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TPS6594-Q1: To_Standby Power Sequence: TPS65941213-Q1 LDO4 and BUCK4 disable timing differ from PDN-0C

Peter Fritzenschaft
Intellectual 361 points
Part Number: TPS6594-Q1
Other Parts Discussed in Thread: DRA829J-Q1, DRA829

Tool/software:

Hello,

I use a DRA829J-Q1 supplied with two PMIC according PDN-0C on my HW.

Measurement of the To_standby Power Sequence compared to SLVUC99A Figure 6-3 show deviation on two supply rails:

TPS65941213-Q1 LDO4 starts switching of at 3090µs after beginning of sequence, expectation would be 500µs.



CH1: TPS65941213-Q1 Enable Pin
CH2: TPS65941213-Q1 LDO4
CH3: TPS65941111-Q1 QPIO3 (EN_VDDR)
CH4: VDDR

PS65941213-Q1 BUCK4 starts switching of at 536µs after beginning of sequence, expectation would be 2500µs.


CH1: TPS65941213-Q1 Enable Pin
CH2: TPS65941213-Q1 BUCK1:3
CH3: TPS65941213-Q1 BUCK4
CH4: TPS65941111-Q1 BUCK1:4

Is this a known behaviour and will be corrected in PDN-0C, or is there somthing wrong in my circuit?

Regards, Peter

  • 0
    TI__Mastermind 25265 points

    Can you read out register 0x03 and 0xA7 for me?

    Peter Fritzenschaft said:
    TPS65941213-Q1 LDO4 starts switching of at 3090µs after beginning of sequence, expectation would be 500µs.

    Are you certain this scope measurement is for LDO4 and not LDO1? TPS65941213 LDO1 is also 1.8V, but shuts down at the 3ms mark.

    Peter Fritzenschaft said:
    PS65941213-Q1 BUCK4 starts switching of at 536µs after beginning of sequence, expectation would be 2500µs.

    Similarly, can you confirm this is BUCK4 and not BUCK5? TPS65941213 BUCK5 is also 0.85V, but shuts down at the 500us mark. 

  • 0 in reply to Michael Gambrill
    Intellectual 361 points

    Hello Michael,

    Here the screenshots of registers 0x03 and 0xA7 from Scalable-PMICs-GUI:

    I repeated measurement for TPS65941213 LDO4 and included LDO1, both shut down at the 3ms mark:

    I repeated measurement for TPS65941213 BUCK4 and TPS65941213 BUCK5, it confirms that  TPS65941213 BUCK4 shuts down at 500µs.

    TPS65941213 BUCK5 is a 1.8V supply (also according to PDN-0C) and shuts down at 3ms as expected.

    I added TPS65941111 BUCK5 which is 0.85V and shuts down at 500us as expected.

    So this is the sequencing I measured, all supplies shut down as expected, only TPS65941213 LDO4 and BUCK4 behave different:

    Regards, Peter

  • +1 in reply to Peter Fritzenschaft
    TI__Mastermind 25265 points

    Hello Peter,

    After doing some digging, I can confirm that the discrepancy is real. 

    Your timing measurements of the power down sequence align with the programming of the TPS65941213 and the sequence expected by the DRA829 platform. The error is in the figure in the user guide. It needs to be corrected.