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BQ76200: bq 76200 and bq 76940 driving capiability

Kuo John
Expert 1075 points
Part Number: BQ76200
Other Parts Discussed in Thread: BQ76940, BQ78350-R1

Hi Team,

May I know bq76200 max source/sink capability? since we plan use bq76940/bq78350-r1/bq76200 application our EV BMS.
Our total capacity is 240A. Looks TI document just have 60A parallel 8 N-FET.(SLVA729A)

1. if bq76200 not enough driving capability. Do you have any schematic share to me? or comment for it?
2. if we implement Low side disconnected via bq76940. May I know bq76940 max source/sink capability?

  • 0
    TI__Guru 54715 points

    Hi Kuo John,

    The drivers are resistive, so switching does slow down when capacitance increases.

    The bq76200 shows on and off resistances for the FET drivers under certain conditions.  For turn on of CHG an estimate is the VDDCP-BAT voltage divided by the internal and external resistance.  For DSG the current would appear higher since the voltage potential is VDDCP-0, but the circuit effectively limits the current to around 30mA.  See the application report bq76200 Beyond the Simple Application Schematic figure 13 for example. Remember that the drive voltage comes from the charge pump so the DC current must be low.  Turn off can also be estimated from the data sheet resistances, DSG will turn off with initially about 10 mA and CHG with about 33 mA.  Current drops off as the gate voltage falls.

    The bq76940 also has resistive drivers.  The on resistance for both drivers is approximately 5k, so peak current is about 2.2 mA, CHG may be higher if the FET source and gate are below VSS.  Turn off current for DSG would initially be about 4.8 mA.  The CHG pull down is much weaker for the load detect feature and initial turn off current will be approximately 12 uA, the turn off of the charge FET is also from the gate-source resistor.