max187 ADC converter differential input

First of all, MAX187 does not seem to be a differential input ADC.

Differential Input :

You will need additional interfacing circuitry, mainly a differential amplifier with enough common-mode range, which should be higher than the amount by which your differential signal is above your ground. The differential amplifier will then bring the differential signal to your ground, which is your ADC's ground. Now your ADC is able to input a differential signal.

Input Range :

The MAX187 has an internal reference of Vref = 4.096V. Assuming your are using its internal reference, then the analog input range is from 0 to 4.096V. Your specification of +/- 2.5V would result in a span of 5V, thus exceeding the analog input with internal reference. Not only this won't work, but it may exceed the absolute maximums. Read the 'Input Protection' section in the datasheet.

One possible solution is to incorporate some attenuation in the differential amplifier we talked about earlier. The differential amplifier should then bring a differential signal of +/- 2.5V into a single ended signal in the vicinity of 4V.

Here's an integrated solution :

INA159 ==> MAX187

Look at page 8 of the INA159 Datasheet, and page 7 of MAX187.

The INA159 is used to interface +/- 10V signal to single supply ADCs. Its gain fairly accurate, but I don't know if its linearity can satisfy a 12-bit performance.

Instead of this, you can also find differential input ADCs. But this doesn't mean you won't need any interfacing circuitries. It depends on what you are interfacing to...

maxi wrote:

Thanks Adelec,

've understand the question.

If i lower the input to + - 0.3 volt is it possible in some way to lift the gnd point at the input of the negative of ADC??

Thanks,

MAX Adelec Bakkal ha scritto: