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TMS320DM6437 question

Gheorghe Plasoianu
Prodigy 30 points
Other Parts Discussed in Thread: TMS320DM6437, TS3A4751

we are using TMS320DM6437 in an automotive application. In stand-by mode the power supply of TMS320DM6437 is being switched off (all 3.3V, 1.8V and 1.2V) while the MCU of the device is still supplied. Therefore, the TMS320DM6437 get power supply from the MCU through different GPIO which accidentally remain high. Please comment if this procedure is ok for TMS320DM6437? If not, could we switch only 1.8V and 1.2V off and keep 3.3V alive to avoid supplying it through the GPIO and ESD diodes?

Thanks for your support,

Gheorghe Plasoianu

  • 0
    TI__Guru* 84110 points

    Gheorghe Plasoianu,

    I may need your to explain your situation with additional detail. It may not be clear to me what is happening.

    It appears that when you switch off the power supplies, a GPIO pin is being driven high.

    Leaving the DVDD33 supply on for a long time with DVDDR2 and CVDD off will violate the datasheet requirement in Section 6.3.1 Power-Supply Sequencing:

    • The power ramp order must be DVDD33 before DVDDR2, and DVDDR2 before CVDD
    • From the time that power ramp begins, all power supplies (DVDD33, DVDDR2, CVDD) must be stable within 200 ms.

    TI makes Load Switches that could be used to disconnect the GPIO under these circumstances. That would be one option for a fix, but leaving one supply rail on will not be an acceptable fix.

    Regards,
    RandyP 

  • 0 in reply to RandyP
    Prodigy 30 points

    Hello Randy,

    thank you for your answer. I understand that all supplies must be stable within 200ms but I don't understand why the first requirement is being violated (The power ramp order...). Load Switches would be too expensive; we need one for every GPIO which might stay high. What we need is a kind of Signal Switch, maybe a multichanel one; do you make such an IC ?

    Regards, Gheorghe

     

     

  • 0 in reply to Gheorghe Plasoianu
    TI__Guru* 84110 points

    Gheorghe,

    Being a DSP and Embedded Processor guy, I do not know much about the details of TI's analog portfolio. I learn a little as I go through system design processes with our Analog experts.

    But what I do know is that the answer to "Does TI make such an IC?" is almost always Yes! TI makes just about everything, and the terminology is very broad so I make mistakes in what I call things sometimes.

    We have a line of Signal Switches that would probably do exactly what you need. Please take a look at the 4-channel TS3A4751.

    Do you have a way to put those GPIO pins into a high-impedance state?

    Regards,
    RandyP