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TPS659037: Issue with PMIC:: occasionally locks

Rakesh M
Prodigy 40 points
Part Number: TPS659037
Other Parts Discussed in Thread: AM5718

Issue with PMIC TPS6590379ZWSR for AM5718

PMIC VCC1 supply is 3.6V
Reset chipest : TPS3808G33

In Application i use a processor to power PMIC+AM5718 (Custom board) combo

TO power ON I follow this sequence to tun on AM5718 board.
1. Apply 3.6V
2. Apply a 1ms pulse to PWRON (I have a Switch and BSS138 connected to PWR ON). I apply a 1ms high going pulse to base gate of BSS138.
3. This normally power on PMIC +AM5718 combo

Issue
Occassionaly i encounter a PMIC latch Up condition. PMIC does not power ON. it only recovers on a power cycle.

In this condition
1. Once it occurs I can never turn ON the device by activating Switch or BSS138.
2. I have measured the Voltage on PWRON which seems to be 3.6V and once I activate switch it drops to 0V.
3. I tried applying MR reset manually to reset circuit TPS3808G33 & probed RESET_IN it gets activated
But even after applying RESET_IN PMIC did not power up on activation of switch


4. I checked for OSC16 and could observe 16.384MHz
5. Tried turning ON via PowerHold jumper . I could not succeed.
6. measured VCC1 = 3.6V,LDOVRTC_OUT = 1.75V,LDOUSB_IN2&LDO7_LDOUSB_IN = 5V

My concern is what could cause this non recoverable issue?? 

 How to avoid it??

  • 0
    TI__Genius 12735 points

    Hi Rakesh,

    I have assign this thread to the expert for this part, however he is out of office today. Please expect a response by Tuesday.

    Best regards,

    Layne J

  • 0
    Prodigy 40 points

    Hi,

    I would also like to add a few more details.

    In order to segregate between PMIC turn ON event (applying pulse to PWRON) and Power cycle (applying VCC1 3.6V) event causing issue

    I tried a continuous loop of ON - OFF event by applying pulse to gate  BSS138 with VCC1 (3.6V ) always present.

    I could successfully run this loop for a count of more than 100. So i guess latching issue due to pulse durations could be avoided.

    Since I applied reset and still PMIC could not recover once latching occurs , means issue causing this latch-up is continuously present.

  • 0 in reply to Rakesh M
    TI__Expert 6700 points

    Rakesh,

    Have you tried a longer pulse on PWRON? I am wondering if the behavior will change if that 1ms pulse is extended out to 10, 20 or even 100ms. This may tell us if the device is not fully responding to a short pulse and/or if the power sequence is getting interrupted somehow and requires the PWRON signal to be hi for a longer period.


    Regards,

    Alex

  • 0 in reply to Alex Saenz
    Prodigy 40 points

    Hi,

    I will try this out. But i have observed device not responding for 1ms pulse when applied after 100us from a PWRON turn off attempt. But PMIC will recover when i apply power ON via switch SW or applying PWRON after a delay.

    But PMIC entering lock status (ie Not recovering when applying RESET_IN , recovers only on power cycling ) is strange. PMIC either in BACKUP state or OFF state.

  • 0 in reply to Rakesh M
    TI__Expert 6700 points

    Rakesh,

    OK understood please let me know the results. I would rather address the "How to avoid it?" question first assuming we can find a simple fix. 

    In the meantime I will consult with my design team to see if there is an explanation for the issue. The fact that it happens intermittently is puzzling and leads me to believe it may be a combination of a setup improvement that we could make in addition to working around potential device features. 

    Regards,

    Alex