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AD5421 Powering up

Question asked by embedded_ca on Feb 22, 2016
Latest reply on Feb 23, 2016 by embedded_ca

Hi,

 

I have design AD5421 based 4-20mA loop powered system. The schematic is attached. I see following problem:

1. The D_VDD always outputs 4.2V but datasheet says 3.3V but can have 5.5V overdrive.

2. If REG_OUT pin floating instead of tying to D_VDD and IOD_VDD and measure voltage at REG_OUT then it measures 2.7V.

The REG_SEL0 and REG_SEL1 is tied to 3.3V and REG_SEL2 is tied to GND.

3. The range resistors are tied to ground to configure output to 4-2mA.

4. The ADuM1447 is disconnected from the system.

 

Could anyone guide me what is wrong happening? Did I miss anything?AD5421.png

 

Regards

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