I have an analog amplifier which is powered at single-supply power and have an analog ground of 1.25V.
I want to perform sdadc for my analog output. I am using STM32F373 (48pins), which is an ARM Cortex-M4.
I am confused with the circuit connection between MCU and amplifier. (analog output, analog ground and VREFSD+ and VREFSD- pins)
1. Analog Output from my amplifier
Refer to stm32f373 datasheet, page 33, pins definition table.
Since I am using SDADC1 for my application, so I connect my analog output as SDADC input for the mcu.
2. Amplifier Analog ground and VREF_SD+
Refer to technical reference manual, page 225, 13.3 SDADC pins, Table 36.
Since I am have an analog ground for my amplifier, so I think I should make the VREF_SD+ as external reference. With the description of
When the external reference is selected (REFV=00), this pin must be driven externally to a voltage between 1.1 V and VDDSDx.
Therefore, I connect the VREF_SD+ pins in between the VDD (3.3V) and my analog ground (1.25V)
I connect the VREF_SD- to 0V ground.
Below is the overall view of my circuit connection:
I am not sure about the connection for part 2 (VREFSD+), am I doing the right thing?
I also not very sure, what is the need of VREFSD+ and - in SDADC application. From what i understanding is to set the input voltage range limit with VREFSD+ and VREFSD-. Can someone elaborate a bit further on this? Some background explanation is great.