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# How to use AD7124 to measure a series battery module ？

Dear，

I use AD7124 to measure a series batteries ， when i connect only one battery ，it works better，

when i connect the three batteries ，the results are wrong .

How to measure many more batteries use AD7124，for example，10-series-battery

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• Hi,

I think what you need to consider here are the accepted input voltage ranges of AD7124 such as Absolute input voltage range (AIN+ or AIN- to GND), Differential Input voltage range (AIN+ - AIN-) and the common mode voltage (AIN+ + AIN-)/2.

The datasheet provided all of the restriction regarding these inputs. For example the absolute AIN voltage limits at a gain = 1 (unbuffered) is specified from AVSS - 0.05V to AVDD + 0.05V. If you were to take a look at the above schematic. assuming you have AVDD=3.3V and AVSS=0V, having a 5V input at AIN1 violates this restriction. I'm afraid it may also violated the abs max rating of the part.

So in general, you need to condition your battery output signal to operate within the ADC input range.

If you do not want a complex AFE design. I think there is an ADI part that is designed for this type of application. You can check AD7280A (Rev. 0) (analog.com) and then you can ask someone from Q&A - Power By Linear - EngineerZone (analog.com) community to support you on this product,

Thanks,

Jellenie

• Hi,

I think what you need to consider here are the accepted input voltage ranges of AD7124 such as Absolute input voltage range (AIN+ or AIN- to GND), Differential Input voltage range (AIN+ - AIN-) and the common mode voltage (AIN+ + AIN-)/2.

The datasheet provided all of the restriction regarding these inputs. For example the absolute AIN voltage limits at a gain = 1 (unbuffered) is specified from AVSS - 0.05V to AVDD + 0.05V. If you were to take a look at the above schematic. assuming you have AVDD=3.3V and AVSS=0V, having a 5V input at AIN1 violates this restriction. I'm afraid it may also violated the abs max rating of the part.

So in general, you need to condition your battery output signal to operate within the ADC input range.

If you do not want a complex AFE design. I think there is an ADI part that is designed for this type of application. You can check AD7280A (Rev. 0) (analog.com) and then you can ask someone from Q&A - Power By Linear - EngineerZone (analog.com) community to support you on this product,

Thanks,

Jellenie

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