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AM263P4: VPP supply requirements different from launchpad and migration guide.

Andy MacGregor
Prodigy 247 points
Part Number: AM263P4

Tool/software:

In the AM263Px datasheet rev C, the VPP voltage maximum is listed as 1.75V. Also the datasheet requires "The VPP power supply must be disabled when not programming OTP registers."

However the AM263 to AM263P Migration Overview (Rev. A). recommends supplying VPP directly with ANALDO (also named VDDA18_LDO) which outputs 1.8V.

The LP-AM263P4 board schematic supplies VPP with VDDA18_LDO in this way.

It would be easier to design our board VPP supply like LPAM263P4, however we want to be careful to follow the datasheet requirements if those are required.

Which raises two questions:

  1. Is it OK to supply VPP with 1.8V?
  2. Is it OK to supply VPP when not programming OTP registers?
  • 0
    TI__Guru*** 135155 points

    Hello Andy,

    The design suggestion allows for the AM263P to source the voltage when doing the OTP programming as previously the only method was to use an external LDO - which I realize looking at this that I put the wrong voltage on that LDO, should have read 1.7V and not 1.8V.

    Let me verify with design experts on the datasheet requirements but if my understanding is correct you'd use a temporary bridge to make the connection to program the eFuse once during factory programming flows and then disconnect the bridge so the connection is not made again. If so I think perhaps a switch might be a better circuit to show rather than the resistor. If this is how it works, the advantage you get is instead of needing an LDO on the PCB for a single use, now the AM263P can source the voltage with just a zero ohm or switch used.

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Prodigy 247 points

    Explaining the intent helps very much, thank you.

    To clarify my understanding:

    During manufacturing we can supply VPP (ball N3) temporarily from VDDA18_LDO (ball R6) to do OTP programming.

  • 0 in reply to Andy MacGregor
    TI__Guru*** 135155 points

    Hi Andy,

    Yes, I just need to clarify the specific conditions here like if you need to program the 1.8V rail to go down to 1.7V before supplying the VPP I/O. I've sent a message regarding this and am awaiting feedback.

    Best Regards,

    Ralph Jacobi

  • 0
    Prodigy 247 points

    I've reviewed the AM263Px reference manal Rev B. I'm concerned that I do not see any configurations to program the VDDA18_LDO pin to output 1.7V. Could you please clarify how to do this? or how to alternately supply VPP?

  • +1 in reply to Andy MacGregor
    TI__Guru*** 135155 points

    Hi Andy,

    It looks like the current revision of the AM263P TRM doesn't have the information for this present yet as it was pulled together after the last release.

    The AM261 TRM does have the information in Section 6.2.1.1 Using the Device Analog LDO for VPP Supply

    You can reference that for the set of steps: https://www.ti.com/lit/ug/sprujb6/sprujb6.pdf#page=225

    Best Regards,

    Ralph Jacobi