Hi,

I am wanting to create a circuit board with a Bipolar ADC on it and not sure what the best option would be.

I am using an esp32 but wanted to use an external ADC (surface mount) for better accuracy. The range that I want to measure is -2.4V->+2.4V. My first attempt I thought to just use a simple voltage divider, an ADC (ADS1115) and the 3V3 on the ESP32 to boost the signal so I could measure negatives which worked ok but the 3V3 fluctuates a lot with temperature which decreases the accuracy dramatically. I did do some calibration that made it a bit better but I feel it would be much easier to just use a bipolar ADC.

Is getting a bipolar ADC the easier way? What types of bipolar ADC's should I go for? Any specific recommendations? I would like to have 4 channels with mV accuracy if possible.

Sorry if I am asking a stupid question or it has been asked before. I did search the forum and couldn't find anything.

 

Hello there
An onboard•INTERNAL PGA is available on the ADS1114 and ADS1115 that•I2C ™ INTERFACE: Pin-Selectable Addresses offers input ranges from the supply to as low as±256mV.

 

I could measure negatives which worked ok but the 3V3 fluctuates a lot with temperature which decreases the accuracy dramatically.

You could use a reference voltage IC to generate a stable reference. such as the LT1634 or, the somewhat less stable TL431.
(What are your stability requirements?)

 

There are many variations of ADC input configurations so what type of bipolar ADC do you really want?

https://www.analog.com/media/en/new...ection-guide/Precision-ADC-Selector-Guide.pdf

 

There are many variations of ADC input configurations so what type of bipolar ADC do you really want?

https://www.analog.com/media/en/new...ection-guide/Precision-ADC-Selector-Guide.pdf

Had a look there and I guess I am looking for either a Single-Ended True Bipolar or a Pseudo-Differential True Bipolar. I can't see on this list any that are 3.3V supply and multi channel?

You could use a reference voltage IC to generate a stable reference. such as the LT1634 or, the somewhat less stable TL431.
(What are your stability requirements?)

I have kind of figured out the problem for the circuit that I was using and it turns out that it wasn't the supply 3V3 that was fluctuating with temperature but the protection diodes that I was using which was causing the fluctuations with temperature. Removing them fixed the issue so I should be able to keep using it and think about something else for protection.

Thanks for the help however I am still keen to find out if there is a much simpler option.