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I have a problem with AD8279. Please help.

Question asked by Alecksey on Mar 20, 2013
Latest reply on Mar 23, 2013 by Alecksey

Hallo.

The first time I have used AD8279 was a project for railroad generator control system. I have made all analog data convertion from current, voltage and thermo sensors to ADC of microcontroller on it. And was very glad because today I have about 50 devices in work without any problems.

Next time I designed controller for frequency converters and power supply systems and some of the AD8279 burned down during the testings. I have made some experiments and find out that the problem happens only if I connect the sourse of the signal to analog input during operation. But this situation is possible during exploitation of my devices and I have never met this before using another solution.

Before using AD8279 I have designed all analog convertion on TL074 Texas Instruments OA with great number of external resistors. But it works good and I have got no failures for many years.

What can be the source of my problem? Is it static electricity, rapidly changing signal or something else?

The first scheme with TL074 OA,

mk106.GIF

And the next with AD8279.

mk107.GIF

Thank you.

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