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TMS320F28P550SJ: VDD ramp rate

Kien
Expert 4001 points
Part Number: TMS320F28P550SJ

Tool/software:

Hi Champs,

It is stated in the datasheet that the VDD ramp rate should be in a range of 20 to 100mV/us.

I've seen that even the TPS7A3701DRVR device that is used on the Launchpad can't meet this high ramp rate. So, I have few questions:

1. Is it a must to meet this requirement?

2. Why?

3. How?

Regards,

Kien Nguyen

  • 0
    TI__Mastermind 45166 points

    Hi Kien Nguyen,

    I believe with an external supervisor holding XRSn low until the power rails ramp past the minimums that you don't need to meet this spec. However let me check with another expert to confirm.

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    TI__Guru* 80180 points

    Kien.

    Kevin is correct, if there is external SVS then we do not have to meet these ramp rates.

    We need to add some additional clarification to the DS for this spec item, however.  This ramp rate is recommended to avoid spurious glitches on the XRSn line as VDDIO comes active.  However, a slower ramp will be OK, but you will see XRSn come inactive as the voltage on VDDIO passes the stabilization region of the PMM on the device.  There is no risk here, as device code execution will not be passed to customer main code, and BROM is guaranteed to work correctly at lower VDDIO levels.

    I've given some calculations on what would be acceptable slower ramp rate, but I need to find those and reply back.

    Best,

    Matthew