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LP87524Q1EVM: Thresholds of PGOOD

koji otsubo
Prodigy 40 points
Part Number: LP87524Q1EVM

Regarding Output voltage monitoring for PGOOD pin in the Datasheet SNVSB21-OCT2017 Page.8.

What is Min / Typ / Max of threshold values for the following case of output voltage of Overvoltage monitoring and Undervoltage monitoring?

3.3V
1.8V
1.2V
1.1V

I am not sure because the datasheet mentioned as "This condition is for Typical values are at TJ = 25°C, VVANA = VVIN_Bx = 3.7 V, and VOUT = 1 V".

  • 0
    TI__Genius 10000 points
    Hi,

    Welcome to E2E! I have assigned this thread to the device expert. They will get back to you shortly.

    Thanks,
    Nastasha
  • 0
    TI__Genius 11020 points
    Hello,

    For Overvoltage monitoring the thresholds are 39mV / 50mV / 64mV (min / typ / max). Values are referenced to the DC output voltage level.

    For undervoltage monitoring the thresholds are -53mV / -40mV / -29mV (min / typ / max).

    This is taking temperature, process etc. variation into account.

    Hope this helps.

    Regards,
    Tomi Koskela
  • 0 in reply to Tomi Koskela
    Prodigy 40 points
    Thank you for your reply. It is a correct value, but with Vout = 1 V. In my application it is 3.3 V output +/- 2%. In that case, the threshold values of your data sheet will be violated, resulting in an invalid design.
  • 0 in reply to koji otsubo
    TI__Genius 11020 points
    Hello,

    No that is not correct. If you read carefully the note on top of the page the values are for full temperature range, output voltage range etc. Typical values (denoted with TYP in the electrical table) are for TJ 25degC, supply voltage 3.7V and Vout 1V).

    The monitoring window accuracy will be on top of the output voltage DC accuracy, so you won't trigger the PGOOD if your output voltage is for example 3.3V - 2%. The PGOOD window will be referenced to the actual DC output voltage level.

    Hope this clarifies the issue.

    Regards,
    Tomi Koskela
  • 0 in reply to Tomi Koskela
    Prodigy 40 points
    I see. That is in case of 3.3V output, the overvoltage threshold is 3.405 V (worst case) for high output 3.366 V.
    Undervoltage threshold 3.205 V (worst case) for low output 3.234 V.
    Is my understanding correct?
  • 0 in reply to koji otsubo
    TI__Genius 11020 points
    Hello,

    It depends what you consider as worst case. If we consider the highest/lowest possible output voltage where the PGOOD will trigger it would be 3.366V + 64mV = 3.43V for the OVP and 3.234V - 53mV = 3.181V for the UVP. Anyway your understanding is correct that the PGOOD OVP/UVP thresholds are on top of the output voltage accuracy.

    Regards,
    Tomi Koskela
  • 0 in reply to Tomi Koskela
    Prodigy 40 points
    I understood well. Thank you for answering specific examples!