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LM51521-Q1: Start-up sequence regarding BIAS pin

Kazuki Kuramochi
Genius 9445 points
Part Number: LM51521-Q1

Hello team, 

We have question for start-up sequence.
In data sheet, BIAS become high with EN simultaneously.


However, they system will be BIAS is suppled earlier than EN become high due to power supply for BIAS is always on power rail but output of LM51521-Q1 is not  always on power rail.
Regarding this use case, it is similar as Fast boot condition but datasheet only cover the case of ”Reboot”.

Then, could we use LM51521-Q1 under their use case as like as toggling EN much after BIAS become high?

Best regards,
Kazuki Kuramochi

  • +1
    TI__Genius 10385 points

    Hi Kazuki,

    Thank you for using E2E forums, regarding your query I am not sure I understand what you mean by Reboot, but BIAS pin connects the input voltage to the VCC regulator and the VCC regulator will only work when the EN pin reaches certain thresholds. So, normally if you supply the UVLO separate from the Vin and Vout, as long as you are not powering up the UVLO/EN pin the device will not do anything, the BIAS pin will be connected to the Vin in this case and it can be high, but when UVLO/EN is powered up only then the device will start switching or enable different modes.

    BR,

    Haroon