSSP, CSSN Input Voltage Range 8 28 V ICHG Accuracy % INPUT-CURRENT REGULATION CSSP-to-CSSN Full-Scale Current-Sense Voltage VCLS = VREF Input Current-Limit Accuracy VDCIN = 0 CSSP, CSSN Input Current (MAX1908/MAX8724 Only) 1 VCSSP = VCSSN = VDCIN > 8V CSSP Input Current (MAX8765 Only) VCSSP = VCSSN = 28V CSSN Input Current (MAX8765 Only) VCSSP = VCSSN = 28V 600 VDCIN = 0V 1 VDCIN = 28V 650 VDCIN = 0V 1 VDCIN = 28V 1 mV % µA µA µA CLS Input Range (MAX1908/MAX8724 Only) 1.6 REF V CLS Input Range (MAX8765 Only) 1.1 REF V IINP Transconductance (MAX1908/MAX8724 Only) IINP Transconductance (MAX8765 Only) IINP Transconductance Error (MAX8765 Only) GIINP VCSSP - VCSSN = 75mV 2.7 3.3 µA/mV GIINP VCSSP - VCCSN = 75mV 2.785 3.225 µA/mV -7.5 +7.5 % -12 +12 µA VCSSP - VCSSN = 75mV -7.5 +7.5 VCSSP - VCSSN = 37.5mV -7.5 +7.5 IINP Transconductance Offset (MAX8765 Only) IINP Accuracy 8 _______________________________________________________________________________________ % Low-Cost Multichemistry Battery Chargers (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = FLOAT, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SUPPLY AND LDO REGULATOR DCIN Input Voltage Range VDCIN DCIN Quiescent Current IDCIN BATT Input Current IBATT 8 8V < VDCIN < 28V VBATT = 19V, VDCIN = 0 8V < VDCIN < 28V, no load LDO Load Regulation 0 < ILDO < 10mA V 6 mA 1 VBATT = 2V to 19V, VDCIN = 19.3V LDO Output Voltage 28 500 5.25 µA 5.55 V 100 mV 4.065 4.120 V VDCIN falling, referred to VCSIN (MAX1908/MAX8724 only) 50 150 VCSSP falling, referred to VCSIN (MAX8765 only) 50 150 ACIN rising (MAX8765 only) 2.028 2.068 ACIN rising (MAX1908/MAX8724 only) 2.007 2.089 DHI Off-Time VBATT = 16V, VDCIN = 19V, VCELLS = VREFIN 0.35 0.45 µs DHI Minimum Off-Time VBATT = 16V, VDCIN = 17V, VCELLS = VREFIN 0.24 0.33 µs DHI Maximum On-Time 2.5 7.5 ms DHI Maximum Duty Cycle 99 REFERENCE REF Output Voltage 0 < IREF < 500µA TRIP POINTS BATT Power-Fail Threshold ACIN Threshold mV V SWITCHING REGULATOR Battery Undervoltage Charge Current Battery Undervoltage Current Threshold % VBATT = 3V per cell (RS2 = 15mΩ), MAX1908 only, VBATT rising 150 450 CELLS = GND, MAX1908 only, VBATT rising 6.09 6.30 CELLS = float, MAX1908 only, VBATT rising 9.12 9.45 CELLS = VREFIN, MAX1908 only, VBATT rising 12.18 12.60 mA V DHI On-Resistance High VBST - VLX = 4.5V, IDHI = +100mA 7 Ω DHI On-Resistance Low VBST - VLX = 4.5V, IDHI = -100mA 3.5 Ω DLO On-Resistance High VDLOV = 4.5V, IDLO = +100mA 7 Ω DLO On-Resistance Low VDLOV = 4.5V, IDLO = -100mA 3.5 Ω _______________________________________________________________________________________ 9 MAX1908/MAX8724/MAX8765 ELECTRICAL CHARACTERISTICS (continued) MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers ELECTRICAL CHARACTERISTICS (continued) (VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = FLOAT, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1µF, LDO = DLOV, CREF = 1µF; CCI, CCS, and CCV are compensated per Figure 1a; TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.0625 0.250 µA/mV ERROR AMPLIFIERS GMV VVCTL = VLDO, VBATT = 16.8V, CELLS = VREFIN GMI Amplifier Transconductance GMI VICTL = VREFIN, VCSIP - VCSIN = 75mV 0.5 2.0 µA/mV GMS Amplifier Transconductance GMS VCLS = VREF, VCSSP - VCSSN = 75mV 0.5 2.0 µA/mV 0.25V < VCCV,CCS,CCI < 2V 150 600 mV 0.4 V (VREFIN / 2) + 0.2V V GMV Amplifier Transconductance CCI, CCS, CCV Clamp Voltage LOGIC LEVELS CELLS Input Low Voltage CELLS Input Float Voltage (VREFIN / 2) 0.2V CELLS = float VREFIN - 0.4V CELLS Input High Voltage V ACOK AND SHDN ACOK Input Voltage Range 0 ACOK Sink Current V A COK = 0.4V, VACIN = 3V 28 1 SHDN Input Voltage Range 0 SHDN Threshold V SHDN falling V mA 22 LDO V 25 % of VREFIN Note 1: If both ICTL and VCTL use default mode (connected to LDO), REFIN is not used and can be connected to LDO. Note 2: Specifications to -40°C are guaranteed by design and not production tested. Typical Operating Characteristics (Circuit of Figure 1, VDCIN = 20V, TA = +25°C, unless otherwise noted.) LOAD-TRANSIENT RESPONSE (BATTERY INSERTION AND REMOVAL) MAX1908 toc01 MAX1908 toc03 MAX1908 toc02 ADAPTER CURRENT 5A/div IBATT 2A/div LOAD CURRENT 5A/div VBATT 5V/div CCV CCI VCCI 500mV/div VCCV 500mV/div ICTL = LDO VCTL = LDO 10 LOAD-TRANSIENT RESPONSE (STEP IN-LOAD CURRENT) LOAD-TRANSIENT RESPONSE (STEP IN-LOAD CURRENT) 1ms/div 0 0 VBATT 2V/div VCCI 500mV/div VCCS 500mV/div 16.8V CCS CCI CCS 1ms/div ICTL = LDO CHARGING CURRENT = 3A VBATT = 16.8V LOAD STEP = 0 TO 4A ISOURCE LIMIT = 5A LOAD CURRENT 5A/div 0 ADAPTER CURRENT 5A/div 0 CHARGE CURRENT 2A/div CCI 0 VBATT 2V/div 1ms/div ICTL = LDO CHARGING CURRENT = 3A VBATT = 16.8V LOAD STEP = 0 TO 4A ISOURCE LIMIT = 5A ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers LDO LOAD REGULATION MAX1908 toc04 LDO LINE REGULATION VDCIN 10V/div -0.1 -0.2 INDUCTOR CURRENT 500mA/div -0.3 -0.4 -0.5 -0.6 0.03 0 -0.03 VLDO = 5.4V -0.9 -0.04 -1.0 -0.05 0 1 2 3 4 5 6 7 8 9 10 8 0.08 0.06 -0.04 -0.05 -0.06 0.04 90 80 EFFICIENCY (%) VREF ERROR (%) VREF ERROR (%) -0.03 100 MAX1908 toc08 0.02 0 -0.02 VBATT = 16V 70 60 VBATT = 12V 50 VBATT = 8V 40 -0.07 -0.04 30 -0.08 -0.06 20 -0.09 -0.08 10 -0.10 -0.10 300 400 500 0 -40 -15 10 REF CURRENT (μA) 350 4 CELLS 300 250 200 150 ICHARGE = 3A VCTL = ICTL = LDO 100 50 3 CELLS 0.3 0.2 0.1 0 4 CELLS -0.1 -0.2 -0.3 -0.5 0 2 4 6 8 10 12 14 16 18 20 22 (VIN - VBATT) (V) 0.08 0.07 10 0.06 0.05 0.04 0.03 0.02 4 CELLS REFIN = 3.3V NO LOAD 0.01 -0.4 0 1 BATT VOLTAGE ERROR vs. VCTL 2 CELLS 0.4 0.1 CHARGE CURRENT (A) OUTPUT V/I CHARACTERISTICS MAX1908 toc10 3 CELLS 400 0.01 85 0.5 BATT VOLTAGE ERROR (%) 450 60 TEMPERATURE (°C) FREQUENCY vs. VIN - VBATT 500 35 BATT VOLTAGE ERROR (%) 200 MAX1908 toc11 100 MAX1908 toc12 -0.02 EFFICIENCY vs. CHARGE CURRENT REF VOLTAGE ERROR vs. TEMPERATURE 0.10 MAX1908 toc07 -0.01 VIN (V) MAX1908 toc09 REF VOLTAGE LOAD REGULATION 0 10 12 14 16 18 20 22 24 26 28 LDO CURRENT (mA) 0 FREQUENCY (kHz) 0.01 -0.02 -0.8 ICTL = LDO VCTL = LDO ICHARGE = 3A LINE STEP 18.5V TO 27.5V 0.02 -0.01 -0.7 10ms/div ILDO = 0 VLDO = 5.4V 0.04 VLDO ERROR (%) VLDO ERROR (%) VBATT 500mV/div 0.05 MAX1908 toc05 0 MAX1908 toc06 LINE-TRANSIENT RESPONSE 0 0 1 2 BATT CURRENT (A) 3 4 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 VCTL/REFIN (%) ______________________________________________________________________________________ 11 MAX1908/MAX8724/MAX8765 Typical Operating Characteristics (continued) (Circuit of Figure 1, VDCIN = 20V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (Circuit of Figure 1, VDCIN = 20V, TA = +25°C, unless otherwise noted.) ICHG ERROR vs. CHARGE CURRENT CURRENT-SETTING ERROR vs. ICTL 4 MAX1908 toc14 5.0 MAX1908 toc13 4.5 4.0 VREFIN = 3.3V VREFIN = 3.3V 3.5 3 ICHG (%) CURRENT-SETTING ERROR (%) 5 2 1 3.0 VBATT = 16V VBATT = 12V VBATT = 8V 2.5 2.0 1.5 1.0 0 0.5 0 -1 0 0.5 1.0 1.5 0 2.0 0.5 1.0 IINP ERROR vs. SYSTEM LOAD CURRENT 2.0 2.5 3.0 IINP ERROR vs. INPUT CURRENT 30 MAX1908 toc16 80 MAX1908 toc15 40 60 20 40 IINP ERROR (%) IBATT = 0 10 0 -10 ERROR DUE TO SWITCHING NOISE 20 0 -20 -20 -40 -30 -60 -40 SYSTEM LOAD = 0 -80 0 1 2 3 SYSTEM LOAD CURRENT (A) 12 1.5 IBATT (A) VICTL (V) IINP ERROR (%) MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers 4 0 0.5 1.0 1.5 2.0 INPUT CURRENT (A) ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers PIN NAME 1 DCIN Charging Voltage Input. Bypass DCIN with a 1µF capacitor to PGND. FUNCTION 2 LDO Device Power Supply. Output of the 5.4V linear regulator supplied from DCIN. Bypass with a 1µF capacitor to GND. 3 CLS Source Current-Limit Input. Voltage input for setting the current limit of the input source. 4 REF 4.096V Voltage Reference. Bypass REF with a 1µF capacitor to GND. 5 CCS Input-Current Regulation Loop-Compensation Point. Connect a 0.01µF capacitor to GND. 6 CCI Output-Current Regulation Loop-Compensation Point. Connect a 0.01µF capacitor to GND. 7 CCV Voltage Regulation Loop-Compensation Point. Connect 1kΩ in series with a 0.1µF capacitor to GND. 8 SHDN Shutdown Control Input. Drive SHDN logic low to shut down the MAX1908/MAX8724/MAX8765. Use with a thermistor to detect a hot battery and suspend charging. 9 ICHG Charge-Current Monitor Output. ICHG is a scaled-down replica of the charger output current. Use ICHG to monitor the charging current and detect when the chip changes from constant-current mode to constantvoltage mode. The transconductance of (CSIP - CSIN) to ICHG is 3µA/mV. 10 ACIN AC Detect Input. Input to an uncommitted comparator. ACIN can be used to detect AC-adapter presence. 11 ACOK AC Detect Output. High-voltage open-drain output is high impedance when VACIN is less than VREF / 2. 12 REFIN Reference Input. Allows the ICTL and VCTL inputs to have ratiometric ranges for increased accuracy. 13 ICTL Output Current-Limit Set Input. ICTL input voltage range is VREFIN / 32 to VREFIN. The MAX1908/MAX8724 shut down if ICTL is forced below VREFIN / 100 while the MAX8765 does not. When ICTL is equal to LDO, the set point for CSIP - CSIN is 45mV. 14 GND Analog Ground 15 VCTL Output Voltage-Limit Set Input. VCTL input voltage range is 0 to VREFIN. When VCTL is equal to LDO, the set point is (4.2 x CELLS)V. 16 BATT Battery Voltage Input 17 CELLS 18 CSIN Output Current-Sense Negative Input 19 CSIP Output Current-Sense Positive Input. Connect a current-sense resistor from CSIP to CSIN. 20 PGND 21 DLO Low-Side Power MOSFET Driver Output. Connect to low-side nMOS gate. 22 DLOV Low-Side Driver Supply. Bypass DLOV with a 1µF capacitor to GND. Cell Count Input. Tri-level input for setting number of cells. GND = 2 cells, float = 3 cells, REFIN = 4 cells. Power Ground 23 LX 24 BST High-Side Power MOSFET Driver Power-Return Connection. Connect to the source of the high-side nMOS. High-Side Power MOSFET Driver Power-Supply Connection. Connect a 0.1µF capacitor from LX to BST. 25 DHI High-Side Power MOSFET Driver Output. Connect to high-side nMOS gate. 26 CSSN Input Current-Sense Negative Input 27 CSSP Input Current-Sense Positive Input. Connect a current-sense resistor from CSSP to CSSN. 28 IINP Input-Current Monitor Output. IINP is a scaled-down replica of the input current. IINP monitors the total system current. The transconductance of (CSSP - CSSN) to IINP is 3µA/mV. ______________________________________________________________________________________ 13 MAX1908/MAX8724/MAX8765 Pin Description MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers Detailed Description The MAX1908/MAX8724/MAX8765 include all the functions necessary to charge Li+ batteries. A high-efficiency synchronous-rectified step-down DC-DC converter controls charging voltage and current. The device also includes input-source current limiting and analog inputs for setting the charge current and charge voltage. Control charge current and voltage using the ICTL and VCTL inputs, respectively. Both ICTL and VCTL are ratiometric with respect to REFIN, allowing compatibility with DACs or microcontrollers (µCs). Ratiometric ICTL and VCTL improve the accuracy of the charge current and voltage set point by matching VREFIN to the reference of the host. For standard applications, internal set points for ICTL and VCTL provide 3A charge current (with 0.015Ω sense resistor), and 4.2V (per cell) charge voltage. Connect ICTL and VCTL to LDO to select the internal set points. The MAX1908 safely conditions overdischarged cells with 300mA (with 0.015Ω sense resistor) until the battery-pack voltage exceeds 3.1V × number of series-connected cells. The SHDN input allows shutdown from a microcontroller or thermistor. The DC-DC converter uses external n-channel MOSFETs as the buck switch and synchronous rectifier to convert the input voltage to the required charging current and voltage. The Typical Application Circuit shown in Figure 1 uses a µC to control charging current, while Figure 2 shows a typical application with charging voltage and current fixed to specific values for the application. The voltage at ICTL and the value of RS2 set the charging current. The DC-DC converter generates the control signals for the external MOSFETs to regulate the voltage and the current set by the VCTL, ICTL, and CELLS inputs. The MAX1908/MAX8724/MAX8765 feature a voltage regulation loop (CCV) and two current regulation loops (CCI and CCS). The CCV voltage regulation loop monitors BATT to ensure that its voltage does not exceed the voltage set by VCTL. The CCI battery current regulation loop monitors current delivered to BATT to ensure that it does not exceed the current limit set by ICTL. A third loop (CCS) takes control and reduces the batterycharging current when the sum of the system load and the battery-charging input current exceeds the input current limit set by CLS. external resistor mismatch error is reduced from 1% to 0.05% of the regulation voltage. Therefore, an overall voltage accuracy of better than 0.7% is maintained while using 1% resistors. The per-cell battery termination voltage is a function of the battery chemistry. Consult the battery manufacturer to determine this voltage. Connect VCTL to LDO to select the internal default setting VBATT = 4.2V × number of cells, or program the battery voltage with the following equation: ⎛ ⎛ ⎞⎞ V VBATT = CELLS × ⎜ 4 V + ⎜ 0.4 × VCTL ⎟ ⎟ VREFIN ⎠ ⎠ ⎝ ⎝ CELLS is the programming input for selecting cell count. Connect CELLS as shown in Table 2 to charge 2, 3, or 4 Li+ cells. When charging other cell chemistries, use CELLS to select an output voltage range for the charger. The internal error amplifier (GMV) maintains voltage regulation (Figure 3). The voltage error amplifier is compensated at CCV. The component values shown in Figures 1 and 2 provide suitable performance for most applications. Individual compensation of the voltage regulation and current regulation loops allows for optimal compensation (see the Compensation section). Table 1. Versions Comparison DESCRIPTION MAX1908 MAX8724 MAX8765 Conditioning Charge Feature Yes No No ICTL Shutdown Mode Yes Yes No REFIN must be ready REFIN must be ready Independent of REFIN ACOK Enable Condition Table 2. Cell-Count Programming CELLS CELL COUNT Setting the Battery-Regulation Voltage GND 2 The MAX1908/MAX8724/MAX8765 use a high-accuracy voltage regulator for charging voltage. The VCTL input adjusts the charger output voltage. VCTL control voltage can vary from 0 to VREFIN, providing a 10% adjustment range on the VBATT regulation voltage. By limiting the adjust range to 10% of the regulation voltage, the Float 3 VREFIN 4 14 ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers AC ADAPTER INPUT 8.5V TO 28V RS1 0.01Ω D1 0.1μF D2 R6 59kΩ 1% R7 19.6kΩ 1% TO EXTERNAL LOAD CSSP CSSN CELLS DCIN C5 1μF C1 2 × 10μF 0.1μF FLOAT (3 CELLS SELECT) LDO LDO C13 1μF VCTL R13 33Ω D3 BST DAC OUTPUT ICTL DLOV 12.6V OUTPUT VOLTAGE VCC C15 0.1μF REFIN R8 1MΩ ACIN OUTPUT SHDN ADC INPUT ICHG N1a DHI ACOK C16 1μF LX N1b DLO MAX1908 MAX8724 MAX8765 IINP ADC INPUT CCV C14 0.1μF R9 20kΩ C20 0.1μF R10 10kΩ HOST L1 10μH PGND CSIP R5 1kΩ RS2 0.015Ω C11 0.1μF CSIN CCI CCS C9 0.01μF C10 0.01μF GND REF AVDD/REF R19, R20, R21 10kΩ BATT+ BATT C12 1μF C4 22μF CLS 7.5A INPUT CURRENT LIMIT SMART BATTERY SCL SCL SDA SDA ADC INPUT TEMP GND BATT- PGND GND Figure 1. µC-Controlled Typical Application Circuit ______________________________________________________________________________________ 15 MAX1908/MAX8724/MAX8765 MAX1908/MAX8724 Typical Application Circuits Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765 Typical Application Circuits (continued) AC ADAPTER INPUT 8.5V TO 28V RS1 0.01Ω P1 TO EXTERNAL LOAD R11 15kΩ C1 2 × 10μF 0.01μF 0.01μF R12 12kΩ LDO R6 59kΩ 1% CSSP ACOK DCIN D2 R7 19.6kΩ 1% CSSN CELLS C5 1μF R14 10.5kΩ 1% LDO VCTL LDO C13 1μF R13 33Ω D3 REFIN BST R15 8.25kΩ 1% DLOV 16.8V OUTPUT VOLTAGE 2.5A CHARGE LIMIT R16 8.25kΩ 1% FROM HOST μP (SHUTDOWN) REFIN (4 CELLS SELECT) N C15 0.1μF ICTL C16 1μF N1a DHI ACIN LX R19 10kΩ 1% C12 1.5nF DLO MAX1908 MAX8724 MAX8765 SHDN R20 10kΩ 1% ICHG N1b L1 10μH PGND IINP CSIP CCV R5 1kΩ RS2 0.015Ω C11 0.1μF CSIN CCI C10 0.01μF BATT+ BATT CCS C9 0.01μF GND REF CLS C4 22μF BATTERY THM BATT- C12 1μF R17 19.1kΩ 1% PGND GND R18 22kΩ 1% 4A INPUT CURRENT LIMIT Figure 2. Typical Application Circuit with Fixed Charging Parameters 16 ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers MAX1908 MAX8724 MAX8765 DCIN SHDN 23.5% REFIN LDO RDY GND LOGIC BLOCK 5.4V LINEAR REGULATOR 4.096V REFERENCE REF MAX1908/MAX8724 ONLY 1/55 GND REFIN ICTL SRDY ACIN ACOK DCIN N REF/2 CCS x CLS CSSP 75mV REF CSIP GM ICHG CSI LEVEL SHIFTER CSIN IINP GMS LEVEL SHIFTER CSSN GM BST GMI 75mV x REFIN ICTL LEVEL SHIFTER DRIVER DHI CCI MAX1908 ONLY 3.1V/CELL BATT BAT_UV LX LVC LVC REFIN CELLS R1 DC-DC CONVERTER GMV CELL SELECT LOGIC DLOV DRIVER DLO CCV PGND VCTL 400mV x REFIN 4V Figure 3. Functional Diagram ______________________________________________________________________________________ 17 MAX1908/MAX8724/MAX8765 MAX1908/MAX8724 Functional Diagram MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers Setting the Charging-Current Limit The ICTL input sets the maximum charging current. The current is set by current-sense resistor RS2, connected between CSIP and CSIN. The full-scale differential voltage between CSIP and CSIN is 75mV; thus, for a 0.015Ω sense resistor, the maximum charging current is 5A. Battery-charging current is programmed with ICTL using the equation: ICHG = VICTL 0.075 × VREFIN RS2 The input voltage range for ICTL is V REFIN / 32 to VREFIN. The MAX1908/MAX8724 shut down if ICTL is forced below VREFIN / 100 (min), while the MAX8765 does not. Connect ICTL to LDO to select the internal default fullscale, charge-current sense voltage of 45mV. The charge current when ICTL = LDO is: ICHG = 0.045V RS2 where RS2 is 0.015Ω, providing a charge-current set point of 3A. The current at the ICHG output is a scaled-down replica of the battery output current being sensed across CSIP and CSIN (see the Current Measurement section). When choosing the current-sense resistor, note that the voltage drop across this resistor causes further power loss, reducing efficiency. However, adjusting ICTL to reduce the voltage across the current-sense resistor can degrade accuracy due to the smaller signal to the input of the current-sense amplifier. The chargingcurrent-error amplifier (GMI) is compensated at CCI (see the Compensation section). Setting the Input Current Limit The total input current (from an AC adapter or other DC source) is a function of the system supply current and the battery-charging current. The input current regulator limits the input current by reducing the charging current when the input current exceeds the input current-limit set point. System current normally fluctuates as portions of the system are powered up or down. Without input current regulation, the source must be able to supply the maximum system current and the maximum charger input current simultaneously. By using the input current limiter, the current capability of the AC adapter can be lowered, reducing system cost. The MAX1908/MAX8724/MAX8765 limit the battery charge current when the input current-limit threshold is 18 exceeded, ensuring the battery charger does not load down the AC adapter voltage. An internal amplifier compares the voltage between CSSP and CSSN to the voltage at CLS. VCLS can be set by a resistive divider between REF and GND. Connect CLS to REF for the full-scale input current limit. The CLS voltage range for the MAX1908/MAX8724 is from 1.6V to REF, while the MAX8765 CLS voltage is from 1.1V to REF. The input current is the sum of the device current, the charger input current, and the load current. The device current is minimal (3.8mA) in comparison to the charge and load currents. Determine the actual input current required as follows: ⎛I × VBATT ⎞ IINPUT = ILOAD + ⎜ CHG ⎟ VIN × η ⎝ ⎠ where η is the efficiency of the DC-DC converter. V CLS determines the reference voltage of the GMS error amplifier. Sense resistor RS1 and VCLS determine the maximum allowable input current. Calculate the input current limit as follows: V 0.075 IINPUT = CLS × VREF RS1 Once the input current limit is reached, the charging current is reduced until the input current is at the desired threshold. When choosing the current-sense resistor, note that the voltage drop across this resistor causes further power loss, reducing efficiency. Choose the smallest value for RS1 that achieves the accuracy requirement for the input current-limit set point. Conditioning Charge The MAX1908 includes a battery-voltage comparator that allows a conditioning charge of overdischarged Li+ battery packs. If the battery-pack voltage is less than 3.1V × number of cells programmed by CELLS, the MAX1908 charges the battery with 300mA current when using sense resistor RS2 = 0.015Ω. After the battery voltage exceeds the conditioning charge threshold, the MAX1908 resumes full-charge mode, charging to the programmed voltage and current limits. The MAX8724/MAX8765 do not offer this feature. AC Adapter Detection Connect the AC adapter voltage through a resistive divider to ACIN to detect when AC power is available, as shown in Figure 1. ACIN voltage rising trip point is VREF / 2 with 20mV hysteresis. ACOK is an open-drain output and is high impedance when ACIN is less than VREF / 2. Since ACOK can withstand 30V (max), ACOK ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers Current Measurement Use ICHG to monitor the battery-charging current being sensed across CSIP and CSIN. The ICHG voltage is proportional to the output current by the equation: VICHG = ICHG x RS2 x GICHG x R9 where ICHG is the battery-charging current, GICHG is the transconductance of ICHG (3µA/mV typ), and R9 is the resistor connected between ICHG and ground. Leave ICHG unconnected if not used. Use IINP to monitor the system input current being sensed across CSSP and CSSN. The voltage of IINP is proportional to the input current by the equation: VIINP = IINPUT x RS1 x GIINP x R10 where IINPUT is the DC current being supplied by the AC adapter power, GIINP is the transconductance of IINP (3µA/mV typ), and R10 is the resistor connected between IINP and ground. ICHG and IINP have a 0 to 3.5V output voltage range. Leave IINP unconnected if not used. LDO Regulator LDO provides a 5.4V supply derived from DCIN and can deliver up to 10mA of load current. The MOSFET drivers are powered by DLOV and BST, which must be connected to LDO as shown in Figure 1. LDO supplies the 4.096V reference (REF) and most of the control circuitry. Bypass LDO with a 1µF capacitor to GND. Shutdown The MAX1908/MAX8724/MAX8765 feature a low-power shutdown mode. Driving SHDN low shuts down the MAX1908/MAX8724/MAX8765. In shutdown, the DCDC converter is disabled and CCI, CCS, and CCV are pulled to ground. The IINP and ACOK outputs continue to function. SHDN can be driven by a thermistor to allow automatic shutdown of the MAX1908/MAX8724/MAX8765 when the battery pack is hot. The shutdown falling threshold is 23.5% (typ) of VREFIN with 1% VREFIN hysteresis to provide smooth shutdown when driven by a thermistor. CCV, CCI, CCS, and LVC Control Blocks The MAX1908/MAX8724/MAX8765 control input current (CCS control loop), charge current (CCI control loop), or charge voltage (CCV control loop), depending on the operating condition. The three control loops, CCV, CCI, and CCS are brought together internally at the LVC amplifier (lowest voltage clamp). The output of the LVC amplifier is the feedback control signal for the DC-DC controller. The output of the GM amplifier that is the lowest sets the output of the LVC amplifier and also clamps the other two control loops to within 0.3V above the control point. Clamping the other two control loops close to the lowest control loop ensures fast transition with minimal overshoot when switching between different control loops. DC-DC Controller The MAX1908/MAX8724/MAX8765 feature a variable offtime, cycle-by-cycle current-mode control scheme. Depending upon the conditions, the MAX1908/MAX8724/ MAX8765 work in continuous or discontinuous-conduction mode. Continuous-Conduction Mode With sufficient charger loading, the MAX1908/MAX8724/ MAX8765 operate in continuous-conduction mode (inductor current never reaches zero) switching at 400kHz if the BATT voltage is within the following range: 3.1V x (number of cells) < VBATT < (0.88 x VDCIN ) The operation of the DC-DC controller is controlled by the following four comparators as shown in Figure 4: • IMIN—Compares the control point (LVC) against 0.15V (typ). If IMIN output is low, then a new cycle cannot begin. • CCMP—Compares the control point (LVC) against the charging current (CSI). The high-side MOSFET ontime is terminated if the CCMP output is high. • IMAX—Compares the charging current (CSI) to 6A (RS2 = 0.015Ω). The high-side MOSFET on-time is terminated if the IMAX output is high and a new cycle cannot begin until IMAX goes low. • ZCMP—Compares the charging current (CSI) to 333mA (RS2 = 0.015Ω). If ZCMP output is high, then both MOSFETs are turned off. DC-DC Converter The MAX1908/MAX8724/MAX8765 employ a buck regulator with a bootstrapped nMOS high-side switch and a low-side nMOS synchronous rectifier. ______________________________________________________________________________________ 19 MAX1908/MAX8724/MAX8765 MAX1908/MAX8724 can drive a p-channel MOSFET directly at the charger input, providing a lower dropout voltage than a Schottky diode (Figure 2). In the MAX1908/MAX8724 the ACOK comparator is enabled after REFIN is ready. In the MAX8765, the ACOK comparator is independent of REFIN. Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765 DC-DC Functional Diagram 5ms S RESET CSSP BST R 1.8V CSS X20 MAX1908 MAX8724 MAX8765 IMAX Q R AC ADAPTER RS1 D3 BST Q CCMP N1a DHI DHI LDO CSSN CBST LX CHG S IMIN Q 0.15V DLO N1b DLO L1 tOFF GENERATOR CSIP ZCMP 0.1V CSI X20 LVC RS2 CSIN GMS BATT COUT BATTERY GMI GMV SETV CONTROL SETI CLS CELLS CCS CCI CELL SELECT LOGIC CCV Figure 4. DC-DC Functional Diagram 20 ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers V − VBATT t OFF = 2.5μs × DCIN VDCIN t ON = L × IRIPPLE VCSSN − VBATT where: V ×t IRIPPLE = BATT OFF L f= 1 t ON + t OFF These equations result in fixed-frequency operation over the most common operating conditions. At the end of the fixed off-time, another cycle begins if the control point (LVC) is greater than 0.15V, IMIN = high, and the peak charge current is less than 6A (RS2 = 0.015Ω), IMAX = high. If the charge current exceeds IMAX, the on-time is terminated by the IMAX comparator. IMAX governs the maximum cycle-by-cycle current limit and is internally set to 6A (RS2 = 0.015Ω). IMAX protects against sudden overcurrent faults. If, during the off-time, the inductor current goes to zero, ZCMP = high, both the high- and low-side MOSFETs are turned off until another cycle is ready to begin. There is a minimum 0.3µs off-time when the (VDCIN VBATT) differential becomes too small. If VBATT ≥ 0.88 × V DCIN , then the threshold for minimum off-time is reached and the tOFF is fixed at 0.3µs. A maximum ontime of 5ms allows the controller to achieve > 99% duty cycle in continuous-conduction mode. The switching frequency in this mode varies according to the equation: 1 f= L × IRIPPLE + 0.3μs (VCSSN − VBATT ) Discontinuous Conduction The MAX1908/MAX8724/MAX8765 enter discontinuousconduction mode when the output of the LVC control point falls below 0.15V. For RS2 = 0.015Ω, this corresponds to 0.5A: IMIN = 0.15V = 0.5A 20 × RS2 for RS2 = 0.015Ω. In discontinuous mode, a new cycle is not started until the LVC voltage rises above 0.15V. Discontinuousmode operation can occur during conditioning charge of overdischarged battery packs, when the charge current has been reduced sufficiently by the CCS control loop, or when the battery pack is near full charge (constant-voltage-charging mode). MOSFET Drivers The low-side driver output DLO switches between PGND and DLOV. DLOV is usually connected through a filter to LDO. The high-side driver output DHI is bootstrapped off LX and switches between VLX and VBST. When the low-side driver turns on, BST rises to one diode voltage below DLOV. Filter DLOV with a lowpass filter whose cutoff frequency is approximately 5kHz (Figure 1): fC = 1 1 = = 4.8kHz 2πRC 2π × 33Ω × 1μF Dropout Operation The MAX1908/MAX8724/MAX8765 have 99% duty-cycle capability with a 5ms (max) on-time and 0.3µs (min) offtime. This allows the charger to achieve dropout performance limited only by resistive losses in the DC-DC converter components (D1, N1, RS1, and RS2, Figure 1). Replacing diode D1 with a p-channel MOSFET driven by ACOK improves dropout performance (Figure 2). The dropout voltage is set by the difference between DCIN and CSIN. When the dropout voltage falls below 100mV, the charger is disabled; 200mV hysteresis ensures that the charger does not turn back on until the dropout voltage rises to 300mV. Compensation Each of the three regulation loops—input current limit, charging current limit, and charging voltage limit—are compensated separately using CCS, CCI, and CCV, respectively. ______________________________________________________________________________________ 21 MAX1908/MAX8724/MAX8765 MAX1908/MAX8724 In normal operation, the controller starts a new cycle by turning on the high-side n-channel MOSFET and turning off the low-side n-channel MOSFET. When the charge current is greater than the control point (LVC), CCMP goes high and the off-time is started. The off-time turns off the high-side n-channel MOSFET and turns on the low-side n-channel MOSFET. The operational frequency is governed by the off-time and is dependent upon VDCIN and VBATT. The off-time is set by the following equations: MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers where RL varies with load according to RL = VBATT / ICHG. Output zero due to output capacitor ESR: BATT fZ _ ESR = GMOUT RESR RL The loop transfer function is given by: LTF = GMOUT × RL × GMV × ROGMV × CCV GMV RCV COUT ROGMV (1+ sCOUT × RESR )(1+ sCCV × RCV ) (1+ sCCV × ROGMV )(1+ sCOUT × RL ) REF Assuming the compensation pole is a very low frequency, and the output zero is a much higher frequency, the crossover frequency is given by: CCV fCO _ CV = Figure 5. CCV Loop Diagram CCV Loop Definitions Compensation of the CCV loop depends on the parameters and components shown in Figure 5. CCV and RCV are the CCV loop compensation capacitor and series resistor. RESR is the equivalent series resistance (ESR) of the charger output capacitor (COUT). RL is the equivalent charger output load, where R L = VBATT / ICHG. The equivalent output impedance of the GMV amplifier, R OGMV ≥ 10MΩ. The voltage amplifier transconductance, GMV = 0.125µA/mV. The DC-DC converter transconductance, GMOUT = 3.33A/V: GMOUT = 1 ACSI × RS2 where A CSI = 20, and RS2 is the charging currentsense resistor in the Typical Application Circuits. The compensation pole is given by: fP _ CV = 1 2πROGMV × CCV The compensation zero is given by: fZ _ CV = 1 2πRCV × CCV fP _ OUT = 1 2πRL × COUT GMV × RCV × GMOUT 2πCOUT To calculate RCV and CCV values of the circuit of Figure 2: Cells = 4 COUT = 22µF VBATT = 16.8V ICHG = 2.5A GMV = 0.125µA/mV GMOUT = 3.33A/V ROGMV = 10MΩ f = 400kHz Choose crossover frequency to be 1/5th the MAX1908’s 400kHz switching frequency: fCO _ CV = GMV × RCV × GMOUT = 80kHz 2πCOUT Solving yields RCV = 26kΩ. Conservatively set RCV = 1kΩ, which sets the crossover frequency at: fCO_CV = 3kHz Choose the output-capacitor ESR so the output-capacitor zero is 10 times the crossover frequency: RESR = 1 2π × 10 × fCO _ CV × COUT The output pole is given by: 22 1 2πRESR × COUT fZ _ ESR = = 0.24Ω 1 = 2.412MHz 2πRESR × COUT ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers The output pole is set at: fP _ OUT = 1 = 1.08kHz 2πRL × COUT where: RL = ΔVBATT = Battery ESR ΔICHG Set the compensation zero (fZ_CV) so it is equivalent to the output pole (fP_OUT = 1.08kHz), effectively producing a pole-zero cancellation and maintaining a singlepole system response: fZ _ CV = 1 2πRCV × CCV CCI Loop Definitions Compensation of the CCI loop depends on the parameters and components shown in Figure 7. CCI is the CCI loop compensation capacitor. ACSI is the internal gain of the current-sense amplifier. RS2 is the charge current-sense resistor, RS2 = 15mΩ. ROGMI is the equivalent output impedance of the GMI amplifier ≥ 10MΩ. GMI is the charge-current amplifier transconductance = 1µA/mV. GMOUT is the DC-DC converter transconductance = 3.3A/V. The CCI loop is a single-pole system with a dominant pole compensation set by fP_CI: fP _ CI = 1 2πROGMI × CCI The loop transfer function is given by: LTF = GMOUT × A CSI × RS2 × GMI ROGMI 1+ sROGMI × CCI Since: 1 CCV = = 147nF 2πRCV × 1.08kHz GMOUT = Choose CCV = 100nF, which sets the compensation zero (fZ_CV) at 1.6kHz. This sets the compensation pole: fP _ CV = 1 2πROGMV × CCV The loop transfer function simplifies to: = 0.16Hz LTF = GMI × ROGMI 1+ sROGMI × CCI CCV LOOP PHASE vs. FREQUENCY CCV LOOP GAIN vs. FREQUENCY 80 -45 60 -60 PHASE (DEGREES) 40 GAIN (dB) 1 ACSI × RS2 20 0 -20 -75 -90 -105 -120 -40 -60 -135 1 10 100 1k 10k 100k FREQUENCY (Hz) 1M 1 10 100 1k 10k 100k 1M FREQUENCY (Hz) Figure 6. CCV Loop Gain/Phase vs. Frequency ______________________________________________________________________________________ 23 MAX1908/MAX8724/MAX8765 MAX1908/MAX8724 The 22µF ceramic capacitor has a typical ESR of 0.003Ω, which sets the output zero at 2.412MHz. CSIP To calculate the CCI loop compensation pole, CCI: GMI = 1µA/mV GMOUT = 3.33A/V ROGMI = 10MΩ f = 400kHz Choose crossover frequency f CO_CI to be 1/5th the MAX1908/MAX8724/MAX8765 switching frequency: CSIN GMOUT RS2 CSI GMI ROGMI CCI GMI = 80kHz 2πCCI fCO _ CI = CCI Solving for CCI, CCI = 2nF. To be conservative, set CCI = 10nF, which sets the crossover frequency at: ICTL fCO _ CI = Figure 7. CCI Loop Diagram The crossover frequency is given by: fCO _ CI = GMI = 16kHz 2π10nF The compensation pole, fP_CI is set at: GMI 2πCCI fP _ CI = GMI = 0.0016Hz 2πROGMI × CCI The CCI loop dominant compensation pole: fP _ CI = CCS Loop Definitions 1 2πROGMI × CCI where the GMI amplifier output impedance, ROGMI = 10MΩ. Compensation of the CCS loop depends on the parameters and components shown in Figure 9. CCS is the CCS loop compensation capacitor. ACSS is the internal gain of the current-sense amplifier. RS1 is the input currentsense resistor, RS1 = 10mΩ. ROGMS is the equivalent output impedance of the GMS amplifier ≥ 10MΩ. GMS is CCI LOOP GAIN vs. FREQUENCY CCI LOOP PHASE vs. FREQUENCY 100 0 80 -15 PHASE (DEGREES) 60 GAIN (dB) MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers 40 20 0 -30 -45 -60 -75 -20 -90 -40 -60 -105 0.1 1 10 100 1k FREQUENCY (Hz) 10k 100k 1M 0.1 1 10 100 1k 10k 100k 1M FREQUENCY (Hz) Figure 8. CCI Loop Gain/Phase vs. Frequency 24 ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers fP _ CS = CSSP CSSN GMIN RS1 1 2πROGMS × CCS CSS The loop transfer function is given by: LTF = GMIN × A CSS × RS1× GMS × CCS ROGMS 1 + sROGMS × CCS GMS Since: ROGMS CCS CLS 1 GMIN = ACSS × RS1 Then, the loop transfer function simplifies to: LTF = GMS × Figure 9. CCS Loop Diagram ROGMS 1+ sROGMS × CCS The CCS loop dominant compensation pole: fP _ CS = The crossover frequency is given by: fCO _ CS = 1 2πROGMS × CCS where the GMS amplifier output impedance, ROGMS = 10MΩ. To calculate the CCI loop compensation pole, CCS: GMS = 1µA/mV GMS 2πCCS GMIN = 3.33A/V ROGMS = 10MΩ f = 400kHz CCS LOOP GAIN vs. FREQUENCY CCS LOOP PHASE vs. FREQUENCY 100 0 80 -15 PHASE (DEGREES) GAIN (dB) 60 40 20 0 -30 -45 -60 -75 -20 -90 -40 -60 -105 0.1 1 10 100 1k 10k FREQUENCY (Hz) 100k 1M 0.1 1 10 100 1k 10k 100k 1M FREQUENCY (Hz) Figure 10. CCS Loop Gain/Phase vs. Frequency ______________________________________________________________________________________ 25 MAX1908/MAX8724/MAX8765 MAX1908/MAX8724 the charge-current amplifier transconductance = 1µA/mV. GM IN is the DC-DC converter transconductance = 3.3A/V. The CCS loop is a single-pole system with a dominant pole compensation set by fP_CS: Choose crossover frequency fCO_CS to be 1/5th the MAX1908/MAX8724/MAX8765 switching frequency: fCO _ CS = GMS = 80kHz 2πCCS where: tOFF = 2.5µs × (VDCIN – VBATT) / VDCIN VBATT < 0.88 × VDCIN or: tOFF = 0.3µs Solving for CCS, CCS = 2nF. To be conservative, set CCS = 10nF, which sets the crossover frequency at: fCO _ CS = GMS = 16kHz 2π10nF The compensation pole, fP_CS is set at: fP _ CS = 1 = 0.0016Hz 2πROGMS × CCS Component Selection Table 3 lists the recommended components and refers to the circuit of Figure 2. The following sections describe how to select these components. Inductor Selection Inductor L1 provides power to the battery while it is being charged. It must have a saturation current of at least the charge current (ICHG), plus 1/2 the current ripple IRIPPLE: ISAT = ICHG + (1/2) IRIPPLE Ripple current varies according to the equation: IRIPPLE = (VBATT) × tOFF / L RIPPLE CURRENT vs. BATTERY VOLTAGE 1.5 3 CELLS RIPPLE CURRENT (A) MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers 4 CELLS 1.0 0.5 VDCIN = 19V VCTL = ICTL = LDO 0 8 9 10 11 12 13 14 15 16 17 18 VBATT (V) Figure 11. Ripple Current vs. Battery Voltage 26 VBATT > 0.88 × VDCIN Figure 11 illustrates the variation of ripple current vs. battery voltage when charging at 3A with a fixed 19V input voltage. Higher inductor values decrease the ripple current. Smaller inductor values require higher saturation current capabilities and degrade efficiency. Designs for ripple current, IRIPPLE = 0.3 × ICHG usually result in a good balance between inductor size and efficiency. Input Capacitor Input capacitor C1 must be able to handle the input ripple current. At high charging currents, the DC-DC converter operates in continuous conduction. In this case, the ripple current of the input capacitor can be approximated by the following equation: IC1 = ICHG D − D2 where: IC1 = input capacitor ripple current. D = DC-DC converter duty ratio. ICHG = battery-charging current. Input capacitor C1 must be sized to handle the maximum ripple current that occurs during continuous conduction. The maximum input ripple current occurs at 50% duty cycle; thus, the worst-case input ripple current is 0.5 × ICHG. If the input-to-output voltage ratio is such that the DC-DC converter does not operate at a 50% duty cycle, then the worst-case capacitor current occurs where the duty cycle is nearest 50%. The input capacitor ESR times the input ripple current sets the ripple voltage at the input, and should not exceed 0.5V ripple. Choose the ESR of C1 according to: ESRC1 < 0.5V IC1 The input capacitor size should allow minimal output voltage sag at the highest switching frequency: IC1 dV = C1 dt 2 ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers I 2.5μs C1 > C1 × 2 0.5V Both tantalum and ceramic capacitors are suitable in most applications. For equivalent size and voltage rating, tantalum capacitors have higher capacitance, but also higher ESR than ceramic capacitors. This makes it more critical to consider ripple current and power-dissipation ratings when using tantalum capacitors. A single ceramic capacitor often can replace two tantalum capacitors in parallel. Output Capacitor The output capacitor absorbs the inductor ripple current. The output capacitor impedance must be significantly less than that of the battery to ensure that it absorbs the ripple current. Both the capacitance and ESR rating of the capacitor are important for its effectiveness as a filter and to ensure stability of the DC-DC converter (see the Compensation section). Either tantalum or ceramic capacitors can be used for the output filter capacitor. MOSFETs and Diodes Schottky diode D1 provides power to the load when the AC adapter is inserted. This diode must be able to deliver the maximum current as set by RS1. For reduced power dissipation and improved dropout performance, replace D1 with a p-channel MOSFET (P1) as shown in Figure 2. Take caution not to exceed the maximum VGS of P1. Choose resistors R11 and R12 to limit the VGS. The n-channel MOSFETs (N1a, N1b) are the switching devices for the buck controller. High-side switch N1a should have a current rating of at least the maximum charge current plus one-half the ripple current and have an on-resistance (RDS(ON)) that meets the power dissipation requirements of the MOSFET. The driver for N1a is powered by BST. The gate-drive requirement for N1a should be less than 10mA. Select a MOSFET with a low total gate charge (Q GATE ) and determine the required drive current by IGATE = QGATE × f (where f is the DC-DC converter’s maximum switching frequency). The low-side switch (N1b) has the same current rating and power dissipation requirements as N1a, and should have a total gate charge less than 10nC. N2 is used to provide the starting charge to the BST capacitor (C15). During the dead time (50ns, typ) between N1a and N1b, the current is carried by the body diode of the MOSFET. Choose N1b with either an internal Schottky diode or body diode capable of carrying the maximum charging current during the dead time. The Schottky diode D3 provides the supply current to the high-side MOSFET driver. Layout and Bypassing Bypass DCIN with a 1µF capacitor to power ground (Figure 1). D2 protects the MAX1908/MAX8724/ MAX8765 when the DC power source input is reversed. A signal diode for D2 is adequate because DCIN only powers the internal circuitry. Bypass LDO, REF, CCV, CCI, CCS, ICHG, and IINP to analog ground. Bypass DLOV to power ground. 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 MAX1908 evaluation kit for examples. Separate analog and power grounds are essential for optimum performance. Use the following step-by-step guide: 1) Place the high-power connections first, with their grounds adjacent: a) Minimize the current-sense resistor trace lengths, and ensure accurate current sensing with Kelvin connections. b) Minimize ground trace lengths in the high-current paths. c) Minimize other trace lengths in the high-current paths. d) Use > 5mm wide traces. e) Connect C1 to high-side MOSFET (10mm max length). f) LX node (MOSFETs, inductor (15mm max length)). 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. The resulting top-layer power ground plane is connected to the normal ground plane at the MAX1908/MAX8724/MAX8765s’ backside exposed pad. Other high-current paths should also be minimized, but focusing primarily on short ground and current-sense connections eliminates most PC board layout problems. ______________________________________________________________________________________ 27 MAX1908/MAX8724/MAX8765 MAX1908/MAX8724 where dV is the maximum voltage sag of 0.5V while delivering energy to the inductor during the high-side MOSFET on-time, and dt is the period at highest operating frequency (400kHz): MAX1908/MAX8724/MAX8765 Low-Cost Multichemistry Battery Chargers 2) Place the IC and signal components. Keep the main switching node (LX node) 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, DLO, and BST) 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. 3) Use a single-point star ground placed directly below the part at the backside exposed pad of the MAX1908/MAX8724/MAX8765. Connect the power ground and normal ground to this node. Table 3. Component List for Circuit of Figure 2 DESIGNATION QTY C1 C4 C5 C9, C10 C11, C14, C15, C20 C12, C13, C16 D1 (optional) D2 DESCRIPTION DESIGNATION QTY DESCRIPTION 2 10µF, 50V 2220-size ceramic capacitors TDK C5750X7R1H106M D3 1 Schottky diode Central Semiconductor CMPSH1-4 L1 1 1 22µF, 25V 2220-size ceramic capacitor TDK C5750X7R1E226M 10µH, 4.4A inductor Sumida CDRH104R-100NC TOKO 919AS-100M N1 1 Dual, n-channel, 8-pin SO MOSFET Fairchild FDS6990A or FDS6990S 1 1µF, 25V X7R ceramic capacitor (1206) Murata GRM31MR71E105K Taiyo Yuden TMK316BJ105KL TDK C3216X7R1E105K P1 1 Single, p-channel, 8-pin SO MOSFET Fairchild FDS6675 2 0.01µF, 16V ceramic capacitors (0402) Murata GRP155R71E103K Taiyo Yuden EMK105BJ103KV TDK C1005X7R1E103K 4 0.1µF, 25V X7R ceramic capacitors (0603) Murata GRM188R71E104K TDK C1608X7R1E104K 3 1µF, 6.3V X5R ceramic capacitors (0603) Murata GRM188R60J105K Taiyo Yuden JMK107BJ105KA TDK C1608X5R1A105K 1 10A Schottky diode (D-PAK) Diodes, Inc. MBRD1035CTL ON Semiconductor MBRD1035CTL 1 Schottky diode Central Semiconductor CMPSH1–4 R5 1 1kΩ ±5% resistor (0603) R6 1 59kΩ ±1% resistor (0603) R7 1 19.6kΩ ±1% resistor (0603) R11 1 12kΩ ±5% resistor (0603) R12 1 15kΩ ±5% resistor (0603) R13 1 33Ω ±5% resistor (0603) R14 1 10.5kΩ ±1% resistor (0603) R15, R16 2 8.25kΩ ±1% resistors (0603) R17 1 19.1kΩ ±1% resistor (0603) R18 1 22kΩ ±1% resistor (0603) R19, R20 2 10kΩ ±1% resistors (0603) RS1 1 0.01Ω ±1%, 0.5W 2010 sense resistor Vishay Dale WSL2010 0.010 1.0% IRC LRC-LR2010-01-R010-F RS2 1 0.015Ω ±1%, 0.5W 2010 sense resistor Vishay Dale WSL2010 0.015 1.0% IRC LRC-LR2010-01-R015-F U1 1 MAX1908ETI, MAX8724ETI, or MAX8765ETI Chip Information TRANSISTOR COUNT: 3772 PROCESS: BiCMOS 28 ______________________________________________________________________________________ Low-Cost Multichemistry Battery Chargers QFN THIN.EPS D2 D CL D/2 MARKING k b 0.10 M C A B D2/2 L AAAAA E/2 E2/2 CL (NE-1) X e E DETAIL A PIN # 1 I.D. E2 PIN # 1 I.D. 0.35x45° e/2 e (ND-1) X e DETAIL B e L L1 CL CL L L e e 0.10 C A C 0.08 C A1 A3 PACKAGE OUTLINE, 16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm -DRAWING NOT TO SCALE- COMMON DIMENSIONS A1 A3 b D E e PKG. CODES 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0 0.02 0.05 0 0.02 0.05 0 0.02 0.05 1 2 EXPOSED PAD VARIATIONS PKG. 16L 5x5 20L 5x5 28L 5x5 32L 5x5 40L 5x5 SYMBOL MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. A I 21-0140 0 0.02 0.05 0 E2 exceptions MIN. NOM. MAX. ±0.15 T1655-2 3.00 T1655-3 3.00 T1655N-1 3.00 T2055-3 3.00 3.00 T2055-4 T2055-5 3.15 T2855-3 3.15 T2855-4 2.60 T2855-5 2.60 3.15 T2855-6 T2855-7 2.60 T2855-8 3.15 T2855N-1 3.15 T3255-3 3.00 T3255-4 3.00 T3255-5 3.00 T3255N-1 3.00 T4055-1 3.20 0.02 0.05 0.20 REF. 0.20 REF. 0.20 REF. 0.20 REF. 0.20 REF. 0.25 0.30 0.35 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 0.15 0.20 0.25 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 0.65 BSC. 0.50 BSC. 0.80 BSC. 0.50 BSC. 0.40 BSC. - 0.25 - 0.25 - 0.25 0.35 0.45 0.25 - 0.25 0.30 0.40 0.50 0.45 0.55 0.65 0.45 0.55 0.65 0.30 0.40 0.50 0.40 0.50 0.60 L1 0.30 0.40 0.50 16 20 28 32 N 40 ND 10 4 5 7 8 10 4 5 7 8 NE WHHC WHHD-1 WHHD-2 ----WHHB JEDEC k L NOTES: 1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. 2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. 3. N IS THE TOTAL NUMBER OF TERMINALS. L D2 MIN. NOM. MAX. 3.10 3.10 3.10 3.10 3.10 3.25 3.25 2.70 2.70 3.25 2.70 3.25 3.25 3.10 3.10 3.10 3.10 3.30 3.20 3.20 3.20 3.20 3.20 3.35 3.35 2.80 2.80 3.35 2.80 3.35 3.35 3.20 3.20 3.20 3.20 3.40 3.00 3.00 3.00 3.00 3.00 3.15 3.15 2.60 2.60 3.15 2.60 3.15 3.15 3 3.00 3 3.00 3.00 3.00 3.20 3.10 3.10 3.10 3.10 3.10 3.25 3.25 2.70 2.70 3.25 2.70 3.25 3.25 3.10 3.10 3.10 3.10 3.30 3.20 3.20 3.20 3.20 3.20 3.35 3.35 2.80 2.80 3.35 2.80 3.35 3.35 .20 .20 3.20 3.20 3.40 ** ** ** ** ** 0.40 ** ** ** ** ** 0.40 ** ** ** ** ** ** DOWN BONDS ALLOWED YES NO NO YES NO YES YES YES NO NO YES YES NO YES NO YES NO YES ** SEE COMMON DIMENSIONS TABLE 4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. 5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm FROM TERMINAL TIP. 6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. 7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. 8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. 9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT EXPOSED PAD DIMENSION FOR T2855-3 AND T2855-6. 10. WARPAGE SHALL NOT EXCEED 0.10 mm. 11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY. 12. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY. 13. LEAD CENTERLINES TO BE AT TRUE POSITION AS DEFINED BY BASIC DIMENSION "e", ±0.05. -DRAWING NOT TO SCALE- PACKAGE OUTLINE, 16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm 21-0140 I 2 2 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 29 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc. MAX1908/MAX8724/MAX8765 MAX1908/MAX8724 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)