Having some trouble with AD7685 in CS mode 3 wire without busy indicator. Both Vref and VDD are tied to 3.3V and i am getting 3.3V output on VIO. 


As mentioned in Page 19 of the datasheet, I have tied the SDI pin to VIO (through a 5.1kΩ resistor).


But the setup didnt work and later I found that the SDI pin is showing directing short to GND.


So I guess the Pin 9 (SDI) is burned, without which will I be able to use AD7685 in SPI-CS mode? What could have caused this problem? I am working with an lpc2148 as host, with ~800kHz CLK and CNV in every 10uS.





  • 0
    •  Analog Employees 
    on Sep 21, 2017 1:13 AM

    Hi Mahesh,

       We are looking into this, I'll get back to you soon.



  • 0
    •  Analog Employees 
    on Sep 21, 2017 11:06 AM

    Hi Mahesh,

    If it is okay. Can you share your schematic. I'd like to get more details on the issue. It might you have to much load on the supply. Also i would not recommend to tied your Vref to your Vdd. ADC depends on the accuracy, stability and drive capability on the reference voltage  must able to handle and throughput dependent currents. Please refer to this article looks at the challenges and requirements involved with the reference circuit design and in the front-end and RC circuit design.Hope this helps.



  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:56 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin