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BQ76200: CHG and DSG paths separate on BQ76200

Albert Galofre
Intellectual 600 points
Part Number: BQ76200

Hi there,

I'm developing a BMS with a 14S batteries and up to 100A on discharge.

I have to use a separate path to charge and discharge the battery in order to reduce as minimum as possible the discharge path. SO I need a parallel configuration.

In this scenario, according the SLVA729A (page 13) the PRECHARGE feature is not possible.

This is right? Why? I don't understand why the precharge feature is not available with a parallel configuration....¿?¿¿?

Attach a pdf screenshot and the PMOSFET precharge suggestion by me.

thanks in advance

  • 0
    TI__Guru 54715 points

    Hi Albert,

    The PCHG output is driven with respect to the higher of the BAT or PACK pins. If perhaps your battery was in a condition the BMS did not want it charged at ~ 30V, but the charger was connected at 50V, The source of the precharge FET would be at 50V, but the gate would be near the BAT voltage of 30V, so the FET would already be on (and likely at its maximum voltage). So your BMS would not have control of the precharge path.  If the BMS decided to turn on the precharge path, the gate voltage would be pulled to about 12V below BAT or 18V, so the gate-source voltage would be about -32V which would exceed the maximum of many FETs.

    A precharge circuit could be added as you sketched the FET but it should be controlled by a N-ch signal FET or NPN at GND with a resistor  to the gate or the resistor and zener clamp  across the 10M you sketched. 

  • 0 in reply to WM5295
    Intellectual 600 points

    ok.

    thanks a lot!!!!