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Original question:

BQ27426: largest acceptable current sense resistor

BQ27426: Current report delay

Will Wang47
Expert 7670 points
Part Number: BQ27426

Hi team,

Customer use BQ27426 in their project. Now they report one issue about the current detect delay.

As could see in the following log, they send charge command at 11:28:28:770, they measure use a external probe, it shows the current coming out after this command; after ~8s, they read the current, it report 0mA, voltage does change; then after  another 10s, they get the correct current.

They total delay is ~18s. The voltage does see immediately change when read, so questions is why their is 18s delay? How should we further debug this?

Thanks and Best Regards,

Will

  • 0
    TI__Genius 10370 points

    Will,

    When the gauge is in sleep mode the current measurement is delayed to happen only every 20seconds. The slow down in measurement is how the gauge saves power. So this is an expected delay (it will vary) depending on when current is applied in the measurement cycle

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    TI__Expert 7670 points

    Hi Vos,

    Does all the measurement take every 20seconds? I find the voltage is changing from 4100mV to 4131mV with in 10 second, so does it mean the part already get out of sleep mode? Could you help share more comments?

    Thanks and Best Regards,

    Will

  • 0 in reply to Will Wang47
    TI__Genius 10370 points

    Will,

    Voltage updates at a faster rate in sleep mode. By default it updates every 5 seconds. 

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Prodigy 10 points

    Hi eric:

            About BQ27426,tif the temperature change from -10℃ to 45℃，the Battery Indicator change 1%, In theory, it should not change，how to deal with，tks!

  • 0 in reply to pei xu
    TI__Genius 10370 points

    Pei,

    Is this a different issue? Please submit a different ticket so others can find it easily in the future. With the temperature changing -10 to 45 i expect you would increase your available capacity by much more than 1%. Our algorithm has a smoothing function which doesn't allow SOC to increase unless charging. 

    You could disable smoothing to see the true value (could go up). or if it went down by 1% the gauge most likely counted some small charge which is a real decrease.

    Thanks,

    Eric Vos