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19-3885; Rev 0; 12/05
KIT ATION EVALU E AILABL AV
Low-Cost Battery Charger
General Description Features
Small Inductor (3.5H) 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
MAX8730
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.
Ordering Information
PART MAX8730ETI+ TEMP RANGE -40C to +85C PINPACKAGE 28 Thin QFN (5mm x 5mm) PKG CODE T2855-5
+Denotes lead-free package.
Typical Operating Circuit
ADAPTER INPUT SYSTEM LOAD
Applications
Notebook Computers Tablet PCs Portable Equipment with Rechargeable Batteries
CSSP PDS SRC
CSSN DHIV PDL
DHI ASNS
MAX8730
CSIP CSIN BATT SWREF REF
BATTERY
LDO REF
ACIN ACOK VCTL CLS MODE ICTL REFON INPON
HOST
RELTH LDO CCS CCV GND
Pin Configuration appears at end of data sheet.
IINP CCI
________________________________________________________________ Maxim Integrated Products
1
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Low-Cost Battery Charger MAX8730
ABSOLUTE MAXIMUM RATINGS
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) RELTH, VCTL, ICTL, REFON, CLS, LDO, INPON to GND .....................................................-0.3V to +6V LDO Short-Circuit Current...................................................50mA Continuous Power Dissipation (TA = +70C) 28-Pin TQFN (derate 20.8mW/C above +70C) .......1667mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ............................................................+150C Storage Temperature Range .............................-60C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER CHARGE-VOLTAGE REGULATION VCTL Range VVCTL = 3.6V or 0V Not including resistor tolerances Including 1% resistor tolerances 0 -1.0 -1.05 -0.5 4.4 0 0 4 16 A 3.6 +1.0 +1.05 +0.5 V % V SYMBOL CONDITIONS MIN TYP MAX UNITS
Battery-Regulation Voltage Accuracy
VVCTL = VLDO (3 or 4 cells) VVCTL Default Threshold VCTL Input Bias Current CHARGE-CURRENT REGULATION ICTL Range Full-Charge-Current Accuracy (CSIP to CSIN) Trickle-Charge-Current Accuracy Charge-Current Gain Error Charge-Current Offset Error BATT/CSIP/CSIN Input Voltage Range Charging enabled CSIP/CSIN Input Current Charging disabled, SRC = BATT, ASNS = GND or VICTL = 0V VICTL = 3.6V VICTL = 2.0V VICTL = 120mV Based on VICTL = 3.6V and VICTL = 0.12V Based on VICTL = 3.6V and VICTL = 0.12V VVCTL rising VVCTL = 3V SRC = BATT, ASNS = GND INPON = REFON = 0, VVCTL = 5V
0 128.25 -5 71.25 -5 2.5 -1.9 -2 0 300 8 4.5 75 135
3.6 141.75 +5 78.75 +5 7.5 +1.9 +2 19 600 16
V mV % mV % mV % mV V
A
2
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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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER ICTL Power-Down Mode Threshold ICTL Input Bias Current 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 CLS Input Range CLS Input Bias Current IINP Transconductance VCLS = 2.0V VCSSP - VCSSN = 56mV VCSSP - VCSSN = 100mV, VIINP = 0 to 4.5V IINP Accuracy VCSSP - VCSSN = 75mV VCSSP - VCSSN = 56mV VCSSP - VCSSN = 20mV IINP Gain Error IINP Offset Error IINP Fault threshold SUPPLY AND LINEAR REGULATOR SRC Input Voltage Range SRC Undervoltage Lockout Threshold SRC falling SRC rising 8.0 7 7.4 7.5 8 28 V V Based on VICTL = REF x 0.5 and VICTL = REF Based on VICTL = REF x 0.5 and VICTL = REF IINP rising VCSSP = VCSSN = VSRC > 8.0V VSRC = 0V 1.1 -1 2.66 -5 -8 -5 -12.5 -7 -2 4.1 4.2 2.8 SYMBOL ICTL falling ICTL rising VICTL = 3V SRC = BATT, ASNS = GND, VICTL = 5V CONDITIONS MIN 50 70 -1 -1 72.75 72.75 -4 50 -5.6 36 -6.6 8.0 400 0.1 38 53 75.75 75.75 TYP 65 90 MAX 80 110 +1 +1 78.75 78.75 +4 56 +5.6 40.5 +6.6 28 800 1 REF +1 2.94 +5 +8 +5 +12.5 +7 +2 4.3 % mV V % UNITS mV A mV mV % mV % mV % V A V A A/mV
MAX8730
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Low-Cost Battery Charger MAX8730
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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER SYMBOL Normal mode VINPON =VREFON = low SRC Quiescent Current (INPON/REFON = Don't Care) VSRC = VBATT = 12V, ASNS = GND (Note 2) VINPON = low, VREFON = high VINPON = high, VREFON = low VINPON = VREFON = high BATT Input Current VBATT = 16.8V, VSRC = 19V, ICTL = 0 VBATT = 2V to 19V, VSRC > VBATT + 0.3V ICSIP + ICSIN + IBATT, ASNS = GND Battery-Leakage Current ICSIP + ICSIN + IBATT + ICSSP + ICSSN + ISRC, ASNS = REFON = GND 8.0V < VSRC < 28V, no load 0 < ILDO < 10mA VSRC = 8.0V VREFON = 5.4V INPON = GND 5.2 CONDITIONS MIN TYP 4 10 300 300 350 8 300 2 300 2 5.35 20 4 MAX 6 20 600 A 600 600 16 600 5 600 5 5.5 50 V mV V A A UNITS mA
LDO Output Voltage LDO Load Regulation LDO Undervoltage Lockout Threshold REFERENCES REF Output Voltage REF Undervoltage Lockout Threshold SWREF Output Voltage SWREF Load Regulation TRIP POINTS ACIN Threshold ACIN Threshold Hysteresis ACIN Input Bias Current SWITCHING REGULATOR DHI Off-Time DHI Off-Time K Factor Sense Voltage for Minimum Discontinuous Mode Ripple Current Cycle-by-Cycle Current-Limit Sense Voltage Charge Disable Threshold DHIV Output Voltage DHIV Sink Current Ref
4.18 REF falling 8.0V < VSRC < 28V, no load 0.1mA < ISWREF < 20mA ACIN rising VACIN = 2.048V VBATT = 16.0V VBATT = 16.0V VCSIP - VCSIN 2.037 -1 300 4.8 3.234
4.20 3.1 3.3 20 2.1 60
4.22 3.9 3.366 50 2.163 +1
V V V mV V mV A ns V x s mV
350 5.6 7
400 6.4
160 VSRC - VBATT, SRC falling With respect to SRC 40 -4.3 10
200 60 -4.8
240 80 -5.5
mV mV V mA
4
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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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER DHI Resistance Low DHI Resistance High ERROR AMPLIFIERS GMV Loop Transconductance GMI Loop Transconductance GMS Loop Transconductance CCI/CCS/CCV Clamp Voltage LOGIC LEVELS MODE, REFON Input Low Voltage MODE Input Middle Voltage MODE, REFON Input High Voltage MODE, REFON, INPON Input Bias Current INPON Threshold ADAPTER DETECTION ACOK Voltage Range ACOK Sink Current ACOK Leakage Current BATTERY DETECTION BATT Overvoltage Threshold BATT Overvoltage Hysteresis RELTH Operating Voltage Range RELTH Input Bias Current BATT Minimum Voltage Trip Threshold PDS, PDL SWITCH CONTROL Adapter-Absence Detect Threshold Adapter-Detect Threshold PDS Output Low Voltage PDS/PDL Output High Voltage PDS/PDL Turn-Off Current VASNS - VBATT, VASNS falling VASNS - VBATT Result with respect to SRC, IPDS = 0 Result with respect to SRC, IPD_ = 0 VPDS = VSRC - 2V, VSRC = 16V 6 -300 -140 -8 -280 -100 -10 -0.2 12 -240 -60 -12 -0.5 mV mV V V mA VRELTH = 0.9V to 2.6V VBATT falling VRELTH = 0.9V VRELTH = 2.6V 0.9 -50 4.42 12.77 4.5 13.0 VVCTL = VLDO , BATT rising; result with respect to battery-set voltage VMODE = VLDO VMODE = FLOAT +140 mV +100 100 2.6 +50 4.58 13.23 mV V nA V VACOK = 0.4V, ACIN = 1.5V VACOK = 28V, ACIN = 2.5V 0 1 1 28 V mA A MODE = 0 or 3.6V VINPON rising VINPON falling 1.9 3.4 -2 2.2 0.8 +2 2.65 0.5 3.3 V V V A V V VCTL = 3.6V, VBATT = 16.8V, MODE = LDO VCTL = 3.6V, VBATT = 12.6V, MODE = FLOAT ICTL = 3.6V, VCSSP - VCSIN = 75mV VCLS = 2.048V, VCSSP - VCSSN = 75mV 1.1V < VCCV < 3.0V, 1.1V < VCCI < 3.0V, 1.1V < VCCS < 3.0V 0.0625 0.0833 0.5 0.5 150 0.125 0.167 1 1 300 0.250 0.333 2 2 600 mA/V mA/V mA/V mV SYMBOL IDHI = -10mA IDHI = 10mA CONDITIONS MIN TYP 2 1 MAX 4 2 UNITS
MAX8730
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Low-Cost Battery Charger MAX8730
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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER PDS Turn-On Current PDL Turn-On Resistance PDS/PDL Delay Time SYMBOL PDS = SRC PDL = GND CONDITIONS MIN 6 50 TYP 12 100 5.0 200 MAX UNITS mA k s
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 = -40C to +85C, unless otherwise noted.)
PARAMETER CHARGE-VOLTAGE REGULATION VCTL Range VVCTL = 3.6V or 0V Not including resistor tolerances Including 1% resistor tolerances 0 -1.2 -1.25 -0.8 4.4 0 16 3.6 +1.2 +1.25 +0.8 V A % V SYMBOL CONDITIONS MIN TYP MAX UNITS
Battery-Regulation-Voltage Accuracy
VVCTL = VLDO (3 or 4 cells) VVCTL Default Threshold VCTL Input Bias Current CHARGE-CURRENT REGULATION ICTL Range Full-Charge-Current Accuracy (CSIP to CSIN) Trickle-Charge-Current Accuracy Charge-Current Gain Error Charge-Current Offset Error BATT/CSIP/CSIN Input Voltage Range Charging enabled CSIP/CSIN Input Current ICTL Power-Down Mode Threshold Charging disabled, SRC = BATT, ASNS = GND, or VICTL = 0V ICTL falling ICTL rising VICTL = 3.6V VICTL = 2.0V VICTL = 120mV Based on VICTL = 3.6V and VICTL = 0.12V Based on VICTL = 3.6V and VICTL = 0.12V VVCTL rising SRC = BATT, ASNS = GND INPON = REFON = 0, VVCTL = 5V
0 128.25 -5 70 -6.7 2 -1.9 -2 0
3.6 141.75 +5 80 +6.7 10 +1.9 +2 19 1000 16
V mV % mV % mV % mV V
A
50 70
80 110
mV
6
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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 = -40C to +85C, unless otherwise noted.)
PARAMETER INPUT-CURRENT REGULATION CSSP-to-CSSN Full-Scale Current-Sense Voltage VCLS = REF (trim point) Input Current-Limit Accuracy CSSP/CSSN Input Voltage Range CSSP/CSSN Input Current CLS Input Range IINP Transconductance VCSSP - VCSSN = 56mV VCSSP - VCSSN = 100mV, VIINP = 0 to 4.5V IINP Accuracy VCSSP - VCSSN = 75mV VCSSP - VCSSN = 56mV VCSSP - VCSSN = 20mV IINP Gain Error IINP Offset Error IINP Fault Threshold SUPPLY AND LINEAR REGULATOR SRC Input Voltage Range SRC Undervoltage Lockout Threshold SRC falling SRC rising Normal mode VINPON = VREFON = low SRC Quiescent Current (INPON/REFON = Don't Care) SRC = VBATT = 12V, ASNS = GND (Note 2) VINPON = low, VREFON = high VINPON = high, VREFON = low VINPON = VREFON = high BATT Input Current Battery Leakage Current LDO Output Voltage LDO Load Regulation VBATT = 2V to 19V, VSRC > VBATT + 0.3V ICSIP + ICSIN + IBATT + ICSSP + ICSSN + ISRC, ASNS = REFON = GND 0 < ILDO < 10mA VREFON = 5.4V INPON = GND 5.2 8.0 7 8 6 20 600 A 600 600 600 600 A 16 5.5 50 V mV A 28 V V mA Based on VICTL = REF x 0.5 and VICTL = REF Based on VICTL = REF x 0.5 and VICTL = REF IINP rising VCSSP = VCSSN = VSRC > 8.0V 1.1 2.66 -5 -8 -5 -12.5 -7 -2 4.1 VCLS = REF x 0.7 VCLS = REF x 0.5 72.75 72.75 50.0 36.00 8.0 78.25 78.25 56.0 40.50 28 1000 REF 2.94 +5 +8 +5 +12.5 +7 +2 4.3 % mV V % mV mV mV mV V A V A/mV SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX8730
8.0V < VSRC < 28V, no load
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Low-Cost Battery Charger MAX8730
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 = -40C to +85C, unless otherwise noted.)
PARAMETER REFERENCES REF Output Voltage REF Undervoltage Lockout Threshold SWREF Output Voltage SWREF Load Regulation TRIP POINTS ACIN Threshold SWITCHING REGULATOR DHI Off-Time DHI Off-Time K Factor Cycle-by-Cycle Current-Limit Sense Voltage DHIV Output Volatge DHIV Sink Current DHI Resistance Low DHI Resistance High ERROR AMPLIFIERS GMV Loop Transconductance GMI Loop Transconductance GMS Loop Transconductance CCI/CCS/CCV Clamp Voltage LOGIC LEVELS MODE, REFON Input Low Voltage MODE Input Middle Voltage MODE, REFON Input High Voltage INPON Threshold ADAPTER DETECTION ACOK Voltage Range ACOK Sink Current VACOK = 0.4V, ACIN = 1.5V 0 1 28 V mA VINPON rising VINPON falling 1.9 3.4 2.2 0.8 0.5 3.3 V V V V VCTL = 3.6V, VBATT = 16.8V, MODE = LDO VCTL = 3.6V, VBATT = 12.6V, MODE = FLOAT ICTL = 3.6V, VCSSP - VCSIN = 75mV VCLS = 2.048V, VCSSP - VCSSN = 75mV 1.1V < VCCV < 3.0V, 1.1V < VCCI < 3.0V, 1.1V < VCCS < 3.0V 0.0625 0.0833 0.5 0.5 150 0.250 0.333 2 2 600 mA/V mA/V mA/V mV IDHI = -10mA IDHI = 10mA With respect to SRC VBATT = 16.0V VBATT = 16.0V 300 4.8 160 -4.3 10 4 2 400 6.4 240 -5.5 ns V x s mV V mA ACIN rising 2.037 2.163 V Ref 0 < IREF < 500A REF falling 8.0V < VSRC < 28V, no load 0.1mA < ISWREF < 20mA 3.224 4.16 4.24 3.9 3.376 50 V V V mV SYMBOL CONDITIONS MIN TYP MAX UNITS
8
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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 = -40C to +85C, unless otherwise noted.)
PARAMETER BATTERY DETECTION RELTH Operating Voltage Range BATT Minimum Voltage Trip Threshold PDS, PDL SWITCH CONTROL Adapter-Absence-Detect Threshold Adapter-Detect Threshold PDS Output Low Voltage PDS/PDL Output High Voltage PDS/ PDL Turn-Off Current PDS Turn-On Current VASNS - VBATT, VASNS falling VASNS - VBATT Result with respect to SRC, IPDS = 0 Result with respect to SRC, IPD_ = 0 VPDS = VSRC - 2V, VSRC = 16V PDS = SRC 6 6 50 100 200 -310 -140 -7 -240 -60 -12 -0.5 mV mV V V mA mA k VBATT falling VRELTH = 0.9V VRELTH = 2.6V 0.9 4.42 12.77 2.6 4.58 13.23 V V SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX8730
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.
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Low-Cost Battery Charger MAX8730
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 = +25C, unless otherwise noted.)
INPUT CURRENT-LIMIT ERROR vs. CLS
MAX8730 toc01
INPUT CURRENT-LIMIT ERROR vs. SYSTEM CURRENT
5.0 4.5 INPUT CURRENT-LIMIT ERROR (%) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 VCLS = VREF x 0.7 0 0 0.5 1.0 1.5 2.0 2.5 SYSTEM CURRENT (A) 3.0 3.5 0 VIN = 17V VIN = 19V VIN = 24V INPUT CURRENT-LIMIT ERROR (%) 6 5 4 3 2 1 7
INPUT CURRENT-LIMIT ERROR vs. SYSTEM CURRENT
MAX8730 toc03
15 INPUT CURRENT-LIMIT ERROR (%) 10 5 0 -5 -10 -15 1.1 1.6 2.1 2.6 VCLS (V) 3.1 3.6 4.1 MINIMUM TYPICAL UNIT MAXIMUM
VCLS = VREF / 2
VCLS = VREF
VCLS = VREF x 0.7
0
1
2 3 SYSTEM CURRENT (A)
4
5
IINP ERROR vs. VCSSP - VCSSN
MAX8730 toc04
CHARGE-CURRENT ERROR vs. CHARGE-CURRENT SETTING
MAX8730 toc05
CHARGE-CURRENT ERROR vs. BATTERY VOLTAGE
VICTL = 2V 1.3 CHARGE-CURRENT ERROR (%) 1.0 0.7 0.4 0.1 -0.2 -0.5 VICTL = 3.6V
MAX8730 toc06
15 10 IINP ERROR (%) 5 0 -5 -10 -15 0 MINIMUM MAXIMUM
20 15 CHARGE-CURRENT ERROR (%) 10 5 0 TYPICAL UNIT -5 -10 -15 -20 0 0.6 1.2 1.8 2.4 VICTL (V) 3.0 MINIMUM ERROR MAXIMUM ERROR
1.6
10 20 30 40 50 60 70 80 90 100 VCSSP - VCSSN
3.6
0
5
10 15 BATTERY VOLTAGE (V)
20
TRICKLE-CHARGE CURRENT vs. BATTERY VOLTAGE
MAX8730 toc07
BATTERY-VOLTAGE ERROR vs. CHARGE CURRENT
MAX8730 toc08
BATTERY-VOLTAGE ERROR vs. VCTL
0.8 CHARGE-VOLTAGE ERROR (%) 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8
MAX8730 toc09
25 TRICKLE-CHARGE-CURRENT ERROR (%) 20 15 10 5 0 -5 -10 -15 -20 -25 0 3 6 9 12 BATTERY VOLTAGE (V) 15 CHARGE CURRENT = 150mA
0
1.0
BATTERY-VOLTAGE ERROR (%)
-0.05
-0.10 4 CELLS -0.15 3 CELLS
-0.20
18
-0.25 0 0.5 1.0 1.5 2.0 2.5 CHARGE CURRENT (A) 3.0 3.5
-1.0 0 0.5 1.0 1.5 2.0 VCTL (V) 2.5 3.0 3.5
10
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Low-Cost Battery Charger 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 = +25C, unless otherwise noted.)
OUTPUT RIPPLE VOLTAGE vs. BATTERY VOLTAGE
MAX8730 toc10
SWITCHING FREQUENCY vs. BATTERY VOLTAGE
MAX8730 toc11
0.18 OUTPUT RIPPLE VOLTAGE (mVP-P) 0.15 0.12 0.09 0.06 0.03 0 0 5 10 15 BATTERY VOLTAGE (V)
1000
SWITCHING FREQUENCY (kHz)
800
600
400
200 20 0 3 6 9 12 BATTERY VOLTAGE (V) 15 18
BATTERY REMOVAL
MAX8730toc12
ADAPTER INSERTION
MAX8730toc13
CHARGE CURRENT = 12V COUT = 4.7F
ADAPTER ADAPTER INSERTION 13V 12.5V PDS
20V 0V 20V 0V 20V
COUT = 10F
PDL
0V 20V 0V 100s/div
SYSTEM LOAD 4s/div
ADAPTER REMOVAL
MAX8730toc14
SYSTEM LOAD TRANSIENT
MAX8730toc15
ADAPTER
BATTERY VOLTAGE = 16.8V
20V 0V 20V
LOAD CURRENT ADAPTER CURRENT INDUCTOR CURRENT COMPENSATION CCI CCI
5A 0A 5A 0A 5A 0A 500mV/div
PDS 0V 20V PDL 0V 20V 0V 4ms/div
CCS
SYSTEM LOAD
CCS 200s/div
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Low-Cost Battery Charger 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 = +25C, unless otherwise noted.)
PEAK-TO-PEAK INDUCTOR CURRENT vs. BATTERY VOLTAGE
MAX7830 toc16
EFFICIENCY vs. CHARGE CURRENT
MAX8730 toc17
2.5 PEAK-TO-PEAK INDUCTOR CURRENT (A) 2.3 2.1 1.9 1.7 1.5 1.3 1.1 0.9 0.7 0.5 0 3 6 9 12 BATTERY VOLTAGE (V) 15
100
90 EFFICIENCY (%) 3 CELLS 80 4 CELLS
70
18
60 0 0.5 1.0 1.5 2.0 2.5 3.0 CHARGE CURRENT (A) 3.5 4.0
ADAPTER QUIESCENT CURRENT vs. ADAPTER VOLTAGE
BATTERY ABSENT ADAPTER QUIESCENT CURRENT (mA) 2.5 2.0 1.5 1.0 0.5 0 0 5 10 15 20 ADAPTER VOLTAGE (V) 25 REFON = 1 INPON = 1
MAX8730 toc18
BATTERY LEAKAGE CURRENT vs. BATTERY VOLTAGE
REFON = INPON = 1 BATTERY-LEAKAGE CURRENT (A) 400 REFON = 0 INPON = 1
MAX8730 toc19
3.0
500
300
200 REFON = 1 INPON = 0 REFON = INPON = 0
100
REFON = 0 INPON = 0
0 0 3 6 9 12 BATTERY VOLTAGE (V) 15 18
CHARGE CURRENT vs. TIME
INITIAL CONDITION: 4 CELLS 10V BATTERY FULL CHARGE = 16.8V
MAX8730 toc20
LDO LOAD REGULATION
-0.1 -0.2 LDO ERROR (%) -0.3 -0.4 -0.5 -0.6 -0.7 CHARGER DISABLED
MAX8730 toc21
3.5 3.0 CHARGE CURRENT (A) 2.5 2.0 1.5 1.0 0.5 0 0 0.5 1.0 1.5 2.0 TIME (h) 2.5
0
-0.8 -0.9 3.0 0 10 20 30 ILDO (mA) 40 50
12
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Low-Cost Battery Charger 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 = +25C, unless otherwise noted.)
LDO LINE REGULATION
MAX8730 toc22
REFERENCE LOAD REGULATION
CHARGER DISABLED -0.13 -0.15 REF (%) -0.17 -0.19 -0.21 -0.23 -0.25
MAX8730 toc23
-0.350 -0.355 -0.360 -0.365 LDO ERROR (%) -0.370 -0.375 -0.380 -0.385 -0.390 -0.395 -0.400 8 13 18 23 INPUT VOLTAGE (V)
-0.11
28
0
100
200 300 IREF (A)
400
500
REF ERROR vs. TEMPERATURE
MAX8730 toc24
SWREF LOAD REGULATION
MAX8730 toc25
0 -0.05 -0.10 REF ERROR (%) -0.15 -0.20 -0.25
0
-0.3 SWREF ERROR (%)
-0.6
-0.9
-1.2 -0.30 -0.35 -40 -20 0 20 40 TEMPERATURE (C) 60 80 -1.5 0 10 20 30 SWREF OUTPUT CURRENT (mA) 40
SWREF VOLTAGE vs. TEMPERATURE
MAX8730 toc26
DISCONTINUOUS MODE SWITCHING WAVEFORM
MAX8730toc27
3.32 3.31 SWREF VOLTAGE (V) 3.30
1A 0 20V
INDUCTOR CURRENT
3.29 LX 3.28 0 3.27 3.26 3.25 -40 -20 0 20 40 TEMPERATURE (C) 60 80 1s/div CHARGE CURRENT = 20mA 0 20V DHI
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13
Low-Cost Battery Charger MAX8730
Pin Description
PIN 1 2 NAME ASNS LDO FUNCTION 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. Linear-Regulator Output. LDO is the output of the 5.35V linear regulator supplied from SRC. Bypass LDO with a 1F ceramic capacitor from LDO to GND. 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 1F capacitor to GND. 4.2V Voltage Reference. Bypass REF with a 1F capacitor to GND. 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. 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. 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 10k 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 2.8A/mV (typ). Charge-Current-Control Input. Pull ICTL to GND to shut down the charger. SWREF Enable. Drive REFON high to enable SWREF. Input Current-Monitor Enable. Drive INPON high to enable IINP. Output Current-Regulation Loop Compensation Point. Connect a 0.01F capacitor from CCS to GND. Voltage-Regulation Loop Compensation Point. Connect a 10k resistor in series with a 0.01F capacitor to GND. Input Current-Regulation Loop Compensation Point. Connect a 0.01F capacitor from CCS to GND. Analog Ground Battery-Voltage Feedback Input Charge-Current-Sense Negative Input Charge-Current-Sense Positive Input. Connect a current-sense resistor from CSIP to CSIN. High-Side Driver Supply. Connect a 0.1F capacitor from DHIV to CSSN. High-Side Power MOSFET Driver Output. Connect to high-side, p-channel MOSFET gate. DC Supply Input Voltage and Connection for Driver for PDS/PDL Switches. Bypass SRC to power ground with a 1F capacitor. Input Current Sense for Negative Input Input Current Sense for Positive Input. Connect a 15m current-sense resistor from CSSP to CSSN. Power-Source PMOS Switch Driver Output. When the adapter is absent, the PDS output is pulled to SRC through an internal 1M resistor. System-Load PMOS Switch Driver Output. When the adapter is absent, the PDL output is pulled to ground through an internal 100k resistor.
3 4 5 6 7 8
SWREF REF CLS ACIN VCTL RELTH
9
ACOK
10
MODE
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
IINP ICTL REFON INPON CCI CCV CCS GND BATT CSIN CSIP DHIV DHI SRC CSSN CSSP PDS PDL
Backside Backside Paddle. Connect the backside paddle to analog ground. Paddle
14
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Low-Cost Battery Charger MAX8730
P1 ADAPTER INPUT C1 32nF R1 R3 3k
P2
RS1 15m C2 10nF CSSP R6 6k PDS CSSN DHIV PDL DHI P4 C12 0.1F
SYSTEM LOAD CIN1 4.7F
R5 18k
P3
C3 1F
SRC
ASNS C4 0.1F R4 75k
D1 L1 3.5H
MAX8730
ACIN REF CSIP CSIN ICTL R8 50k BATT COUT1 4.7F COUT2 4.7F RS2 30m BATTERY COUT
R2 R7 37.4k LDO R9 10k INPUT REF INPUT
REF ACOK MODE SWREF C5 1F LDO REF VCTL CLS REFON INPON IINP R10 15k C6 0.1F CCV R11 10k CCI C8 0.01F GND CCS C9 0.01F RELTH R12 50k C10 1F R13 50k
C11 1F
HOST
OUTPUT OUTPUT A/D INPUT
LDO
C7 0.01F
Figure 1. Typical Application Circuit
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15
Low-Cost Battery Charger MAX8730
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. 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 (4A), 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 GND Float LDO CELL COUNT Relearn mode 3 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 = 30m). Set ICTL according to the following equation: VICTL = ICHG x RS2 x 3.6V 135mV
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 + VVCTL ) 9
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.
16
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Low-Cost Battery Charger MAX8730
IINP
RELTH
ASNS
PDS
PDL
BATT
CSSP CSSN INPON CCS A = 20V/V
CURRENT-SENSE AMPLIFIER GM = 2.8A/mV REF
SRC CSSP SYSTEM OVERCURRENT PDS PDL LOGIC SRC - 10V SRC HIGHSIDE DRIVER
REL_EN VCTL + 40mV
GND
SRC DHI
GMS CLS CCV BATT MODE VCTL REF CCI CSIP IMAX CSIN A = 15V/V CURRENT-SENSE AMPLIFIER REF/2 N CSI GMI 6.56A CELLSELECT LOGIC SELECTOR (DEFAULT = 4.2V) 222mA IMIN GMV LOWEST VOLTAGE CLAMP LVC
OVP
DC-DC CONVERTER
-5V REGULATOR
DHIV SRC
CCMP
5.4V CHARGER REGULATOR
LDO
CHARGER BIAS LOGIC
REFERENCE 4.2V BATT SRC
REF
MAX8730
ADAPTER DETECT
ICTL
65mV
REL_EN CHARGER SHUTDOWN
N
REFERENCE 3.3V
REFON
6A
ACOK
GND
ACIN
SWREF
Figure 2. Functional Diagram
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17
Low-Cost Battery Charger MAX8730
The MAX8730 includes a foldback feature, which reduces the Schottky requirement at low battery voltages. See the Foldback Current Section. where I INPUT is the DC current supplied by the AC adapter, G IINP is the transconductance of IINP (2.8A/mV typ), and R 10 is the resistor connected between IINP and ground. Connect a 0.1F 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 10A, drive INPON to low. Charging is disabled when INPON is low, even if the adapter is present.
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 where is the efficiency of the DC-DC converter (typically 85% to 95%). 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 = 15m). Set CLS according to the following equation: VCLS = ILIMIT x RS1 x VREF 75mV
AC-Adapter Detection and Power-Source Selection
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 5s 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 10k 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: VADAPTER _ THRESHOLD > VADAPTER _ MAX 3
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
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
18
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Low-Cost Battery Charger
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. * The IMIN comparator sets the peak inductor current in discontinuous mode. IMIN compares the control signal (LVC) against 100mV (corresponding to 222mA when RS2 = 30m). 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 = 30m). 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.
MAX8730
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 1F 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.
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 R Q DH DRIVER
CCMP 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 S OFF-TIME ONE-SHOT BATT OFF-TIME COMPUTE Q
Figure 3. DC-DC Converter Block Diagram 19
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Low-Cost Battery Charger MAX8730
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). 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 = 30m, this corresponds to a peak inductor current of 222mA: IDIS = 1 100mV x = 111mA 2 15 x RS2
The MAX8730 implements slope compensation in discontinuous mode to eliminate multipulsing. This prevents audible noise and minimizes the output ripple.
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 = 5.6s/VBATT for VBATT > 4V. The switching frequency in continuous mode varies according to the equation: f= 1 1 1 5.6V x s x + VBATT VSRC - VBATT
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 GMV RCV CCV ROGMV REF RL
CCV
Figure 4. CCV Loop Diagram
20
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Low-Cost Battery Charger
amplifier, ROGMV, is greater than 10M. The voltage amplifier transconductance, GMV = 0.125A/mV for 4 cells and 0.167A/mV for 3 cells. The DC-DC converter transconductance is dependent upon the charge current-sense resistor RS2: GMOUT = 1 ACSI x RS2 COUT is typically much lower impedance than RL near crossover so the parallel impedance is mostly capacitive and: RL (1 + sCOUT x RL) 1 sCOUT
MAX8730
where ACSI = 15V/V and RS2 = 30m in the typical application circuits, so GMOUT = 2.22A/V. The loop transfer function is given by: LTF = GMOUT x RL x GMV x ROGMV x (1 + sCOUT x RESR)(1 + sCCV x RCV) (1 + sCCV x ROGMV)(1 + sCOUT x RL) 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 x RCV) RCV (1 + sCCV x ROGMV)
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 x RCV GMV sCOUT
Setting the LTF = 1 to solve for the unity-gain frequency yields: fCO _ CV = GMOUT x GMV x RCV 2 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 = 10k: RCV = 2 x COUT x fCO _ CV 10k GMV x GMOUT
Table 2. CCV Loop Poles and Zeros
NAME CCV pole EQUATION 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 > 10M). 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 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 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.
fP _ CV =
1 2ROGMV x CCV
CCV zero
fZ _ CV =
1 2RCV x CCV
Output pole
fP _ OUT =
1 2RL x COUT
Output zero
fZ _ OUT =
1 2RESR x COUT
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21
Low-Cost Battery Charger MAX8730
where: VBATT = 16.8V GMV = 0.125A/mV GMOUT = 2.22A/V COUT = 10F f OSC = 350kHz (minimum occurs at V IN = 19V and VBATT = 16.8V) RL = 0.2 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 (30m). ROGMI is the equivalent output impedance of the GMI amplifier, which is greater than 10M. GMI is the charge-current amplifier transconductance = 1A/mV. GMOUT is the DC-DC converter transconductance = 2.22A/V. The loop transfer function is given by:
LTF = GMOUT x ACSI x RS x GMI ROGMI 1 + sROGMI x CCI
that describes a single-pole system. Since: GMOUT = 1 ACSI x RS
the loop-transfer function simplifies to: LTF = GMI ROGMI 1 + sROGMI x CCI
The crossover frequency is given by: fCO _ CI = GMI 2CCI
For stability, choose a crossover frequency lower than 1/10 of the switching frequency: CCI > 10 x GMI = 4nF 2 x 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.
80 60 40 20 0 -20 -40 0.1 1 10 100 1k 10k 100k FREQUENCY (Hz) MAG PHASE
0 GMOUT
CSIP RS2
CSIN
-45
PHASE (DEGREES)
MAGNITUDE (dB)
CSI
-90
CCI GMI CCI -135 1M ROGMI ICTL
Figure 5. CCV Loop Response 22
Figure 6. CCI Loop Diagram
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Low-Cost Battery Charger
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 = 10m in the typical application circuits. ROGMS is the equivalent output impedance of the GMS amplifier, which is greater than 10M. GMS is the charge-current amplifier transconductance = 1A/mV. GMIN is the DC-DC converter's input-referred transconductance = GMOUT/D = 2.22A/V/D. The loop-transfer function is given by:
ROGMS LTF = GMIN x ACSS x RSI x GMS 1 + SROGMS x CCS
ADAPTER INPUT CSSP CLS CSS RS1 CSSI GMS
For stability, choose a crossover frequency lower than 1/10 of the switching frequency: CCS = 5 x VIN _ MAX GMS x 2fOSC VBATT _ MIN
MAX8730
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.
Since GMIN =
1 ACSS x RS2
the loop-transfer function simplifies to: LTF = GMS ROGMS x RS1/ RS2 1 + SROGMS x CCS
CCS CCS ROGMS GMIN SYSTEM LOAD
The crossover frequency is given by: fCO _ CS = VIN _ MAX GMS x 2CCS VBATT _ MIN
Figure 8. CCI Loop Diagram
100 80 MAGNITUDE (dB) 60 40 MAG PHASE
0
100 80 MAGNITUDE (dB) 60 40 MAG PHASE
0
-45 20 0 -20 -40 0.1 10 1k FREQUENCY (Hz) 100k -90
-45 20 0 -20 -40 0.1 10 1k FREQUENCY (Hz) 100k -90 10M
Figure 7. CCI Loop Response
Figure 9. CCS Loop Response 23
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PHASE (DEGREES)
Low-Cost Battery Charger MAX8730
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 1 sourcing and 4 sinking. where CRSS is the reverse transfer capacitance of the MOSFET, and IGATE is the peak gate-drive source/sink current. 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.
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 x RDS(ON) VSRC
Schottky Selection
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: JA < TJ _ MAX - TA _ MAX V VF x ICHG x 1 - BATT _ MIN VSRC _ MAX
Calculate the switching losses according to the following equation:
PDSWITCHING = 1 x 2
2 xQG x VSRC (MAX) x ICHG + VSRC (MAX)2 x CRSS I GATE f
(
)
Table 3. Recommended MOSFETs
CHARGE CURRENT (A) 3 2.5 3.5 3.5 4 4 4.5 MOSFET Si3457DV FDC658P FDS9435A NDS9435A FDS4435 FDS6685 FDS6675A PIN-PACKAGE 6-SOT23 6-SOT23 8-SO 8-SO 8-SO 8-SO 8-SO MAX QG (nC) 8 12 14 14 24 24 34 RDSON (m) 75 75 80 80 35 35 19 RJA (/W) 78 78 50 50 50 50 50 TMAX (C) +150 +150 +175 +175 +175 +175 +175
24
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Low-Cost Battery Charger
where JA 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. The Schottky size and cost can be reduced by utilizing the MAX8730 foldback function. See the Foldback Current section for more information. Select the Schottky diode to minimize the battery leakage current when the charger is shut down. The ripple current is determined by: IL = k OFF L
MAX8730
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. See Table 4 for suggestions about inductor selection.
Inductor 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: L= k OFF 0.4 x ICHG
Input Capacitor Selection
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: 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 10C. 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.
where kOFF is the off-time constant (5.6V x s 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
Table 4. Recommended Inductors
APPLICATION (A) 2.5 2.5 3.5 INDUCTOR CDRH6D38 CDRH8D28 CDRH8D38 SIZE (mm) 8.3 x 8.3 x 3 7x7x4 8.3 x 8.3 x 4 L (H) 3.3 4.7 3.5 ISAT (A) 3.5 3.4 4.4 RL (m) 20 24.7 24
Table 5. Recommended Input Capacitors
APPLICATION (A) <3 <4 <4 INPUT CAPACITOR GMK316F47S2G GMK325F106ZH TMK325BJ475MN CAPACITANCE( F) 4.7 4.7 10 VOLTS (V) 35 35 25 RMS AT 10C (A) 1.8 2.4 2.5
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25
Low-Cost Battery Charger MAX8730
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 = VSST GIINP x RS1 x ISST x 0.7 - R10
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.
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
ADAPTER CSS1 32nF RSS2 6k
SYSTEM LOAD CSS2 10nF IINP
R15
C13 RSS1 18k
C6
R10
MAX8730
SRC PDS
Figure 10. Adapter Soft-Start Modification
Figure 11. System Short-Circuit IINP Configuration
26
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Low-Cost Battery Charger
REF
R7 R14 ICTL R8
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.
MAX8730
Figure 12. ICTL Foldback Current Adjustment
For typical applications, choose t Delay = 20s (depends on the p-MOSFET selected for the PDS switch). The following components can be used for a 10A system short-current design: R10 = 8.66k C6 = 0.1F R15 = 7.15k 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 6A. 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 6A R7 +R8 135 V m R7 +R8
Layout and Bypassing
Bypass SRC, ASNS, LDO, DHIV, and REF as shown in Figure 1.
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27
Low-Cost Battery Charger MAX8730
Chip Information
CSIN CSIP
Pin Configuration
BATT GND CCS CCV CCI
TRANSISTOR COUNT: 3307 PROCESS: BiCMOS
TOP VIEW
21 DHIV 22 DHI 23 SRC 24 CSSN 25 CSSP 26 PDS 27 PDL 28 1
ASNS
20
19
18
17
16
15 14 13 12 INPON REFON ICTL IINP MODE ACOK RELTH
MAX8730
*EXPOSED PADDLE +
11 10 9 8
2
LDO
3
SWREF
4
REF
5
CLS
6
ACIN
7
VCTL
5mm x 5mm THIN QFN
28
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Low-Cost Battery Charger
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.)
QFN THIN.EPS
MAX8730
D2 D D/2 MARKING k L E/2 E2/2 E (NE-1) X e
C L C L
b D2/2
0.10 M C A B
AAAAA
E2
PIN # 1 I.D.
DETAIL A
e (ND-1) X e
e/2
PIN # 1 I.D. 0.35x45 DETAIL B
e
L1
L
C L
C L
L
L
e 0.10 C A 0.08 C
e
C
A1 A3
PACKAGE OUTLINE, 16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm
-DRAWING NOT TO SCALE-
21-0140
I
1
2
COMMON DIMENSIONS
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.
EXPOSED PAD VARIATIONS PKG. CODES T1655-2 T1655-3 T1655N-1 T2055-3
D2
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
E2
exceptions
L
A A1 A3 b D E e k L
MIN. NOM. MAX. MIN. NOM. MAX. 0.15
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 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.
DOWN BONDS ALLOWED
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 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. 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.
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
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 ** ** ** ** ** **
YES NO NO YES NO YES YES YES NO NO YES YES NO YES NO YES NO YES
** SEE COMMON DIMENSIONS TABLE
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
-DRAWING NOT TO SCALE-
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 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

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