AD5940 open circuit potentiometry

Hi,

We will look into this, I'll contact the product owner and get back to you.

Regards,

Andrei

Hi,

     LPTIA may be used as voltage follower:

PH sensor input maybe given to RC0_0 pin,

AIN4/LPF0 is the output of LPTIA, which can be given as input to ADC MUX.

Refer to diagram above to find desirable switch states for voltage follower configuration.

Switch configuration and RTIA, Rload values maybe set in AppAMPSeqCfgGen() function.

Thanks

It seems that it is possible to configure the LPTIA as an inverting voltage follower, but then the input impedance would still only be as much as Rload? Could pH measurements work, or would I still need an external high impedance voltage buffer.

You may disconnect SW7 from Rload and connect SW7 to feedback path,

and give the input to RC0_0.

This way, Rload doesn't come into picture.

Hi, it seems that I am missing something.

I can connect SW7 to the feedback path to use the TIA as a voltage buffer, but then I don't see a good path for connecting the positive input of the TIA to the RC0_0 (pH sensor) pin.

If SW0 is closed, RC0_0 becomes negative input to TIA. 

Positive input of TIA maybe connected to Vzero through a resistor.

Vzero value maybe set in register as per requirement.

Akila said:

You may disconnect SW7 from Rload and connect SW7 to feedback path,

and give the input to RC0_0.

This way, Rload doesn't come into picture.

Hi  Akila ,

If I don't have access to any RC0_0/1/2 pins in my design, could I obtain the same result by using SE0 pin and closing SW1, SW7 (and SW0 if needed)?

Thank you very much!

Hi,

Kindly refer to this

https://urldefense.com/v3/__https:/xbnc1s3g.r.us-east-1.awstrack.me/L0/https:*2F*2Fez.analog.com*2Fdata_converters*2Fprecision_adcs*2Ff*2Fq-a*2F116440*2Fvoltage-measurement-ocp-open-circuit-potential-using-the-ad5940-resp-aducm355*2F510505/1/0100018bdb9127f7-a40c5302-9595-4ae3-a5b5-8b53e829c376-000000/bbdgmStOgnxcIKUHe9Y7NqxMOHs=348__;JSUlJSUlJSUl!!A3Ni8CS0y2Y!6kH3dDRUKBjXmi1y0XngNPvqrYY34tMH_ydi4ZAzcDNg4mrZWl8Jk9nL6lJRqSB5E8rdzfYRBPndfgzTzoH98qHjDMcCglWmAwruc0A$