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LP87702-Q1: LP87702KRHBR LP87702DRHBRQ1 IWR6843ISK

Robert Schmidt
Prodigy 30 points
Part Number: LP87702-Q1
Other Parts Discussed in Thread: IWR6843ISK, , LP87702

Hello,

we used the the LP87702DRHBRQ1 in our Projekt to manage the power supply for our IWR6843ISK Board.

Due to availability issues of the of the LP87702DRHBRQ1 we were considering, using the LP87702KRHBR.
As far as i understand, the only difference of these is the OTP-Memory which leads to a 1V output at Buck Converter 1 instead of 1.24V. Apart from this, it is the same chip.

Is it a valid workaround, to add a series resistance to the feedback input 1 to adjust the voltage of the LP87702KRHBR Buck Converter to 1.24V?

Thanks and greetings
Robert Schmidt

  • 0
    TI__Expert 4985 points

    Hi Robert,

    There are some other differences between the devices as well. The differences between LP87702KRHBRQ1 and LP87702DRHBRQ1 are described in the technical reference manual. LP87702KRHBR is the industrial variant of LP87702KRHBRQ1 but the OTP settings are the same.

    https://www.ti.com/lit/pdf/snvu593

    Unfortunately LP87702-Q1 does not support voltage scaling with a feedback voltage divider. It would be possible to change the output voltage through I2C though but the setting would be stored in volatile memory and it would be lost on reset.

    BR,

    Samuli

  • 0 in reply to Samuli Piispanen
    Prodigy 30 points

    Hi Samuli,

    thanks for the fast response.

    Can you please explain me, why the LP87702-Q1 or the LP87702 doesn't support voltage scaling with a feedback voltage divider?

    The Image of the Buck Converter Block Diagram is showing a voltage divider for the error amp feedback.

    The voltage divider is not specified in the datasheet and the voltage scaling it not mentioned in the datasheet but in a functional view it should work, shouldn't it?

    BR,
    Robert

  • 0 in reply to Robert Schmidt
    TI__Expert 4985 points

    Hi Robert,

    The internal loop compensation has been design without external voltage divider on the feedback pin. Using feedback divider may degrade stability and it has not been validated by TI.

    BR,

    Samuli