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TPS1H100-Q1: OUT voltage not present despite VS receiving power

Part Number: TPS1H100-Q1

Greetings TI,

I have a design that utilises the TPS1H100BQPWPRQ1 as shown below:

The input voltage can go as high as 36V before the OVP circuit cuts in, and I have verified that VS pins 8,9,10 have voltage present. However pins OUT 5,6,7 don't appear to be energised and I'm confused.

Is there something in the schematic that isn't right?

I thought that perhaps I have a fault in the Ground network, so I replaced R25 with a direct short to GND, but still no output. The current limit has been set to 1.8A using R10.

The voltage on CS appears to be 0V, which is confusing as well.

Can you please help?

Best regards,

Hemon Dey

Quantum Sensing Limited

  • Hi Hemon,

    Welcome to E2E!

    The CS voltage being a very load voltage indicates an open load or a short to battery battery.

    Would you be able to try out a test load and check for any shorts?

  • Hi Anthony,

    Thanks for your prompt reponse. 

    Anthony P Pham said:

    Would you be able to try out a test load and check for any shorts?

    Yes, I am able to bypass the current limiter and power the board, and it powers up just fine and works. However with the current limiter in place, the voltage just never makes its way to the OUT pins. 
    Any ideas I can try? 
    Regards,
    Hemon 
  • I think I worked out why the IC is misbehaving in this way.

    There are two issues here, which I'm hoping you can verify:

    1/

    I think the Ground Network is an issue, as the IC behaves a lot more predictably when R25 is replaced with a zero ohm link. I suspect this is because R10 and R23 are not referencing the the IC ground, but going via the Ground Network. This could have the offset voltage from D11 in its path, which could throw off the thresholds?? I understand that this Ground Network is for detecting ground disconnections, is that right? In our case this IC is feeds the rest of the circuit, and really unlikely to ever have the ground disconnected - so is it safe for R25 to be zero linked all the time? 

    2/

    The IN signal is connected to 5V line, which is only energised when the OUT signal is energised (via a buck regulator on the main circuit, post this IC). I'm using this current limiter as a gateway device into the board, rather than a current limit controller out of the board. Unfortunately the IN signal can only tolerate voltages up to 7V abs max. Do you have any suggestions as to how this IN pin can be configured so that it defaults to ON when the VS voltage is present? Unfortunately for us, this IC is already part of our 2nd generation PCB - is there some simple way the IN signal can be asserted without putting excessive voltage on it from VS? .... I'm thinking perhaps a 5V zener with series resistor might do the trick, but am I missing something here? 

    Regards,

    Hemon 

  • Hi Hemon,

    The R10 needs to be connected to the device's GND pin if using a GND network. R23 is for measuring current externally if needed for example through a microcontroller. The ground network is to create protection against reverse current..

    As long as you are able to operate within recommended specifications for the IN pin (which is 5V recommended) and under the absolute max ratings (7V and between -30 and 2mA), I do not believe there is a problem.