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TPL5110: Difficulty getting TPL5110 to start up with different input sources (battery vs power supply, etc)

Thomas Hayden
Prodigy 10 points
Part Number: TPL5110

I'm having some issues with one of your ICs: TPL5110DDCR and I hope you can help. 

Anyway, our issue is the following:

· When powered via our on-board battery (LifePO4) it works great. It fires up the MCU, I invoke the DONE pin and it goes into sleep for the right amount of time.
· When we power it via a DC power supply, it doesn't work at all. Specifically, it ends up in some weird mode where it consumes around 200uA but doesn't really do anything - no power to the MCU or anything. Sometimes our analog power supply works.
· If I power with on-board battery but put an ammeter in serial (so I can measure current load) I experience the same problem, 200uA power draw but no power to the MCU or anything. I can send ammeter data if it helps. It's literally the same as the working setup but with a Power Profiler Kit II in serial!

It seems like having increased impedance of some kind on the VIN would be responsible for this but we can't necessarily isolate the cause. I can't imagine why this would be, though!


We're pretty stumped with this issue. Our engineer had previously asked in the e2e forums, but the solution didn't work. I'm wondering if you can take a quick look at our specs and see if anything stands out to you that might be responsible for this issue.

His question: e2e.ti.com/.../4817249


Here's a picture of the relevant part of our schematics.

We're pretty stumped. Is the TP5110 very sensitive to input voltages and input resistance/impedance? Help!

  • 0
    TI__Genius 9550 points

    Hi Thomas, 

    Just to confirm, are you hooking up your external power supply to pin 3 on J11? Also when you mention no power getting to your MCU, are you talking about the VSYS net? 

    Since the supply current is around 200 uA, it seems like the TPL5110 is getting stuck in the start-up state for some reason. I'm not sure why this would be happening unless the voltage at the VDD pin is dropping below 1.8V or there's some issue with the initial resistance measurement. Another possibility I can think of is that low frequency noise could be coming through and it's not properly getting filtered out by the 100 nF cap. This seems unlikely since there's still issues when an ammeter is placed in series with the battery. 

    Would it be possible to use an oscilloscope to measure the VDD pin of the TPL5110 during power on? I'm curious if there's any big difference in the ramp-up time for VDD when you're using the battery vs. an external power supply. 

    Regards, 

    Connor 

  • 0
    Prodigy 10 points

    Hey Connor - thanks for following up! I think we figured it out. It was definitely noise being introduced by the wires, either to the ammeter or to the external power source. We were able to fix this by adding a bigger capacitor (10uF) and it worked well after that. 

  • 0 in reply to Thomas Hayden
    TI__Genius 9550 points

    Hi Thomas, 

    Great, I'm glad to hear that fixed your issue. I'll go ahead and close this thread, let me know if you have any other questions. 

    Regards, 

    Connor