End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix Dual-Cell Lithium Ion Battery Control IC DESCRIPTION FEATURES The Si9730 monitors the charging and discharging of dualcell lithium-ion battery packs (carbon or coke chemistry) ensuring that battery capacity is fully utilized while ensuring safe operation. The Si9730 provides protection against overcharge, over-discharge, and short circuit conditions which are hazardous to the battery and the environment. * * * * * * * * Battery voltages of each individual cell are monitored at the center-tap connection by an internal A/D converter through the VC pin. If one or both of the cells is determined to be overcharged, an internal cell balancing network "bleeds" off current at 15 A until both cells are charged to the same maximum level. Depending on the condition of each cell, the Si9730 will switch two external source-connected N-Channel MOSFETs on or off to allow the cells to be charged or to provide current to the load. * * * * Over-Charge Protection Over-Discharge Protection Short Circuit Current Limiting Battery Open-Circuit Center Tap Protection Cell Voltage Balancing Undervoltage Lockout Individual Cell Voltage Monitoring Low Operating Current (30 A) and Shutdown Current (1 A) Internal N-Channel MOSFET Driver High Noise Immunity Accurate ( 1.19 %) Over-Charge Voltage Detection Four Different Cell Types Covered The Si9730 is available in an 8-pin SOIC package with an operating temperature range of - 25 to 85 C. The Si9730 is available in both standard and lead (Pb)-free packages. FUNCTIONAL BLOCK DIAGRAM AND PIN CONFIGURATION C VDD + VC1 Undervoltage Lockout Cell Balancing Network - A/D Converter VC Timer CDELAY Time Out CLK Control Logic OUT + VC2 - Oscillator SOUT 1.2 VREF VSS VSS DCO VM ILIMIT GS Generator IS Document Number: 70658 S-40135-Rev. F, 16-Feb-04 VM www.vishay.com 1 Si9730 End of Life. Last Available Purchase Date is 31-Dec-2014 Vishay Siliconix ABSOLUTE MAXIMUM RATINGS Parameter VM VDD VC Limit VDD - 1.5 V to VDD + 15 V VSS - 0.3 V to VSS + 12 V VSS - 0.3 V to VDD + 0.3 V VM - 0.3 V to VDD + 0.3 V VSS - 0.3 V to VDD + 0.3 V 125 200 80 - 55 to 150 (VSS VM) (VM VSS ) IS Maximum Operating Junction Temperature Power Dissipation Thermal Impedance (PJA) Storage Temperature Unit V C mW C/W 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. RECOMMENDED OPERATING RANGE Parameter CVC < 10 pF from VC to VDD and VSS , Total CD RIS series resistance to sense resistor DCO Load Capacitance VDD to VSS VDD to VM Operating Temperature Range Limit Unit Open to 1.0 < 27 0 to 2000 9 12 - 25 to 85 F k pF V C SPECIFICATIONS Parameter Power Supply Supply Current, Charging Operation Supply Current, Normal Operation Undervoltage Lockout Threshold Symbol IDD_C IDD IDD_UVL VUVL Test Conditions Unless Otherwise Specified VC1 = VC2 = 2.6 V, VDD - VM = 8.4 V VC1 = VC2 = 4.05 V, VM = VSS VM = VDD, VC1 = VC2 = 1.7 V Measured at VDD - VSS (Falling) VC1 = VC2, VDD - VM = 5.5 V Limits TA = - 25 to 85 C Mina 3.5 Typb 3.7 Unit Maxa 60 30 1 A 4.0 V VM Leakage Current IVM_UVL VC1 = VC2 = 1.7 V, VDD = VM 1 VM Operating Current IVM VC1 = VC2 = 2.6 V, VDD - VM = 8.4 V 30 VOH IOH = - 10 A, VC1 = VC2 = 3.3 V VDD - VM = 6.6 V tr tf VC1 = 2 V, VC2 = 2.4 V VDD - VM = 8.4 V CL = 500 pF, DCO to VSS A Control Logic DCO Output High Voltage DCO Rise Time (10 % to 80 %) DCO Fall Time (80 % to 10 %) DCO Output Low Voltage VOL IOL = 10 A VDD - 0.1 V 7.5 1 VM = VDD VC1 = 2 V, VC2 = 2.4 V VSS + 0.4 VM = VSS VC1 = VC2 = 4.4 V, IS = VDD VM + 0.52 s V Analog Section Current-Limit Comparator Trip Point Current-Limit Comparator Temperature Coefficient Current-Limit Comparator Response Time Current Limit Comparator Input Bias Current www.vishay.com 2 VILIMIT VC1 = VC2 = 4.05 V, VM = VSS + 0.25 V IS Rising, TA = 25 C 25.5 dVILIMIT/dT 28 32 0.18 tILIMIT VC1 = VC2 = 3.3 V, VM = VSS + 0.25 V CL = 50 pF, DCO to VSS, See Figure 2 IIS VC1 = VC2 = 3.3 V, VDD = VM, VIS = VSS %/C 25 - 125 mV s nA Document Number: 70658 S-40135-Rev. F, 16-Feb-04 End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix SPECIFICATIONS Parameter Symbol Test Conditions Unless Otherwise Specified Limits TA = - 25 to 85 C Mina Typb Maxa 4.15 4.1 4.1 4.15 4.1 4.1 4.2 4.15 4.15 4.2 4.15 4.15 4.18 4.12 4.12 4.18 4.12 4.12 4.28 4.22 4.22 4.28 4.22 4.22 4.20 4.25 4.27 4.27 4.25 4.27 4.27 4.30 4.32 4.32 4.30 4.32 4.32 4.25 4.30 4.25 4.25 4.30 4.25 4.35 4.40 4.35 4.35 4.40 4.35 20 10 10 2.3 2.3 30 30 Unit Analog Section (cont'd) VOC1 Cell 1 VC2 = 4.05 V VDD - VM = 8.6 V VOC2 Cell 2 VC1 = 4.05 V VDD - VM = 8.6 V VOC1 Cell 1 VC2 = 4.05 V VDD - VM = 8.6 V VOC2 Cell 2 VC1 = 4.05 V VDD - VM = 8.6 V VOC1 Cell 1 VC2 = 4.05 V VDD - VM = 8.6 V VOC2 Cell 2 VC1 = 4.05 V VDD - VM = 8.6 V VOC1 Cell 1 VC2 = 4.05 V VDD - VM = 8.6 V VOC2 Cell 2 VC1 = 4.05 V VDD - VM = 8.6 V A Suffix B Suffix Over-Charge Detect Threshold (Rising) C Suffix D Suffix Over-Charge Threshold Difference Cell 1 Over-Charge Detect Threshold Hysteresisc Cell 2 Cell 1 Over-Discharge Detect Threshold (Falling) Cell 2 Cell 1 Cell Balancing Current Cell 2 Timer Charge Current TA = 25 C TA = - 25 C TA = 85 C TA = 25 C TA = - 25 C TA = 85 C TA = 25 C TA = - 25 C TA = 85 C TA = 25 C TA = - 25 C TA = 85 C TA = 25 C TA = - 25 C TA = 85 C TA = 25 C TA = - 25 C TA = 85 C TA = 25 C TA = - 25 C TA = 85 C TA = 25 C TA = - 25 C TA = 85 C |VOC1 - VOC2| VOC_H1 VC2 = 4.05 V VDD - VM = 8 6 V VOC_H2 VC1 = 4.05 V VODC1 VC2 = 2.6 V VODC2 VC1= 2.6 V VM = VSS VC1 = 4.4 V, VC2 = 4.05 V IBAL1 IBAL2 VC2 = 4.4 V, VC1 = 4.05 V VC2 = 3.3 V, VM = VSS ITIMER(C) VC = VSS, TA = 25 C 2.1 2.1 9 9 4.20 4.25 4.25 4.22 4.22 4.32 4.32 2.2 2.2 15 15 V mV V A - 0.5 Timer Discharge Current ITIMER(D) VC1 = VC2 = 3.3 V, VDD = VM VDD - VC = 6.1 V, TA = 25 C DL2 Time (Over-Charge) tDL2OC VC1 = 4.05 V, VDD - VM = 10 V CD = 500 pF, TA = 25 C, See Figure 4 27 40 60 DL2 Time (Over-Discharge) tDL2ODC VC1 = 2.6 V, VM = VSS, CD = 500 pF TA = 25 C, See Figure 5 27 40 60 30 42 -2 60 300 100 2 A mV A 40 s 1.1 V External Short Circuit Sense Current Reset Threshold Center Tap, Average Bias Current Overcharge Load Detect Power-Down Charger Detect Threshold IVMSHORT VRTH IVC tOCC VCHPD VC1 = VC2 = 4.4 V, VM = VDD VC1 = VC2 = 4.05 V, See Figure 3 VC1 = VC2 = 4.05 V, VM = VDD VC1 = VC2 = 4.4 V, CD = 500 pF CL = 500 pF, DCO to VSS, See Figure 1 1.0 ms VC1 = 2 V, VC2 = 2.4 V, See Figure 6 CL = 500 pF, DCO to VSS, See Figure 7 tPW DCO Pulse Width Notes: a. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum. b. Typical values are for DESIGN AID ONLY, not guaranteed nor subject to production testing. c. Guaranteed by design, not subject to production test. Document Number: 70658 S-40135-Rev. F, 16-Feb-04 mA 520 s www.vishay.com 3 End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix TIMING DIAGRAMS 200 mV VM Waveform 50 % tr VSS 100 nS High DCO Waveform 50 % VSS tOCC Figure 1. OC Load Detect 50 % VSS tr VRTH VSS 100 nS VDD tILIMIT DCO Waveform VDD VSS 50 % DCO Waveform VDD VM Waveform (After Short is Removed) 60 mV IS Input VSS VRTH = VM - VSS at DCO Transition Figure 3. Reset Threshold Figure 2. Current-Limit Comparator Response Time 2.6 V VC2 Waveform 2.0 V 4.4 V VC2 Waveform 4.0 V t30 t30 C Waveform C Waveform VSS VSS 1 1 31 31 32 x t 30 30 32 x t 30 t DL20C = 30 t DL20DC = Figure 4. DL2 Time (Over-Charge) Figure 5. DL2 Time (Over-Discharge) VSS VM Waveform + VCHPD - VM Waveform VSS ^VRTH High DCO Waveform Low VCHPD = VSS - VM at DCO Transition Figure 6. Power-Down Charger Detect Threshold www.vishay.com 4 VDD DCO Waveform tpw VSS Figure 7. Load Detection in Overcharge Mode Document Number: 70658 S-40135-Rev. F, 16-Feb-04 End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix TYPICAL CHARACTERISTICS 25 C, unless otherwise noted 100.0 100.0 25 C 10.0 t DL20C - Time (s) t DL20C - Time (s) 25 C TA = 85 C - 25 C 1.0 0.1 10.0 1.0 0.1 0.01 0.1 1 0.01 0.1 CD - Capacitance (F) DL2 Period (Over Discharge) vs. Capacitance 1.08 100 1.06 V R T H - Threshold (Normalized) 120 t I L I M I T (S) 80 60 40 20 0 20 40 60 1 CD - Capacitance (F) DL2 Period (Over Charge) vs. Capacitance 80 1.04 1.02 1.00 0.98 0.96 0.94 - 25 100 VIS - VSS (mV) 0 25 50 75 100 Temperature (C) Reset Threshold vs. Temperature Over Current Sense Voltage vs. Current Sense Time 4.2050 6.5 Overcharge Threshold V OCC (V) 6.0 5.5 t O C C (s) - 25 C TA = 85 C 5.0 4.5 4.0 3.5 50 75 100 125 150 175 200 4.2025 4.2000 4.1975 4.1950 2.5 3.0 3.5 4.0 Opposing Cell Voltage (V) VM - VSS (mV) Load Detect Time vs. VM - VSS Document Number: 70658 S-40135-Rev. F, 16-Feb-04 Overcharge Threshold vs. Opposing Cell Voltage www.vishay.com 5 End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix TYPICAL CHARACTERISTICS 25 C, unless otherwise noted 1000.00 100.00 Time (s) 10.00 Rise 1.00 Fall TA = 85 C 0.10 TA = - 25 C 0.01 100 1000 10000 DCO Capacitance (pF) DCO Rise and Fall Times vs. Capacitance PIN CONFIGURATION ORDERING INFORMATION Part Number SO-8 Si9730ABY-T1 Si9730ABY-T1-E3 (Lead Free) VM 1 8 DCO NC 2 7 VSS VDD 3 6 IS Si9730CBY-T1 CD 4 5 VC Si9730CBY-T1-E3 (Lead Free) Si9730BBY-T1 Si9730BBY-T1-E3 (Lead Free) Si9730DBY-T1 Top View Si9730DBY-T1-E3 (Lead Free) VOC1/2 Typ. Temp Range 4.20 V 4.25 V - 25 to 85 C 4.22 V 4.32 V PIN DESCRIPTION Pin Number Symbol 1 VM Negative Battery Pack Terminal - connection for external negative terminal of the battery pack. 2 NC No Connection, do not connect this pin. 3 VDD Dual Cell Positive Terminal - connection for positive terminal of dual series connected LiI+ cells. 4 CD Delay Capacitor Connection - an external capacitor connected across CD and Vss allows additional charge time (DL2, see Detailed Description ) after a charge error has occurred. Suggested capacitor values are shown in DL2 Period vs. Capacitance Curves. 5 VC Dual Cell Center Tap Connection - monitors individual battery voltages for overcharge and overdischarge errors. 6 Is Current Sense Comparator Input - monitors load current for short circuit conditions . If VILIMIT is exceeded, then DCO opens the low-side switch, disconnecting the cell 7 VSS Dual Cell Negative Terminal - connection for negative terminal of dual series connected LiI+ cells. 8 DCO Low-side Switch Gate Driver Output - drives the gate of two external source connected N-Channel MOSFETs. DCO swings from VOL to VDD. www.vishay.com 6 Description Document Number: 70658 S-40135-Rev. F, 16-Feb-04 End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix DETAILED DESCRIPTION Overview Normal Discharging The purpose of the Si9730 is to safely and reliably control the charging and discharging of a two-cell lithium-ion battery (carbon or coke chemistry). It provides protection against all possible fault conditions, including: The cells are in normal discharging conditions if a, b, and c above are satisfied, and if in addition d) the load current is less than the discharge current limit. With no charger present, the switch will be on, discharging the cells and powering the load. * external short circuits * reversed charger * overcharged cell or cells * undervoltage * battery open center-tap General Concepts The Si9730 operates by connecting or disconnecting the negative terminal of the battery to the negative side of the load and/or charger (see Figure 8); that is, it does ground side switching. It is important to bear the distinction between these two "grounds" in mind in order to understand the operation of the Si9730. The switching is accomplished by controlling two "back-to-back" MOSFETs: having the two MOSFETs in this arrangement is mandatory to ensure that current cannot flow in either direction when the MOSFETs are off. To turn the switch on, the Si9730 applies a gatesource voltage to both MOSFETs (from the DCO pin) that is high with respect to the sources. The Si9730 DCO signal is referenced to the VM pin while the battery is being charged, and to the Vss pin while the battery is being discharged. The Si9730 causes the DCO to be referenced to the lower of the two voltages. This prevents the switch from turning on or off unintentionally. The Si9730 is designed to operate only with a current-limited lithium-ion battery charger. Specifically, the battery charger must have an open-circuit voltage that does not exceed the absolute maximum IC voltage, and it must have a limited short-circuit current that does not exceed the allowed charging current of the battery. The following descriptions cover all the common operational scenarios; additional information on unusual battery conditions can be found in the state transition table. Normal Charging The cells are in normal charging conditions if a) both cells are above the Over-Discharge Detect Threshold (VODC ~ 2.2 V); b) both cells are under the Over-Charge Detect Threshold (VOC ~ 4.2 V); and c) the center tap is connected to the VC pin. When a charger is present in these conditions, the switch will be on, charging the cells at the current limit of the charger. Document Number: 70658 S-40135-Rev. F, 16-Feb-04 Overcharged Cell(s) Charging The most destructive condition that a LiI+ cell can experience is overcharging. If the cell becomes overcharged beyond its recommended limits, it can become permanently disabled. If one or both cells rise above the over-charge detect threshold (VOC1 and VOC2), and a charger is present, the Si9730 will open the switch (to prevent further charging) and begin bleeding off charge (15 A typical) from the overcharged cell or cells. The details of this operation depend on the fact that the voltage level of lithium-ion batteries drops for a short time after charging ceases (due to momentary changes in battery chemistry, ESR, etc.). Because of this recovery, the Si9730 allows the battery to continue charging for a short time (the overcharge time, tDL2OC). This additional charge time only occurs if the overcharge condition persists for more than 8 msec (two periods of an internal 4msec oscillator). TDL2OC is determined by the capacitor attached to the CD pin, see Figure 8. Once the overcharge time has ended, the switch is opened, preventing the battery from further overcharging. Now, the Si9730 begins bleeding current off the overcharged cell or cells (IBAL1 and IBAL2), as long as a charger is present. Eventually, the cell(s) will return into their normal range, and charging will begin, starting the whole cycle over again. Overcharged Cell(s) Discharging If one or more cells is overcharged, and a load is connected, the switch is turned on, permitting the battery to power the load. Over-Discharged Cell(s) Discharging Repeated over-discharging of LiI+ cells can cause irreversible reactions in the cells which lead to decreased cycle life. To avoid this, if one or both cells becomes over-discharged (VCELL < VODC) and no charger is present, the Si9730 opens the switch to prevent further discharging, and goes into a shutdown mode in which it draws minute power from the battery (IDD_UVL < 1 A). www.vishay.com 7 Si9730 End of Life. Last Available Purchase Date is 31-Dec-2014 Vishay Siliconix Over-Discharged Cell(s) Charging Open Center Tap If one or both cells is over-discharged, and a charger is present, charging can begin, and so the Si9730 closes the switch. However, removal of the charger in this condition could potentially damage the battery if the removal is not recognized and the cells are discharged. Since the voltage drop across the switch is small, the Si9730 actually cycles the switch at a 7/8 duty cycle; during the 1/8 time when the switch is open, the IC checks that the charger is still present. Once both cells are back into the normal operating range, normal charging resumes. An open center tap is a mechanical failure of the battery pack such that the Si9730's VC pin is disconnected from the center point of the two-cell battery. If this connection is open, the IC opens the switch, as it cannot measure the cell voltages in this condition. The switch is left open until connection is reestablished. If the battery is under-voltaged and the charger is present in this case, the battery is allowed to charge even with the center tap open. In this state, batteries are almost impossible to damage by 1/8 duty cycle charging. Once the battery voltage reaches the over-discharged voltage, the switch is turned off. Undervoltage Charging State Transition Table If for some reason the battery drops below about 3.7 V (VUVL), there is insufficient voltage for the Si9730 to properly monitor fault conditions. Of course, the switch is already open, since VUVL < VODC x 2. However, when a charger is detected, the Si9730 recovers and goes into an undervoltage mode. (A charger is detected if the VS pin is higher than the VM pin by at least VCHPD = 1.1 V, see Figure 6). In this undervoltage mode, the switch is on at a 1/8 duty cycle, to limit the power dissipation across the switch, and, again, to detect the continuing presence of the charger. The number of different states of the Si9730 can seem overwhelming at first. This state transition table will help to organize thinking about the different operational conditions of the IC, by listing each possible transition from one condition to another. Once the battery voltage is above VUVL, the charging continues in the over-discharged state. Reading the table is straightforward. There are two cells constituting the battery, one with its positive terminal connected to VDD and its negative terminal connected to VC, referred to as the high cell (see Figure 8); and one cell with its positive terminal connected to VC and its negative terminal connected to VSS, referred to as the low cell. Each cell can be in one of three voltages: Output Short * Over-discharge (ODC), where VCELL < VODC; If too much current is drawn from the battery due to a load short, the switch must be opened quickly to prevent damage to the battery. The Si9730 monitors the load current by looking at the voltage across an external sense resistor (see Figure 8). If the voltage across the sense resistor exceeds VILIMIT ~ 28 mV, the switch is opened. The Si9730 leaves the switch open until the load is completely removed. Of course, the IC must have some way of detecting that the load has been removed. For this purpose, a small current (IVMSHORT) passes through the Si9730, from pin VM to pin VSS once the short is detected and the switch is turned off. The IVMSHORT current causes the voltage on the VM pin to equal the voltage on the VDD pin while the short is present, or the voltage on the VM pin to equal the voltage on the VSS pin if the short is removed. If the short is not removed, IVMSHORT current will continue to flow until the battery voltage becomes overdischarged. Once the short is removed, the IC is allowed to turn the switch back on. The current limit threshold has a temperature coefficient of 0.18 %/C. This can partially compensate for a copper circuit board trace being used as the sense resistor. www.vishay.com 8 * Normal Operation (NO), where VODC < VCELL < VOC; or * Overcharge (OC), where VOC < VCELL. Additionally, the battery as a whole can be undervoltage (UV), where VBATTERY < VUVL. Note that this final condition is not necessarily (though normally) mutually exclusive with the other cell conditions: if one cell were at 0 V, the other cell could be in NO, and the battery could still be in UV. The charger can be either present (ON) or not present (OFF); the "X" in the table means the condition is true regardless of the state of the charger. The load current can be either 0, normal (0 < ILOAD < IILIMIT) or a short (IILIMIT< ILOAD) where IILIMIT is set by VILIMIT/RSENSE; the "X" in the table refers to a load current that can be either 0 or normal. Finally, the switch can be either ON, OFF, or cycling at either 1/8 or 7/8 duty cycle, where the duty cycle refers to the portion of the period when the switch is on; the notation On->On simply means that the switch does not change state, it remains on; the notation ->Off means that the switch turns off regardless of its previous state. Document Number: 70658 S-40135-Rev. F, 16-Feb-04 End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix STATE TRANSITION TABLE High-Cell Voltage Low-Cell Voltage Charger On/Off Load Current Switch State NO NO Off>On X On->On NO->OC NO Off 0 On->Off NO NO->OC Off 0 On->Off NO->OC NO Off Normal Cycles at very high duty cycle NO NO->OC Off Normal Cycles at very high duty cycle OC NO Off->On X Off->Off NO OC Off->On X Off->Off OC OC Off->On X Off->Off NO NO Off Normal->Short On->Off OC NO Off Normal->Short On->Off NO OC Off Normal->Short On->Off NO->ODC NO Off 0 On->Off NO NO->ODC Off 0 On->Off NO->ODC NO Off Normal On->Off NO NO->ODC Off Normal On->Off ODC NO Off->On X Off->Cycle at 7/8 duty cycle NO ODC Off->On X Off->Cycle at 7/8 duty cycle ODC ODC Off->On X Off->Cycle at 7/8 duty cycle Off->On X Off->Cycle at 1/8 duty cycle NO->ODC UV OC Off 0 Cycle->Off OC NO->OC Off 0 Off NO NO V<0 X Off On Center Tap->Open Cycle at 1/8 duty cycle ODC UV ODC X Center Tap->Open -.>Off NO ODC X Center Tap->Open -.>Off ODC NO X Center Tap->Open -.>Off NO NO X Center Tap->Open -.>Off OC OC X Center Tap->Open -.>Off Document Number: 70658 S-40135-Rev. F, 16-Feb-04 www.vishay.com 9 Si9730 End of Life. Last Available Purchase Date is 31-Dec-2014 Vishay Siliconix APPLICATION CIRCUIT + 10 F Si9730 100 VDD C 4 3 CD Cell 1 VC1 C1 0.1 F Undervoltage Lockout Cell Balancing Network 100 VC 5 A/D Converter Timer CDELAY Time Out CLK Control Logic OUT Load Cell 2 VC2 100 Current Sense 14 M Chgr. 8.4 V 1A Oscillator VSS 7 SOUT 1.2 VREF VSS GS Gen. Comparator C2 0.47 F VM ILIMIT Filter IS 6 8 RIS 47 k 1 VM DCO Si9936DY Figure 8. Typical 2 -Cell Circuit GENERAL CONSIDERATIONS Figure 8 shows a typical application of the Si9730, controlling a 2-cell lithium-ion battery (carbon or coke chemistry). Specifics of the selection of MOSFETs, current sensing resistor, and output capacitor are detailed below. In addition, there are several typical features of this circuit to be observed. First, each connection from a cell to the IC has a 100 resistor in series with it. The purpose of the resistor is to ensure that in the unlikely event of the IC shorting, the cells themselves will not see a short. The maximum size of this resistance is set by the current drain of the IC; for example, the VDD pin draws a maximum of 60 A, which will drop V = 60 A * 100 = 6 mV across the resistor. This drop con- www.vishay.com 10 stitutes an error in the measured cell voltage, and so the resistor must be small enough that the error voltage is acceptable. A second typical feature demonstrated in Figure 8 is the current sense filter formed by RIS and C2. This provides a noise filter, to prevent the Si9730 from opening the connection to the battery if there is noise on its current sense pin. It also causes a delay in the response of the IC to a genuine overcurrent, the amount of the delay being inversely proportional to the amount of overcurrent, since the Is pin senses a voltage. Increasing this filter's time constant could be used to allow short-time surges of current out of the battery without compromising its ability to protect the battery. Document Number: 70658 S-40135-Rev. F, 16-Feb-04 End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix Output Capacitor MOSFET Selection Depending on the MOSFET selected, the Si9730 can open the switch quite rapidly, in a matter of a few microseconds. However, the various monitoring operations take 10-100 times longer than this, and the basic period of the Si9730's oscillator is 4 msec. In order to prevent false readings by the Si9730, it is necessary to attach a capacitor across the output of the battery charger/load (this is not in parallel with the battery, because of the switch). A 10 F capacitor is recommended for this purpose; see Figure 8. Two MOSFETs in series, with their sources and gates connected together, are used as the switch. This prevents current from flowing in either direction when the gate is low; if only one MOSFET were used, the body diode could conduct current in the opposing direction. Selecting a Current Sense Resistor The current sense resistor should be selected based on the maximum current the battery can source or charge at; above this current, the Si9730 will open the switch, disconnecting the battery from its load or charger. Rsense = VILIMIT/IILIMIT 28 mV/IILIMIT Of course, the resistor must be rated to take the power dissipated in it as well: PRSENSE = IILIMIT* VILIMIT 28 mV * IILIMIT For example, suppose that the maximum current the battery will see is 1.8 A. Then, ILIMIT might be chosen to be 2 A. We would then select a resistor of RSENSE = 28 mV/2 A = 14 m. The power dissipation in this resistor is PRSENSE = 28 mV * 2 A = 56 mW and so a 100 mW surface mount resistor would be suitable. Another possibility is to use a thin copper trace as the sense resistor. The copper has a temperature coefficient of 0.39 %/C, but this is partially compensated for by the temperature coefficient of the current limit comparator in the Si9730, which is 0.18 %/C. A simple formula for selecting a trace to act as a current sensor is: R 0.5 m x length 1 oz. Copper width LITTLE FOOT MOSFETs are recommended for this application, because of their size, performance and cost benefits. SO-8 and TSSOP-8 MOSFETs allow for space efficient designs with performance equal to or better than their DPAK and TO-220 predecessors. Further, their availability from multiple sources permits a cost effective solution. There are two important parameters to consider in MOSFET selection: gate threshold voltage; and on-resistance, which determines power dissipation. Even when the DCO pin of the Si9730 is low, the specification allows its value to be as high as 0.4 V. If this voltage were close to the gate threshold voltage, leakage current through the MOSFETs could be hundreds of microamps, which would result in the battery quickly becoming discharged. To ensure that leakage is minimized, N-Channel MOSFETs with a minimum gate threshold voltage of 0.8 V should be chosen. On resistance of the MOSFETs needs to be selected to limit power dissipation into the MOSFETs' package. For example, a dual MOSFET SO-8 package is rated at 2 W, and a dual MOSFET TSSOP-8 package is rated at 1 W (both at 25 C; if the ambient temperature is higher, the allowable power dissipation in these packages is less). For example, if the maximum current is 2 A, and a dual MOSFET SO-8 package is being used, the maximum on-resistance of the two MOSFETs in series must not exceed 1 W = (2 A)2 * RON or RON = 0.25 ; each MOSFET can be allotted half of this, RON = 125 m. Account must also be taken of the fact that MOSFETs' on-resistance is a function of temperature; a conservative approach would give a discount of 1/3, RON = 125 m * (2/3) = 80 m per MOSFET. A list of recommended MOSFETs, which Vishay Siliconix supplies, follows. For example, to get a 14 m. resistor, we need length/width = 28; with a trace width of 0.01", the length of the trace should be 0.28". Document Number: 70658 S-40135-Rev. F, 16-Feb-04 www.vishay.com 11 Si9730 End of Life. Last Available Purchase Date is 31-Dec-2014 Vishay Siliconix N-CHANNEL MOSFET SELECTION GUIDE Recommended Application Current (A) at 25 C Part Number rDS (on) () at VGS = 10 V rDS(on) () at VGS = 4.5 V ID (A) VGS(th) (V) Config. Si4410DY 0.0135 0.020 10 1.0 Single SO-8 9 Si4412DY 0.028 0.042 7 1.0 Single SO-8 6.3 Package Si6434DQ 0.028 0.042 5.6 1.0 Single TSSOP-8 4.9 Si4936DY 0.037 0.055 5.8 1.0 Dual SO-8 3.5 Si9936DY 0.050 0.080 5 1.0 Dual SO-8 2.9 Si6954DQ 0.065 0.095 3.9 1.0 Dual TSSOP-8 1.9 V+ 100 Si9730 1 VM DCO 2 NC 3 VDD 100 8 VSS 7 4 CD IS 6 VC 5 10 nF 100 + 15 M 470 nF 47 k 100 F Si9936 100 Si9730 1 VM DCO 2 NC 4 CD 100 F VSS 7 3 VDD 100 + 8 IS 6 VC 5 470 nF 10 nF 100 47 k 15 M V- Si9936 Figure 9. 4-Cell Battery Circuit www.vishay.com 12 Document Number: 70658 S-40135-Rev. F, 16-Feb-04 End of Life. Last Available Purchase Date is 31-Dec-2014 Si9730 Vishay Siliconix observing that the current through it is limited by the 100 resistor. A trade off can be made here between the power rating of the zener, which can be decreased by increasing the resistor value, and the accuracy of the voltage measurement by the Si9730, which can be increased by decreasing the resistor value. Four Cell Application Figure 9 shows a method for using the Si9730 in a 4-cell application. Basically, this is two complete 2-cell circuits stacked in series. Each half of the complete circuit monitors its own 2-cell portion of the battery, and opens its own MOSFET switch under any of the appropriate conditions. Observe that the total percent power loss in this circuit is identical to that in the 2-cell application; although there are now two sets of MOSFETs in series, there is also double the battery voltage, and so total efficiency is the same. Reset from Shutdown There are two specialized conditions that can place the Si9730 in shutdown mode. The first condition can occur when the circuit is first attached to a battery in the factory. When the IC comes up, it will be in the undervoltage shutdown mode. The Si9730 may also enter this mode when the ambient temperature drops and the battery is nearly in UV. When the temperature drops, the battery pack voltage will drop and the IC may enter the shutdown mode. In either case, the Si9730 must be reset by raising the VSS pin higher than the VM pin by VCPHD. Figure 10 shows a circuit that resets the circuit once it has entered the shutdown mode. One novel feature of this 4-cell circuit is the increase in the size of the bypass capacitors. Each half of the circuit retains its own output cap, to reduce noise seen by the circuit. Since the two halves interact with each other (when one opens its switch, the other one is also opened), there can be additional noise, which must be rejected for proper operation. The capacitors have been increased to 100 F for this reason; remember that they must be rated to take the full maximum voltage rating of the charger, not half of it, since if one switch is closed and the other open, the charger (minus two cells' voltage drop, which might be zero) is applied across the other capacitor. The circuit works by initially connecting the 0.1 F capacitor to the battery's center tap and placing the switch in position #1. Although the MOSFETs are open, the 1 m resistor is sufficient to allow the capacitor to charge up in about 300 400 msec. Once the capacitor is charged, the switch is placed in position #2, momentarily making VSS higher than VM, thus placing the Si9730 in the normal operating mode. The entire circuit provides a leakage of only a few microamps, which is much lower than the self discharge current of the LiIon battery. A second addition on this circuit is the (optional) two zeners, one each for each Si9730, placed from VDD to VM. These are necessary only if the charger voltage is higher than the 15 V absolute maximum of the IC plus two cells' voltage drop. Just as with the capacitor, if one switch is open and the other closed, the IC will see this charger voltage, and must be protected. The power rating of the zener can be inferred by Si9730 1 VM 2 NC 3 VDD 4 CD DCO 8 #2 #1 VSS 7 IS 6 VC SPDT 5 15 M 1 M 0.1 F Figure 10. Factory Startup Circuit Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon Technology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and reliability data, see http://www.vishay.com/ppg?70658. Document Number: 70658 S-40135-Rev. F, 16-Feb-04 www.vishay.com 13 Package Information Vishay Siliconix SOIC (NARROW): 8-LEAD JEDEC Part Number: MS-012 8 6 7 5 E 1 3 2 H 4 S h x 45 D C 0.25 mm (Gage Plane) A e B All Leads q A1 L 0.004" MILLIMETERS INCHES DIM Min Max Min Max A 1.35 1.75 0.053 0.069 A1 0.10 0.20 0.004 0.008 B 0.35 0.51 0.014 0.020 C 0.19 0.25 0.0075 0.010 D 4.80 5.00 0.189 0.196 E 3.80 4.00 0.150 e 0.101 mm 1.27 BSC 0.157 0.050 BSC H 5.80 6.20 0.228 0.244 h 0.25 0.50 0.010 0.020 L 0.50 0.93 0.020 0.037 q 0 8 0 8 S 0.44 0.64 0.018 0.026 ECN: C-06527-Rev. I, 11-Sep-06 DWG: 5498 Document Number: 71192 11-Sep-06 www.vishay.com 1 Legal Disclaimer Notice www.vishay.com Vishay Disclaimer ALL PRODUCT, PRODUCT SPECIFICATIONS AND DATA ARE SUBJECT TO CHANGE WITHOUT NOTICE TO IMPROVE RELIABILITY, FUNCTION OR DESIGN OR OTHERWISE. Vishay Intertechnology, Inc., its affiliates, agents, and employees, and all persons acting on its or their behalf (collectively, "Vishay"), disclaim any and all liability for any errors, inaccuracies or incompleteness contained in any datasheet or in any other disclosure relating to any product. Vishay makes no warranty, representation or guarantee regarding the suitability of the products for any particular purpose or the continuing production of any product. To the maximum extent permitted by applicable law, Vishay disclaims (i) any and all liability arising out of the application or use of any product, (ii) any and all liability, including without limitation special, consequential or incidental damages, and (iii) any and all implied warranties, including warranties of fitness for particular purpose, non-infringement and merchantability. Statements regarding the suitability of products for certain types of applications are based on Vishay's knowledge of typical requirements that are often placed on Vishay products in generic applications. Such statements are not binding statements about the suitability of products for a particular application. It is the customer's responsibility to validate that a particular product with the properties described in the product specification is suitable for use in a particular application. Parameters provided in datasheets and / or specifications may vary in different applications and performance may vary over time. All operating parameters, including typical parameters, must be validated for each customer application by the customer's technical experts. Product specifications do not expand or otherwise modify Vishay's terms and conditions of purchase, including but not limited to the warranty expressed therein. Except as expressly indicated in writing, Vishay products are not designed for use in medical, life-saving, or life-sustaining applications or for any other application in which the failure of the Vishay product could result in personal injury or death. Customers using or selling Vishay products not expressly indicated for use in such applications do so at their own risk. Please contact authorized Vishay personnel to obtain written terms and conditions regarding products designed for such applications. No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted by this document or by any conduct of Vishay. Product names and markings noted herein may be trademarks of their respective owners. (c) 2017 VISHAY INTERTECHNOLOGY, INC. ALL RIGHTS RESERVED Revision: 08-Feb-17 1 Document Number: 91000 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Vishay: SI9730DBY SI9730CBY SI9730ABY SI9730BBY SI9730ABY-E3 SI9730ABY-T1-E3 SI9730BBY-E3 SI9730BBYT1-E3 SI9730CBY-E3 SI9730DBY-E3 SI9730DBY-T1-E3 SI9730ABY-T1 SI9730BBY-T1 SI9730CBY-T1-E3 SI9730DBY-T1