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TPS61092 Load Disconnect

Daniel Sisson
Prodigy 30 points

Other Parts Discussed in Thread: TPS61092, TPS61230

I'm using a TPS61092 in my design for various reasons, but I need load disconnect.

For some reason, the voltage on Vout is around 3.2V (Single cell LiPo input), even when the converter is disabled. Pulling the enable pin high does as expected and Vout jumps to 5V .. but I'm not sure why I'm getting 3.2V out of it (seems to be battery voltage minus a diode drop, perhaps?). I have stuck an LED on the output just to confirm it wasn't floating and the LED lights brightly, so it's definitely coming from somewhere.

Not sure if this works but here is my schematic, I don't really see anywhere else it could be coming from (USB is disconnected, so no Vbus). 

dl.dropboxusercontent.com/.../Sheet1.pdf

I soldered the chip by hand using hot air at 250C. I'm wondering whether I perhaps managed to kill the load disconnect circuitry but somehow left the rest of it untouched, but I've done this many times before and never had an issue. Just odd.

Thanks

  • 0
    Prodigy 30 points
    Not sure if I can edit my first post, but I just tried another one hand soldered with an iron, and exact same deal.
  • 0 in reply to Daniel Sisson
    TI__Mastermind 46905 points
    1. What is the voltage of VBUS at this state? remove the inductor L2 and discharge the COUT with 100Kohm resistor, if the 3.2V output does not disappear. it proves that the current flow from other device.

    2. you use LBI and LBO to achieve UVLO from the schematic. this circuit doesn't work. because the LBO is high impedance when the device is disable.

    3. what is the output current. I would suggest using other device like TPS61230 which is designed for li-ion battery input.

    thanks
    Jasper lI
  • 0 in reply to Jasper Li
    Prodigy 30 points

    Thanks for the information. I had a good look over my schematic again today and realized where the problem was, I have the battery connected to an ADC on the microcontroller, and forgot that they have ESD protection diodes on the pins, so it was actually backfeeding through the microcontroller. Totally overlooked it at the time, figured it was pretty unlikely I managed to kill 2 boost IC's in the exact same manner :)

    Thanks