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AD5446 Daisy Chain help

Hello everyone,

I've been using an Arduino to communicate with an AD5446 in the AD5443/46/53 Eval Board. I was able to communicate to one chip, sending it 16 bits and receiving the correlated voltage. However, I tried to send it 32 bits, so the first 16 bits would ripple out to the SDO line, but when I measured it, nothing came out of the oscilloscope. It seems to still read the last 16 bits, IE, if I were to send it 0FFF3FFF, it still reads the 3FFF and changes it, but the 0FFF doesn't appear on the SDO line. Does anyone know why nothing is showing out of the SDO line? 

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  • Here is the oscilloscope reading for the 32 bit data. The purple is what I'm sending (3FF3FF), the light blue is the SDO line, the yellow is clock, and dark blue is sync. The clock pulses are around 150 microseconds if that matters. There's a lot of noise because I used an Arduino with a lot of wires connected to the Eval Board. 

  • Hi, 

    your data transfer seems fine. Now normally this should be working as expected with the first 16bits of data clocking out of the SDO. Looking at the eval board schematics, the SDO's are connected to some switch mux, ADG701/2 powered by a 3.3V supply. Based on your plot, the SPI is at 5V VOH which conflicts with the input range of the sw mux. This might cause some unexpected response. Could you try and do your test on a 3.3V supply for the AD5446, or remove the ADG701/2 on the board.

    Best regards,


  • I removed the 2 sw muxes, and then did the same test again, but ended up with the same thing. 

    Light Blue - Clock   /   yellow - sync  /           dark blue - SDO     /       pink - SDA (3FFF3FFF)

    The Arduino GPIO outputs 5V VOH but I could possible try to lower it to 3.3v if needed too.

  • Everything seems to be in order. the only thing left is that the device so might already be damaged. I don't have an eval board with me atm so I can't confirm it with actual testing.