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ADS124S06: ADS124S06 LL Filter Freq Response vs. internal oscillator deviation across temperature

Masa Katayama
Intellectual 970 points
Part Number: ADS124S06

Dear Sir,

May I ask if Filter Response will mainly get impact from internal oscillator temperate deviation?

I am estimating filter response using ADS1x4S0x Caluculator.xls.

My idea is; 

I get Filter frequency response of Low-Latency Filter with 16.6SPS for example:

I understand that 50Hz notch is centered when fCLK=4.0960MHz.

I am keen to the internal oscillator will move the filter response, then

I refer to the following internal oscillator spec

and read min and max values of 28 samples in Figure 25.

then below is summary;

The accuracy of +/-1.5% will rigidly cover across PVT.

Now I get filter response by changing max deviation of fCLK to 4.157MHz as follows;

 It is till -29.09dB attenuation for 50Hz line cycle.

If there is another factor to consider which will impact the filter frequency response, please let me know. 

Best regards,

Masa

  • 0
    TI__Guru** 112765 points

    Hi Masa,

    The filter response is directly proportional to the clock frequency (fclk) of the device, the filter mode selected and the data rate used. The maximum (or worst case) range of the internal oscillator is specified in the table in section 7.5 as +/- 1.5%. No device will exceed this range for the internal oscillator over all operating temperatures. Figure 25 shows the typical response from device characterization of 28 units. The graph is shown to help you determine if the internal oscillator will stay accurate enough to be used within the operating range of the system. It may not be necessary to use the worst case numbers as the oscillator response shifts the greatest at the lowest and highest operating temperatures.

    From the calculator using the worst case value of the internal oscillator + 1.5%, there will still be a minimum attenuation of -29.09 dB at 50 Hz. If higher accuracy is required, an external clock of greater precision can be used and provided at the CLK pin of the ADS124S06.

    Best regards,
    Bob B

  • 0 in reply to Bob Benjamin
    Intellectual 970 points
    Hi Bob,
    Thank you very for your clarification.
    Masa