19-1605; Rev 0; 1/00 Lithium-Ion Battery Pack Protector ____________________________Features The MAX1665 provides protection against overvoltage, undervoltage, overcharge current, and overdischarge current for 2-cell to 4-cell lithium-ion (Li+) battery packs. Very low operating current ensures that cells are not overdischarged during long storage periods. ♦ Complete Protection Against: Cell Overvoltage Cell Undervoltage ♦ Pack Protection for Excessive Charge and Discharge The MAX1665 controls two external N-channel MOSFETs to limit the charge and discharge voltages. Charging is allowed when the per-cell voltage is below +4.3V. When the voltage on any cell rises above +4.3V (overvoltage limit), the MAX1665 turns off the charge MOSFET. This safety feature prevents overcharge of any cell within the battery pack. ♦ Very Low Supply Current: 16µA typ ♦ Low Standby Current: 1µA max ♦ Matched Cell Input Bias Current (<500pA) Preserves Cell Balance Discharge is allowed when the per-cell voltage is above +2.5V (undervoltage limit). If the voltage across any cell falls below +2.5V, the MAX1665 turns off the discharge MOSFET. This safety feature prevents overdischarge of any cell within the battery pack. Charging and discharging are allowed if the voltage between PKN and BN is less than 250mV. This safety feature prevents excessive pack current. Ordering Information TEMP. RANGE PINPACKAGE CELL COUNT MAX1665SESA -40°C to +85°C 8 SO 2 MAX1665VESA MAX1665XESA -40°C to +85°C -40°C to +85°C 8 SO 8 SO 3 4 PART Applications Lithium-Ion Battery Packs Pin Configuration Typical Operating Circuit TOP VIEW (+) I.C. (B4P) 1 DSG 2 B4P B3P B2P DSG CHG 3 PKN 4 MAX1665S MAX1665V MAX1665X 8 I.C. [B3P] 7 B2P 6 B1P 5 BN MAX1665X CHG B1P BN (-) PKN SO NOTES: I.C. = INTERNAL CONNECTION. MAKE NO CONNECTIONS TO THIS PIN. ( ) ARE FOR THE MAX1665X. [ ] ARE FOR THE MAX1665V AND MAX1665X. ________________________________________________________________ Maxim Integrated Products 1 For free samples and the latest literature visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX1665S/V/X General Description MAX1665S/V/X Lithium-Ion Battery Pack Protector ABSOLUTE MAXIMUM RATINGS B3P to BN (MAX1665V)..........................................-0.3V to +18V B4P to BN (MAX1665X)..........................................-0.3V to +24V Continuous Power Dissipation (TA= +70°C) 8-Pin SO (derate 5.88mW/°C above +70°C)...............471mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Temperature Range...........................................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C B4P to PKN (MAX1665X)........................................-0.3V to +24V B3P to PKN (MAX1665V)........................................-0.3V to +18V B2P to PKN (MAX1665S)........................................-0.3V to +12V B1P to PKN, B2P to B1P, B3P to B2P, B4P to B3P...-0.3V to +6V CHG to PKN, DSG to BN MAX1665S............................................-0.3V to (VB2P + 0.3V) MAX1665V............................................-0.3V to (VB3P + 0.3V) MAX1665X............................................-0.3V to (VB4P + 0.3V) B2P to BN (MAX1665S)..........................................-0.3V to +12V 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 (VB2P = 8V (MAX1665S), VB3P = 12V (MAX1665V), VB4P = 16V (MAX1665X), TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) MAX UNITS B2P Voltage Range PARAMETER VB2P MAX1665S 4 10 V B3P Voltage Range VB3P MAX1665V 4 15 V B4P Voltage Range VB4P MAX1665X 20 V Overvoltage Threshold VOV Cell voltage rising 4.34 V Overvoltage Hysteresis VCE Undervoltage Threshold VUV Undervoltage RESET VRE Overcurrent Sense Threshold VCH Overcurrent Hysteresis VCH2 Overvoltage/Undervoltage Delay tUV Overcurrent Detection Delay tIO CONDITIONS MIN TYP 4 4.26 4.3 0.10 VBN - VPKN V 2.4 2.5 2.6 V 0 18 30 mV ±200 ±250 ±300 mV (Note 1) 5 mV 200 ms 10 ms MAX1665S VB2P - 1.8 VB2P - 0.54 MAX1665V VB3P - 1.8 VB3P - 0.54 MAX1665X VB4P - 1.8 VB4P - 0.54 CHG, DSG Output Voltage High IOUT = 100µA DSG Output Voltage High (Note 2) MAX1665X, IOUT = 100µA, VB4P = 24V, VBN = 100mV 17 20 V V VPKN + 0.1 V VBN + 0.1 V CHG Output Voltage Low VCHGL ICHG = -100µA DSG Output Voltage Low VDSGL IDSG = -1µA CHG, DSG Output Source Current IOH CHG = PKN, DSG = BN 10 25 mA CHG Output Sink Current IOL VCHG = VPKN + 3.0V 0.5 2 mA DSG Output Sink Current IOL VDSG = VBN + 3.0V 0.5 2 µA Overcurrent Sampling - tON tON VPKN = ±300mV 8.2 ms Overcurrent Sampling - tOFF tOFF VPKN = ±300mV 135 Input Bias Current (Note 3) 2 SYMBOL IBIAS ms MAX1665SESA, VB1P = 4V 3 10 MAX1665VESA, VB1P = 4V, VB2P = 8V 3 10 MAX1665XESA, VB1P = 4V, VB2P = 8V, VB3P = 12V 3 10 _______________________________________________________________________________________ nA nA Lithium-Ion Battery Pack Protector (VB2P = 8V (MAX1665S), VB3P = 12V (MAX1665V), VB4P = 16V (MAX1665X), TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Input Bias Current Matching SYMBOL ∆IBIAS Supply Current ICC Standby Mode Current ILP Undervoltage Lockout VUVLO CONDITIONS MIN TYP MAX ±500 (Notes 3, 4) UNITS pA 16 25 µA (Note 5) 0.7 1 µA DSG = CHG = low 4.0 4.7 V ELECTRICAL CHARACTERISTICS (VB2P = 8V (MAX1665S), VB3P = 12V (MAX1665V), VB4P = 16V (MAX1665X), TA = -40°C to +85°C, unless otherwise noted.) (Note 6) MAX UNITS B2P Voltage Range PARAMETER SYMBOL VB2P MAX1665S 4 10 V B3P Voltage Range VB3P MAX1665V 4 15 V B4P Voltage Range VB4P MAX1665X Overvoltage Threshold VOV Cell voltage rising Undervoltage Threshold VUV Undervoltage RESET VRE Overcurrent Sense Threshold VCH CONDITIONS VBN- VPKN MIN TYP 4 20 V 4.20 4.24 V 2.4 2.6 V 0 30 mV ±180 ±320 mV MAX1665S VB2P - 2 VB2P - 0.5 MAX1665V VB3P - 2 VB3P - 0.5 MAX1665X VB4P - 2 VB4P - 0.5 CHG, DSG Output Voltage High IOUT = 100µA DSG Output Voltage High (Note 2) MAX1665X, IOUT = 100µA, VB4P = 24V, VBN = 100mV 20 V V VPKN + 0.1 V VBN + 0.1 V CHG Output Voltage Low VCHGL ICHG = -100µA DSG Output Voltage Low VDSGL IDSG = -1µA CHG, DSG Output Source Current IOH CHG = PKN, DSG = BN 10 mA CHG Output Sink Current IOL VCHG = VPKN + 0.3V 0.2 mA DSG Output Sink Current IOL VDSG = VBN + 0.3V 0.2 µA Input Bias Current (Note 3) IBIAS Supply Current ICC Standby Mode Current ILP Undervoltage Lockout VUVLO Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: MAX1665SESA, VB1P = 4V 10 MAX1665VESA, VB1P = 4V, VB2P = 8V 10 MAX1665XESA, VB1P = 4V, VB2P = 8V, VB3P = 12V 10 (Note 5) DSG = CHG = low nA 30 µA 2 µA 4.7 V Applies to the differential voltage measured on any cell. DSG is internally clamped to a maximum of 20V to protect the external MOSFET (VGS). Guaranteed by design. The input bias matching between cells is measured with a 4V voltage between cells. At least one cell is <VUV. Specifications to -40°C are guaranteed by design, not production tested. _______________________________________________________________________________________ 3 MAX1665S/V/X ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) OVERVOLTAGE THRESHOLD vs. TEMPERATURE 4.26 HYSTERESIS 4.22 4.18 2.50 2.49 2.48 2.47 VBN - VPKN 252 249 246 243 VBN - VPKN 4.14 VBN - VPKN 2.46 -15 10 35 60 85 240 -40 -15 10 35 60 85 -40 -15 10 35 TEMPERATURE (°C) TEMPERATURE (°C) OVERDISCHARGE THRESHOLD vs. TEMPERATURE SUPPLY CURRENT vs. TEMPERATURE STANDBY MODE CURRENT vs. TEMPERATURE SUPPLY CURRENT (µA) -244 -246 -248 -250 -252 -254 17.5 17.0 16.5 -256 1.0 STANDBY CURRENT (µA) -242 85 MAX1665 toc06 18.0 MAX1665 toc04 -240 0.9 0.8 0.7 0.6 -258 VBN - VPKN -260 16.0 -15 10 35 60 85 -40 -20 0 20 40 60 80 100 0.5 -40 -20 0 20 40 80 100 TEMPERATURE (°C) TEMPERATURE (°C) QUIESCENT CURRENT vs. SUPPLY VOLTAGE CONTINUOUS OVERCHARGE CONDITION CONTINUOUS OVERDISCHARGE CONDITION 17.6 MAX1665 toc08 MAX1665 toc07 18.0 17.2 16.8 DSG 2V/div CHG 2V/div 16.4 NORMALIZED TO ONE CELL 16.0 2.5 60 TEMPERATURE (°C) MAX1665 toc09 -40 3.0 3.5 4.0 4.5 5.0 50ms/div 50ms/div SUPPLY VOLTAGE PER CELL (V) 4 60 TEMPERATURE (°C) MAX1665 toc05 -40 OVERDISCHARGE THRESHOLD (mV) 255 MAX1665 toc03 2.51 OVERCURRENT THRESHOLD (mV) 4.30 OVERCURRENT THRESHOLD vs. TEMPERATURE MAX1665 toc02 MAX1665 toc01 UNDERVOLTAGE THRESHOLD vs. TEMPERATURE UNDERVOLTAGE THRESHOLD (V) THRESHOLD VOLTAGE (V) 4.34 QUIESCENT CURRENT (µA) MAX1665S/V/X Lithium-Ion Battery Pack Protector _______________________________________________________________________________________ Lithium-Ion Battery Pack Protector PIN NAME FUNCTION MAX1665S MAX1665V MAX1665X 1, 8 1 — I.C. Internally Connected. Make no connection to this pin. — — 1 B4P Cell 4 Positive Input. Connect to the positive terminal of the fourth series Li+ cell. 2 2 2 DSG Discharge Control Output. Drives the gate of an external N-channel MOSFET to control the discharge path. 3 3 3 CHG Charge Control Output. Drives the gate of an external N-channel MOSFET to control the charge path. 4 4 4 PKN Pack Negative Input 5 5 5 BN Connect to the negative terminal of the first series Li+ cell. 6 6 6 B1P Cell 1 Positive Input. Connect to the positive terminal of the first series Li+ cell. 7 7 7 B2P Cell 2 Positive Input. Connect to the positive terminal of the second series Li+ cell. — 8 8 B3P Cell 3 Positive Input. Connect to the positive terminal of the third series Li+ cell. Table 1. Functionality Truth Table for VBN < VPKN + 0.018V (Discharge Mode) CHARGE OVERCURRENT DISCHARGE OVERCURRENT OVERVOLTAGE UNDERVOLTAGE CHG DSG GATE CLOCKED MAX SUPPLY CURRENT* (µA) 0 0 0 0 High High No 25 0 0 0 1 Low Low No 1 0 0 1 0 Low High No 25 0 0 1 1 Low Low No 1 0 1 0 0 Gated Gated Yes 25 0 1 0 1 Low Low No 1 0 1 1 0 Low Gated Yes 25 0 1 1 1 Low Low No 1 *Assuming no load on CHG or DSG. _______________________________________________________________________________________ 5 MAX1665S/V/X Pin Description Table 2. Functionality Truth Table for VBN > VPKN + 0.018V (Charge Mode) DSG GATE CLOCKED MAX SUPPLY CURRENT* (µA) High High No 25 1 High High No 25 0 Low High No 25 1 1 Low High No 25 0 0 0 Gated Gated Yes 25 1 0 0 1 Gated Gated Yes 25 1 0 1 0 Low High No 25 1 0 1 1 Low High No 25 CHARGE OVERCURRENT DISCHARGE OVERCURRENT OVERVOLTAGE UNDERVOLTAGE CHG 0 0 0 0 0 0 0 0 0 1 0 0 1 *Assuming no load on CHG or DSG. POWER ON POWER ON SLEEP CHARGE = 1 DSG = 0 CHG = 0 SUPPLIES RDY = 1 ON DSG = 0 CHG = 0 START START-UP ∆T = COUNTER ∆T = ZCHK DSG = 0 2.4ms DSG = 0 160µs CHG = 0 CHG = 0 START-UP MEASURE DSG = 0 CHG = 0 NORMAL PULSE OFF ∆T = DSG = * 96ms CHG = * NORMAL PULSE ON ∆T = DSG = 1 6.4ms CHG = 1 NORMAL ZCHK DSG = 1 CHG = 1 ∆T = 160µs UV = 0 OV = 1 OV DSG = 1 CHG = 0 ∆T = 2.4ms OV PULSE OFF ∆T = 96ms DSG = 1 CHG = 0 OV PULSE ON ∆T = DSG = 1 6.4ms CHG = 0 OV ZCHK DSG = 1 CHG = 0 ∆T = 160µs UV = 1 OV = 0 UV DSG = 1 CHG = 1 ∆T = UV PULSE OFF ∆T = DSG = * 96ms CHG = * UV PULSE ON ∆T = DSG = 1 6.4ms CHG = 1 UV ZCHK DSG = 1 CHG = 1 2.4ms CHARGE = 0 OV & UV DSG = 1 CHG = 0 ∆T = 2.4ms OV & UV PULSE OFF ∆T = DSG = 1 96ms CHG = 0 CHARGE = 0 OV & UV PULSE ON ∆T = DSG = 1 6.4ms CHG = 0 160µs WAIT FOR BLANK = 0 DSG = 0 CHG = 0 ∆T = 2.4ms NORMAL MEASURE DSG = 1 CHG = 1 ∆T = 640µs OV MEASURE DSG = 1 CHG = 0 ∆T = 640µs UV MEASURE DSG = 1 CHG = 1 ∆T = 640µs CHARGE = 0 OV & UV ZCHK DSG = 1 CHG = 0 SHORT = 1 UV = 1 OV = 1 CHARGE = 0 ∆T = SHORT = 1 ∆T = 2.4ms SHORT = 1 OV = 0 NORMAL DSG = 1 CHG = 1 UV = 0 ∆T = 640µs SHORT = 1 CHARGE = 0 MAX1665S/V/X Lithium-Ion Battery Pack Protector ∆T = 160µs OV & UV MEASURE DSG = 1 CHG = 0 ∆T = 640µs * = 0 FOR OVERCURRENT FAULT; 1 OTHERWISE Figure 1. State Diagram _______________Detailed Description The MAX1665S, MAX1665V, and MAX1665X supervise the charging and discharging processes on Li+ cells. Designed for 2, 3, and 4-cell applications, these devices monitor the voltage across each cell to provide protection against overcurrent, overvoltage, and undervoltage. 6 Figure 1 shows the MAX1665 state diagram. Two control pins, CHG and DSG, drive the gates of two seriesconnected external N-channel MOSFETs, enabling/ disabling the charging/discharging process as necessary (see Typical Operating Circuit). The voltages at B1P, B2P, B3P, and B4P are measured differentially _______________________________________________________________________________________ Lithium-Ion Battery Pack Protector Overvoltage Protection When any individual cell voltage rises above VOV (overvoltage limit), the charge MOSFET control pin (CHG) is driven to PKN, thereby disconnecting the charger from the cells. The MAX1665 measures each cell of the pack differentially to prevent overcharging on a cell-by-cell basis. The charging process resumes when the highest cell voltage drops below VOV - 100mV (see Typical Operating Circuit). Undervoltage/Overdischarge Protection Discharge can occur whenever the voltage of each cell is above the undervoltage threshold voltage (VUV, typically 2.50V). If the voltage on any of the cells falls below VUV, CHG latches to PKN and DSG latches to BN. Quiescent current falls to under 1µA as the device enters the standby mode. The latch resets when BN exceeds PKN by 18mV. During charge mode, when BN is greater than PKN, the latch is held in reset, which disables the undervoltage comparator feature and allows charging on the cells. During the initialization process, as cells are connected to the MAX1665, the device considers this a low-voltage condition and disables CHG and DSG until a charging source is applied to create at least an 18mV differential between BN and PKN. During long-term storage, the battery will self-discharge until it reaches the undervoltage threshold. When this happens, the MAX1665 enters standby mode. Normal operating mode resumes when a charger is connected, causing BN to rise 18mV above PKN. Overcurrent Protection When the MAX1665 detects overcurrent in the system, it disables the charge or discharge process by connecting CHG to PKN and DSG to BN, turning off the external MOSFETs (see Typical Operating Circuit). In charge mode, the MAX1665 detects overcharge when the voltage from BN to PKN exceeds +250mV. In discharge mode, overdischarge occurs when the differential voltage is less than -250mV. During any overcurrent condition, CHG and DSG are gated at 12Hz until the overcurrent is removed. If both an overvoltage and overcharge condition exist, the overvoltage condition takes priority. Likewise, if undervoltage and overdischarge conditions exist, the overdischarge condition takes priority. For more details, see Tables 1 and 2. Cell Current Balancing When the battery cells are matched, the MAX1665 draws zero current from the intermediate nodes. The MAX1665 draws current from the top terminal only. Figure 2 shows a simplified diagram of the voltage sampling scheme. The following equations show that, for balanced cells, the differential discharge currents are zero: 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. Due to process variations, the MAX1665 does draw a minute current (70nA ~ 150nA) from the intermediate node even when the cells are matched. This current difference exists in the sampling mode, which is 1/32 of the whole time period, making the average of this current 2nA to 5nA. _______________________________________________________________________________________ 7 MAX1665S/V/X across each cell to determine if the voltage levels are within operating range. As depicted in the typical operating circuit, when CHG and DSG are high, the MOSFETs are on, allowing the cells to charge or discharge. However, when the charge or discharge current becomes excessive, the device turns off the FETs, enters a standby mode, and periodically samples the current to determine if the fault condition is removed. The MAX1665 does not sample the current directly, but rather measures the differential voltage across BN and PKN produced by the charge or discharge current flowing through the drain-to-source resistance of the MOSFETs. A preset voltage threshold is used to prevent excess current flow (see Electrical Characteristics). In operating mode, all of the MAX1665 versions consume less than 25µA of quiescent current, allowing long-term battery storage without significantly affecting battery life. In standby mode, these devices consume less than 1µA of quiescent current. MAX1665S/V/X Lithium-Ion Battery Pack Protector Table 3. Recommended MOSFETs BP4 + V4 + V3 I4 BP3 I3 I3P B3P1 ICB V4 R BP2 + V2 I2 I1 TYPICAL RDS(ON) (Ω) MAX VGS (V) IRF9956 0.10 ±20 FDS6990A 0.018 ±20 Si9936 0.050 ±20 B2P1 I2P ICB V4 R + V2 B1P1 BP1 + V1 DUAL N-CHANNEL MOSFETs ICB V4 R I1P + V1 + V3 R + V4 R R R 1 V1 R V2 R V3 R 8 V4 R 7 PACK+ CELL 2 Figure 2. Sampling Mode Equivalent Circuit CELL 1 Applications Information 6 5 I.C. I.C. B2P B1P BN MAX1665S IRF7101 Choosing an External MOSFET The external N-channel MOSFETs act as gated switches to enable or disable the charging/discharging process. CHG and DSG control the gate of these external MOSFETs to prevent damage to the Li+ cells. For overcurrent conditions, the voltage at DSG equals the voltage at BN, thereby reducing all current flow, including the path through the body diode of the N-channel MOSFET. Note that the MAX1665X clamps the VGS voltage to a maximum of 20V. The IRF7101 is a low-cost, dual N-channel MOSFET that is available in a small 8-pin SO package. Depending on the maximum charge and discharge rates, use different MOSFETs to optimize each application. Table 3 summarizes recommended MOSFETs. OVERDISCHARGE PROTECTION 2 DSG IRF7101 OVERCHARGE PROTECTION PACK- 3 4 CHG PKN Figure 3. Typical 2-Cell Operating Circuit 2, 3, and 4-Cell Applications Figures 3 through 5 depict circuits for 2, 3, and 4-cell applications. Note that the two series MOSFETs (IRF7101 dual N-channel MOSFETs) are oriented to prevent body diode current flow. The indicated polarity symbols show the connection for the external source required to charge the Li+ cells. This external charger source also supplies the gate drive to the MOSFETs through pack + voltage / pack. 8 _______________________________________________________________________________________ Lithium-Ion Battery Pack Protector 1 PACK+ I.C. CELL 4 8 PACK+ CELL 3 CELL 2 CELL 1 7 B3P CELL 3 B2P CELL 2 6 B1P CELL 1 5 BN MAX1665V 2 DSG OVERDISCHARGE PROTECTION PACK- 3 4 6 5 B3P B2P B1P BN MAX1665X 2 DSG IRF7101 IRF7101 OVERCHARGE PROTECTION 7 B4P IRF7101 IRF7101 OVERDISCHARGE PROTECTION 8 MAX1665S/V/X 1 CHG OVERCHARGE PROTECTION PKN PACK- Figure 4. Typical 3-Cell Operating Circuit 3 4 CHG PKN Figure 5. Typical 4-Cell Operating Circuit _______________________________________________________________________________________ 9 MAX1665S/V/X Lithium-Ion Battery Pack Protector ________________________________________________________Package Information 10 ______________________________________________________________________________________ Lithium-Ion Battery Pack Protector MAX1665S/V/X NOTES ______________________________________________________________________________________ 11 MAX1665S/V/X Lithium-Ion Battery Pack Protector NOTES 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. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.