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PGA411-Q1: VCC and VIO load current question

Sulyn ZHANG
Expert 8700 points
Part Number: PGA411-Q1

Hi Expert,

We are penetrating our PGA411 to replace ADI solution. Here comes some questions about the VCC and VIO from my customer, can you help check, thanks for the support, below are the questions:

1.  In our old version datasheet(2016 version), it don't have the 9.1 part as showed in the latest datasheet, so not sure why we add this change? For example, if

     these is some bug found during our internal test?

2. The VCC and VIO output current during normal operation or during stable operation status?

3. The maximum transient load current of VCC pin(5V) and VIO pin(3.3V) during power up? About how long will these transient load current continue respectively?

4. Is it the must have that the VCC(5V) need to power up prior to the VIO(3.3V)? Why?

5. If customer power up the VCC(5V) and VIO(3.3V), is these any risk? If customer already fixed the hardware design, can they have some solution to escape from this risk from software side?

Appreciate your strong support on my customer's urgent questions, thanks a lot!

Best regards,

Sulyn

  • 0
    TI__Mastermind 23810 points
    Sulyn,

    1.) We found that powering up VIO first could cause a large current draw. We also found that if VCC and VIO are powered from the same supply and powered at the same time, that there can be a surge current that can cause a weak power supply to never fully turn-on. That is why we recommend that the power supply is capable of supplying at least 400mA.

    2.) I've answered this before, so let me look up what the typical currents are. Note that most of the VCC current will depend on the VEXT boost voltage and the resolver load.

    3.) The transient current can be up to 300mA, but it is only during the ramp-up time of VCC. Note that this value is for VIO = 5V, so VIO = 3.3V should be less.

    4.) If VIO is powered first, there will be higher current consumption until VCC powers up.

    5.) If the power supply is capable of handling the current, then there should not be an issue. Do they already have boards? Are they powering up VIO and VCC together?

    Thanks,

    -Clancy
  • 0 in reply to Clancy Soehren
    TI__Expert 8700 points

    Clancy,

    Thanks for your support! As for your questions:

    1. Customer already fixed their PCB and PCB come back. The power supply they used 5V for VCC and VIO for 3.3V, but both power supply can't support >300mA. And both 5V and 3.3V supply were generated from same supply, so that means both 5V and 3.3V will power up at the same time.

    2. VEXT and the load of the resolver and specifics are as below table, can you help check the VCC and VIO supply current during normal operation?

    As customer hardware already fixed, not sure do we have some solution by using software solution? Any suggestion for this? For the VCC and VIO supply current during normal operation under the above VEXT and Resolver load, appreciate your help to check, thanks a lot!

    Sulyn

    Best regards,

  • 0 in reply to Sulyn ZHANG
    TI__Expert 8700 points

    Hi Clancy,

    Can you help reply the questions last mail asap? Thanks.

    What's important, now customer finished the board and they use our TPS65381 to provide 5V and 3.3V for PGA411, and because this 5V and 3.3V supply also provide supply for other devices, so the current that can provide to PGA411 will be less than 300mA maximum and the 5V and 3.3V will be power up at the same time, so it seems this power solution can't meet our datasheet's requirement. Correct?

    As we need to push customer to go ahead, thus we can kick out ADI solution. If we want to convince customer to change the design, can you help suggest an available low cost solution asap? It's better that already been used by some other customers, thanks a lot for the support!

    Sulyn

    Best regards,

     

  • 0 in reply to Sulyn ZHANG
    TI__Expert 8700 points

    Hi  Clancy and all,

    Could you pls help support my above mail questions, thanks a lot! It's better that we can provide them a cost effective power supply solution for customer, then I will let customer re-design the board upon our recommendation asap.

    Best regards,

    Sulyn  

  • 0 in reply to Sulyn ZHANG
    TI__Mastermind 23810 points

    Sulyn,

    If VIO pulls a lot of current, pulling the VIO voltage level down, will the VCC rail still power-up? If so, then they should be in good shape. However, since VIO and VCC are generated from the same power supply, I'm not sure if that will be the case. What power part are they using?

    Thanks,

    -Clancy