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BQ500212A: Sleep signal during power up

Ruixin Feng
Intellectual 2115 points
Part Number: BQ500212A

Tool/software:

Hi team,

customer design sleep pin as datasheet recommended, that is connect sleep pin to EN pin of 3.3V. But we found that during 3.3V power up. The sleep signal will randomly give out pull-high signal and cause LDO disable.  You can check the waveform as below.  So I want to check why Sleep is triggered during power up. Could you pls help to clarify how sleep works here? Or any design suggestion to share? Thanks!

 

The circuit of LDO is shown like below.

Rayna

  • 0
    TI__Guru 71166 points

    Hi Rayna 

    The Sleep pin will pulse high when it does not detect a receiver on the charging pad.  The LDO is working correctly, Sleep will pulse an unit turns off.

    A few Troubleshooting Tips:

    When testing a new TX for the first time we recommend:
    – Test with a known good RX, TI has several EVMs that would work well.
    – Disable Sleep / Snooze mode by shorting the LED Mode resistor to ground. The Sleep & Snooze function will be internally controlled. Note-LED will be off.
    – Disable FOD and PMOD by removing resistors on Mod_Threshold pin. Open on the pins is disable.

  • 0 in reply to Bill Johns
    TI__Intellectual 2115 points

    Hi Johns,

    In this case, the BQ500212A hasn't been powered up, and it gave out sleep, which cause BQ500212A can't power up and work normally. I understand "The Sleep pin will pulse high when it does not detect a receiver on the charging pad.", but the BQ500212A hasn't been powered up, how can it detect receiver? 

    I was wondering why sleep pin will pulse during power up because this issue cause the TX can't power up and the system can't work normally. 

    Thanks!

    Rayna

  • 0 in reply to Ruixin Feng
    TI__Guru 71166 points

    Hi Rayna

    Check the capacitor divider connection on Pin 25 (BPCAP) should have 1uF pin 35 to GND and 2.2uF pin 35 to 3.3V.

  • 0 in reply to Bill Johns
    TI__Intellectual 2115 points

    Hi Johns,

    Customer has 1uF to GND and 1uF to 3.3V. And we tried 2.2uF to 3.3V. It helps. May I know the reason? How sleep work here? Thanks!

    Rayna

  • 0 in reply to Ruixin Feng
    TI__Guru 71166 points

    Hi Rayna

    Some applications are sensitive to noise on the I/O lines at start up, they are powered with the input 3.3V.  

    The 2.2uF / 1uF capacitor configuration will help to prevent noise pulses at start up.