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ADC1173: ADC1173 input range

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Part Number: ADC1173

I was looking at the ADC1173 data sheet (8 bit 15 MSPS 3.3V ADC).

According to what I read, if VRTS is shorted to VRT and VRB is shorted to VRBS (self bias) the input range is of 1.2V (from 0.36V to 1.56V).

However in the datasheet (page 7) is stated that VRT - VRB  can be between 1V and VAA (from 2.7V to 3.6). It would be helpful to have the full input range 0 - 3.3V (with VAA = 3.3V). Is it possible to operate the device in this way by connecting VRT to the output of a voltage regulator of 3.3V (the same of VAA) and VRB to ground while leaving unconnected VRTS and VRBS?

If not, how the device must be configured to have the input full range 0 - 3.3V?

Thanks for your support.

  • Hi Marco,

    we can only go by what the data sheet explicitly says.

    Looking at the data sheet, the optimal range for V_RT and V_RB (when V_RT = V_RTS and V_RB=V_RBS) is about a 1.2V delta, as you mentioned.

    Further in the datasheet (page 19), it says, “To minimize noise effects and ensure accurate conversions” you have a 2V delta to play with (VRT minimum = VRB+1, VRT maximum = V_A; VRB minimum = 0V, VRB maximum = V_A - 1). Assume V_A = 3V.

    At this time, we don’t know what will happen if you exceed this 2V delta since there doesn’t appear to be any additional information in the data sheet, so I would not advise operating the ADC1173 outside of this range.

    Unfortunately, the original Evaluation Module (EVM) made by National Semiconductor is no longer supported, so we are in the process of designing a new EVM for the ADC117x family. There is not an official release date yet, but this type of measurement can be made when the EVM is available.

    Regards,

    Dan

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