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AD5422 output issue

Toni
on Jul 29, 2020

Hello

Im trying to get the AD5422 to work but the output stays constant at 1V no matter what i write into the data register.

The output is 0 to 5v range.

This is my schematic:

I connected -Vsense to ground and +Vsense to Vout but no change.

My SPI looks like this.

Blue = Latch, Green = SDI, Red = Clock

reset:

control register: enable out

data register:

When i readback the registers it returns the right values.

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  • +1
    •  Analog Employees 
    •  Super User 
    on Jul 30, 2020 4:49 AM

    Hello Toni,

    I can't see anything wrong with the spi data. I'm curious about the AVSS connection, as it is connected to GNDA? is it also connected to  your other GND?

    Have you tried checking the output impedance of the vout? Where does the vout connect to? I want to isolate if first from the protection diodes and measure the vout only. You could try removing the 100ohm series R and measure the vout directly. 

    I hope you can also probe the output voltage when you send the data register settings. 

    I'll look into it a bit more. For now, this is all I have. 

    Best regards,

    Ian

Reply
  • +1
    •  Analog Employees 
    •  Super User 
    on Jul 30, 2020 4:49 AM

    Hello Toni,

    I can't see anything wrong with the spi data. I'm curious about the AVSS connection, as it is connected to GNDA? is it also connected to  your other GND?

    Have you tried checking the output impedance of the vout? Where does the vout connect to? I want to isolate if first from the protection diodes and measure the vout only. You could try removing the 100ohm series R and measure the vout directly. 

    I hope you can also probe the output voltage when you send the data register settings. 

    I'll look into it a bit more. For now, this is all I have. 

    Best regards,

    Ian

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