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BQ25713: Time to complete default VINDPM threshold setting

S.Satoshi
Guru 21685 points
Part Number: BQ25713

Hi,

I understand that the default VINDPM threshold is set after VBUS is connected as following flow.

    #1 VBUS detected -> #2 Start to measure VBUS voltage -> #3 Complete to set REG0x0B/0A -> #4 Enable converter

Then please let me ask following question.

  1. The bq25713 detect VBUS voltage when it rises to 3.5V. Is my understanding correct?
  2. Please let me know the wait time from VBUS detected (#1) to measure VBUS (#2)
  3. Please let me know required time from measure VBUS (#2) to complete to set REG0x0B/0A (#3)

Best Regards,

Satoshi

  • 0
    TI__Expert 5330 points
    Hi Satoshi-san,

    1. Yes, the adapter is considered present when 3.5V is reached on VBUS
    2. It is approximately 50 mSec after 3.5V adapter detection, introduced to allow power supply to reach steady-state value (details below)
    3. I do not know how to measure this, so I cannot give you an exact number. It should be much less than the (purposeful) 50 mSec delay before measuring VBUS because it is driven into the register by hardware.

    Detail on #2:
    To determine 50 mSec, I powered the board with a 0 --> 20V ramp at various slew rates. Here are readings of register 0x3D for each rate

    11.456 w/ ramp from 0V to 20V in 100 mSec
    15.936 w/ ramp from 0V to 20V in 75 mSec
    18.240 w/ ramp from 0V to 20V in 50 mSec
     note that 18.240 is max value even with instantaneous ramp
    18.048 w/ ramp from 0V to 20V in 70 mSec

    Since 11.456 V in register 0x3D corresponds to a reading of about 13V on VBUS, the measurement was taken about 65 mSec after the start of the ramp, which is approximately 50 mSec after the 3.5V threshold was reached.

    Regards,
    Steve
  • 0 in reply to Steve Preissig
    Guru 21685 points

    Hi Steve,

    I really appreciate for your support. Your actual measurement result is enough information to the customer.

    Best Regards,

    Satoshi

  • 0 in reply to S.Satoshi
    Guru 21685 points

    Hi Steve,

    I also tried to confirm the REG0x3D value with slow ramp input voltage as attached. I understand that the REG0x3D value is "Measured voltage - 1.28V" so I checked the duration from 3.5V to REG0x3D + 1.28V. Then it seems that the duration is longer than 50msec and it's varied. 

    Best Regards,

    Satoshi

  • 0 in reply to S.Satoshi
    Guru 21685 points
    Hi Steve,

    I can take more waveform, so please let me know if you need.

    Best Regards,
    Satoshi