19-3885; Rev 0; 12/05 KIT ATION EVALU LE B A IL A AV Low-Cost Battery Charger The MAX8730 highly integrated, multichemistry, batterycharger control IC simplifies construction of accurate and efficient chargers. The MAX8730 operates at high switching frequency to minimize external component size and cost. The MAX8730 uses analog inputs to control charge current and voltage, and can be programmed by a microcontroller or hardwired. The MAX8730 reduces charge current to give priority to the system load, effectively limiting the adapter current and reducing the adapter current requirements. The MAX8730 provides a digital output that indicates the presence of an AC adapter, and an analog output that monitors the current drawn from the AC adapter. Based on the presence and absence of the AC adapter, the MAX8730 automatically selects the appropriate source for supplying power to the system by controlling two external switches. Under system control, the MAX8730 allows the battery to undergo a relearning cycle in which the battery is completely discharged through the system load and then recharged. An analog output indicates adapter current or batterydischarge current. The MAX8730 provides a low-quiescent-current linear regulator, which may be used when the adapter is absent, or disabled for reduced current consumption The MAX8730 is available in a small, 5mm x 5mm, 28pin, thin (0.8mm) QFN package. An evaluation kit is available to reduce design time. The MAX8730 is available in a lead-free package. Applications Features ♦ ♦ ♦ ♦ Small Inductor (3.5µH) Programmable Charge Current > 4.5A Automatic Power-Source Selection Analog Inputs Control Charge Current and Charge Voltage ♦ Monitor Outputs for AC Adapter Current Battery-Discharge Current AC Adapter Presence ♦ Independent 3.3V 20mA Linear Regulator ♦ Up to 17.6V (max) Battery Voltage ♦ +8V to +28V Input Voltage Range ♦ Reverse Adapter Protection ♦ System Short-Circuit Protection ♦ Cycle-by-Cycle Current Limit Ordering Information PINPACKAGE PART TEMP RANGE MAX8730ETI+ -40°C to +85°C 28 Thin QFN (5mm x 5mm) PKG CODE T2855-5 +Denotes lead-free package. Typical Operating Circuit SYSTEM LOAD ADAPTER INPUT Notebook Computers CSSP PDS SRC Tablet PCs CSSN DHIV PDL Portable Equipment with Rechargeable Batteries DHI ASNS MAX8730 HOST LDO ACIN ACOK VCTL REF CLS CSIP CSIN BATT SWREF REF MODE ICTL RELTH REFON INPON Pin Configuration appears at end of data sheet. BATTERY IINP CCI LDO CCS CCV GND ________________________________________________________________ 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 MAX8730 General Description MAX8730 Low-Cost Battery Charger ABSOLUTE MAXIMUM RATINGS RELTH, VCTL, ICTL, REFON, CLS, LDO, INPON to GND .....................................................-0.3V to +6V LDO Short-Circuit Current...................................................50mA Continuous Power Dissipation (TA = +70°C) 28-Pin TQFN (derate 20.8mW/°C above +70°C) .......1667mW 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 CSSP, SRC, A C O K, ASNS, DHIV, BATT, CSIP to GND.......................................................-0.3V to +30V CSIP to CSIN or CSSP to CSSN ............................-0.3V to +0.3V DHIV to SRC .................................................-6V to (SRC + 0.3V) DHI to DHIV ...............................................-0.3V to (SRC + 0.3V) PDL, PDS to GND ........................................-0.3V to (SRC + 0.3) CCI, CCS, CCV, IINP, SWREF, REF, MODE, ACIN to GND.............................-0.3V to (LDO + 0.3V) 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 (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0 3.6 V Not including resistor tolerances -1.0 +1.0 Including 1% resistor tolerances -1.05 +1.05 VVCTL = VLDO (3 or 4 cells) -0.5 +0.5 VVCTL rising 4.4 VVCTL = 3V 0 4 SRC = BATT, ASNS = GND INPON = REFON = 0, VVCTL = 5V 0 16 CHARGE-VOLTAGE REGULATION VCTL Range Battery-Regulation Voltage Accuracy VVCTL Default Threshold VCTL Input Bias Current VVCTL = 3.6V or 0V % V µA CHARGE-CURRENT REGULATION ICTL Range Full-Charge-Current Accuracy (CSIP to CSIN) 0 VICTL = 3.6V VICTL = 2.0V 128.25 3.6 V 135 141.75 mV +5 % 75 78.75 mV +5 % 7.5 mV -5 71.25 -5 Trickle-Charge-Current Accuracy VICTL = 120mV 2.5 Charge-Current Gain Error Based on VICTL = 3.6V and VICTL = 0.12V -1.9 +1.9 % Charge-Current Offset Error Based on VICTL = 3.6V and VICTL = 0.12V -2 +2 mV 0 19 V BATT/CSIP/CSIN Input Voltage Range Charging enabled CSIP/CSIN Input Current 2 Charging disabled, SRC = BATT, ASNS = GND or VICTL = 0V 4.5 300 600 8 16 _______________________________________________________________________________________ µA Low-Cost Battery Charger (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL ICTL Power-Down Mode Threshold ICTL Input Bias Current CONDITIONS MIN TYP ICTL falling 50 65 80 ICTL rising 70 90 110 VICTL = 3V -1 +1 SRC = BATT, ASNS = GND, VICTL = 5V -1 +1 CSSP-to-CSSN Full-Scale Current-Sense Voltage VCLS = REF (trim point) Input Current-Limit Accuracy VCLS = REF x 0.7 VCLS = REF x 0.5 CSSP/CSSN Input Voltage Range CSSP/CSSN Input Current mV 72.75 75.75 78.75 mV -4 50 53 -5.6 +4 % 56 mV +5.6 % 40.5 mV -6.6 +6.6 % 8.0 28 V 36 38 VSRC = 0V 0.1 1 1.1 VCLS = 2.0V VCSSP - VCSSN = 56mV µA 78.75 800 IINP Transconductance mV 75.75 400 CLS Input Bias Current UNITS 72.75 VCSSP = VCSSN = VSRC > 8.0V CLS Input Range IINP Accuracy MAX REF -1 2.66 2.8 µA V +1 µA 2.94 µA/mV VCSSP - VCSSN = 100mV, VIINP = 0 to 4.5V -5 +5 VCSSP - VCSSN = 75mV -8 +8 VCSSP - VCSSN = 56mV -5 +5 VCSSP - VCSSN = 20mV -12.5 +12.5 % IINP Gain Error Based on VICTL = REF x 0.5 and VICTL = REF -7 +7 % IINP Offset Error Based on VICTL = REF x 0.5 and VICTL = REF -2 +2 mV IINP Fault threshold IINP rising 4.1 4.3 V 28 V 4.2 SUPPLY AND LINEAR REGULATOR SRC Input Voltage Range SRC Undervoltage Lockout Threshold 8.0 SRC falling SRC rising 7 7.4 7.5 8 V _______________________________________________________________________________________ 3 MAX8730 ELECTRICAL CHARACTERISTICS (continued) MAX8730 Low-Cost Battery Charger ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 4 6 mA VINPON =VREFON = low 10 20 VINPON = low, VREFON = high 300 600 VINPON = high, VREFON = low 300 600 VINPON = VREFON = high 350 600 Normal mode SRC Quiescent Current (INPON/REFON = Don’t Care) VSRC = VBATT = 12V, ASNS = GND (Note 2) µA VBATT = 16.8V, VSRC = 19V, ICTL = 0 BATT Input Current VBATT = 2V to 19V, VSRC > VBATT + 0.3V ICSIP + ICSIN + IBATT, ASNS = GND ICSIP + ICSIN + IBATT + ICSSP + ICSSN + ISRC, ASNS = REFON = GND Battery-Leakage Current 8 16 300 600 2 5 VREFON = 5.4V 300 600 INPON = GND 2 5 µA LDO Output Voltage 8.0V < VSRC < 28V, no load 5.35 5.5 V LDO Load Regulation 0 < ILDO < 10mA 20 50 mV VSRC = 8.0V 4 LDO Undervoltage Lockout Threshold REFERENCES REF Output Voltage Ref 5.2 µA 4.18 REF Undervoltage Lockout Threshold REF falling SWREF Output Voltage 8.0V < VSRC < 28V, no load SWREF Load Regulation 0.1mA < ISWREF < 20mA 3.234 V 4.20 4.22 V 3.1 3.9 V 3.3 3.366 V 20 50 mV 2.1 2.163 TRIP POINTS ACIN Threshold ACIN rising 2.037 ACIN Threshold Hysteresis ACIN Input Bias Current 60 V mV VACIN = 2.048V -1 +1 µA DHI Off-Time VBATT = 16.0V 300 350 400 ns DHI Off-Time K Factor VBATT = 16.0V 4.8 5.6 6.4 V x µs Sense Voltage for Minimum Discontinuous Mode Ripple Current VCSIP - VCSIN SWITCHING REGULATOR Cycle-by-Cycle Current-Limit Sense Voltage Charge Disable Threshold VSRC - VBATT, SRC falling DHIV Output Voltage With respect to SRC DHIV Sink Current 4 7 mV 160 200 240 mV 40 60 80 mV -4.3 -4.8 -5.5 10 _______________________________________________________________________________________ V mA Low-Cost Battery Charger (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) TYP MAX UNITS DHI Resistance Low PARAMETER SYMBOL IDHI = -10mA CONDITIONS MIN 2 4 Ω DHI Resistance High IDHI = 10mA 1 2 Ω ERROR AMPLIFIERS GMV Loop Transconductance VCTL = 3.6V, VBATT = 16.8V, MODE = LDO 0.0625 0.125 0.250 VCTL = 3.6V, VBATT = 12.6V, MODE = FLOAT 0.0833 0.167 0.333 mA/V GMI Loop Transconductance ICTL = 3.6V, VCSSP - VCSIN = 75mV 0.5 1 2 mA/V GMS Loop Transconductance VCLS = 2.048V, VCSSP - VCSSN = 75mV 0.5 1 2 mA/V CCI/CCS/CCV Clamp Voltage 1.1V < VCCV < 3.0V, 1.1V < VCCI < 3.0V, 1.1V < VCCS < 3.0V 150 300 600 mV 0.5 V MODE Input Middle Voltage 1.9 2.65 3.3 V MODE, REFON Input High Voltage 3.4 LOGIC LEVELS MODE, REFON Input Low Voltage MODE, REFON, INPON Input Bias Current INPON Threshold MODE = 0 or 3.6V -2 VINPON rising 2.2 V +2 µA V VINPON falling 0.8 V ADAPTER DETECTION ACOK Voltage Range 0 ACOK Sink Current VACOK = 0.4V, ACIN = 1.5V ACOK Leakage Current VACOK = 28V, ACIN = 2.5V 28 1 V mA 1 µA BATTERY DETECTION BATT Overvoltage Threshold VVCTL = VLDO , BATT rising; result with respect to battery-set voltage VMODE = VLDO +140 VMODE = FLOAT +100 mV BATT Overvoltage Hysteresis 100 RELTH Operating Voltage Range RELTH Input Bias Current VRELTH = 0.9V to 2.6V BATT Minimum Voltage Trip Threshold VBATT falling mV 0.9 2.6 V -50 +50 nA VRELTH = 0.9V 4.42 4.5 4.58 VRELTH = 2.6V 12.77 13.0 13.23 V PDS, PDL SWITCH CONTROL Adapter-Absence Detect Threshold VASNS - VBATT, VASNS falling -300 -280 -240 mV Adapter-Detect Threshold VASNS - VBATT -140 -100 -60 mV PDS Output Low Voltage Result with respect to SRC, IPDS = 0 -8 -10 -12 V PDS/PDL Output High Voltage Result with respect to SRC, IPD_ = 0 -0.2 -0.5 PDS/PDL Turn-Off Current VPDS = VSRC - 2V, VSRC = 16V 6 12 V mA _______________________________________________________________________________________ 5 MAX8730 ELECTRICAL CHARACTERISTICS (continued) MAX8730 Low-Cost Battery Charger ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) MIN TYP PDS Turn-On Current PARAMETER SYMBOL PDS = SRC CONDITIONS 6 12 PDL Turn-On Resistance PDL = GND 50 100 PDS/PDL Delay Time MAX UNITS mA 200 5.0 kΩ µs ELECTRICAL CHARACTERISTICS (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0 3.6 V Not including resistor tolerances -1.2 +1.2 Including 1% resistor tolerances -1.25 +1.25 +0.8 CHARGE-VOLTAGE REGULATION VCTL Range Battery-Regulation-Voltage Accuracy VVCTL = 3.6V or 0V VVCTL = VLDO (3 or 4 cells) -0.8 VVCTL Default Threshold VVCTL rising 4.4 VCTL Input Bias Current SRC = BATT, ASNS = GND INPON = REFON = 0, VVCTL = 5V 0 % V 16 µA CHARGE-CURRENT REGULATION ICTL Range Full-Charge-Current Accuracy (CSIP to CSIN) VICTL = 3.6V VICTL = 2.0V 0 3.6 V 128.25 141.75 mV -5 +5 % 70 80 mV -6.7 +6.7 % mV Trickle-Charge-Current Accuracy VICTL = 120mV 2 10 Charge-Current Gain Error Based on VICTL = 3.6V and VICTL = 0.12V -1.9 +1.9 % Charge-Current Offset Error Based on VICTL = 3.6V and VICTL = 0.12V -2 +2 mV 0 19 V BATT/CSIP/CSIN Input Voltage Range Charging enabled 1000 CSIP/CSIN Input Current Charging disabled, SRC = BATT, ASNS = GND, or VICTL = 0V ICTL Power-Down Mode Threshold ICTL falling 50 80 ICTL rising 70 110 6 16 _______________________________________________________________________________________ µA mV Low-Cost Battery Charger (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 72.75 78.25 mV VCLS = REF (trim point) 72.75 78.25 mV VCLS = REF x 0.7 50.0 56.0 mV VCLS = REF x 0.5 36.00 40.50 mV INPUT-CURRENT REGULATION CSSP-to-CSSN Full-Scale Current-Sense Voltage Input Current-Limit Accuracy CSSP/CSSN Input Voltage Range CSSP/CSSN Input Current 8.0 CLS Input Range IINP Transconductance IINP Accuracy 28 V 1000 µA 1.1 REF V µA/mV VCSSP = VCSSN = VSRC > 8.0V VCSSP - VCSSN = 56mV 2.66 2.94 VCSSP - VCSSN = 100mV, VIINP = 0 to 4.5V -5 +5 VCSSP - VCSSN = 75mV -8 +8 VCSSP - VCSSN = 56mV -5 +5 VCSSP - VCSSN = 20mV % -12.5 +12.5 IINP Gain Error Based on VICTL = REF x 0.5 and VICTL = REF -7 +7 % IINP Offset Error Based on VICTL = REF x 0.5 and VICTL = REF -2 +2 mV IINP Fault Threshold IINP rising 4.1 4.3 V 8.0 28 V SUPPLY AND LINEAR REGULATOR SRC Input Voltage Range SRC Undervoltage Lockout Threshold SRC falling 7 SRC rising 8 Normal mode 6 VINPON = VREFON = low 20 VINPON = low, VREFON = high 600 VINPON = high, VREFON = low 600 VINPON = VREFON = high 600 BATT Input Current VBATT = 2V to 19V, VSRC > VBATT + 0.3V 600 VREFON = 5.4V 600 Battery Leakage Current ICSIP + ICSIN + IBATT + ICSSP + ICSSN + ISRC, ASNS = REFON = GND INPON = GND 16 SRC Quiescent Current (INPON/REFON = Don’t Care) SRC = VBATT = 12V, ASNS = GND (Note 2) V mA µA µA µA LDO Output Voltage 8.0V < VSRC < 28V, no load LDO Load Regulation 0 < ILDO < 10mA 5.2 5.5 V 50 mV _______________________________________________________________________________________ 7 MAX8730 ELECTRICAL CHARACTERISTICS (continued) MAX8730 Low-Cost Battery Charger ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 4.24 V 3.9 V REFERENCES REF Output Voltage Ref 0 < IREF < 500µA REF Undervoltage Lockout Threshold REF falling SWREF Output Voltage 8.0V < VSRC < 28V, no load SWREF Load Regulation 0.1mA < ISWREF < 20mA 4.16 3.224 3.376 V 50 mV 2.037 2.163 V TRIP POINTS ACIN Threshold ACIN rising SWITCHING REGULATOR DHI Off-Time VBATT = 16.0V 300 400 ns DHI Off-Time K Factor VBATT = 16.0V 4.8 6.4 V x µs 160 240 mV -4.3 -5.5 Cycle-by-Cycle Current-Limit Sense Voltage DHIV Output Volatge With respect to SRC DHIV Sink Current 10 V mA DHI Resistance Low IDHI = -10mA 4 Ω DHI Resistance High IDHI = 10mA 2 Ω ERROR AMPLIFIERS GMV Loop Transconductance VCTL = 3.6V, VBATT = 16.8V, MODE = LDO 0.0625 0.250 VCTL = 3.6V, VBATT = 12.6V, MODE = FLOAT 0.0833 0.333 mA/V GMI Loop Transconductance ICTL = 3.6V, VCSSP - VCSIN = 75mV 0.5 2 mA/V GMS Loop Transconductance VCLS = 2.048V, VCSSP - VCSSN = 75mV 0.5 2 mA/V CCI/CCS/CCV Clamp Voltage 1.1V < VCCV < 3.0V, 1.1V < VCCI < 3.0V, 1.1V < VCCS < 3.0V 150 600 mV 0.5 V 3.3 V LOGIC LEVELS MODE, REFON Input Low Voltage MODE Input Middle Voltage 1.9 MODE, REFON Input High Voltage INPON Threshold 3.4 VINPON rising V 2.2 VINPON falling 0.8 V ADAPTER DETECTION ACOK Voltage Range ACOK Sink Current 8 0 VACOK = 0.4V, ACIN = 1.5V 1 _______________________________________________________________________________________ 28 V mA Low-Cost Battery Charger (Circuit of Figure 1. VSRC = VASNS = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VVCTL = VICTL = 1.8V, MODE = float, ACIN = 0, CLS = REF, REFON = LDO, INPON = LDO, RELTH = 2V. TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V BATTERY DETECTION RELTH Operating Voltage Range BATT Minimum Voltage Trip Threshold VBATT falling 0.9 2.6 VRELTH = 0.9V 4.42 4.58 VRELTH = 2.6V 12.77 13.23 V PDS, PDL SWITCH CONTROL Adapter-Absence-Detect Threshold VASNS - VBATT, VASNS falling -310 -240 mV Adapter-Detect Threshold VASNS - VBATT -140 -60 mV PDS Output Low Voltage Result with respect to SRC, IPDS = 0 -7 -12 V PDS/PDL Output High Voltage Result with respect to SRC, IPD_ = 0 -0.5 V PDS/ PDL Turn-Off Current VPDS = VSRC - 2V, VSRC = 16V 6 PDS Turn-On Current PDS = SRC 6 PDL Turn-On Resistance PDL = GND Note 1: Accuracy does not include errors due to external-resistance tolerances. Note 2: In this mode, SRC current is drawn from the battery. 50 mA mA 100 200 kΩ _______________________________________________________________________________________ 9 MAX8730 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (Circuit of Figure 1, adapter = 19.5V, VBATT = 12V, VICTL = 2.4V, MODE > 1.8V, REFON = INPON = LDO, VRELTH = VREF/2, TA = +25°C, unless otherwise noted.) 0 TYPICAL UNIT -5 MINIMUM -10 3.5 3.0 VIN = 19V VIN = 17V 2.5 2.0 1.5 1.0 0.5 -15 2.6 3.1 3.6 4.1 0.5 1.0 1.5 2.0 2.5 SYSTEM CURRENT (A) VCLS (V) MAXIMUM 5 0 -5 MINIMUM 15 MAXIMUM ERROR 10 0 TYPICAL UNIT -5 -10 MINIMUM ERROR 1 0.6 1.2 1.8 2.4 VICTL (V) 3.0 0 -5 -10 -15 4 5 VICTL = 2V 1.3 1.0 0.7 0.4 0.1 VICTL = 3.6V 0 3.6 -0.10 4 CELLS 3 CELLS -0.15 10 15 BATTERY VOLTAGE (V) 20 BATTERY-VOLTAGE ERROR vs. VCTL MAX8730 toc08 -0.05 5 -0.20 -20 1.0 0.8 CHARGE-VOLTAGE ERROR (%) 5 0 BATTERY-VOLTAGE ERROR (%) 10 2 3 SYSTEM CURRENT (A) 1.6 BATTERY-VOLTAGE ERROR vs. CHARGE CURRENT MAX8730 toc07 CHARGE CURRENT = 150mA 1 -0.5 0 TRICKLE-CHARGE CURRENT vs. BATTERY VOLTAGE 15 VCLS = VREF x 0.7 -0.2 VCSSP - VCSSN 20 2 CHARGE-CURRENT ERROR vs. BATTERY VOLTAGE 5 10 20 30 40 50 60 70 80 90 100 25 VCLS = VREF 3 0 -20 0 4 3.5 -15 -15 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -25 0 10 3.0 20 CHARGE-CURRENT ERROR (%) IINP ERROR (%) MAX8730 toc04 15 -10 5 CHARGE-CURRENT ERROR vs. CHARGE-CURRENT SETTING IINP ERROR vs. VCSSP - VCSSN 10 VCLS = VREF / 2 0 0 CHARGE-CURRENT ERROR (%) 2.1 MAX8730 toc05 1.6 6 VCLS = VREF x 0.7 0 1.1 MAX8730 toc03 4.0 MAX8730 toc06 5 VIN = 24V 4.5 MAX8730 toc09 10 7 5.0 INPUT CURRENT-LIMIT ERROR (%) MAXIMUM INPUT CURRENT-LIMIT ERROR (%) MAX8730 toc01 INPUT CURRENT-LIMIT ERROR (%) 15 INPUT CURRENT-LIMIT ERROR vs. SYSTEM CURRENT INPUT CURRENT-LIMIT ERROR vs. SYSTEM CURRENT INPUT CURRENT-LIMIT ERROR vs. CLS TRICKLE-CHARGE-CURRENT ERROR (%) MAX8730 Low-Cost Battery Charger 3 6 9 12 BATTERY VOLTAGE (V) 15 18 -0.25 -1.0 0 0.5 1.0 1.5 2.0 2.5 CHARGE CURRENT (A) 3.0 3.5 0 0.5 1.0 1.5 2.0 VCTL (V) ______________________________________________________________________________________ 2.5 3.0 3.5 Low-Cost Battery Charger SWITCHING FREQUENCY vs. BATTERY VOLTAGE OUTPUT RIPPLE VOLTAGE vs. BATTERY VOLTAGE SWITCHING FREQUENCY (kHz) 0.15 0.12 0.09 0.06 MAX8730 toc11 1000 MAX8730 toc10 OUTPUT RIPPLE VOLTAGE (mVP-P) 0.18 800 600 400 0.03 200 0 0 5 10 15 BATTERY VOLTAGE (V) 0 20 BATTERY REMOVAL 3 6 9 12 BATTERY VOLTAGE (V) 15 18 ADAPTER INSERTION MAX8730toc12 MAX8730toc13 CHARGE CURRENT = 12V 20V ADAPTER COUT = 4.7µF ADAPTER INSERTION 13V 0V 20V PDS 0V 12.5V 20V COUT = 10µF PDL 0V 20V SYSTEM LOAD 4µs/div 0V 100µs/div ADAPTER REMOVAL SYSTEM LOAD TRANSIENT MAX8730toc14 BATTERY VOLTAGE = 16.8V ADAPTER MAX8730toc15 20V 0V 20V PDS 0V 20V PDL 0V 5A LOAD CURRENT 0A ADAPTER CURRENT 5A INDUCTOR CURRENT 0A 5A 0A COMPENSATION CCS 500mV/div CCI CCI 20V SYSTEM LOAD 0V 4ms/div CCS 200µs/div ______________________________________________________________________________________ 11 MAX8730 Typical Operating Characteristics (continued) (Circuit of Figure 1, adapter = 19.5V, VBATT = 12V, VICTL = 2.4V, MODE > 1.8V, REFON = INPON = LDO, VRELTH = VREF/2, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (Circuit of Figure 1, adapter = 19.5V, VBATT = 12V, VICTL = 2.4V, MODE > 1.8V, REFON = INPON = LDO, VRELTH = VREF/2, TA = +25°C, unless otherwise noted.) PEAK-TO-PEAK INDUCTOR CURRENT vs. BATTERY VOLTAGE EFFICIENCY vs. CHARGE CURRENT 2.3 2.1 MAX8730 toc17 100 MAX7830 toc16 90 1.9 EFFICIENCY (%) 1.7 1.5 1.3 3 CELLS 80 1.1 70 0.9 0.7 0.5 3 6 9 12 BATTERY VOLTAGE (V) 15 60 18 0 2.5 2.0 REFON = 1 INPON = 1 1.5 1.0 0.5 3.5 4.0 REFON = 0 INPON = 0 500 REFON = INPON = 1 BATTERY-LEAKAGE CURRENT (µA) MAX8730 toc18 BATTERY ABSENT 1.0 1.5 2.0 2.5 3.0 CHARGE CURRENT (A) BATTERY LEAKAGE CURRENT vs. BATTERY VOLTAGE ADAPTER QUIESCENT CURRENT vs. ADAPTER VOLTAGE 3.0 0.5 MAX8730 toc19 0 ADAPTER QUIESCENT CURRENT (mA) 4 CELLS REFON = 0 INPON = 1 400 300 200 REFON = 1 INPON = 0 100 REFON = INPON = 0 0 0 0 5 10 15 20 ADAPTER VOLTAGE (V) 0 25 15 0 MAX8730 toc20 INITIAL CONDITION: 4 CELLS 10V BATTERY FULL CHARGE = 16.8V 3.0 6 9 12 BATTERY VOLTAGE (V) 18 LDO LOAD REGULATION CHARGE CURRENT vs. TIME 3.5 3 -0.2 LDO ERROR (%) 1.5 CHARGER DISABLED -0.1 2.5 2.0 MAX8730 toc21 PEAK-TO-PEAK INDUCTOR CURRENT (A) 2.5 CHARGE CURRENT (A) MAX8730 Low-Cost Battery Charger -0.3 -0.4 -0.5 -0.6 1.0 -0.7 0.5 -0.8 -0.9 0 0 12 0.5 1.0 1.5 2.0 TIME (h) 2.5 3.0 0 10 20 30 ILDO (mA) ______________________________________________________________________________________ 40 50 Low-Cost Battery Charger REFERENCE LOAD REGULATION LDO LINE REGULATION -0.360 CHARGER DISABLED -0.13 -0.15 -0.370 -0.17 REF (%) -0.365 -0.375 -0.380 -0.385 -0.19 -0.21 -0.390 -0.23 -0.395 -0.25 -0.400 8 13 18 23 INPUT VOLTAGE (V) 0 28 REF ERROR vs. TEMPERATURE 100 200 300 IREF (µA) 400 500 SWREF LOAD REGULATION -0.05 -0.3 SWREF ERROR (%) -0.10 -0.15 -0.20 MAX8730 toc25 0 MAX8730 toc24 0 REF ERROR (%) MAX8730 toc23 -0.355 LDO ERROR (%) -0.11 MAX8730 toc22 -0.350 -0.6 -0.9 -0.25 -1.2 -0.30 -0.35 -1.5 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 0 10 20 30 SWREF OUTPUT CURRENT (mA) 40 DISCONTINUOUS MODE SWITCHING WAVEFORM SWREF VOLTAGE vs. TEMPERATURE MAX8730toc27 MAX8730 toc26 3.32 3.31 1A SWREF VOLTAGE (V) 0 INDUCTOR CURRENT 3.30 20V 3.29 LX 3.28 0 3.27 20V DHI 3.26 CHARGE CURRENT = 20mA 0 3.25 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 1µs/div ______________________________________________________________________________________ 13 MAX8730 Typical Operating Characteristics (continued) (Circuit of Figure 1, adapter = 19.5V, VBATT = 12V, VICTL = 2.4V, MODE > 1.8V, REFON = INPON = LDO, VRELTH = VREF/2, TA = +25°C, unless otherwise noted.) Low-Cost Battery Charger MAX8730 Pin Description PIN NAME FUNCTION 1 ASNS Adapter Voltage Sense. When VASNS > VBATT - 280mV, the battery switch is turned off and the adapter switch is turned on. Connect to the adapter input using an RC filter as shown in Figure 1. 2 LDO Linear-Regulator Output. LDO is the output of the 5.35V linear regulator supplied from SRC. Bypass LDO with a 1µF ceramic capacitor from LDO to GND. 3 SWREF 3.3V Switched Reference. SWREF is a 1% accurate linear regulator that can deliver 20mA. SWREF remains active when the adapter is absent and may be disabled by setting REFON to zero. Bypass SWREF with a 1µF capacitor to GND. 4 REF 4.2V Voltage Reference. Bypass REF with a 1µF capacitor to GND. 5 CLS 6 ACIN Source Current-Limit Input. Voltage input for setting the current limit of the input source. AC-Adapter-Detect Input. ACIN is the input to an uncommitted comparator. ACIN does not influence adapter and battery selection. 7 VCTL 8 RELTH 9 ACOK 10 MODE 11 IINP AC Detect Output. This open-drain output pulls low when ACIN is greater than REF/2 and ASNS is greater than BATT - 100mV. The ACOK output is high impedance when the MAX8730 is powered down. Connect a 10kΩ pullup resistor from LDO to ACOK. Tri-Level Input for Setting Number of Cells or Asserting the Conditioning Mode: MODE = GND; asserts relearn mode. MODE = Float; charge with 3 times the cell voltage programmed at VCTL. MODE = LDO; charge with 4 times the cell voltage programmed at VCTL. Input-Current-Monitor Output. IINP sources the current proportional to the current sensed across CSSP and CSSN. The transconductance from (CSSP – CSSN) to IINP is 2.8µA/mV (typ). 12 ICTL 13 REFON SWREF Enable. Drive REFON high to enable SWREF. 14 15 INPON CCI Input Current-Monitor Enable. Drive INPON high to enable IINP. Output Current-Regulation Loop Compensation Point. Connect a 0.01µF capacitor from CCS to GND. 16 CCV Voltage-Regulation Loop Compensation Point. Connect a 10kΩ resistor in series with a 0.01µF capacitor to GND. 17 CCS Input Current-Regulation Loop Compensation Point. Connect a 0.01µF capacitor from CCS to GND. 18 19 GND BATT Analog Ground Battery-Voltage Feedback Input 20 CSIN Charge-Current-Sense Negative Input 21 CSIP Charge-Current-Sense Positive Input. Connect a current-sense resistor from CSIP to CSIN. 22 23 DHIV DHI High-Side Driver Supply. Connect a 0.1µF capacitor from DHIV to CSSN. High-Side Power MOSFET Driver Output. Connect to high-side, p-channel MOSFET gate. 24 SRC DC Supply Input Voltage and Connection for Driver for PDS/PDL Switches. Bypass SRC to power ground with a 1µF capacitor. 25 26 CSSN CSSP 27 PDS Power-Source PMOS Switch Driver Output. When the adapter is absent, the PDS output is pulled to SRC through an internal 1MΩ resistor. 28 PDL System-Load PMOS Switch Driver Output. When the adapter is absent, the PDL output is pulled to ground through an internal 100kΩ resistor. 29 14 Charge-Voltage-Control Input. Connect VCTL to LDO for default 4.2V/cell. Relearn Threshold for Relearn Mode. In relearn mode, when VBATT < 5 x VRELTH, the MAX8730 drives PDS low and drives PDL high to terminate relearning of a discharged battery. See the Relearn Mode section for more details. Charge-Current-Control Input. Pull ICTL to GND to shut down the charger. Input Current Sense for Negative Input Input Current Sense for Positive Input. Connect a 15mΩ current-sense resistor from CSSP to CSSN. Backside Backside Paddle. Connect the backside paddle to analog ground. Paddle ______________________________________________________________________________________ Low-Cost Battery Charger P2 RS1 15mΩ R3 3kΩ CSSN DHIV PDL R6 6kΩ R5 18kΩ PDS P4 D1 ASNS C4 0.1µF P3 DHI SRC C3 1µF CIN1 4.7µF C12 0.1µF CSSP R1 SYSTEM LOAD C2 10nF C1 32nF MAX8730 P1 ADAPTER INPUT L1 3.5µH R4 75kΩ MAX8730 ACIN REF RS2 30mΩ CSIP R2 CSIN R7 37.4kΩ R9 10kΩ R8 50kΩ BATT REF INPUT ACOK MODE SWREF REF INPUT C5 1µF HOST LDO REF REFON OUTPUT INPON A/D INPUT R13 50kΩ VCTL CLS OUTPUT C6 0.1µF C11 1µF RELTH R12 50kΩ LDO C10 1µF IINP R10 15kΩ COUT2 4.7µF COUT1 4.7µF ICTL LDO BATTERY COUT CCV R11 10kΩ C7 0.01µF GND CCI C8 0.01µF CCS C9 0.01µF Figure 1. Typical Application Circuit ______________________________________________________________________________________ 15 MAX8730 Low-Cost Battery Charger Detailed Description The MAX8730 includes all the functions necessary to charge Li+, NiMH, and NiCd batteries. A high-efficiency, step-down, DC-DC converter is used to implement a precision constant-current, constant-voltage charger. The DC-DC converter drives a p-channel MOSFET and uses an external free-wheeling Schottky diode. The charge current and input current-sense amplifiers have low-input offset errors, allowing the use of small-value sense resistors for reduced power dissipation. Figure 2 is the functional diagram. The MAX8730 features a voltage-regulation loop (CCV) and two current-regulation loops (CCI and CCS). The loops operate independently of each other. The CCV voltage-regulation loop monitors BATT to ensure that its voltage never exceeds the voltage set by VCTL. The CCI battery current-regulation loop monitors current delivered to BATT to ensure that it never exceeds the current limit set by ICTL. The charge-current-regulation loop is in control as long as the battery voltage is below the set point. When the battery voltage reaches its set point, the voltage-regulation loop takes control and maintains the battery voltage at the set point. A third loop (CCS) takes control and reduces the charge current when the adapter current exceeds the input current limit set by CLS. The ICTL, VCTL, and CLS analog inputs set the charge current, charge voltage, and input-current limit, respectively. For standard applications, default set points for VCTL provide 4.2V per-cell charge voltage. The MODE input selects a 3- or 4-cell mode. Based on the presence or absence of the AC adapter, the MAX8730 provides an open-drain logic output signal (A C O K) and connects the appropriate source to the system. P-channel MOSFETs controlled from the PDL and PDS select the appropriate power source. The MODE input allows the system to perform a battery relearning cycle. During a relearning cycle, the battery is isolated from the charger and completely discharged through the system load. When the battery reaches 100% depth of discharge, PDL turns off and PDS turns on to connect the adapter to the system and to allow the battery to be recharged to full capacity. Setting Charge Voltage The VCTL input adjusts the battery output voltage, VBATT. This voltage is calculated by the following equation: VBATT = CELLS x (4 V + 16 VVCTL ) 9 where CELLS is the number of cells selected with the MODE input (see Table 1). Connect MODE to LDO for 4cell operation. Float the MODE input for 3-cell operation. The battery-voltage accuracy depends on the absolute value of VCTL, and the accuracy of the resistive voltage-divider that sets VCTL. Calculate the battery voltage accuracy according to the following equation: x RVCTL I VBATT _ ERROR = E0 + 100% x VCTL − 1 36 where E0 is the worst-case MAX8730 battery voltage error when using 1% resistors (0.83%), IVCTL is the VCTL input bias current (4µA), and RVCTL is the impedance at VCTL. Connect VCTL to LDO for the default setting of 4.20V/cell with 0.7% accuracy. Connect MODE to GND to enter relearn mode, which allows the battery to discharge into the system while the adapter is present; see the Relearn Mode Section. Table 1. Cell-Count Programming CELLS CELL COUNT GND Relearn mode Float 3 LDO 4 Setting Charge Current ICTL sets the maximum voltage across current-sense resistor RS2, which determines the charge current. The full-scale differential voltage between CSIP and CSIN is 135mV (4.5A for RS2 = 30mΩ). Set ICTL according to the following equation: VICTL = ICHG x RS2 x 3.6V 135mV The input range for ICTL is 0 to 3.6V. To shut down the charger, pull ICTL below 65mV. Choose a current-sense resistor (RS2) to have a sufficient power rating to handle the full-charge current. The current-sense voltage may be reduced to minimize the power dissipation. However, this can degrade accuracy due to the current-sense amplifier’s input offset (±2mV). See the Typical Operating Characteristics to estimate the charge-current accuracy at various set points. The charge-current error amplifier (GMI) is compensated at the CCI pin. See the Compensation section. ______________________________________________________________________________________ Low-Cost Battery Charger ASNS PDS MAX8730 RELTH IINP PDL BATT CSSP CSSN SRC CURRENT-SENSE AMPLIFIER CSSP SYSTEM OVERCURRENT GM = 2.8µA/mV A = 20V/V PDS PDL LOGIC REF INPON SRC - 10V SRC REL_EN CCS GND VCTL + 40mV HIGHSIDE DRIVER SRC DHI OVP GMS CLS CCV BATT MODE 222mA CELLSELECT LOGIC GMV LOWEST VOLTAGE CLAMP SELECTOR (DEFAULT = 4.2V) VCTL -5V REGULATOR IMIN DC-DC CONVERTER LVC SRC CCMP REF CCI CHARGER BIAS LOGIC CSIP IMAX CSIN ICTL A = 15V/V CSI LDO REFERENCE 4.2V REF BATT MAX8730 CURRENT-SENSE AMPLIFIER 65mV 5.4V CHARGER REGULATOR 6.56A GMI ADAPTER DETECT REL_EN CHARGER SHUTDOWN DHIV SRC REF/2 N N REFERENCE 3.3V REFON 6µA ACOK GND ACIN SWREF Figure 2. Functional Diagram ______________________________________________________________________________________ 17 MAX8730 Low-Cost Battery Charger The MAX8730 includes a foldback feature, which reduces the Schottky requirement at low battery voltages. See the Foldback Current Section. Setting Input-Current Limit The total input current, from a wall adapter or other DC source, is the sum of the system supply current and the current required by the charger. When the input current exceeds the set input current limit, the MAX8730 decreases the charge current to provide priority to system load current. System current normally fluctuates as portions of the system are powered up or put to sleep. The input-current-limit circuit reduces the power requirement of the AC wall adapter, which reduces adapter cost. As the system supply rises, the available charge current drops linearly to zero. Thereafter, the total input current can increase without limit. The total input current is the sum of the device supply current, the charger input current, and the system load current. The total input current can be estimated as follows: I x VBATTERY IINPUT = ILOAD + CHARGE VIN x η where I INPUT is the DC current supplied by the AC adapter, G IINP is the transconductance of IINP (2.8µA/mV typ), and R 10 is the resistor connected between IINP and ground. Connect a 0.1µF filter capacitor from IINP to GND to reduce ripple. IINP has a 0 to 4.5V output-voltage range. Connect IINP to GND if it is not used. The MAX8730 provides a short-circuit latch to protect against system overload or short. The latch is set when VIINP rises above 4.2V, and disconnects the adapter from the system by turning PDS off (PDL does not change). The latch is reset by bringing SRC below UVLO (remove and reinsert the adapter). Choose a filter capacitor that is large enough to provide appropriate debouncing and prevent accidental faults, yet results in a response time that is fast enough to thermally protect the MOSFETs. See the System Short Circuit section. IINP can be used to measure battery-discharge current (see Figure 1) when the adapter is absent. To disable IINP and reduce battery consumption to 10µA, drive INPON to low. Charging is disabled when INPON is low, even if the adapter is present. where η is the efficiency of the DC-DC converter (typically 85% to 95%). AC-Adapter Detection and Power-Source Selection CLS sets the maximum voltage across the currentsense resistor RS1, which determines the input current limit. The full-scale differential voltage between CSSP and CSSN is 75mV (5A for RS1 = 15mΩ). Set CLS according to the following equation: The MAX8730 includes a hysteretic comparator that detects the presence of an AC power adapter and automatically selects the appropriate power source. When the adapter is present (V ASNS > V BATT -100mV) the battery is disconnected from the system load with the p-channel (P3) MOSFET. When the adapter is removed (VASNS < VBATT - -270mV), PDS turns off and PDL turns on with a 5µs break-beforemake sequence. The A C O K output can be used to indicate the presence of the adapter. When VACIN > 2.1V and VASNS > VBATT - 100mV, A C O K becomes low. Connect a 10kΩ pullup resistor between LDO and A C O K. Use a resistive voltage-divider from the adapter’s output to the ACIN pin to set the appropriate detection threshold. Since ACIN has a 6V absolute maximum rating, set the adapter threshold according to the following equation: VCLS = ILIMIT x RS1 x VREF 75mV The input range for CLS is 1.1V to VREF. Choose a current-sense resistor (RS1) to have a sufficient power rating to handle the full system current. The current-sense resistor may be reduced to improve efficiency, but this degrades accuracy due to the current-sense amplifier’s input offset (±3mV). See the Typical Operating Characteristics to estimate the input current-limit accuracy at various set points. The input current-limit error amplifier (GMS) is compensated at the CCS pin; see the Compensation section. Input-Current Measurement IINP monitors the system-input current sensed across CSSP and CSSN. The voltage of IINP is proportional to the input current according to the following equation: VIINP = IINPUT x RS1 x GIINP x R10 18 VADAPTER _ THRESHOLD > VADAPTER _ MAX 3 Relearn Mode The MAX8730 can be programmed to perform a relearn cycle to calibrate the battery’s fuel gauge. This cycle consists of isolating the battery from the charger and discharging it through the system load. When the battery ______________________________________________________________________________________ Low-Cost Battery Charger LDO Regulator, REF, and SWREF An integrated linear regulator (LDO) provides a 5.35V supply derived from SRC, and delivers over 10mA of load current. LDO biases the 4.2V reference (REF) and most of the control circuitry. Bypass LDO to GND with a 1µF ceramic capacitor. An additional standalone 1%, 3.3V linear regulator (SWREF) provides 20mA and can remain on when the adapter is absent. Set REFON low to disable SWREF. Set REFON high for normal operation. SWREF must be enabled to allow charging. • The IMIN comparator sets the peak inductor current in discontinuous mode. IMIN compares the control signal (LVC) against 100mV (corresponding to 222mA when RS2 = 30mΩ). The comparator terminates the switch on-time when IMIN exceeds the threshold. • The CCMP comparator is used for current-mode regulation in continuous conduction mode. CCMP compares LVC against the charging-current feedback signal (CSI). The comparator output is high and the MOSFET on-time is terminated when the CSI voltage is higher than LVC. • The IMAX comparator provides a cycle-by-cycle current limit. IMAX compares CSI to 2.95V (corresponding to 6.56A when RS2 = 30mΩ). The comparator output is high and the MOSFET on-time is terminated when the current-sense signal exceeds 6.56A. A new cycle cannot start until the IMAX comparator output goes low. • The OVP comparator is used to prevent overvoltage at the output due to battery removal. OVP compares BATT against the set voltage; see the Setting Charge Voltage section. When BATT is 20mV x CELLS above the set value, OVP goes high and the MOSFET ontime is terminated. Operating Conditions • Adapter present: The adapter is considered to be present when: VSRC > 8V (max) VASNS > VBATT - 300mV (max) • Charging: The MAX8730 allows charging when: VSRC - VCSIN > 100mV (typ) 3 or 4 cells selected (MODE float or high condition) ICTL > 110mV (max) INPON is high • Relearn mode: The MAX8730 enables relearn mode when: VBATT / 5 > VRELTH MODE is grounded BATT/CELLS OVP VCTLSETPOINT + 20mV CSI IMAX 2.95V CCMP R Q S Q DH DRIVER LVC DC-DC Converter The MAX8730 employs a step-down DC-DC converter with a p-channel MOSFET switch and an external Schottky diode. The MAX8730 features a constant-current-ripple, current-mode control scheme with cycle-bycycle current limit. For light loads, the MAX8730 operates in discontinuous conduction mode for improved efficiency. The operation of the DC-DC controller is determined by the following four comparators as shown in the functional block diagram in Figure 3: IMIN 100mV OFF-TIME ONE-SHOT BATT OFF-TIME COMPUTE Figure 3. DC-DC Converter Block Diagram ______________________________________________________________________________________ 19 MAX8730 reaches 100% depth of discharge, it is then recharged. Connect MODE to GND to place the MAX8730 in relearn mode. In relearn mode, charging stops, PDS turns off, and PDL turns on. To utilize relearn mode, there must be two source-connected MOSFETs to prevent the AC adapter from supplying current to the system through the P1’s body diode. Connect SRC to the common source node of two MOSFETs. The system must alert the user before performing a relearn cycle. If the user removes the battery during relearn mode, the MAX8730 detects battery removal and reconnects the AC adapter (PDS turns on and PDL turns off). Battery removal is detected when the battery falls below 5xRELTH. MAX8730 Low-Cost Battery Charger CCV, CCI, CCS, and LVC Control Blocks The MAX8730 controls 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 lowest voltage clamp (LVC) amplifier. The output of the LVC amplifier is the feedback control signal for the DC-DC controller. The minimum voltage at the CCV, CCI, or CCS appears at the output of the LVC amplifier and clamps the other 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 (see the Compensation section). Continuous-Conduction Mode With sufficient charge current, the MAX8730’s inductor current never crosses zero, which is defined as continuous-conduction mode. The controller starts a new cycle by turning on the high-side MOSFET. When the charge-current feedback signal (CSI) is greater than the control point (LVC), the CCMP comparator output goes high and the controller initiates the off-time by turning off the MOSFET. The operating frequency is governed by the off-time, which depends upon VBATT. At the end of the fixed off-time, the controller initiates a new cycle only if the control point (LVC) is greater than 100mV, and the peak charge current is less than the cycle-by-cycle current limit. Restated another way, IMIN must be high, IMAX must be low, and OVP must be low for the controller to initiate a new cycle. If the peak inductor current exceeds the IMAX comparator threshold or the output voltage exceeds the OVP threshold, then the on-time is terminated. The cycle-bycycle current limit protects against overcurrent and short-circuit faults. The MAX8730 computes the off-time by measuring VBATT: tOFF = 5.6µs/VBATT for VBATT > 4V. The switching frequency in continuous mode varies according to the equation: f = 1 1 1 5.6V x µs x + VBATT VSRC − VBATT Discontinuous Conduction The MAX8730 operates in discontinuous conduction mode at light loads to make sure that the inductor current is always positive. The MAX8730 enters discontinuous conduction mode when the output of the LVC control point falls below 100mV. For RS2 = 30mΩ, this corresponds to a peak inductor current of 222mA: IDIS = 1 100mV × = 111mA 2 15 × RS2 The MAX8730 implements slope compensation in discontinuous mode to eliminate multipulsing. This prevents audible noise and minimizes the output ripple. Compensation The charge-voltage and charge current-regulation loops are compensated separately and independently at the CCV, CCI, and CCS pins. CCV Loop Compensation The simplified schematic in Figure 4 is sufficient to describe the operation of the MAX8730 when the voltage loop (CCV) is in control. The required compensation network is a pole-zero pair formed with CCV and RCV. The pole is necessary to roll off the voltage loop’s response at low frequency. The zero is necessary to compensate the pole formed by the output capacitor and the load. RESR is the equivalent series resistance (ESR) of the charger output capacitor (COUT). RL is the equivalent charger output load, where RL = ∆VBATT / ∆ICHG. The equivalent output impedance of the GMV BATT GMOUT RESR COUT CCV GMV RCV ROGMV CCV REF Figure 4. CCV Loop Diagram 20 ______________________________________________________________________________________ RL Low-Cost Battery Charger GMOUT = RL (1 + sCOUT × RL) 1 ACSI × RS2 where ACSI = 15V/V and RS2 = 30mΩ in the typical application circuits, so GMOUT = 2.22A/V. LTF = GMOUT × RL × GMV × ROGMV × (1 + sCOUT × RESR)(1 + sCCV × RCV) (1 + sCCV × ROGMV)(1 + sCOUT × 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: LTF = GMOUT × The loop transfer function is given by: RCV GMV sCOUT Setting the LTF = 1 to solve for the unity-gain frequency yields: The poles and zeros of the voltage-loop transfer function are listed from lowest frequency to highest frequency in Table 2. Near crossover, CCV is much lower impedance than ROGMV. Since CCV is in parallel with ROGMV, CCV dominates the parallel impedance near crossover. Additionally RCV is much higher impedance than CCV and dominates the series combination of RCV and CCV, so: ROGMV x (1 + sCCV × RCV) ≅ RCV (1 + sCCV × ROGMV) COUT is typically much lower impedance than RL near crossover so the parallel impedance is mostly capacitive and: fCO _ CV = GMOUT × GMV × RCV 2π x COUT For stability, choose a crossover frequency lower than 1/5 the switching frequency. For example, choosing a crossover frequency of 45kHz and solving for RCV using the component values listed in Figure 1 yields RCV = 10kΩ: RCV = 2π × COUT × fCO _ CV ≅ 10kΩ GMV × GMOUT Table 2. CCV Loop Poles and Zeros NAME CCV pole EQUATION fP _ CV = 1 2πROGMV × CCV DESCRIPTION Lowest frequency pole created by CCV and GMV’s finite output resistance. Since ROGMV is very large and not well controlled, the exact value for the pole frequency is also not well controlled (ROGMV > 10MΩ). CCV zero fZ _ CV = 1 2πRCV × CCV Voltage-loop compensation zero. If this zero is at the same frequency or 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 fP _ OUT = 1 2πRL × COUT Output pole formed with the effective load resistance RL and output capacitance COUT. RL influences the DC gain but does not affect the stability of the system or the crossover frequency. Output zero fZ _ OUT = 1 2πRESR × COUT 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. ______________________________________________________________________________________ 21 MAX8730 amplifier, ROGMV, is greater than 10MΩ. The voltage amplifier transconductance, GMV = 0.125µA/mV for 4 cells and 0.167µA/mV for 3 cells. The DC-DC converter transconductance is dependent upon the charge current-sense resistor RS2: where: VBATT = 16.8V GMV = 0.125µA/mV GMOUT = 2.22A/V COUT = 10µF The loop transfer function is given by: LTF = GMOUT × ACSI × RS × GMI ROGMI 1 + sROGMI × CCI that describes a single-pole system. Since: f OSC = 350kHz (minimum occurs at V IN = 19V and VBATT = 16.8V) RL = 0.2Ω fCO-CV = 45kHz To ensure that the compensation zero adequately cancels the output pole, select fZ_CV ≤ fP_OUT: CCV ≥ (RL / RCV) COUT CCV ≥ 200pF Figure 5 shows the Bode plot of the voltage-loop frequency response using the values calculated above. CCI Loop Compensation The simplified schematic in Figure 6 is sufficient to describe the operation of the MAX8730 when the battery current loop (CCI) is in control. Since the output capacitor’s impedance has little effect on the response of the current loop, only a simple single pole is required to compensate this loop. ACSI is the internal gain of the current-sense amplifier. RS2 is the charge-currentsense resistor (30mΩ). ROGMI is the equivalent output impedance of the GMI amplifier, which is greater than 10MΩ. GMI is the charge-current amplifier transconductance = 1µA/mV. GMOUT is the DC-DC converter transconductance = 2.22A/V. 80 1 ACSI × RS GMOUT = the loop-transfer function simplifies to: LTF = GMI ROGMI 1 + sROGMI × CCI The crossover frequency is given by: fCO _ CI = GMI 2πCCI For stability, choose a crossover frequency lower than 1/10 of the switching frequency: 10 x GMI = 4nF 2π x CCI CCI > Values for CCI greater than 10 times the minimum value may slow down the current-loop response. Choosing CCI = 10nF yields a crossover frequency of 15.9kHz. Figure 7 shows the Bode plot of the current-loop frequency response using the values calculated above. 0 CSIP CSIN GMOUT 60 RS2 40 -45 20 0 -90 PHASE (DEGREES) MAGNITUDE (dB) MAX8730 Low-Cost Battery Charger CSI CCI GMI -20 MAG PHASE CCI -40 0.1 1 10 100 1k 10k 100k ROGMI -135 1M ICTL FREQUENCY (Hz) Figure 5. CCV Loop Response 22 Figure 6. CCI Loop Diagram ______________________________________________________________________________________ Low-Cost Battery Charger For stability, choose a crossover frequency lower than 1/10 of the switching frequency: CCS = 5 x VIN _ MAX GMS x 2πfOSC VBATT _ MIN Values for CCS greater than 10 times the minimum value may slow down the current-loop response excessively. Figure 9 shows the Bode plot of the input current-limit-loop frequency response using the values calculated above. The loop-transfer function is given by: ADAPTER INPUT ROGMS LTF = GMIN × ACSS × RSI × GMS 1 + SROGMS × CCS Since GMIN = CSSP CLS 1 ACSS × RS2 CSS RS1 CSSI GMS the loop-transfer function simplifies to: ROGMS x RS1/ RS2 1 + SROGMS × CCS CCS GMIN CCS ROGMS SYSTEM LOAD The crossover frequency is given by: fCO _ CS = VIN _ MAX GMS x 2πCCS VBATT _ MIN 100 0 100 MAG PHASE 60 40 -45 20 60 40 -45 20 0 0 -20 -20 -40 -90 0.1 10 1k FREQUENCY (Hz) Figure 7. CCI Loop Response 100k 0 MAG PHASE 80 MAGNITUDE (dB) 80 MAGNITUDE (dB) Figure 8. CCI Loop Diagram -40 0.1 10 1k 100k PHASE (DEGREES) LTF = GMS -90 10M FREQUENCY (Hz) Figure 9. CCS Loop Response ______________________________________________________________________________________ 23 MAX8730 CCS Loop Compensation The simplified schematic in Figure 8 is sufficient to describe the operation of the MAX8730 when the input current-limit loop (CCS) is in control. Since the output capacitor’s impedance has little effect on the response of the input current-limit loop, only a single pole is required to compensate this loop. ACSS is the internal gain of the current-sense amplifier, RS1 = 10mΩ in the typical application circuits. ROGMS is the equivalent output impedance of the GMS amplifier, which is greater than 10MΩ. GMS is the charge-current amplifier transconductance = 1µA/mV. GMIN is the DC-DC converter’s input-referred transconductance = GMOUT/D = 2.22A/V/D. MAX8730 Low-Cost Battery Charger MOSFET Drivers The DHI output is optimized for driving moderate-sized power MOSFETs. This is consistent with the variable duty factor that occurs in the notebook computer environment where the battery voltage changes over a wide range. DHI swings from SRC to DHIV and has a typical impedance of 1Ω sourcing and 4Ω sinking. Design Procedure MOSFET Selection Choose the p-channel MOSFETs according to the maximum required charge current. The MOSFET (P4) must be able to dissipate the resistive losses plus the switching losses at both VSRC(MIN) and VSRC(MAX). The worst-case resistive power losses occur at the maximum battery voltage. Calculate the resistive losses according to the following equation: PDRe sis tan ce = VBATT x ICHG 2 × RDS(ON) VSRC Schottky Selection 1 x 2 ( 2 xQG x VSRC (MAX) x ICHG + VSRC (MAX)2 x CRSS I GATE f These calculations provide an estimate and are not a substitute for breadboard evaluation, preferably including a verification using a thermocoupler mounted on the MOSFET. Generally, a small MOSFET is desired to reduce switching losses at VBATT = VSRC / 2. This requires a tradeoff between gate charge and resistance. Switching losses in the MOSFET can become significant when the maximum AC adapter voltage is applied. If the MOSFET that was chosen for adequate RDS(ON) at low supply voltages becomes hot when subjected to VSRC(MAX), then choose a MOSFET with lower gate charge. The actual switching losses that can vary due to factors include the internal gate resistance, threshold voltage, source inductance, and PC board layout characteristics. See Table 3 for suggestions about MOSFET selection. Calculate the switching losses according to the following equation: PDSWITCHING = where CRSS is the reverse transfer capacitance of the MOSFET, and IGATE is the peak gate-drive source/sink current. The Schottky diode conducts the inductor current during the off-time. Choose a Schottky diode with the appropriate thermal resistance to guarantee that it does not overheat: ) θJA < TJ _ MAX − TA _ MAX V VF x ICHG x 1 − BATT _ MIN VSRC _ MAX Table 3. Recommended MOSFETs CHARGE CURRENT (A) MOSFET PIN-PACKAGE 24 QG (nC) RDSON (mΩ) θJA Rθ (°/W) TMAX (°C) +150 MAX 3 Si3457DV 6-SOT23 8 75 78 2.5 FDC658P 6-SOT23 12 75 78 +150 3.5 FDS9435A 8-SO 14 80 50 +175 3.5 NDS9435A 8-SO 14 80 50 +175 4 FDS4435 8-SO 24 35 50 +175 4 FDS6685 8-SO 24 35 50 +175 4.5 FDS6675A 8-SO 34 19 50 +175 ______________________________________________________________________________________ Low-Cost Battery Charger The ripple current is determined by: The Schottky size and cost can be reduced by utilizing the MAX8730 foldback function. See the Foldback Current section for more information. The ripple current is only dependent on inductance value and is independent of input and output voltage. See the Ripple Current vs. VBATT graph in the Typical Operating Characteristics. Select the Schottky diode to minimize the battery leakage current when the charger is shut down. ∆IL = k OFF L See Table 4 for suggestions about inductor selection. Inductor Selection Input Capacitor Selection The MAX8730 uses a fixed inductor current ripple architecture to minimize the inductance. The charge current, ripple, and operating frequency (off-time) affects inductor selection. For a good trade-off of inductor size and efficiency, choose the inductance according to the following equation: The input capacitor must meet the ripple current requirement (IRMS) imposed by the switching currents. Ceramic capacitors are preferred due to their resilience to power-up surge currents: L = k OFF 0.4 x ICHG where kOFF is the off-time constant (5.6V x µs typically). Higher inductance values decrease the RMS current at the cost of inductor size. Inductor L1 must have a saturation current rating of at least the maximum charge current plus 1/2 of the ripple current (∆IL): ISAT = ICHG + (1/2) ∆IL V BATT ( VSRC − VBATT ) = ICHG IRMS = ICHG VSRC 2 at 50% duty cycle. The input capacitors should be sized so that the temperature rise due to ripple current in continuous conduction does not exceed about 10°C. The maximum ripple current occurs at 50% duty factor or VSRC = 2 x VBATT, which equates to 0.5 x ICHG. If the application of interest does not achieve the maximum value, size the input capacitors according to the worst-case conditions. See Table 5 for suggestions about input capacitor selection. Table 4. Recommended Inductors APPLICATION (A) INDUCTOR SIZE (mm) L (µH) ISAT (A) Ω) RL (mΩ 2.5 CDRH6D38 8.3 x 8.3 x 3 3.3 3.5 20 2.5 CDRH8D28 7x7x4 4.7 3.4 24.7 3.5 CDRH8D38 8.3 x 8.3 x 4 3.5 4.4 24 Table 5. Recommended Input Capacitors APPLICATION (A) INPUT CAPACITOR CAPACITANCE( µF) VOLTS (V) <3 GMK316F47S2G 4.7 35 RMS AT 10°C (A) 1.8 <4 GMK325F106ZH 4.7 35 2.4 <4 TMK325BJ475MN 10 25 2.5 ______________________________________________________________________________________ 25 MAX8730 where θJA is the thermal resistance of the package (in °C/W), TJ_MAX is the maximum junction temperature of the diode, TA_MAX is the maximum ambient temperature of the system, and VF is the forward voltage of the Schottky diode. MAX8730 Low-Cost Battery Charger Output Capacitor Selection The output capacitor absorbs the inductor ripple current and must tolerate the surge current delivered from the battery when it is initially plugged into the charger. As such, both capacitance and ESR are important parameters in specifying the output capacitor as a filter and to ensure stability of the DC-DC converter (see the Compensation section). Beyond the stability requirements, it is often sufficient to make sure that the output capacitor’s ESR is much lower than the battery’s ESR. Either tantalum or ceramic capacitors can be used on the output. Ceramic devices are preferable because of their good voltage ratings and resilience to surge currents. For a ceramic output capacitor, select the capacitance according to the following equation: COUT > k OFF2 1 1 x + VBATT 8 x L x VRIPPLE VSRC − VBATT Applications Information Adapter Soft-Start The adapter selection MOSFETs may be soft-started to reduce adapter surge current upon adapter selection. Figure 10 shows the adapter soft-start application using Miller capacitance for optimum soft-start timing and power dissipation. System Short-Circuit IINP Configuration The MAX8730 has a system short-circuit protection feature. When VIINP is greater than 4.2V, the MAX8730 latches off PDS. PDS remains off until the adapter is removed and reinserted. For fast response to system overcurrent, add an RC (C13 and R15), as shown in Figure 11. Select R15 according to the following equation: R15 = The output ripple requirement of a charger is typically only constrained by the overvoltage protection circuitry of the battery protector and the overvoltage protection of the charger. For proper operation, ensure that the ripple is smaller than the overvoltage protection threshold of both the charger and the battery protector. If the protector’s overvoltage protection is filtered, the battery protector may not be a constraint. VSST GIINP x RS1 x ISST x 0.7 where: VSST = 4.2V. ISST = Short-circuit system current threshold. Since system short-circuit triggers a latch, it is important to choose ISST high enough to prevent unintentional triggers. Select C13 according to the following equation: C13 = t Delay R15 SYSTEM LOAD ADAPTER RSS2 6kΩ CSS1 32nF − R10 R15 IINP CSS2 10nF C13 C6 RSS1 18kΩ MAX8730 SRC PDS Figure 10. Adapter Soft-Start Modification 26 Figure 11. System Short-Circuit IINP Configuration ______________________________________________________________________________________ R10 Low-Cost Battery Charger R7 R14 ICTL R8 Figure 12. ICTL Foldback Current Adjustment For typical applications, choose t Delay = 20µs (depends on the p-MOSFET selected for the PDS switch). The following components can be used for a 10A system short-current design: R10 = 8.66kΩ C6 = 0.1µF R15 = 7.15kΩ C13 = 2.7nF Foldback Current At low duty cycles, most of the charge current is conducted through the Schottky diode (D1). To reduce the requirements of the Schottky diode, the MAX8730 has a foldback charge current feature. When the battery voltage falls below 5 x V RELTH, ICTL sinks 6µA. Add a series resistor to ICTL to adjust the charge current foldback, as shown in Figure 12: R1 4 = 1 R8 I x R S2 x 3.6V R8 x R7 − x VREF − FOLDBACK 6µA R7 +R8 1 3 5m V R7 +R8 Layout and Bypassing Bypass SRC, ASNS, LDO, DHIV, and REF as shown in Figure 1. Good PC board layout is required to achieve specified noise immunity, efficiency, and stable performance. The PC board layout artist must be given explicit instructions—preferably, a sketch showing the placement of the power-switching components and highcurrent routing. Refer to the PC board layout in the MAX8730 evaluation kit for examples. Use the following step-by-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. • Minimize ground trace lengths in the high-current paths. • Minimize other trace lengths in the high-current paths. • Use > 5mm wide traces in the high-current paths. • Connect to the input capacitors directly to the source of the high-side MOSFET (10mm max length). Place the input capacitor between the input current-sense resistor and the source of the high-side MOSFET. 2) Place the IC and signal components. Quiet connections to REF, CCV, CCI, CCS, ACIN, SWREF, and LDO SRC should be returned to a separate ground (GND) island. There is very little current flowing in these traces, so the ground island need not be very large. When placed on an inner layer, a sizable ground island can help simplify the layout because the low current connections can be made through vias. The ground pad on the backside of the package should be the star connection to this quiet ground island. 3) Keep the gate drive trace (DHI) and SRC path as short as possible (L < 20mm), and route them away from the current-sense lines and REF. Bypass DHIV directly to the source of the high-side MOSFET. These traces should also be relatively wide (W > 1.25mm). 4) Place ceramic bypass capacitors close to the IC. The bulk capacitors can be placed further away. ______________________________________________________________________________________ 27 MAX8730 REF Pin Configuration GND CCS CCV CCI 21 CSIN TOP VIEW BATT TRANSISTOR COUNT: 3307 PROCESS: BiCMOS CSIP Chip Information 20 19 18 17 16 15 DHIV 22 14 INPON DHI 23 13 REFON SRC 24 12 ICTL CSSN 25 11 IINP 10 MODE MAX8730 CSSP 26 *EXPOSED PADDLE PDS 27 LDO SWREF 4 5 6 7 VCTL 3 ACIN 2 REF 1 CLS + PDL 28 ASNS MAX8730 Low-Cost Battery Charger 5mm x 5mm THIN QFN 28 ______________________________________________________________________________________ 9 ACOK 8 RELTH Low-Cost Battery Charger QFN THIN.EPS D2 D MARKING b CL 0.10 M C A B D2/2 D/2 k 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 L1 L 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 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 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 0.80 BSC. 0.65 BSC. 0.50 BSC. 0.40 BSC. 0.50 BSC. 0.25 - 0.25 - 0.25 - 0.25 - 0.25 0.35 0.45 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 - 0.30 0.40 0.50 16 40 N 20 28 32 ND 4 10 5 7 8 4 10 5 7 8 NE WHHB ----WHHC WHHD-1 WHHD-2 JEDEC k L L1 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. PKG. CODES T1655-2 T1655-3 T1655N-1 T2055-3 D2 3.00 3.00 3.00 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 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. L E2 exceptions MIN. NOM. MAX. MIN. NOM. MAX. ±0.15 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 33.00 33.00 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 3.20 3.20 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 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. PACKAGE OUTLINE, 16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm 21-0140 -DRAWING NOT TO SCALE- 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. MAX8730 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.)