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TMS320F280049 Simultaneous use of CMPSS and ADC

user4565873
Expert 1250 points
Other Parts Discussed in Thread: TMS320F280049

Hello,

I have a question concerning the analog subsystem of TMS320F280049.

We want to sample 3 currents and have 3 overcurrent protections on those.

We chose 3 analog inputs for the ADC to sample the value of the current for the control loop.

We want to use 3 CMPSS to check for overcurrent protections.

Can we use the same analog input for the same current as for the ADC?

OR, do we need to wire the same signal to 2 différents analog inputs?

According to figure 12.4 of the TRM, it seems one analog input is connected always to one ADC and one CMPSS (or PGA or.)..

Thank you,

PA.

  • 0
    TI__Mastermind 28275 points
    Hi user,

    If those 3 ADC channels you are using are in 3 different analog groups, then you can use 3 CMPSS without any extra wiring. All you will have to do is configure the comparator subsystem mux. If the 3 ADC channels are in the same analog group, then you would have to do some external wiring.
  • 0 in reply to Frank Ankapong
    Expert 1250 points
    Thank you!
    Very good news for our electronics engineer...
    Is there any caution to take when using the ADC on another pin of the same analog subsytem, to not trig the CMPSS?
  • 0 in reply to user4565873
    TI__Mastermind 28275 points
    User,

    The CMPSS and the ADC can be used simultaneously without any issues. The CMPSS inputs are high impedance. By that i mean during operation, the CMPSS diverts negligible current from the ADC's sample/hold circuitry. However, if the CMPSS output is toggling at a high frequency through the GPIO, it can have an effect on the ADC's accuracy. This is no different from a GPIO toggling at a high frequency.
  • 0 in reply to user4565873
    TI__Mastermind 28275 points
    Hi User,

    I'm assuming the last response answered your question so i'm going to go ahead and mark this as closed.