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BQ34Z100-G1: Exit sleep mode takes too long

Jeffrey Wright
Expert 2875 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ76952

Hello;

  When the device is in Sleep mode, waking when a charge or discharge begins takes a very long time - anywhere from 5 to as long as 19 seconds, and anytime in that range. The discharge current is ~40 A. The companion protector (bq76952) wakes immediately, but gauge will not, and reports only the calibrated board offset during this delay. Iwake is disabled.

Why should this delay occur?

  • 0
    TI__Expert 3030 points

    Hi Jeffrey,

    Can you upload your .gg file?

  • 0
    TI__Genius 10370 points

    Jeffery,

    The gauge will wake immediately if the current is above the setting you have in the [IWake][RSNS1][RSNS0] registers.  This will be a value directly across the senseR. So depending on the SenseR size the value needed will change. 

    If you are not woken by the hardware wake comparator, then you will have to wait until the next time the gauge will sample the current. this happens every 20 Seconds which is where you are seeing this delay. If the current is samples above the sleep current it will wake at that point. 

    Thanks,

    Eric Vos 

  • 0 in reply to Vos
    Expert 2875 points

    As I noted, I don't enable the wake comparator, and the simulated current when exiting idle is ~40A, but the delay exiting sleep mode is random, ranging from 5 seconds to ~19 seconds....This, it would seem, is quite long, and would affect the gauging accuracy over time

  • +1 in reply to Jeffrey Wright
    TI__Genius 10370 points

    Jeffery,

    The delay is there because in sleep mode the gauge reduces the interval it is sampling everything to save power. There is a bit called [SleepWakeChg] which will accumulate current as if the current was present for 1/2 the sleep window. Since we don't know when the current was applied we try and minimize the error and over time should equal out. 

    However, overall this is expected behavior. The other options available to you are 1) disable sleep or 2) enable the wake comparator.  if the device wakes via the Wake Comparator it will not accumulate any charge so there is an init time where you lose a very small amount.  

    thanks,

    Eric Vos