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LP87524J-Q1: Some concerns about MMW Radar RF power supply change

Michael JM Zhang
Prodigy 95 points
Part Number: LP87524J-Q1
Other Parts Discussed in Thread: AWR1642

Hello,

After changing PMIC LP87524B to LP87524J, 2 LDOs are deleted and RF power supply decreases from 1.3V to 1V.

According to our own test, AWR1642 TX distance will be a little shorter.

Power ripple also increases for RF 1.3V/1.0V, although we used LC filter solution as TI doc swra577 says.

Theoretically, it can make sense that TX output power decrease when RF power supply decrease.

And also, ripple issue is caused by LDO deleted.

So how can we make sure MMW Radar is still OK when we use low-cost PMIC solution?

Is there any internal test data in TI side to prove it?

Thank you.

  • 0
    TI__Genius 10000 points

    Michael,

    Welcome to E2E. I have assigned this thread to the applications engineer responsible for LP87524. You should hear back shortly.

    Thanks,
    Nastasha

  • 0
    TI__Genius 11020 points

    Hello,

    SWRA577 document has the test data we have for this power concept without LDOs. Do you have some specific concern with this approach? Our radar expert can check do we have more data from the radar operation.

    Thanks.

    Regards,

    Tomi Koskela

  • 0 in reply to Tomi Koskela
    Prodigy 95 points
    Hi,

    Yes, I found IR drop test data in swra577 doc.
    And I want to know more data from radar operation side to make sure it is OK with this IR drop & voltage decreasing from 1.3V -> 1V.

    Thank you.
  • 0 in reply to Michael JM Zhang
    TI__Guru 58035 points
    Hello Michael,
    The swra577 has the full radar system level tests listed in section 4.2. This illustrates the radar operation.

    >>Theoretically, it can make sense that TX output power decrease when RF power supply decrease.

    The RF power supply is not actually reducing in this scenario. When 1.3V supply is provided externally we use internal LDOs to generate 1V for the internal RF blocks. But when 1V is supplied you bypass the internal LDO (using API) so that external 1V supply directly goes to the RF blocks. Only care about is that the ripple requirement for 1V supply is much tighter than 1.3v supply since additional filtering from internal LDO is lost. You can refer to the AWR1642 datasheet to compare the ripple requirements in these 2 modes.

    Regards,
    Vivek
  • 0 in reply to Vivek Dham
    Prodigy 95 points
    Hi，Vivek

    Thank you for your reply.
    It resolves my issue.

    BRs,
    Michael