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TPS54160: Negative pulse on Ground at the startup

Onur Keskin
Intellectual 390 points
Part Number: TPS54160
Other Parts Discussed in Thread: TPS54260

Hi ,

I am using TP54160 and TPS54260 on my project. It is waken up external source via EN pin. But i catched a different condition. 

If voltage is applied to the en pin while the vin is energized, I see a low negative pulse on GND.

If voltage is applied to the VIN pin while the EN is energized, I see a high negative pulse on GND. 

Such a large surge damaged some of my components. The load on 5V hasn't changed when taking these measurements, and I'm not working in light load conditions. My rated output current is at least 800mA.

I'm trying to understand why feeding the EN pin before the VIN makes this difference. And can I solve the problem in a way that will provide this condition?

  • 0
    TI__Guru* 78080 points

    Hi Onur,

    Thank you for using our products. However, I am confused.  What is the trace on your scope picture?  If it is the GND trace, where is your probe's ground lead tied to?

    Also, in your schematic, I cannot tell where your PWRGD is connecting to.  It should be connected to the GND.  Maybe this is the reason for your problem?

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Intellectual 390 points

    Hi Youhao,

    I took a measurement between the ground of a power supply and the ground of a fet. I know it sounds a little weird, but that's how it is. here is the relationship between EN and VIN that I really need to learn. What effect does it have when their order changes?

  • 0 in reply to Onur Keskin
    TI__Guru* 78080 points

    Hi Onur,

    Sorry for the delay. Somehow your post was missed on my radar.  I am still trying to figure out how is the probe was set. Could you draw on you schematic showing where did you place your probe ground lead and where is your probe point?  Also, did you happen to have other probes connected to somewhere although their traces were not shown?

    Thanks,

    Youhao