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AD7606 reading is zero


we are using the AD7606 ADC ( to get values from different sensors.

We use the SPI bus (7,5Mhz clock speed) to read the AD7606 results, using a dsPIC33 Microcontroller.

Sometimes after Power-Up and sometimes while running, the ADC starts returning only  zero (0x0000) on the DOUT lines persistently.

The only way to get back to normal operation is to do the RESET sequence on the AD7606 reset pin.

The datasheet states: "If a RESET pulse is applied during a read, the contents of the output registers reset to all zeros."

Out reset signal is never assigned from the µC after the initial reset and also there is a pull-up resistor on the reset line kepping it high all the time.

Are there any other known ways to get the AD7606 to return only zero ?

The Busy & Firstdata lines are still active, just the output seems to be reset to zero all the time.

   Best regards, Chris

  • Hi,

    Let me check on this. I'll get back to you soon.



  • Hi, Chris.

    Can you share some scope shots of your digital lines as in Figure 2 and 6 of the AD7606 so I can take a closer look? Did you also monitor activity on your reset line when the output goes to all zeros?



  • Hi Karen,

    I attached some scope shots, similar to Figure2&6 of the AD7606 datasheet as you requested.

    I also had a look at the RESET pin, it is a clean 0V all the time, the µC makes sure it is set to logic low all the time (after initial Reset sequence).

    However I can not measure any signals while the PCB is used inside our machine, as it is mounted on a moving part and while operating it is not possible to attach probes to it.

    1a. (similar to Fig.2) CONVST every 1ms + BUSY + CS signals

    1b. (zoom in on 1a) CONVST -> BUSY

    1c. (zoom in on 1a) BUSY -> CS

    2. (similar to Fig.6) CS, DOUTA & FRSTDATA

    3a. (similar to Fig.6) CS, SCLK & DOUTA

    3b. (zoom in on 3a)

  • I just verfied what happens if the Reset pulse is high one time during a read cycle. As described in the datasheet. the output resets to zero, but only for the current cycle, the next reading is fine again.

    A short Reset spike could happen in our setup due to EMI, but I am sure is does not happen all the time. If we get a zero result from the ADC it stays zero until a full power cycle of the ADC.

    It seems as if the ADC gets stuck in some interal state which reset the output to zero constantly. Due you have any clue how or why this could happen so I can investigate further in the right direction ?

  • Hi,

    A private message was sent to you.



  • Hi,

    I was experiencing a similar problem with this part. Could you share the solution if you solved this problem? Thanks.