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PMP9444: how the TRIM signal work? / part replacement LMZ31503 / schematic check?

Alex Wong
Prodigy 170 points
Part Number: PMP9444
Other Parts Discussed in Thread: UCD90120, LMZ31503, TPS84320

I have a project driving a Xilinx Ultrascale FPGA, and my design is referencing PMP9444

1. I see that UCD90120 have a GPIO TRIM signal connect to LMZ31503 with serial resistor.

    I want to ask the function of this signal? and how to calculate the value of the resistor?

2. Can I use TPS84320 replacing LMZ31503?

    

3. Once I finish my schematic, where can I find FAE help to verify the res/cap value is correct?

  • 0
    TI__Expert 5455 points

    Hi Alex,

    1. The GPIO and series resistor are to Margin the output of the power supply, this is usually used in production testing. It is to move the output voltage +/- 5% or so based on the GPIO output. During normal operation the GPIO is open, so the output is not effected.

    2. Yes, TPS84320 can be used to replace LMZ31503. 

    3. Where are you located and what company are you supporting? We will find the right contact.

    Thanks,

    Robert 

  • 0 in reply to Robert Taylor1
    Prodigy 170 points

    Hi Robert,

    Thanks for replying

    1. So the idea is by turning on/off/open 3.3V GPIO to change the voltage level on VADJ pin and adjust the VOUT of LMZ31503. Am I correct?

    if so, how can I calculate the resistor value with TPS84320?

    3. I work in Hong Kong