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PCM1860-Q1: DOUT waveform

user6517935
Prodigy 70 points
Part Number: PCM1860-Q1
Other Parts Discussed in Thread: PCM1860

Hello team,

We checked the operation of PCM1860, referring to the test circuit (page25) described in the specifications. The constants of peripheral parts are the same as the test circuit.

The conditions are as follows;

MD6, MD5, MD2 : 0 1 1 (SE Ch4 with 0dB)

MD1, MD0 : 0 0 (Slave mode)

MD3 : 0 (FIR decimation filter)

MD4 : 0 (I2S)

INT : Terminate to GND at 10kΩ

Analog input signal : silence (terminate to GND at 10uF)

We observed a waveform in which the DOUT waveform is 1 from 1-bit to 17 bit.　

DOUT some fluctuations, but it is about like this waveform.

What is this happening?

I think that if the input waveform is silence, all bit be 0.

Best regards,

Makoto

  • 0
    Prodigy 70 points

    I'm sorry, it seems that the image was not attached well. Reattach.

  • 0 in reply to user6517935
    TI__Mastermind 23050 points

    Hi Makoto,

    The output of the converter is in 2's complement, so small negative values consist primarily of ones and small positive values primarily of 0s. With the input shorted the device will output noise in line with the noise floor of the device. If you observe over a longer period of time I believe you will see that sometimes the output data is primarily 0s and sometimes it is primarily 1's as the noise drives the output between slightly negative and slightly positive values.

    Best,

    Zak