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TMS320 Bandgap Reference

Riccardo Dell'Oro
Prodigy 180 points
Other Parts Discussed in Thread: TMS320F28027, TMS320F28035

I couldn't find any clear information through datasheets and reference guides, so I try to get an answer here.

I'm using TMS320F28035 and TMS320F28027 controller's ADC with internal bandgap reference settled for a fullscale conversion of 3.3V.

Analog supply voltage (VDDA) can range from 2.97V to 3.63V (doc. sprs523h, pag.78).

What happen when an ADC pin input voltage is higher than VDDA voltage (respecting the datasheet limit of 0.3V of course), and how the bandgap remain accurate when VDDA gets lower then its value?

Thank you for your attention.

  • 0
    TI__Guru 60865 points

    The ADC full scale range is indeed 3.3V regardless of VDDA voltage level.

    The only caveat is in the datasheet (SPRS584G) on page 135, table 6-37:

    "The INL will degrade when the ADC input voltage goes above VDDA"

    So the accuracy will be degraded, but only for the portion of a signal which is above VDDA.  

  • 0 in reply to Devin Cottier
    Prodigy 180 points

    Brilliant.

    Thank you Devin, your reply is extremely clear.

  • 0

    well bandgap references are independent  to supply voltage and also little dependency on temprature But its minimum required supply voltage must be in attention.

    Each bandgap has been designed for different minimum supply voltage.

    So if your voltage is less than required voltage in bandgap reference,your circuit will not work.

    Also if your circuit is design for low-power applications your bandgap reference voltage  must be sub-1v and in this way your supply voltage could be low in a way that your circuit works.

    Best wishes