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BQ25622: The power up time is much longer than BQ25898

Kailun Liu
Expert 3943 points

Part Number: BQ25622
Other Parts Discussed in Thread: BQ25898, , BQ25620

Tool/software:

Hi Team, 

Can you help to explain why BQ25622 power up time(from REGN raise to ISYS raise) is much longer than BQ25898? 

240ms in BQ25622. 

40ms in BQ25898

  • 0
    TI__Expert 3943 points

    Hi Team, 

    May I have your feedback? Thanks!

  • 0 in reply to Kailun Liu
    TI__Mastermind 34190 points

    Hi Kailun, 

    I will double check behavior on BQ25622 device and get back to you with further comment. Generally speaking power up time can vary some based on D+/D- detection result, and I believe the waveform you reference from the shared BQ25620/BQ25622 datasheet is taken on a BQ25620 device with D+/D- detection feature. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    TI__Mastermind 34190 points

    Hi Kailun, 

    I have tested in lab and can confirm the power up time from REGN turn on to VSYS voltage increase is a shorter duration on BQ25622 compared to what is shown on the datasheet. The datasheet capture is taken on a BQ25620 device, which has D+/D- feature. 

    In my test results REGN turn on to VSYS voltage increase time on BQ25622 is approx. 78ms. (waveform shown below)

    Compared to the BQ25898 which has REGN turn on to VSYS voltage increase time of approx. 47ms. 

    Overall BQ25898 is expected to have a shorter turn on time, but behavior on BQ25622 is not significantly different. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    TI__Expert 3943 points

    Thanks Garrett, 

    Customer would like to know the reason between 78ms in BQ25622 and 47ms in BQ25898, since they have similar power up sequence. Is that due to different delay time in ADC?

  • +1 in reply to Kailun Liu
    TI__Mastermind 34190 points

    Hi Kailun, 

    Please see my comments below. 

    Firstly, I agree that high level the two devices have the same step by step power up sequence, but BQ25622 is a few generations newer than the BQ25898 and has various differences in its internal design. This leads to a longer power up time from REGN turn on to converter start (i.e. VSYS voltage increase). 

    More specifically, one difference I am able to share is the internal clock of the BQ25622 is approx. 20% slower than BQ25898. This is one factor as to why BQ25622 time is 78ms compared to 47ms observed on BQ25898. 

    Best Regards,

    Garrett