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ADS1258 Bipolar Conversion Formula

Chintan Parekh14719
Prodigy 220 points
Other Parts Discussed in Thread: ADS1258

Hi 

 I am using ADS1258 in bipolar mode i.e AVDD +2.5V and AVSS @ -2.5V and DVDD at 3.3V.I wanted to know how would i convert the received digital data back to analog voltages .Is there a specific formula for conversion

  • 0
    TI__Mastermind 46290 points

    Hi Chintan,

    You'd start first by looking at the MSB of the data to determine if it is positive or negative. If you see a 0 in the MSB you know it's positive, if it's a 1 then you know the data is negative. From there you'd apply the weight of an LSB to determine the magnitude. In the positive case you would just multiply the value directly by 1.06Vref / (223 - 1). In the negative case you would invert all of the bits and add 1, then multiply that "straight binary" value by -1.06Vref / (223 -1). Alternatively you could just sign extend the data to a 32 bit signed integer and simply multiply that integer by 1.06Vref / (223 -1) since the signed integer would inherently carry the correct sign.