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  • TI Thinks Resolved

TPS61202: Blows the inductor (latched internal driver?) under load

Part Number: TPS61202

I'm using the chip in a power bank design with a single Li-pol battery to drive 5V out for phone charging.  It works fine with 20mA LED load (around 5.6V) but smokes the chip and inductor when a phone is connected (high load).  I'm not an experienced power designer.  Did I do something dumb?

"Do or do not, there is no try."  - Yoda

  • Hi Guy,

    Please share the BOM and layout. I will check if there’s any risk.

    Best Regards

    Jasper Li
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  • In reply to Jasper Li:

    Thanks for taking a look Jasper.  Here's the BOM + layout.  I know the layout could be improved - it's a first proto.  I'm baffled why a heavy load causes the chip to lock up and smoke the inductor.  I'm testing on a bench supply because the safety PCB in my 200mAh Li-pol battery would shut down when the circuit shorted out.  It's really tedious to replace the chip - I use a heat gun and low melting point solder paste (Chipquik SMDLTLFP).

    "Do or do not, there is no try."  - Yoda

  • In reply to Guy Marsden:

    I'm hoping someone (Jasper) can respond to this question.  Trying to get this prototype working and tested for pre-production!

    Guy

    "Do or do not, there is no try."  - Yoda

  • In reply to Guy Marsden:

    Hi Guy,

    sorry for the late as busy these day.

    I think the root cause is the layout. the high voltage spike in the SW pin kill the IC. please refer to this application note to modify the layout www.ti.com/.../slva773.pdf: changing the location of the output capacitor in current board or build new board.

    no sure about the output current? from the input and output voltage the TPS61200 is not the suitable solution. a device as TPS61252 should be better.

    Best Regards

    Jasper Li
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  • In reply to Jasper Li:

    What SW pin? And the App note link you gave is bad. You're not being helpful here.

    "Do or do not, there is no try."  - Yoda

  • In reply to Guy Marsden:

    Hi Guy,

    this is the link www.ti.com/.../slva773.pdf
    The SW pin is the L pin in this device, as this pin is always switching.

    Best Regards

    Jasper Li
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  • In reply to Jasper Li:

    Thanks,
    The design note is helpful. I keep thinking like an analog circuit designer and forgetting the high frequency issues in these topologies.

    "Do or do not, there is no try."  - Yoda

  • In reply to Guy Marsden:

    Hi Yoda,

    In the schematic, please place a ceramic output capacitor closed to the IC. or change C8 to ceramic capacitor.
    the PCB is good.

    Best Regards

    Jasper Li
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  • In reply to Jasper Li:

    I built the circuit and used a ceramic 47uF cap at C8 per your suggestion.  It worked fine driving an adjustable load (USB tester) and I ran it up to 1A input (about .82A output when it started to limit.  Using iLim at 10K.  SO far, so good.  Then I connected the output to a small bluetooth speaker via uUSB to charge it.  Input current went to .8A for a few seconds, then the chip blew and shorted the (current limited) power supply I was using to simulate the li-pol battery (set to 3.8V).  SO I'm back to square one.  This is getting annoying and expensive and my client is getting impatient.

    I don't appreciate your taking WEEKS to respond.

    Guy

    "Do or do not, there is no try."  - Yoda

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