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ADS1672: Max system clock frequency

mike lacroix
Prodigy 80 points
Part Number: ADS1672
Other Parts Discussed in Thread: PCM1690-Q1, , ADS1675

In the design of my current project the ADC (ADS1672) and the DAC (PCM1690-Q1) require different system clock values. In an effort to make things easier I would like both devices to run off the same system clock. The DAC clock is 24.5760 MHz while the datasheet shows the clock at 20 MHz. The datasheet for ADS1672 shows characteristics for the device using a 20 MHz clock but it does not state that that is the maximum clock frequency. Would it be possible to run the ADS1672 at a clock frequency of 24.5760MHz? In my system there will be an FPGA which will have a system clock between 100 MHz to 150 MHz which I would like to use to generate the system clock for the ADC and DAC and one clock source is always better than 2.

Regards,

Mike Lacroix

  • 0
    TI__Guru**** 168605 points
    Hi Mike,

    The ADS1672 Master Clock is rated at 20MHz maximum, it's actually defined as tCLK on page 7 with a minimum period (1 / max frequency). While the ADS1672 will probably 'work' with a 24.576MHz clock, we would not be able to guarantee what sort of performance you would get from the device.
  • 0 in reply to Tom Hendrick
    Prodigy 80 points
    Thanks Tom. I agree that the ADS1672 would probably work at the higher frequency but I also get the issue TI not being able to guarantee the unit will function properly. I guess I will just have separate clocks for each device and the FPGA (bummer). Having said that, is there a reason why the ADC and DAC don't operated with the same system clock for the same sample rate (192 KHz in my case)?
    Regards,
    Mike
  • 0 in reply to mike lacroix
    TI__Guru**** 168605 points
    Hi Mike,

    The main reason I suppose is that the ADS1672 is not really marketed as an audio ADC. It's used primarily in vibration analysis and other industrial type applications. Is 192kHz critical for your application? You could always take a look at the ADS1675 instead, same basic part as the ADS1672, just with the ability to run a little faster - with up to a 32MHz master clock.