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TPS25751: Liquid detection configuration

Victor Hansen
Prodigy 60 points

Part Number: TPS25751

Hi TI E2E forum.

I am having some difficulties setting up my liquid detection on the USB-C PD controller.

The hardware aspect of my design follows the diagram shown in figure 9-9 from the tps25751 datasheet, attached here for reference.
image.png

Using the online configuration tool, I am in doubt what to set the GPIOs as. I am using GPIO3 as FET control, but how exactly should this be done when the gpio controls both the PMOS and NMOS gates? For the moment, I have mapped it for liquid_detected (157) event and set is as high Z, as it would otherwise open the PMOS mosfets and go high itself, causing a false detection.
GPIO4 and GPIO5 are multiplexed to ADC.

Thanks in advance.

Kind regards Victor

 

  • 0
    TI__Expert 6240 points

     Hello Victor,

    Thank you for reaching out on E2E. I understand that you would like to use only one GPIO for controlling both the PMOS and NMOS gate pins of the FET. However, using a single GPIO instead of separate GPIOs for NMOS and PMOS control may compromise the liquid detection functionality, as it may not be able to fully utilize the potential of the liquid detection signals.

    Do you have an idea of the expected resistance value when a short is detected on the SBU lines?

    Thank you,

    Katilynn

  • 0 in reply to Katilynn Mar
    Prodigy 60 points

    Hello Katilynn,

    For testing purposes, I've used a 1k leaded resistor when connecting the two SBU lines. I've also tried shorting them directly.
    I agree that using two GPIO control would be easier, but do to legacy reasons I am attempting to manage with 1 GPIO control.

    Going back to my original question, have I made the correct approach when configuring the GPIOs for control and sensing? Am I correct in using high impedance for 1 GPIO control?

  • 0 in reply to Victor Hansen
    TI__Expert 6240 points

    Hello Victor,

    Thank you for your reply. I understand that it is necessary to use one GPIO to drive the GATE pins for your liquid detection application.

    For the configuring only one GPIO, you need to set the gate driving GPIO to either the liquid_nmos_control or liquid_pmos_control. Liquid detected GPIO event only goes high when we see the SBU lines cross into the liquid detection threshold. The liquid detected event cannot enable the FETs to toggle high and low for the sampling on the SBU lines

    Thank you,

    Katilynn