AnsweredAssumed Answered

AD5420 range offset problem, 350uA

Question asked by ksifa on Aug 9, 2013
Latest reply on Aug 27, 2013 by tjohnson

Hello,

I am using AD5420 with external boost npn transitor (exact as in datasheet) and external Rset resistor.

Output range is set to 0 - 24 mA. Analog supply is 12V, digital 3.3V.

There is several identical channels on one PCB controlled by one uC.

Most of the channels work fine, no mater what kind of load I use: resistor, LED or  currentmeter.

However in some channels, output current is shifted up by approximately 350 - 375 uA.

This means that setting output code 0x000 results in output current of 0,350mA,

and setting output code of 0xFFFF results in 24,350mA on output.

Usually problem can be fixed by re-soldering of components in faulty channel,

however it can also disappear or show up after powering up the PCB.

It is hardware issue,  as I noticed with different software and uCs.

 

What may be the reason of such a phenomenon? How should I diagnose it?

Thanks for all help,

ksifa

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