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SS6821-DCVTR Datasheet(PDF) 7 Page - Silicon Standard Corp. |
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SS6821-DCVTR Datasheet(HTML) 7 Page - Silicon Standard Corp. |
7 / 10 page www.SiliconStandard.com 7 of 10 SS6821 APPLICATION INFORMATION OPERATION Over-charge Protection When the voltage of the battery cell exceeds the overcharge protection voltage (VOCP) for longer than the overcharge delay time (TOC) period, charging is halted by turning off the charge control MOSFET M2. The overcharge delay time is fixed to 100ms by circuitry internal to the IC. The over-charge condition is released in one of two ways: 1. The voltage of the battery cell becomes lower than the over-charge release voltage (VOCR or VOCP- VHYS) through self-discharge. 2. The voltage of the battery cell falls below the over-charge protection voltage (VOCP) because a load has been connected. When the battery voltage is above VOCP, the over-charge condition is never released even if a load is connected to the pack. Over-discharge protection When the voltage of the battery cell goes below the over-discharge protection voltage (VODP) for longer than the over-discharge delay time (TOD) period, discharging is halted by turning off the discharge control MOSFET M1. The over-discharge delay time defaults to 10ms. Discharging is immediately resumed when the voltage of the battery cell becomes higher than over-discharge release voltage (VODR) through charging. Over-current protection In normal mode, the SS6821 continuously monitors the discharge current by sensing the voltage of the CS pin. If the voltage of the CS pin exceeds the over-current protection voltage (VOIP) for longer than the over-current delay time (TOI) period, the over-current protection circuit operates and discharging is halted by turning off of the discharge control MOSFET M1. The over-current condition returns to the normal mode when the load is released and the impedance between the BATT+ and BATT- terminals is 1M Ω or higher. The SS6821 is provided with two over- current detection levels (0.2V and 1V) and two over-current delay times (TOI1 and TOI2) corresponding to each over-current detection level. Load detection after overcharge The load detection function after over-charge is implemented by detecting the CS pin voltage. Once a load is connected to the battery pack after an over-charge, discharge current flows through the parasitic diode of MOSFET M2 and there is a diode voltage drop between CS and GND. A load is determined to be connected to the pack if the CS pin voltage is above the load detection threshold voltage (VLD). Power-down after over-discharge When an over-discharge occurs, the SS6821 will go into power-down mode, turning off all the timing generation and detection circuitry to reduce the quiescent current to 0.6 µA (VCC=2.2V). At the same time, the CS pin is pulled high to VCC through a high resistance resistor. Charge detection after over-discharge When over-discharge occurs, the discharge control MOSFET M1 turns off and discharging is halted. However, charging is still permitted through the parasitic diode of M1. Once the charger is connected to the battery pack, the SS6821 immediately turns on all the timing generation and detection circuitry. Charging is determined to be in progress if the voltage between CS and GND is below the charge detection threshold voltage (VCH). . 12/6/2004 Rev.2.02 |
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