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Original question:

TMS320F28032: Maximum Voltage on ADC Input

TMS320F28032: TM320f2812

navin singh1
Prodigy 210 points
Part Number: TMS320F28032

Hi ,

When ever my input to ADC exceed 3.0V, the output I read is 0 volt.

other wise it the input to ADC is less then 3 Volt, i am getting proper output from software.

IS there any setting or changes we need to do to get the output 3 Volt in software when the input to ADC exceeds 3V?

  • 0
    TI__Guru* 80290 points

    Navin,

    Please clarify if this is for the F2812 device or the F28032 device, since they are both listed.

    From the ADC range of 0-3V I'm going to assume this is F281x device for now.

    You are correct that value above 3V should read 4095/saturated ADC value as part of the normal behavior.

    Can you comment on how much >3V your input signal is?  There are some limitations on exceeding VDDA supply(or going below VSSA/ground) that can begin to effect the channel selection MUX.  Typically these violations cause other channels to interfere with the sampled channel, while you are reporting the channel itself is effected.

    Are any of the other channels driven above VDDA/below VSSA in your system?

    Best,
    Matthew

  • 0 in reply to MatthewPate
    Prodigy 210 points

    Hi,

    Its 2812...

    Also my voltage at ADC input is 3.009V. its just 9mV above then 3V.

  • 0 in reply to navin singh1
    TI__Guru* 80290 points

    Navin,

    Thanks for the clarification, this is unexpected behavior that 9mV would cause ADC result to be non saturated(if it was already saturated beforehand).

    Can you measure the following pin voltages with a DMM before and after you see this occur(right below 3V and right above)

    1)ADCREFP

    2)ADCREFM

    3)ADCRESEXT

    4)ADCLO

    Also, can you comment on how you are reading the ADCResult registers?  If you are using the memory watch window, I seem to recall there being an issue with how these got displayed in CCS.  If you are reading via the CPU/C Code and pushing to memory, or have the ADCResult regs in a Watch Window that should be OK.

    Best,

    Matthew