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TPS92515: When is calibration performed?

Kaji@PAN
Mastermind 7795 points
Part Number: TPS92515

Tool/software:

Hello,

The TPS92515 has a power on calibration.
Does this calibration take place during the non-switching period immediately after the input voltage has reached the operating range?
Or is calibration performed after a voltage is applied to IADJ?
In the waveform below, the output current rises about 500 ms after a voltage is applied to IADJ.
If so, what is the maximum time that calibration takes?

Best regards,

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1066622/tps92515-repeatability-error-on-a-design-using-vadj?tisearch=e2e-sitesearch&keymatch=tps92515

  • 0
    TI__Mastermind 23156 points

    Hello Kaji,

    Replied will be delayed due to US Holiday today.

    -fhoude

  • 0
    TI__Expert 5730 points

    Hi Kaji,

    Who is the customer and what is the business opportunity?

    Can you please post a schematic along with input/ output requirements?

    Can you please probe IADJ, COFF, VIN, and BOOT

    Best,
    Daniel

  • 0 in reply to Daniel Louis
    Mastermind 7795 points

    Dear Daniel,

    My customer's current accuracy issue has been resolved.
    Now I want you to answer your calibration question.


    Best regards,

  • 0 in reply to Kaji@PAN
    TI__Expert 5730 points

    That's great, since this is a public post and it seems like you have found a way to solve your issue, can you please explain what you did?


    Best,
    Daniel

  • 0 in reply to Daniel Louis
    Mastermind 7795 points

    Hello,
    You misunderstood my customer's question.
    Even when using the same board, IC, and VIADJ input, the current value changed, and the customer wanted to know the cause.
    Looking at past threads, we found that the cause was due to calibration.
    This matches the customer's symptoms.
    So the next thing the customer is asking about is how the calibration works.
    So I want you to answer the question I asked about calibration.
    Best regards,

  • 0 in reply to Kaji@PAN
    TI__Mastermind 23156 points

    Hello Kaji,

    Calibration is done immediately at power on reset (POR).  It measures the offset voltage and stores that value in the logic block.  That stored value is used to adjust the output current setpoint.  If the offset voltage is on the border between two calibration setpoints, then when doing power cycling you might toggle between two off set voltage settings.  We know that as the VIADJ is larger that error due to offset voltage will be a less significant percentage of the signal.  As VIADJ goes down then Voffset starts to become a larger % of the signal and thus the percent error gets worse.  This is a common issue when using any amplifier or comparator.  If you don't want to use this feature then you can use the TPS92515A, which has this feature disabled.  This device still meets the datasheet specifications either way. 

    -fhoude 

  • 0 in reply to fhoude
    Mastermind 7795 points

    Thank you for your reply.
    I understand that calibration is performed immediately after POR, but the customer applies VIN and then applies VIADJ a while later.
    In this case, is calibration performed based on 2.4V as the reference?
    Or is calibration performed again when VIADJ is applied?
    Best regards,

  • +1 in reply to Kaji@PAN
    TI__Mastermind 23156 points

    Calibration is done after POR and only once.  That calibration stores offset voltage and is stored as longs as Vin/Vcc stay on.