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TPS22967: About power up sequence

Tsukui Yusuke
Guru 21930 points
Part Number: TPS22967
Other Parts Discussed in Thread: TPS22975

Hi,

Let me talk about the TPS22967 power up sequence.
Customer is considering the TPS22967 power up sequence described below.

【Sequence】
1.VIN (1.8V)
2.ON
3.VBIAS(2.5V)



Is there a problem with thirdly applying voltage to VBIAS?
I'm concerned about the following description of the data sheet.



Could you give me advice such as possible problems?

Best Regards,
Yusuke/Japan Disty

  • 0
    TI__Genius 9965 points
    Hey Yusuke,

    Thank you including so much detail, it helps a lot.

    I'll start looking into this, one question I do have is; how much time passes between the device getting enabled (sequence #2) and Vbias reaching 2.5V (sequence #3)?

    Best,
    Nick
  • 0 in reply to Nicholas Carley
    Guru 21930 points

    Nick-san,

    Thank you for your support.
    The delay time is 1～2 ms.
    After the ON, Bias will rise after 1～2ms.

    Could you give me your advice?

    Best Regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    Guru 21930 points

    Hi,

    Can I get the information?
    Customers need that information for design.
    If you need more information or if  I should  clarify my comment ,
    please let me know.

    Best Regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Genius 15780 points

    Hi Yusuke,

    The risk for this power sequencing order is that the device may not have a controlled rise time once VBIAS is applied and the output comes up. 

    For proper timing, we recommend applying VBIAS and VIN before the ON pin voltage.

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    Guru 21930 points

    Alek-san,

    Thank you for your kind support.
    Let me ask you one more thing.
    Customer made the following sequence according to your advice.

    【Sequence】
    1.VBIAS(2.56～5.12V)
    2.VIN (1.8V)
    3.ON

    TPS22967.pdf

    However,
    Customers make VBIAS using voltage divider.
    Therefore, VBIAS is varied in the range of 5.12V from 2.56V.
    Could you tell me the risk of changing VBIAS?

    Best Regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Genius 15780 points

    Hi Yusuke-san,

    Thank you for discussing the power sequencing with the customer. That sequencing order will be very good for the application.

    It is okay for VBIAS to vary as long as it stays within the acceptable range of 2.5V to 6V. If it drops below 2.5V, the device will risk turning off, and above 6V the device will risk getting damaged. If VBIAS varies while the device is on, the customer may see a minor fluctuation in on-resistance, but the device will continue to work. Note that between a VBIAS of 2.5V and 5V, there is only a difference of 4mΩ.

    For future projects, I would also recommend the TPS22975. This pin-to-pin device has better performance (lower on-resistance) and comes with a thermal shutdown protection feature.

    Thanks,

    Alek Kaknevicius