AD7730 Data Ready pin sometimes not going low

Additional information:

These are the voltages at the pins

1- SCLOCK at 4MHz from the controller- checked on oscilloscope and is is showing 3.9 MHz so I think this should be fine

2 and 3 external crystal of 4.9Mhz- checked on oscilloscope. The peak to peak voltage is 1.7V, is this okay?

4- POL pulled low through 100Ohm resistor using GPIO pin The voltage is ~0.8V

5, 6 pulled high through 100 Ohm resistor using GPIO pin. The voltage is 3.2V

7 is not connected and shows 2.48V

18 (STDBY) is 3.3V through 100Ohm resistor and GPIO pin

19 (CS) hard wired to ground

20 (RDY) is always 3.3V

Conversion rate is set at 1024 samples per second and continuous conversion mode. The default registers are being red correctly, I am able to write to the ADC also and I get a few conversions before the (RDY) pin goes high permanently. 

One wild thought, I purchased the ICs locally, can it be a problem of counterfeit?

Hi Nikhil1256 ,

Have you come across this FAQ? (+) AD7730: RDY signal not working - Documents - Precision ADCs - EngineerZone (analog.com)

I'm hoping this FAQ could help you in your query.

Regards,

JC

Hi

Sorry for the late reply, I will check our system based on that thread and let you know here the result.

Thanks
Nikhil

Hi JC

I think we have identified the problem with the controllers 32.768kHz crystal. It was causing the controller to behave in a weird way which was causing the Reset pin to not assert after soft reset. After I replaced the crystals and the capacitors with fresh batch, it seems to be working as intended.

Hi Nikhil1256 ,

Good to know you have resolved your issue. I will be closing this thread. Feel free to post a new thread if you have further questions in the future.

Regards,

JC