Electronics > Beginners
Using a differential ADC as unipolar
(1/1)
Axk:
http://www.ti.com/product/ADS7945

Can I use the differential version of this ADC (more cheaply available from aliexpress) as to measure an ebike battery voltage (13s6p battery) using a resistive divider or do I need the unipolar version?

There are better options available from aliexpress or ebay I'm sure, but this is the first one I found through Digikey that is avilable on aliexpress and that has 2MSps and 14bit for my application.
Kleinstein:
One can often use differential ADCs in a unipolar mode, with one input fixed at ground or a different fixed level. Depending on the model one may not be able to use the full range, but usually one polarity is OK. With some models there will be a slightly higher error due to nonlinearity, as the specified linearity of often for differential input with zero common mode voltage.

The mentioned ADC is anyway not a good choice for measuring an accumulator - it's a rather fast one. No need for 2 MSPS on a battery.  It's also an ADC in a small case and thus difficult to solder by hand. The input may need a buffer, but I have not checked the datasheet.

I would more like consider something like MCP3421 - a slow 18 Bit ADC.
Axk:
My reasoning of why I need this sampling rate is as follows.

I've measured the current waveform between the ebike controller and the battery and it has components of several KHz for sure, and maybe more. Considering the high current in this application the voltage will also vary with the current.

Measuring power I would need 2 ADCs so oversampling at a couple of MHz should give me a good margin for better integration of the consumed power.

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