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EVAL-AD5781 Schematic and Layout Error

al-ad-pcu-1-21
on Sep 22, 2021

Hi, I am struggling to set bipolar output with EVAL-AD5781. 

In the schematic it looks like there might be an error that is preventing negative output. Have checked and looks like schematic matches the layout. 

Should VSS_DAC net be connected to VSS pin 15 instead? Or is this intended?

i.e. pins 15 and 18 on EVAL-5781 are swapped by mistake?

Any help would be much appreciated. Slight smile

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  • +1
    •  Analog Employees 
    •  Super User 
    on Sep 24, 2021 7:15 AM

    Hi, 

    That should be a typo on the schematic only. on the d/s pin 18 is VSS and ping 15 is dgnd. I'll check it on the board layout and get back to you. 

    Can you explain a bit about your setup? Are you using the evaluation software? What exactly are you getting at the output when you try to set it?

    What are your supply and device settings?

  • 0 on Sep 24, 2021 7:37 AM in reply to iandal

    Ah yes, thanks! In that case the layout is correct. Must be something else in my setup. 

    I'm using the EVM without the software. Accessing SPI through J12. Using external controller for SPI master. 

    Powered by external 5V through J11. Using ADR445 reference board as is. 

    LK1 set A. LK2 fit. LK9/LK10 set B. LK8 set B. LK3 fit. All other jumpers nofit. 

    Have removed output clamp, and set output. Seems to change successfully so I think the controls are working Ok. 

    I've tried a few different D codes and it seems to be setting between 0V and 10V. 

    Thanks for sanity checking for me. I'll continue to debug. No doubt it will be something obvious!

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  • 0 on Sep 24, 2021 7:37 AM in reply to iandal

    Ah yes, thanks! In that case the layout is correct. Must be something else in my setup. 

    I'm using the EVM without the software. Accessing SPI through J12. Using external controller for SPI master. 

    Powered by external 5V through J11. Using ADR445 reference board as is. 

    LK1 set A. LK2 fit. LK9/LK10 set B. LK8 set B. LK3 fit. All other jumpers nofit. 

    Have removed output clamp, and set output. Seems to change successfully so I think the controls are working Ok. 

    I've tried a few different D codes and it seems to be setting between 0V and 10V. 

    Thanks for sanity checking for me. I'll continue to debug. No doubt it will be something obvious!

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