[solved] MCP3208 faulty?

[Marxon]

Hi Midiboxers,

 

is it normal that there is some voltage on pin 20 (Vdd) 

if only pin 19 (Vref) is connected to power? 

I measure 4,3 Volt. Maybe the chip is faulty?

 

Best regards 

Marxon

Edited February 13, 2015 by Marxon

[kpete]

The spec indicates that there is ESD protection on all pins.  This tells me that there is a normally reverse biased diode between Vdd and all the pins on the chip.  With the part only drawing 2 micro amps max., I would expect to see an open pin Vdd with a voltage due to any of the other pins having power on them, including the reference pin.  The part is probably OK.

 

Pete

[Marxon]

Hi Pete,

thank you for your help!

Great news:

When digging through my IC-box, I fortunately found another MCP3208.

With this one i meassure no voltage on pin 20 and my AINSER board is working again :smile:

So the old MCP3208 must be faulty. 

 

Best regards

Marxon

Edited February 13, 2015 by Marxon

[kpete]

One question I have is why do you have no power on the Vdd pin and a voltage on the reference pin?   Vdd should never be lower than the reference pin.  Maybe this is why the part failed in the first place.

 

Pete

[Marxon]

The main problem was that my AINSER board did not worked properly. 

I got only random values... Then I noticed that the uc-link and digital-power LEDs remains on

if the core gets disconnected.

To be sure that not maybe the board causes this issue I put the MCP on my experimentation board,

connected Vref to 5V and the issue was still there.