AD5206 Digital Potentiometer overheating

Using Arduino General Electronics
#1

I'm using an AD5206-B10 digital potentiometer chip to tie into the joystick port of an electric wheelchair using an Arduino Uno. I'm powering the SPI portion of the chip from the Arduino, but I'm powering three pot circuits using power from the joystick port in the wheelchair controller. Both grounds are tied together. Unfortunately I'm finding that the AD5206 is heating up after some time. When it gets hot it eventually stops responding to SPI commands.

I'm a bit of an electronics noob so if anyone has a suggestion it would be appreciated. The voltage from the Joystick port is 5v and looks pretty steady when measured with a multimeter. My first thought was that I might be somehow pulling way too much current from the port but when measured it looks like it peaks at about 2.05 ma. Both voltage and current seem like they should be well within the normal operating specs of the chip. Does anyone know if it is normal for these chips to heat up? Is there something else I should be looking at in terms of a bad circuit? Right now this is just breadboarded.

#2

You need to check all the voltages going into the digital pot - they must all lie between the 5V supply and
ground, otherwise you could destroy the part. My suspicion is that one of the analog signals is out of
range and causing high currents to flow in the protection diodes on chip.

#3

The only way things get hot is with too much current, or trying to drop too high a voltage, it which case it is still too much current.

#4

Good advice Mark and Mike. But the actual problem turned out to be something I didn't mention. I neglected to tie the Vss pin to ground. Now it runs cool. I didn't think I needed to tie Vss since I was only using positive voltage. But that is apparently not the case. Definitely a newb mistake.

It's still not quite working as expected but I'm not positive I didn't fry this chip either.

#5

But the actual problem turned out to be something I didn't mention.

Those are always the hardest to spot. :wink:

#6