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TPS65217: AM3352 with TPS65217B

hugo
Intellectual 350 points
Part Number: TPS65217
Other Parts Discussed in Thread: AM3352,

we are designning devices with AM3352 and TPS65217B , 

power rails of Tps65217b can't work normally,   we removed all loads( removed R530,R534,R537,R538,R540,R542,R545), VLDO1 can hold 5 seconds without PWR_EN, only holds 50mS  with PWR_EN. No output  on other rails. following is the schematic of TPS65217B.

  • 0
    TI__Expert 8730 points
    Hi,

    I have assigned your request to responsible Applications Engineer, but due to holidays, please expect some delay in providing the feedback to your question.

    Regards,

    Murthy
  • 0
    TI__Mastermind 30310 points
    Hugo,

    Please share a scope shot of this issue occurring: "VLDO1 can hold 5 seconds without PWR_EN, only holds 50mS with PWR_EN".

    Ch1 = AC
    Ch2 = SYS
    Ch3 = PWR_EN
    Ch4 = LDO1

    If you capture these 4 channels on the scope when the issue occurs, I will understand your problem more clearly.
  • 0 in reply to Brian Berner
    Intellectual 350 points

    Hi, Brian,

                 here are the scope shots you wanted

    Without PWR_EN

    with PWR_EN

    please review.

    Thanks for helps 

    Hugo

  • 0 in reply to hugo
    TI__Mastermind 30310 points
    Hugo,

    In the first scope shot (PWR_EN = low, system shuts off after 5s), the timing is very simple to understand. You can refer to Figure 24. Global State Diagram on page 39 of the TPS65217 datasheet and see the PMIC enters the "WAIT PWR_EN" state after the AC power is applied. If PWR_EN is not set high within 5s, the PMIC transitions to the PRE-OFF state instead of going to the ACTIVE state. If you press the push-button in the PRE-OFF state, the PMIC will go back to the "WAIT PWR_EN" state again and the 5s timer begins again.

    In the second scope shot (PWR_EN = high for 50-60ms, then LOW), the timing is a little more complicated. It is difficult to say if PWR_EN goes low before LDO1 or the other way around, but I think because of the "MIN ON-TIME" of 5s also shown in Figure 24. Global State Diagram that pulling PWR_EN low after 50ms would not have any effect on LDO1 immediately.

    What I think is happening here is that there is a fault on one of the other rails (DCDC1-3, DCDC4, LDO2, LS1/LDO3, or LS2/LDO4) which causes PGOOD or LDO_PGOOD to be low, and this fault conditions causes the whole system to shut down.

    To debug, you will need to zoom in on the part of the scope shot where SYS drops down to 4V (BAT level), LDO1 shuts off, and PWR_EN goes low.
    If LDO2 does not reach 3.3V, LDO_PGOOD will go low and none of the remaining rails will turn on.
    If DCDC1-3, LDO3, or LDO4 fails to reach the desired output voltage, PGOOD will go low and then the system will shut down.
    Or, the fault could be occurring before the PGDLY timer expires and PGOOD will never be high.

    You can refer to Figure 7. Default Power-Up Sequence on page 23 of the TPS65217 datasheet to see the power-up and power-down sequence with a fault occurring on DCDC2 which causes the system to shut down. This should help you find out which DCDC converter or LDO regulator is causing the fault.
  • 0 in reply to hugo
    TI__Mastermind 30310 points
    Hugo,

    One other thing you may want to look at is the USB voltage. Although I don't think this is causing the problem, I see that the USB input is not used but you still populated C518 with a capacitor.

    In the TPS65217 Schematic Checklist (www.ti.com/.../slva686b.pdf), you can see it is recommended to connect USB directly to GND is it is un-used. You can replace C518 with a 0-Ohm resistor if you notice any voltage present on the USB pin that could be interfering with the power-up sequence.
  • 0 in reply to Brian Berner
    Intellectual 350 points

    hi, Brian,

                I replaced C518 with  0-Ohm resistor , there are no impacts for our testing result,   I monitor LDO2 (no load on this rail),   it seems LDO2 can't ramp up to 3.3V ,  but I can't find out rootcause that leads to power fail on LDO2.  I will try to replace TPS65217 ( D/C is 1444  ) with some new parts we just ordered.

    here is the scope shot.

    thanks

    Hugo

  • 0 in reply to hugo
    TI__Mastermind 30310 points
    Hugo,

    Let me know what you observe when you test new samples.

    What do you mean when you say "D/C is 1444"?
  • 0 in reply to Brian Berner
    Intellectual 350 points

    Hi, Brain,

          we bought TPS65217 through China local agent,  date code of the samples is 1444, it should mean these samples shipped from original factory at week 44 in 2014.

    thanks

    Hugo

  • 0 in reply to hugo
    Intellectual 350 points

    we found one schematic net lists exporting issue to PCB tools that led to DCDC1 no input , TPS65217B can work after we reworked PCB to fix the error.
    thanks a lot for helps
    Hugo