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TMS320F28335: Same Clock to DSP and External ADC ADS1278

Sachin Nevase
Intellectual 370 points
Part Number: TMS320F28335
Other Parts Discussed in Thread: ADS1278

Hi Team,

Is it possible to give clock from same crystal to DSP TMS320F28335 and ADC ADS1278 ?

Thanks & Regards,

Sachin

  • 0
    TI__Guru* 80640 points

    Sachin,

    There are 2 factors here, one of which I will ask for another team member to comment.

    1st factor is that the crystal (X1/X2) input to the F28335 is 1.8V level signal.  Reading the ADS1278 DS, it looks like IO range is 1.8 to 3.3V; so if you are using in the 1.8V range this should be OK>

    2nd factor is now discussion driving a CLK input on the ADC device with the output of the F28335 internal oscillator circuit; and this is where I willl need to research if there is any impact to our (C2000) oscillator circuit by adding another clock input load.

    Finally, if you meant driving both devices with a canned oscillator(using XCLKIN on F28335) where the oscillator circuit is external to both devices, that should be OK.

    Best,
    Matthew

  • 0
    TI__Mastermind 28275 points

    Hi Sachin,

    To add to what Matt said, if you mean a quartz crystal, then no, you can't share it between 2 devices. A quartz crystal and electrical oscillator circuit (inside the F28335 device) will form a closed loop system that should not be driven by anything else.

    Moreover, a quick scan of the ADS1278 datasheet shows it does not support a quartz crystal and you can only feed it a single-ended clock from like a can oscillator. You can share the output from a single-ended oscillator among 2 devices but for a more robust design, you might have to buffer the split clocks going to both devices.