PCB mount PSU module causing no output from digital potentiometer wiper

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1

Hi, so I am using an FS02-12 PSU module where the output is scaled based on input voltage. To control this input voltage and thus the output voltage I am using a digital potentiometer (AD5293).

I have the digital potentiometer working to output the right voltage but, the FS02-12 has a disable pin, which when high (5V) disables the PSU and when low enables the PSU. My issue is that the digipot wiper when the power supply is enabled through the disabled pin (0V) causes the digitpot wiper output to go to 0V. And when the disabled pin is at 5V (PSU disabled) the wiper goes back to the voltage I set.

This is frustrating as obviously there is not much use the digipot working when the PSU is disabled lol.

I have attached the schematic of the digipot and the FS02-12 module but can post full schematic if needed just most is unnecessary.

links to data sheets: https://www.analog.com/media/en/technical-documentation/data-sheets/ad5293.pdf

Any help or advice on this would be great.

Thanks,
Dean

FS02-12_PSU

dig_pot_schematic
dig_pot_schematic883×690 7.49 KB

2

Please check Your text. You write that HIGH disable the PSU, and then You write that LOW disables the PSU.
Try making a logic drawing showing what happens.
A link to the PSU datasheet/technical manual would be useful.

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From page 4 of the FS Series datasheet:

image
image1018×81 7.5 KB

Pin 1 is the supply pin, it takes up to 300mA to 1.25A to power the device.

You can't supply that current from an AD5293 digital potentiometer.

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@JohnLincoln Right I see that makes a lot of sense, is it possible to maybe use some form of BJT to amplify the current from the wiper?

5

yes your right my mistake I will edit that now and add the links

6

Rather than just a transistor, I would suggest an opamp/MOSFET combination, with the MOSFET in the opamp feedback loop.

See https://www.allaboutcircuits.com/technical-articles/how-to-buffer-an-op-amp-output-for-higher-current-part-3/ for more details.
(This is part 3 of 4 articles, but there are links to the other parts).

Note that the MOSFET is used in a linear mode, so it will dissipate some power - a heatsink will be necessary.

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Great, thanks for the suggestion I will check out the link.

Thanks,
Dean

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