STM32F753ZI Nucleo – Internal OPAMP output limited to 2.4 V instead of 3.3 V

[Harsh_Shakya]

I am working with the Nucleo-STM32F753ZI board and using the internal OPAMP peripheral. The supply is 3.3 V, and according to the datasheet the OPAMP output should swing close to the rails, but in my case the maximum output I can get is only around 2.4 V.

Has anyone faced this issue on STM32F7 series?

Is there any configuration, calibration, or internal routing limitation that restricts the OPAMP output range on this board?
Any guidance on how to achieve the full output swing (near 3.3 V) would be helpful.

[mƎALLEm]

Hello,

First, you need to ensure that R36 and R37 are available:

Second,

- You didn't tell how did you configure the OPAMP

- What was the hardware setup and the test done to conclude "the maximum output I can get is only around 2.4 V"?

- Is there any load connected to the OPAMP output? if yes, how match in ohm?

- Are you connecting an oscilloscope to measure that voltage level? if yes check the probe scale x10?

[Harsh_Shakya]

Please find the attached main file for the opamp testing.

I given the external voltage supply to the opamp input and checked across the ADC values and converted it to Voltage, and I have observed after increasing the voltage values not going any more than 2.4V and tested ADC code separately ADC can measure up to 3.3V.

As per hardware, selecting R36 and R37 are connected on the nucleo board. 
Suggest any other settings I have to do.

[mƎALLEm · Accepted solution]

Hello,

Could you please share also the ioc file?

What voltage are you testing? are you injecting an external voltage for that Follower config? note that there is a LED connected on PB0 (OPAMP1_VINP) on STM32F753ZI Nucleo board.

So try with OPAMP2.

I've tested with OPAMP2 and I had almost the full rail-to-rail output:

Edit: In the screen shot, I meant OPAMP2 not COMP2

[Harsh_Shakya]

Yes, thanks for the support issue is resolved. 
It was related to LD1, which is connected to the PB0 pin of the controller. 

When we configure the OPAMP2, it is working properly.