Hi

I am looking for a differential ADC for my application but find it hard to choose one for my needs.

I need a differential ADC even that my negative input is preferring to GND.

I have a very low current sense resistor which is located far from the ADC on the board (two different boards).

I am amplifying the signal close to the sense by 20 and add common mode voltage of 2V to increase SNR then run the amplyfied signal along the board differentially to the ADC.

The ADC should be at least 1MSPS

At least 10 bit

Vref must be external since I need it to be 2V.

Serial interface (SPI is preferred)

I also couldn't understand from all datasheets I read how the common mode voltage of the differential input signal is coming into calculation with the ADC conversion since there is no Vcm input in all ADCs I reviewed.

hope someone can help me here.

Thanks

Avi

Hi Avi,

There are a family of parts that you should look at. There are 10,12 bit options as well as fully differential vs pseudo differential options. Are you saying that your negative input to the ADC is tied to GND - this sounds more like a pseduo differential configuration?

All have a serial interface and can take a 2V reference from an external source. The parts can also have a variable common mode on the input.

AD7440 - Fully Differential, 1MSPS, 10 bit

AD7441 - Pseudo Differential, 1MSPS, 10 bit

AD7450A - Fully Differential, 1MSPS, 12 bit

AD7451 - Pseudo Differential, 1MSPS, 12 bit

Regards,

ClaireL