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BQ76200: BQ76200 100ms delay issue

Piero Yu
Intellectual 950 points
Part Number: BQ76200
Other Parts Discussed in Thread: BQ76930

Enable BQ76200 CP_EN。I sent a comand from MCu to the pin managing charge-discharge MOSFET(namely PIN DSG) but got a 100ms delay. The command was transferred to BQ76200 via BQ76930. Is it normal? Actually It had a bad effect on my application. Could you give a hand? thanks!

  • 0
    TI__Guru 54715 points

    Hi Piero,

    The charge pump takes time to  charge the CVDDCP capacitor before the driver can turn on.  The cap charge time is 100ms typical for the 0.47 uF cap. shown in the data sheet.  For the 10 uF cap shown in your schematic it will be much longer.   If CP_EN is brought high long before you need to switch CHG or DSG the capacitor should charge during that setup time.  If CHG or DSG is brought high without CP_EN, the capacitor must charge before the outputs will go active.  If CHG or DSG go high after CP_EN but before the capacitor has reached voltage there will be a delay as the charge pump comes to nearly full voltage. 

    You can estimate the time for the capacitor to charge as i = Cdv/dt where i = charge pump current of about 40 uA, and dv is about 9V to UVLO.