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BQ40Z50-R4-DEVICE-FW: Sleep Current

Steven Carey
Prodigy 70 points

Part Number: BQ40Z50-R4-DEVICE-FW

Hi

I've been monitoring the current draw of the BQ40z50 on the EVKit to get a rough idea of how long my battery will last in sleep mode. The following graph shows the initial wake mode (with a GPIO enabled) followed by sleep mode. I was expecting sleep mode to be fairly constant with the odd spike whenever the guage checked the votlage/current. This is more-or-less what I got, but after about 160s it seems to be doing something much more frequently.

I'm powering the BQ from a PSU @ 10V and I'm basically monitoring the current to the BQ circuit (I'm not measuring the current consumed by the resistors that are emulating the cells). The logging is approx every 0.5s which may be not be fast enoguh to accurately capture the true value, but there's a clear difference in activity. Here's a screenshot of the Bit Registers when the device is woken up again.

 Any ideas what it might be doing?

Thanks

  • 0
    TI__Genius 10370 points

    Steven,

    A few things to not here.

    1) The device will monitor voltage and current at a regular interval. In normal mode this is 1 sec. Then to reduce power we swap to 5 seconds for voltage and 20 seconds for current. (both defaults)

    2) there is a time when in relaxation mode when the device is looking for the [REST] bit to set where it will be in Normal mode (looking for REST) when you assume it is in sleep. 

    3) In the image you have a safety event CUV active. the device will not enter sleep with a protection event triggered.

    Thanks,

    Eric Vos