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TMS320F280049: PGAx_OF can be cascaded to other PGAx_IN ?

jjl3
Intellectual 840 points
Part Number: TMS320F280049
Other Parts Discussed in Thread: ADS7946

Dear all

I have some questions about F280049RSH,

1) I want to get gain 36x, so can I set gain of PGA1 to 6x, and gain of PGA2 to 6x, then I cascade PGA1_OF to PGA2_IN?

2) the output of the sensor is differential output, is there the measurement to be inputted by PGAx? is it possible to combine two PGAx to one PGA with the differential input?

3) if F280049 need connect ADS7946, the frequency of sck for ADS7946 is up to 80MHz, wether the GPIO of F280049 is supported?

thanks!

Br

jjl

  • 0
    TI__Mastermind 28275 points
    Hi jjl3,

    1) Yes, this is possible. You can cascade the PGAs. Just keep in mind that if your signal needs a gain of 36x, you might run into significant signal to noise issues.
    2) The PGA only accepts a single-ended signal referenced to ground. If your signal is differential, you will need to convert it to single-ended. There are single-ended to differential ICs that you can use for this.
    3) If i understand this question correctly, you want to use the PGA to drive the ADS7946. If that's the case, it's not supported. The PGA is only designed to drive the internal ADC. Also the maximum supported rate of the GPIO is 50MHz.