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AM335x preferred way for power-down

Prad1
Genius 3825 points
Other Parts Discussed in Thread: AM3352, TPS65910A

Hi,

Our customer is using discrete TI's power supply ICs instead of the recommended PMIC IC.
(PMIC IC's supply current was not sufficient)

We some problem with the Power-Down sequence.
AM3352 data sheet mentions that the "preferred way sequence power down is
the device must be powered off in reverse order as power-on".

The Power-On Sequence is as per the datasheet order
but the Power-Off Sequence is not per the datasheet, will this be problem?

Actually their power down sequence is.
1. 3.3V Analog and I/O
2. 1.1V Core
3. 1.8V Analog and I/O

But the preferred way should be as shown below.
1. 1.1V Core
2. 3.3V Analog and I/O
3. 1.8V Analog and I/O

Will there be any problem or damage on the device if the core supply is shutdown after 3.3V supply?

Best Regards.
Prad

  • 0
    Genius 3825 points

    Please let me know if there is any advice or
    reference on this.

  • 0 in reply to Prad1
    TI__Guru**** 393215 points
    Hi Prad,
     
    In section 4.1.2 of the AM335X Datasheet it says:
     
    "If it is desired to ramp down VDDS and VDDSHVx [1-6] simultaneously, it should always be ensured that the difference between VDDS and VDDSHVx [1-6] during the entire power-down sequence is <2 V. Any violation of this could cause reliability risks for the device. Further, it is recommended to maintain VDDS ≥ 1.5V as all the other supplies fully ramp down to minimize in-rush currents."
     
    If your powerdown sequence doesn't violate these requirements there should be no problem. Just to mention, TPS65910A powers down all supplies simultaneously.
     
  • 0 in reply to Biser Gatchev-XID
    Genius 3825 points

    Hi Biser,

    Thank you so much for the information.

    One final clarification,
    If it is desired to ramp down simultaneously can we assume the following?

    1.There won't be problem if the sequence is VDDS(1.8V) ->VDDSHV(3.3V)
    2.If the sequence is opposite VDDSHV(3.3V) ->VDDS(1.8V),
       then it will ok if the difference(VDDSHV-VDDS) is <2V.

    Regards.
    Prad.

  • 0 in reply to Prad1
    TI__Guru**** 393215 points
    Hi Prad,
     
    1. This is not OK.
    2. This should work fine.