Differential ADC in stm32h7

[m_kalaiarasi]

I have recently purchased an STM32H753ZI board and want to configure the differential ADC to read signals directly from a function generator. I have configured it based on the following setup, but I am facing several issues with the output.

Issue 1: I am unable to read the ADC value properly. The negative side of the signal is getting clamped. How can I correct this?

Issue 2: When I input a 1V peak-to-peak sine wave to the differential ADC of the STM32H753ZI microcontroller, I am getting a square wave at the output. Why is this happening, and how can I fix it?

I have attached the output below when I am providing 1v peak to peak sine wave.

[TDK]

Are both sides of your signal within the voltage range 0 to VREF+? Negative voltages are not allowed, even in differential mode.

[m_kalaiarasi]

Hi ..My requirement is to read the sine signal of 1 volt peak to peak directly from function generator .But in differential mode can we able to measure the input signal directly without adding external dc offset(to upshift the signal from 0 to 500mV)?

why negative voltages are not allowed, could you elaborate it?

 what is difference between single and differential mode?

since i am beginner. Could you explain it

[TDK · Accepted solution]

ICs in general cannot handle voltages outside of their power rails. This is reflected in the datasheet specifications.

[m_kalaiarasi]

I understand it.. but I am operating inside the power rails right?

[TDK]

If the function generator generates a signal from -500 mV to 500 mV, it will not work.

Based on your plot, which I'm now looking at again, it feels like something else may be going on as well. Is your function generator grounded to your board?