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AD5445 single supply application

Question asked by giggich on Mar 13, 2015
Latest reply on Mar 17, 2015 by giggich

I am using AD5445 to generate output voltage 0-1.25V from a single 5V supply.

I literally implemented circuit from the figure 51.

Vin is supplied from ADR391 (2.5V voltage reference), the bias voltage is exactly 1/2 of the Vref.

My output buffer is designed with LTC6078.

The circuit:

ad5445.jpg

I expected to have 1.25V on the output if the code written into dac is 0x0000, and I expect to have 0V if 0x0FFF is written into the DAC.

If nothing is written I expect to have 1.25V. I am able to read what I wrote into DAC.

The problem is that I always have 11mV on the output of the circuitry.

I checked CCA few times, all voltages are at the correct level, 

The design is done correctly on 6 layers board and assembled and tested by the board house.

Is the problem caused with my usage of LTC6078? Should I switch to AD8066 since the package is the same?

Thank you,

g

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