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RF430FRL153H: ADC input range.

jano notelodigo
Prodigy 140 points
Part Number: RF430FRL153H

Hi!

In the application I'm designing, the ADC needs to handle an input of +-0.8V from a reference point (1.6V total).

In the datasheet (chapter 5.22, pag. 20) the input voltage range is specified from 0 to Vref, Vref in pag. 19 is specified as 900mV. But I can't find a limiting value of Vsvss. 

From SLAU506 pag. 197, it looks like Vref is related to Vsvss, and the input of the PGA is differential. The question then is: can I reference Vsvss as 0.8V and have an ADC input swing from 0 to 1.6V? or is 0.9V a hard limit and I need to divide my signal at the half?

Thanks in advance.

  • 0
    TI__Mastermind 18265 points

    Hello Jano,

    the maximum input voltage for the SD14 is 0.9V. SVSS is either internal switched to GND or to the SVSS generator (125mV typ.) by the VIRTGND bit.

    The SD14UNI and SD14TC bits are selecting only different digital data formats. In your case you have to divide your input signal.

    Best regards,

    Helfried

  • 0 in reply to Helfried Vollbrecht
    Prodigy 140 points

    Hi Helfried!

    What we find confusing is that in SLAU506, pag. 201 chapter 10.2.6:

    For a 0.9-V reference, the maximum full-scale input range for a gain of 1 is shown in Equation 8.

    ±Vfs =  ±Vref =  ±0.9 V

    If the input can only swing up to 0.9V positive: Can be the input negative? or are we reading this wrong?

  • 0 in reply to jano notelodigo
    TI__Mastermind 18265 points

    Hello Jano,

    I was looking for more information and found out that this is indeed confusing.

    The used ADC would be able to handle negative voltages but the PGA in the input does not, which was not reflected in the documentation. You can only apply positive voltages to the ADC input. The datasheet is correct with 0 to +0.9V input voltage.

    Best regards,

    Helfried