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LP87564-Q1: The output 1 not keep the output regulation

Eric Lai
Expert 4940 points
Part Number: LP87564-Q1

Hi Expert,

The deign adopted the LP87564-Q1.

And the output 1 is configured to 1V.

The condition:

The output voltage stay 1V at 0A.

Then switch to continuing 2A,the output become 0.75V continued,

We not found the abnormal from the VSW waveforms, current limit and voltage protection for why the output 1 lost the output regulation.

Can you advice how to debug this?

Best regards,

Eric Lai

 

Field Application Engineer

Texas Instruments Taiwan Limited

O: +886-2-2175-2582

M: +886-909-262-582

E-Mail:Eric.Lai @ti.com  

 

  • 0
    TI__Genius 11020 points

    Hello Eric,

    What is the full part number for this PMIC? Do you have schematic? 

    First thing to check is the FB connection. If the connection is weak to the PMIC, it can cause the output voltage to not stay in regulation. 

    Does PGOOD go down when you increase the load?

    Thanks.

    Regards,

    Tomi Koskela

  • 0
    TI__Genius 11020 points

    Hello Eric,

    Thanks for the schematic. 

    Some clarifying questions:

    • What is the full PN for this PMIC? We have a lot of OTP spins for this product family and having full PN is critical to find out which spin this is.
    • How many units are affected?
    • Have they tried replacing the 10ohm resistor on FB pins with 0ohm resistors?
    • Do they have more output capacitors near the point of load? Single 22uF output capacitor in not enough to keep the converter stable in all conditions. See this app note for more details: https://www.ti.com/lit/an/snva881/snva881.pdf
    • Can they check the state of the PGOOD pin during startup/during loading?
    • Where is the nINT connected to? I don’t see the connection in the schematic.
    • Can they read back fault/status registers of the PMIC through I2C?

    Thanks.

    Regards,

    Tomi Koskela