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TAD5142: Output signal levels that are meaningful.

Mark Allie64173
Prodigy 100 points
Part Number: TAD5142

Tool/software:

In the data sheet for this part the output is specified as 2VRMS without specifying the waveform. As most of you know this is a useless specification. I'm pretty sure this codec could not output 2VRMS of a typical music signal. How about giving a min and max output signal level from each of the output pins. The we can determine for ourselves what the single ended or differential outputs would be before clipping occurred. We would also be able to determine what VRMS one could get out of the device if that is of any interest to people. TI seems to love this RMS spec. It really needs to be accompanied by the specs on the waveform being put out as well as loading on the output pin.

So can you tell me what the min and max output levels are on: OUT1P, OUT1M, OUT2P and OUT2M with respect to the power supply voltage and load on these pins.

Mark Allie

  • 0
    TI__Genius 12965 points

    Hi Mark,

    The device is rated to 2Vrms out of the DAC with a full scale 1kHz input signal and measured differentially, as shown in section 5.5 of the datasheet. From this, we can calculate that the max voltage out (Vpeak) is Vrms * sqrt(2) = 2.828V, or ~5.657Vpp. This corresponds to a full scale digital signal - 0dBFS. So, if your music signal contains a peak value of the digital maximum, the output will be 2.828V relative to the signal's midpoint. This is with AVDD of 3.3V and line out load in differential configuration. Measuring the single ended output will divide all these values by 2. 

    Best,
    Mir