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TMS320F28027 ADC reference

Bhuvaneshwar kanade52509
Prodigy 90 points

Other Parts Discussed in Thread: TMS320F28027

Dear all,

      In TMS320F28027 if i am using Internal Reference & my Supply voltage Varies from 3V to 3.5V then how conversion will be done.

Will it be with reference to 3V of supply or it will be 3.3V according to internal reference ?

& if supply voltage goes upto 3.5V then also will be the reference voltage of internal bandgap referance will be 3.3V

& all conversions will be done according to that only or it will depend on supply voltages at low supply voltages below 3.3V ?

thank you.

  • 0
    Genius 5170 points

    If you are using internal reference then the conversion will be made between 0 and 3.3V fixed. If you are looking for a varibale voltage situation (sounds like, you are looking for ratiomatric operation) then you will need to use external reference and will need to provide references using VREFHI & VREFLO. All these are explained in SPRUGE5B. By the way, which voltage is varying between 3V and 3.5V? You are out of voltage specification and please check the datasheet for the allowed voltage levels.

  • 0
    TI__Guru* 84340 points

    With the internal reference the conversion range is always fixed to 3.3V no matter the supply voltage on VDDA.  The only limitation is that the DS calls for the input votlage applied to the analog inputs to not exceed VDDA.  If this is violated the result will be a degredation in the lineartiy of the converter for voltages in excess of VDDA.

    Best,

    Matthew

  • 0 in reply to Arefeen
    Prodigy 90 points

    Hi ,

        I have seen for voltage range allowed , it is 2.97V to 3.63V .

    I am thinking about voltage variation on Vdio & Vdda pins of PICCOLO , with using internal reference for ADC conversion.

    & this same supply will be used for OPAMP & Other signal conditioning circuitry .

  • 0 in reply to Bhuvaneshwar kanade52509
    Genius 5170 points

    This is within tolerance specified in datasheet and if you select internal reference then the conversion will be made with 3.3V range .. .at least that is my understanding. In order to accomodate a variable range you will need to utilize VREFHI & VREFLO.