19-1465; Rev 1; 7/99 Advanced Lithium-Ion Battery-Pack Protector The MAX1666 provides complete protection against overvoltage, undervoltage, overcharge current, overdischarge current, and cell mismatch for 2-cell to 4-cell Lithium-Ion battery packs. The voltage of each cell in the battery pack is checked and compared to the programmable threshold and to the other cells in the pack. The MAX1666 protects the battery pack in an overcurrent condition by disconnecting the pack from the load at a programmable limit. On-chip power MOSFET drivers control external P-channel MOSFETs to disconnect the cells from external terminals when faults occur. The MAX1666 employs a unique timing scheme that allows three modes of operation, for optimal performance and battery power conservation. The MAX1666 can operate in a stand-alone configuration or in conjunction with a microcontroller. It is available in three versions: the “S” version monitors two Li-Ion cells, the “V” version monitors three cells, and the “X” version monitors four cells. Applications Features ♦ Overvoltage Protection Programmable Limits from +4.0V to +4.4V Accurate to ±0.5% ♦ Undervoltage Protection Programmable Limits from +2.0V to +3.0V Accurate to ±2.5% ♦ Cell Mismatch Protection Programmable Limits from 0 to 500mV Accurate to ±10% ♦ Overcharge Current Protection ♦ Overdischarge Current Protection ♦ Low Operating Supply Current: 30µA typ ♦ Low Standby Current: 1µA max ♦ +28V max Input Voltage ♦ Available in Small 16-Pin QSOP (MAX1666S) and 20-Pin QSOP (MAX1666V/X) Packages 2/3/4-Cell Lithium-Ion Battery Pack Selector Guide Ordering Information PART NUMBER OF LI-ION CELLS PART TEMP. RANGE PIN-PACKAGE MAX1666S 2 MAX1666SEEE -40°C to +85°C 16 QSOP MAX1666V MAX1666X 3 4 MAX1666VEEP MAX1666XEEP -40°C to +85°C -40°C to +85°C 20 QSOP 20 QSOP Typical Operating Circuits appear at end of data sheet. Pin Configurations TOP VIEW SRC 1 16 VCC SRC 1 20 UVO SRC 1 20 UVO DSO 2 15 REF DSO 2 19 VCC DSO 2 19 VCC TKO 3 14 OVA TKO 3 18 REF TKO 3 18 REF 17 OVA CGO 4 16 UVA B4P 5 MAX1666S 13 UVA CGO 4 B2P 5 12 MMA B3P 5 CGO 4 MAX1666V 17 OVA MAX1666X 16 UVA BIP 6 11 PKF B3P 6 15 MMA B3P 6 15 MMA GND 7 10 CGI B2P 7 14 WRN B2P 7 14 WRN PKN 8 9 B1P 8 13 PKF B1P 8 13 PKF GND 9 12 CGI GND 9 12 CGI PKN 10 11 DSI PKN 10 11 DSI QSOP DSI QSOP QSOP ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX1666S/V/X General Description MAX1666S/V/X Advanced Lithium-Ion Battery-Pack Protector ABSOLUTE MAXIMUM RATINGS SRC, DSO, TKO, CGO, UVO, PKF, WRN to GND ...-0.3V to +28V VCC, REF, OVA, UVA, MMA to GND ........................-0.3V to +6V B4P to B3P ...............................................................-0.3V to +6V B3P to B2P ...............................................................-0.3V to +6V B2P to B1P ...............................................................-0.3V to +6V B1P to GND ..............................................................-0.3V to +6V PKN to GND...........................................................................±2V VCC, CGI, DSI to PKN...............................................-0.3V to +6V Continuous Power Dissipation (TA = +70°C) 16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW 20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10sec) .............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 1 UNITS Charge Mode Detection Threshold VSRC - VB_P SRC Input Current Range VSRC - VB_P = 1V 2 10 µA Supply Current No faults, long time average current from the top battery terminal B_P 30 45 µA 1 µA 3.09 3.25 3.41 V 2.7 2.85 3 V Shutdown Supply Current VCC Output Voltage ISUP ISHDN VCC RLOAD ≥ 665Ω, 2V < VCELL < 4.4V VCC Undervoltage Lockout Threshold Reference Output Voltage VREF Pulse on 1.221 OVA = GND Overvoltage Threshold Cell voltage rising 3.980 4.000 4.378 4.400 VOVA = VREF / 2 OVA = REF Cell voltage falling 1.950 VUVA = VREF / 2 UVA = REF 2.925 Above undervoltage threshold, cell voltage falling WRN Early Warning Threshold Hysteresis OVA, UVA, MMA = REF All cells > 2V 2.050 V 3.075 100 mV 100 mV 200 mV 20 nA ±0 VMMA = VREF / 2 MMA = REF 3.000 0.1 MMA = GND Cell Mismatch Threshold 2.000 mV 2.500 Undervoltage Threshold Hysteresis OVA, UVA, MMA Input Current V 4.422 200 UVA = GND WRN Early Warning Threshold V 4.020 4.2 Overvoltage Threshold Hysteresis Undervoltage Threshold V mV ±250 ±450 ±500 ±550 PKN to GND Overdischarge Current Threshold 270 300 330 mV PKN to GND Overcharge Current Threshold -220 -200 -180 mV 2 _______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector (VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) MIN TYP MAX UNITS Overcurrent Fault Timer Delay PARAMETER SYMBOL tP-DELAY CONDITIONS 330 550 770 ms Overdischarge/Overcharge Current Fault Blanking Time tI-DELAY 1.6 2.4 3.2 ms 40 µA DSO, CGO, UVO Output Sink Current No faults, V DSO = V CGO = VUVO = 1V to 27V 20 30 DSO, CGO Output Source Current V DSO = V SRC - 4V and V CGO = V SRC - 4V, fault condition 2 10 DSO, CGO, UVO Leakage Current V DSO = V CGO = VUVO = 27V, fault condition TKO Pull-Down Resistance mA 0.2 µA 100 200 kΩ TKO Source Current TKO = GND 1 8 mA DSI, CGI Input High Voltage Referenced to PKN 2 DSI, CGI Input Low Voltage Referenced to PKN DSI, CGI Input Current VDSI, VCGI = 5V WRN Sink Current Fault condition, V WRN = 0.4V 2 4 PKF Sink Current Fault condition, V PKF = 0.4V 4 8 PKF, WRN Leakage Current V PKF = V WRN = 27V Undervoltage, Overvoltage, or Mismatch Fault, to DSO, CGO, TKO Transition Delay tF-DELAY Fault persistent for 4 consecutive sample periods 180 V 320 0.45 V 1 µA mA mA 0.2 µA 460 ms ELECTRICAL CHARACTERISTICS (VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Charge Mode Detection Threshold VSRC - VB_P SRC Input Current Range VSRC - VB_P = 1V to 4V 10 µA No faults, long time average current from the top battery terminal B_P 45 µA Supply Current ISUP Shutdown Supply Current VCC Output Voltage ISHDN VCC Undervoltage Threshold OVA, UVA, MMA Leakage V 1 µA 3.09 3.41 V 2.7 3 V OVA = GND 3.975 4.025 OVA = REF 4.373 4.427 UVA = GND 1.950 2.050 UVA = REF 2.925 3.075 RLOAD ≥ 665Ω, 2V < VCELL < 4.4V VCC Undervoltage Lockout Threshold Overvoltage Threshold 1 OVA, UVA, MMA = REF 20 V V nA _______________________________________________________________________________________ 3 MAX1666S/V/X ELECTRICAL CHARACTERISTICS (continued) MAX1666S/V/X Advanced Lithium-Ion Battery-Pack Protector ELECTRICAL CHARACTERISTICS (VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL MAX UNITS ±450 ±550 mV PKN to GND Overdischarge Current Threshold 270 330 mV PKN to GND Overcharge Current Threshold -220 -180 mV Cell Mismatch Threshold CONDITIONS All cells > 2V, MMA = REF MIN TYP Overcurrent Fault Timer Delay tP-DELAY 330 770 ms Overdischarge/Overcharge Current Fault Blanking Time tI-DELAY 1.6 3.2 ms 40 µA DSO, CGO UVO Output Sink Current No faults; V DSO, V CGO, VUVO = 1V to 27V 20 DSO, CGO Output Source Current V DSO = V SRC - 4V and V CGO = V SRC - 4V, fault condition 2 DSO, CGO, UVO Leakage Current V DSO = V CGO = VUVO = 27V, fault condition TKO Pull-Down Resistance 0.2 µA 100 kΩ TKO Source Current TKO = GND 1 mA DSI, CGI Input High Voltage Referenced to PKN 2 DSI, CGI Input Low Voltage Referenced to PKN DSI, CGI Input Current VDSI = VCGI = 5V WRN Sink Current Fault condition, V WRN = 0.4V 2 PKF Sink Current Fault condition, V PKF = 0.4V 4 PKF, WRN Leakage Current V PKF = V WRN = 27V Undervoltage, Overvoltage, or Mismatch Fault, to DSO, CGO, TKO Transition Delay tF-DELAY Fault persistent for 4 consecutive sample periods 180 Note 1: Specifications to -40°C are guaranteed by design, not production tested. 4 mA _______________________________________________________________________________________ V 0.45 V 1 µA mA mA 0.2 µA 460 ms Advanced Lithium-Ion Battery-Pack Protector VCELL = 3.6V 750 33 740 730 720 31 29 27 3.0015 MAX1666toc03 35 SUPPLY CURRENT (µA) SUPPLY CURRENT (nA) 760 UNDERVOLTAGE THRESHOLD vs. TEMPERATURE UVA = REF UNDERVOLTAGE THRESHOLD (V) VCELL = 3.6V MAX1666toc01 770 SUPPLY CURRENT vs. TEMPERATURE MAX1666toc02 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE 3.0010 3.0005 710 700 25 40 60 80 3.0000 -40 100 -20 0 TEMPERATURE (°C) MISMATCH VOLTAGE THRESHOLD (mV) MAX1666toc04 4.390 4.385 20 40 80 -40 100 -20 0 60 80 MMA = REF 500 499 498 497 496 -20 0 20 40 301 100 202 201 200 60 80 100 -40 -20 0 20 40 60 80 TEMPERATURE (°C) OVERDISCHARGE PROTECTION OVERDISCHARGE RECOVERY TIME 100 PKN (0.5V/div) PKN (0.5V/div) 300 203 TEMPERATURE (°C) MAX1666toc07 302 80 MAX1666toc08 OVERDISCHARGE THRESHOLD vs. TEMPERATURE 60 199 -40 TEMPERATURE (°C) 40 OVERCHARGE THRESHOLD vs. TEMPERATURE 495 100 20 TEMPERATURE (°C) 501 4.395 OVERDISCHARGE THRESHOLD (mV) UNDERVOLTAGE THRESHOLD (V) OVA = REF 0 60 MISMATCH VOLTAGE THRESHOLD vs. TEMPERATURE 4.400 -20 40 TEMPERATURE (°C) OVERVOLTAGE THRESHOLD vs. TEMPERATURE -40 20 MAX1666toc06 20 MAX1666toc09 0 OVERCHARGE THRESHOLD (mV) -20 MAX1666toc05 -40 299 298 tI-DELAY 297 DSO (10V/div) DSO (10V/div) 296 tP 295 -40 -20 0 20 40 60 80 100 1ms/div 100ms/div TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX1666S/V/X Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) OVERCHARGE MAX1666toc11 MAX1666toc10 OVERVOLTAGE FAULT B1P 4.5V PKN (0.5V/div) 1 2 3 4.1V 4 REF (1V/div) CGO (10V/div) tP-DELAY tF-DELAY 1 2 3 4 tF-DELAY CGO (10V/div) 100ms/div 100ms/div VCELL2 = VCELL3 = VCELL4 = 4.15V, OVERVOLTAGE THRESHOLD = 4.4V UNDERVOLTAGE FAULT 1 2 3 4 1 2 3 4 B1P 3.4V 2.9V 3.4V 2.9V 1 REF (1V/div) REF (1V/div) WRN (10V/div) PKF (10V/div) DSO (10V/div) tF-DELAY 2 3 4 tF-DELAY 1 2 3 tF-DELAY DSO (10V/div) tF-DELAY 100ms/div VCELL2 = VCELL3 = VCELL4 = 3.35V, UNDERVOLTAGE THRESHOLD = 3.0V, UVA = REF 100ms/div VCELL2 = VCELL3 = VCELL4 = 3.6V, CELL MISMATCH THRESHOLD = 0.5V, MMA = REF MAX1666toc14 B1P UNDERVOLTAGE FAULT WITHOUT CHARGE SOURCE (VSRC < VB4P + 1V) 3.4V 2.9V REF (1V/div) VCC (2V/div) DSO (10V/div) 100ms/div VCELL2 = VCELL3 = VCELL4 = 3.35V, UNDERVOLTAGE THRESHOLD = 3.0V, UVA = REF 6 _______________________________________________________________________________________ 4 MAX1666toc13 CELL MISMATCH FAULT MAX1666toc12 B1P MAX1666S/V/X Advanced Lithium-Ion Battery-Pack Protector Advanced Lithium-Ion Battery-Pack Protector PIN NAME FUNCTION MAX1666X MAX1666V MAX1666S 1 1 1 SRC Charge Source Input. Provides current for gate drivers DSO, TKO, CGO, and UVO. 2 2 2 DSO Discharge Driver Output. Drives external P-channel MOSFET to control discharge. 3 3 3 TKO Trickle-Charge Driver Output. Drives external P-channel MOSFET to control trickle-charge current. Internally grounded when inactive. 4 4 4 CGO Fast-Charge Driver Output. Drives external P-channel MOSFET to control fast charge. 5 — — B4P Cell 4 Positive Input. Power supply input for MAX1666X. 6 5, 6 — B3P Cell 3 Positive Input. Power supply input for MAX1666V. 7 7 5 B2P Cell 2 Positive Input. Power supply input for MAX1666S. 8 8 6 B1P Cell 1 Positive Input 9 9 7 GND Ground 10 10 8 PKN Battery Pack Negative Terminal. Connect to bottom of current sense resistor. Ground reference for logic inputs DSI and CGI. 11 11 9 DSI Discharge Control Input 12 12 10 CGI Charge Control Input 13 13 11 PKF Pack Fail Output. PKF goes low when any cell voltage exceeds the mismatch threshold or when a shorted cell is detected. 14 14 — WRN Undervoltage/Overvoltage Warning Output 15 15 12 MMA Mismatch Adjust Input. Set the mismatch threshold by a resistordivider from REF to GND. 16 16 13 UVA Undervoltage Adjust Input. Set the undervoltage threshold with a resistor-divider from REF to GND. 17 17 14 OVA Overvoltage Adjust Input. Set the overvoltage threshold with a resistor-divider from REF to GND. 18 18 15 REF Reference Voltage Output. Minimize PCB stray capacitance on this node. 19 19 16 VCC 3.3V Linear Regulator Output. Bypass with a 0.47µF min capacitor to GND. 20 20 — UVO Undervoltage Fault Output _______________________________________________________________________________________ 7 MAX1666S/V/X Pin Description MAX1666S/V/X Advanced Lithium-Ion Battery-Pack Protector DSI CGO SRC SRC "1" D Q D Q RB CK "1" RB DSO CK N CGI N OV_FAULT CM_FAULT UV_FAULT CQI_FAULT UV_FAULT CM_FAULT DQY_FAULT N N 30µA 30µA GND MAX1666 LATCH_WRN REG EARLY WARNING 50kHZ OSC WARNING GND OSC B4P LATCH_OV B3P CELL VOLTAGE SELECTOR B2P BIP STATE MACHINE LATCH_UV REG OVERVOLTAGE OV-FAULT CMP REG UNDERVOLTAGE UV-FAULT CMP_P GND OVA THRESHOLD VOLTAGE SELECTOR UVA MMA CMP_N LATCH_CM REF REG CELL MISMATCH 1.221V CM-FAULT PKF N GND CQI_HI 200mV CQI_FAULT 550ms TIMER SET/RESET PKN DQI_HI WRN OV_FAULT WARNING UV_FAULT N DQI_FAULT 300mV B4P GND SRC CHARGE SHUTDOWN 1V 3.3V LINEAR REG. VCC UV_FAULT B4P BIAS TKO UVO SRC CM_FAULT UV_FAULT N CGI OV_FAULT CM_FAULT N 30µA GND Figure 1. Functional Diagram 8 _______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector VSRC < VB4P + 1V MAX1666S/V/X YES BATTERY CONNECTED SHUTDOWN VSRC > VB4P + 1V VCC > 2.85V NO YES (DISCHARGE CURRENT · RCS) 300mV (>2.4ms) OVERDISCHARGE DSO = H CHARGE CURRENT MONITOR RESET RESET DS0 = L CGO = L (CHARGE CURRENT · RCS) 200mV (>2.4ms) OVERCHARGE CGO = H 550ms DELAY STANDBY 80ms VCELL < UNDERVOLTAGE THRESHOLD SAMPLE 2.5ms YES CHECK VREF NO NO VREF > 1.1V YES VCELL < UNDERVOLTAGE WARNING THRESHOLD CELL MISMATCH YES NO LATCH UVF = ‘1’ LATCH MMF = ‘1’ VCELL > OVERVOLTAGE THRESHOLD UVF = ‘1’ AND VSRC < VB4P + 1V YES YES NO NO LATCH OVF = ‘1’ GO TO TABLE 3 YES NO LATCH UVW = ‘1’ Figure 2. Cell Fault Monitor _______________________________________________________________________________________ 9 MAX1666S/V/X Advanced Lithium-Ion Battery-Pack Protector parator monitoring VSRC and the top-cell voltage. The MAX1666 remains in shutdown mode as long as VSRC is less than the top-cell voltage. When SRC is connected to an external charger and VSRC is 1V above the top-cell voltage, the device goes into standby mode. The MAX1666 returns to shutdown mode under two conditions: the battery is disconnected and then reconnected, or the device detects an undervoltage fault and no charge source. REF MAX1666 R1 R3 R5 R2 R4 R6 OVA UVA MMA GND Figure 3. Using an External Resistor-Divider to Adjust Overvoltage Threshold Detailed Description The MAX1666 battery-pack protectors supervise the charging and discharging processes of Lithium-Ion battery cells. Designed for 2, 3, and 4-cell applications, these devices monitor the voltage across each cell to provide protection against undervoltage, overvoltage, and overcurrent damage. Control pins CGO, TKO, and DSO allow control of external MOSFET gates. This allows fast charging, trickle charging, and discharging processes (see Typical Operating Circuit). The voltage of each cell is measured individually. Also, each cell is measured differentially between every other cell of the pack. The MAX1666 contains a state machine, a voltage regulator, an oscillator, and other logic functions to selectively drive CGO, UVO, TKO, DSO, WRN, and PKF (Figure 1). Modes of Operation Shutdown Mode The MAX1666 goes into shutdown mode when a battery pack is first connected. The quiescent current is less than 1µA. All circuitry is inactive except the com- Normal Mode The standby state activates the bias circuitry, overcurrent comparator, and timer. The standby state lasts 80ms, then the MAX1666 goes into the sample state for 2.5ms. Within the 2.5ms, the MAX1666 checks for overvoltage, undervoltage, and mismatch between cells sequentially, and it stores the results in internal latches. The MAX1666 drives the outputs according to the faults (if any) detected by reading the latches (Figure 2) at the end of the sample state. Then the MAX1666 returns to the standby state. Overvoltage Protection The MAX1666 provides overvoltage protection to avoid overcharging of any cell. When any cell is at overvoltage, CGO and TKO go high, turning off the external MOSFETs and stopping the charging process ( Typical Operating Circuits). WRN goes low. Overvoltage is set when any cell voltage exceeds the overvoltage threshold. Overvoltage threshold is linearly adjustable through an external 1% resistor-divider (Figure 3) from REF. Determine the overvoltage threshold (VOVT) required. VOVT must be between 4V and 4.4V. Set RTOTAL = R1 + R2 = 1MΩ. Calculate R1 and R2 as follows: R2 = [(VOVT - 4V) / (4.4V- 4V)] · RTOTAL R1 = RTOTAL - R2 Table 1. Operating Modes MODE STATE TIME TYPICAL QUIESCENT CURRENT (µA) Standby 80ms 24 Only bias circuitry, overcurrent comparator, and timer are active. Sample 2.5ms 250 All circuitry active. — — 0.7 All circuitry inactive. Device enters shutdown when it detects an undervoltage fault and VSRC < VTOP-CELL + 1V (no charge source). CONDITION Normal Shutdown 10 ______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector I4 + V4 - ICB = V4 R Undervoltage Warning When any cell drops to 100mV above the undervoltage threshold, WRN goes low. WRN returns high when all cells are 300mV above the undervoltage threshold. B3P I3P + V3 - ICB = V4 R I3 Cell-Mismatch Protection B2P I2P + V2 - I2 + V1 - I1 ICB = V4 R B1P I1P + V1 - + V2 - R V1 R + V3 - R V2 R + V4 - R V3 R R V4 R R6 = (VCMT / 500mV) RTOTAL R5 = RTOTAL - R6 Figure 4. Cell Voltage Sampling Maximum mismatch of 1% external resistor-dividers is ±2%. The external adjusted overvoltage threshold accuracy includes the internal overvoltage threshold accuracy (±0.5%) and the error due to the external resistor-divider multiplied by maximum adjustment. ±2% 4.4V − 4.0V 4.4V The MAX1666 disables charging or discharging when mismatch occurs. When any two cells are mismatched, TKO, CGO, UVO, and DSO go high, turning off the external MOSFETs. PKF goes low. PKF has a strong pull-down current (>4mA), and can be used to control an external thermal fuse. The cell-mismatch threshold is linearly adjustable through an external resistor-divider (Figure 3) from REF. Determine the cell-mismatch threshold (VCMT) required. VCMT has to be between 0 and 500mV. Set RTOTAL = R5 + R6 = 1MΩ. Calculate R5 and R6: = ± 0.2% The total external adjusted overvoltage threshold (VOVT) accuracy is ±0.7%. Undervoltage Protection The MAX1666 provides undervoltage protection to avoid overdischarging the cells. When any cell is under voltage, UVO, DSO, and CGO go high, turning off the external charging and discharging MOSFETs. TKO remains low to keep the trickle charge current on. Undervoltage threshold is linearly adjustable through an external resistor-divider (Figure 3) from REF. Determine the undervoltage threshold (VUVT) required. VUVT must be between 2V and 3V. Set RTOTAL = R3 + R4 = 1MΩ. Calculate R3 and R4 as follows: R4 = [(VUVT - 2V) / (3V - 2V)] RTOTAL R3 = RTOTAL - R4 Maximum mismatch of 1% external resistor-dividers is ±2.0%, and the error due to the external resistor-divider multiplied by maximum adjustment is ±2% (3V - 2V) / 3V = ±0.7%. The total external adjusted undervoltage Maximum mismatch of 1% external resistor-divider is ±2%. The total external adjusted cell-mismatch threshold accuracy, including the internal cell-mismatch threshold accuracy (±10%), is ±12%. Cell Voltage Sampling The MAX1666 does not introduce cell mismatch. When the battery cells are matched, the MAX1666 draws close to zero current from the intermediate cells. Figure 4 shows a simplified diagram of the voltage sampling scheme. B4P: I4 = 3ICB + V4 / R = 4V4 / R = BAT4 Current B3P: I3 = I3P + I4 = BAT3 Current I3P + ICB = V3 / R ⇒ I3P = V3 / R - V4 / R I3 = I4 + (V3 - V4) / R = (3V4 + V3) / R B2P: I2 = I2P + I3 = BAT2 Current I2P + ICB = V2 / R ⇒ I2P = V2 / R - V4 / R I2 = I3 + V2 / R - V4 / R = I4 + (V3 - V4) / R + (V2 - V4) / R = (2V4 + V3 + V2) / R B1P: I1 = I1P + I2 = BAT1 Current I1P + ICB = V1 / R ⇒ I1P = V1 / R - V4 / R I1 = I2 + V1 / R - V4 / R = I4 + (V3 - V4) / R + (V2 - V4) / R + (V1 - V4) / R = (V4 + V3 + V2 + V1) / R When V1 = V2 = V3 = V4, I1P = I2P = I3P = 0, and I1 = I2 = I3 = I4 = 4V4 / R ______________________________________________________________________________________ 11 MAX1666S/V/X threshold (VUVT) accuracy including the internal undervoltage threshold accuracy (±2.5%) is ±3.2%. B4P MAX1666S/V/X Advanced Lithium-Ion Battery-Pack Protector Overcharge/Overdischarge Current Protection The MAX1666 checks for overcharge or overdischarge current in standby and sample states. The thresholds are factory preset to 200mV and 300mV, respectively. A charge current makes PKN go below GND. A discharge current makes PKN go above GND. When PKN exceeds the threshold, a fault is acknowledged. CGO goes high when the overcharge threshold is exceeded. DSO goes high when the overdischarge threshold is exceeded. An internal 550ms timer starts. At the end of 550ms, DSO or CGO goes low, while the MAX1666 rechecks for an overcharge/overdischarge fault. A persistent fault causes DSO and CGO to return high and restarts the 550ms timer again. Table 3. MOSFET Selection P-CHANNEL MOSFETs MAXIMUM DRAIN CURRENT (A) IRF7404 5.3 IRF7406 4.7 Si4431 4.5 Si4947 (dual) 2.5 EA Truth Table The MAX1666 has a total of eight signal inputs and six outputs. Table 2 lists all the possible states. Applications Information Choosing an External MOSFET The external P-channel MOSFETs act as a gated switch to enable or disable the charging/discharging process. CGO controls the MOSFET for normal charging of the battery. TKO controls the MOSFET for trickle charge of the cells. DSO controls the discharging MOSFET. Use different MOSFETs to optimize each function depending on the maximum charge and discharge rates. Table 3 lists some suitable MOSFETs in a small SO-8 package. Layout Considerations and Bypassing As with all printed circuit board designs, a careful layout is suggested. Minimize lead lengths to reduce losses in the traces. 12 ______________________________________________________________________________________ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 OVF 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 MMF 1 1 0 0 1 1 0 0 1 1 1 0 0 0 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 1 0 0 0 1 1 0 0 1 1 1 0 0 0 0 0 CGI Control Inputs 1 0 1 0 1 0 1 0 1 0 0 1 1 0 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 0 1 0 0 1 0 1 0 1 0 0 1 1 0 0 0 DSI 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 OCC 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1 0 ODC H H H H H H H H H PS L H H L PS L H H H H H H H H H H H H H H H H H PS L H PS L H H H H H PS L H H L PS L DSO H H H H H H H H H H H PS L PS L L H H H H H H H H H H H H H H H H H H H H H H H H H H H H H PS L PS L L H H H H H H H H H H H L L L L L H H H H H H H H H H L L H H H H H H H H H H H H H H H H H L L L L L TKO L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L H H H H H H H H H H H H WRN L L L L L L L L H H H H H H H H L L L L L L L L H H H H L L L L H H H H H H L L L L H H H H H H H H PKF Control Outputs CGO H H H H H H H H L L L L L L L L H H H H H H H H H H H H H H H H L L L L L L H H H H L L L L L L L L UVO UVF: Undervoltage fault ODC: Overdischarge current fault UVW: Undervoltage fault early warning OCC: Overcharge current fault Notes Undervoltage fault early warning, overvoltage fault, mismatch fault, disable charge and discharge path Undervoltage fault early warning, overvoltage fault, mismatch fault, disable charge path Undervoltage fault early warning, overvoltage fault, mismatch fault, disable discharge path Undervoltage fault early warning, overvoltage fault, mismatch fault Undervoltage fault early warning, mismatch fault, disable charge and discharge path Undervoltage fault early warning, mismatch fault, disable charge path Undervoltage fault early warning, mismatch fault, disable discharge path Undervoltage fault early warning, mismatch fault Undervoltage fault early warning, disable charge and discharge path Undervoltage fault early warning, disable charge path, overdischarge current fault Undervoltage fault early warning, disable charge path Undervoltage fault early warning, disable discharge path, overcharge current fault Undervoltage fault early warning, disable discharge path Undervoltage fault early warning, overcharge current fault Undervoltage fault early warning, overdischarge current fault Undervoltage fault early warning Undervoltage fault, overvoltage fault, mismatch fault, disable charge and discharge path Undervoltage fault, overvoltage fault, mismatch fault, disable charge path Undervoltage fault, overvoltage fault, mismatch fault, disable discharge path Undervoltage fault, overvoltage fault, mismatch fault Undervoltage fault, mismatch fault, disable charge and discharge path Undervoltage fault, mismatch fault, disable charge path Undervoltage fault, mismatch fault, disable discharge path Undervoltage fault, mismatch fault Undervoltage fault, disable charge and discharge path Undervoltage fault, disable charge path Undervoltage fault, disable discharge path Undervoltage fault Overvoltage fault, mismatch fault, disable charge and discharge path Overvoltage fault, mismatch fault, disable charge path Overvoltage fault, mismatch fault, disable discharge path Overvoltage fault, mismatch fault Overvoltage fault, disable charge and discharge path Overvoltage fault, disable charge path, overdischarge current fault Overvoltage fault, disable charge path Overvoltage fault, disable discharge path Overvoltage fault, overdischarge current fault Overvoltage fault Mismatch fault, disable charge and discharge path Mismatch fault, disable charge path Mismatch fault, disable discharge path Mismatch fault Disable charge and discharge path Disable charge path, overdischarge current fault Disable charge path Disable discharge path, overcharge current fault Disable discharge path Overcharge current fault Overdischarge current fault Normal operation MMF: Mismatch fault DSI: Discharge control input OVF: Overvoltage fault CGI: Charge control input PS: Overcurrent fault pulse sampling. (Output goes high for 500ms then resets low to monitor charge/discharge current. Output goes high again if fault persists.) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 UVF UVW MAX1666S/V/X Table 2. Truth Table Advanced Lithium-Ion Battery-Pack Protector ______________________________________________________________________________________ 13 Advanced Lithium-Ion Battery-Pack Protector MAX1666S/V/X Typical Operating Circuits OVERDISCHARGE PROTECTION PACK+ P 1 470k 270Ω 470k SRC 2 VCC DSO 19 P 4 CGO P OVERCHARGE PROTECTION 3 TRICKLE CHARGE DSI CGI TKO WRN 5 6 8 9 UVO 14 20 18 B2P 499k 1% 499k 1% 499k 1% 499k 1% 499k 1% 499k 1% MAX1666X GND PKN 10 RSENSE 0.05Ω 12 PKF B3P B1P 0.47µF 13 B4P REF 7 11 +3.3V 5mA 17 OVA 16 UVA 15 MMA PACK- 14 ______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector OVERDISCHARGE PROTECTION PACK+ P 470k 270Ω 470k 1 SRC 2 VCC DSO 19 P P OVERCHARGE PROTECTION 3 DSI CGI TKO WRN 5 6 7 8 9 220k VCC OUT1 11 OUT2 14 IN1 IN2 PKF UVO B3P 20 IN3 18 B2P B1P 100k 12 13 B4P REF PACK CONTROLLER 499k 1% 499k 1% 499k 1% MAX1666X GND PKN 10 RSENSE 0.05Ω 100k 1µF 4 CGO TRICKLE CHARGE +3.3V 5mA GND 17 OVA 16 UVA 15 MMA 499k 1% 499k 1% 499k 1% PACK- ___________________Chip Information TRANSISTOR COUNT: 4835 ______________________________________________________________________________________ 15 MAX1666S/V/X Typical Operating Circuits (continued) ________________________________________________________Package Information QSOP.EPS MAX1666S/V/X Advanced Lithium-Ion Battery-Pack Protector 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. 16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.