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TMS320VC5510A: High current on CVDD at power-up

Koichiro Tashiro
Mastermind 22290 points
Part Number: TMS320VC5510A

Hi,

My customer found high current flow(~50mA) on Cvdd at power-up.
The same board shows different behaviors.

Case1: Cvdd current during power-up is less than 10mA.


Case2:Cvdd current during power-up is ~50mA.


What is potential cause of the high current?
And customer wants to know what is power-up sequence requirement for the device.
I found below old E2E. Is this still valid?
https://e2e.ti.com/support/processors-group/processors/f/processors-forum/812391/tms320vc5410a-the-power-sequne-of-tms320vc5410a/3007189#3007189

Thanks and regards,
Koichiro Tashiro

  • +1
    TI__Mastermind 18130 points

    Hi Koichiro, 

    I see that in the high current scenario, the CVDD seems to come on just slightly ahead of the DVDD - that should be a valid startup sequence. But in the low current scenario, the start of the CVDD and DVDD power-on voltages track much closer together.

    In this system, is it possible to delay the DVDD turn-on more or ensure closer synchronization? What I suspect is that there may be a current path which is being enabled by the DVDD turn-on in some cases. I am speculating that depending on the ramp-rate of the CVDD, these paths may or may not be active before DVDD ramps. 

    The recommendations in that referenced e2e post should still be valid, but it's possible we need to add some additional constraints. 

    Thank you,

    -Randy

  • 0 in reply to Randy Rosales
    TI__Mastermind 22290 points

    Hi Randy,

    Sorry for my late reply.

    Randy Rosales said:
    In this system, is it possible to delay the DVDD turn-on more or ensure closer synchronization?

    Yes and it worked!
    After customer changed CVDD => DVDD sequence,  the issue was gone.

    Thanks and regards,
    Koichiro Tashiro