Hello, guys I have a very simple circuit with a PIC16F628 connected directly to a digital potentiometer MAX5389. All powered by a 5V source through an LM7805.

Initially, I had a problem with the Max5386, which returned the resistance to the initial position, after I put a 100nF capacitor between Vcc and the IC's gnd, the problem resolved. But now after a few days on, the Max5389 always burns, I believe it is some transient in the power supply.

Can putting a TVS diode on can prevent this from happening?
Which TVS diode would be indicated?

 

I'm not sure that will help, and I've never seen or heard of anybody doing this. Something else is going on.

 

I believe it is some transient in the power supply.

I think not but.
Please post the schematic.
Where are you getting the power from?
Are there wires that go off board? !!!
What capacitors are around the LM7805?

 

What would be the TVS Diode options to protect the MAX5389 when it is powered by a 5V source?

 

What would be the TVS Diode options to protect the MAX5389 when it is powered by a 5V source?

I'm not sure there are any that work at such a low voltage. There is something else going on. Please post a schematic diagram of what you have built. That is literally the ONLY way to move forward. You can choose to ignore this request, but you are on your own if you do that.

 

I think not but.
Please post the schematic.
Where are you getting the power from?
Are there wires that go off board? !!!
What capacitors are around the LM7805?

I don't have the schema. There are capacitors in the LM7805. There is no wire coming out of the board. On a certain occasion I burn the PIC16F628, but only once, what is burning each week is the Max5389


As I have no idea of the burn, please try using a TVS diode but don't know which ones I can try to use?

 

I doubt it is the supply, but if you really want to try that, just use normal diodes. That chip is rated for -.3v to 6v in, so put a fuse and then a pair of diodes (that will short and blow that fuse, just like a higher voltage TVS would) across the power rail. One 1N4004 to short any reverse voltage below -.7v (probably too late, might want a germanium diode) and a 5.6v zener to clip anything over that.

If I had to guess, I'd suspect those tap to tap switching transients shown in the datasheet. Is there an inductive load connected to that digital pot?

 

I don't have the schema. There are capacitors in the LM7805. There is no wire coming out of the board. On a certain occasion I burn the PIC16F628, but only once, what is burning each week is the Max5389


As I have no idea of the burn, please try using a TVS diode but don't know which ones I can try to use?

HTH can you build something without a schematic? I've NEVER in my life tried to do that. It is complete and utter madness.

 

See

 

Instability can be fickle!
I‘ve always preferred the cheapest possible 10uF electrolytic with plenty of ESR on the output of a 7805. It acts like a zone network. I think I read it in one of Bob Pease’s articles.

 

Just in case you cannot read the 1001 words in Bordodynov post, capacitors, large capacitors, input and output.

 

As I have no idea of the burn, please try using a TVS diode but don't know which ones I can try to use?

You don't have much choice. With a 5V supply, you'd use a 5V TVS diode.



Note that the minimum breakdown voltage is 6.4V.

 

You don't have much choice. With a 5V supply, you'd use a 5V TVS diode.
View attachment 278112
View attachment 278113

Note that the minimum breakdown voltage is 6.4V.

Those aren't going to be much use on the output of a +5V regulator. The TS is STILL barking up the WRONG tree. Is there some ethereal reason he cannot accept good advice?