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PCM1792a and OPA1632 together

Alexei Petrov
Prodigy 30 points
Other Parts Discussed in Thread: PCM1792A, OPA1632, NE5534

Hello.

I have some questions on application PCM1792a.

1. How much precisely it is necessary to withstand ground potential on the current outputs of a DAC PCM1792a (Iout pins)? If the potential changes in small limits - for example, from-0.1 volt to +0.6 volt, whether to degradation DAC parameters (TDH, linearity)? This question is connected by that in I/U circuit operational amplifier OPA1632 application is planned. How it fully differential it is necessary to support zero potential on the current outputs (Iout pins) by means of submission of a current of offset from an external voltage source through resistors.

2. Influence of an input current of the operational amplifier in I/U circuit DAC parameters is how much strong?

3. How much strongly influence performance of a digital-to-analog coder presence of condensers on the current outputs? I want to apply condensers to simplification of operation of input cascades of I/U and lowering of noises of switching of a DAC. The condenser nominal will be is in limits 4000-10000 pF between outputs Iout- and Iout+, and also 1000 pF between these outputs and the common wire.

4. Application in the i/U operational amplifier OPA1632 will provide performance of a PCM1792a?

5. Whether has sense to do separate power supply circuits for outputs Vcc2L, Vcc2R, Vcc1? I have a theory that a partite supply modulator stages will lower noises on an output.

Best regards,

Alexei

  • 0 in reply to Don Dapkus
    Prodigy 30 points

    Hello Don!

    Thanks for your recommendation.

    In the recommended document the circuit as in datasheet is used. I don't doubt objectivity of such decision and in its optimal cost. There are some arguments against usage op NE5534.

    1. In the market it is a lot of fakes and bad quality clones of this chip. It is almost impossible to find the original.

    2. There is a generated subjective judgement of community of fans of music - this op badly approaches for high-class equipment. In other words, he doesn't allow to implement all potential excellent DAC PCM1792a, according to huge number of people.

    For commercial project success I should consider subjective judgement of community.
    Therefore on my question the answer isn't received yet.

    I have developed the servo-amplifier circuit дла ground potential maintainings on outputs DAC. But from for short precision of resistors and as bias voltage the servo amplifier, there will be a small difference in potentials - about 10 millivolt. The absolute error of setting of ground potential will make +-50... 70 millivolt. Whether such error of degradation of productivity DAC will lead?
    There was one more question. How parameters of the filter after I/U the transformer are selected? Why in datasheet different values Passband Frequency for different applications are resulted? In other words - what least frequency of the Delta-Sigma modulator? What order (2 or 3) and type (Bessel, Butterworth, Phase Linear) the filter to select?

    Best regards,
    Alexei Perov.