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ADS8584S: Data converters forum

Monica
Prodigy 60 points
Part Number: ADS8584S

HI,

I am using ADS8584 ADC in serial mode with a 16.5 MHz SCLK frequency in the sampling frequency of 100ksps. I am not able to get proper output for the continuous analog signal which is generated by a function generator.

And I am getting exact output while giving a constant DC line 1.2v from the battery.

Configuration setup:

Range: ±5-V

Input analog signal frequency: up to 20KHz

sampling rate: 100Ksps

ref selection: internal reference

OS[2:0] = 3'd0

PAR/SER/BYTE SEL = 1'd1

DB15/BYTE SEL = 1'd0

Thanks in advance!

  • +1
    TI__Mastermind 46360 points

    Hello Monica,

    The ADS8584 has an internal filter with a -3dB frequency of 16kHz.  If you input a sinewave of frequency 16kHz, the output will only be about 70% of the input amplitude.  At 20kHz, you will get quite a bit more attenuation of the signal.  Also, at 20kHz, you will only see 5 samples per period due to the 100ksps sample rate.  If you plot this waveform, it will look not look like a sinewave.

    Can you include a picture of the input waveform, and the resulting converted waveform?  If you input a sinewave at 1kHz frequency, then you should get an output sinewave with almost the exact same amplitude and shape.

    Regards,
    Keith Nicholas
    Precision ADC Applications