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PCM1792A: PCM1792A reset operation

Mark Willerton
Prodigy 140 points
Part Number: PCM1792A

Hello

I am working on a DAC project using the PCM1792A. It is a project that passes the time during the dark winter months here in Scandinavia! The setup uses a PIC MCU to control things like volume etc. based on input data.

One thing that concerns me is that if the MCU should fail or simply not start up, the DAC will be left unconfigured which means no attenuation. This would mean full volume through the audio channel. When looking at this last year, I used a GPIO from the MCU (with resistor to pull down) and connected this to the /RST pin on the DAC. This only releases when the MCU software is happy that all is in order. That way, the audio is blocked in the following two cases (just as I want):

- no MCU startup following POR

- MCU resets during operation

So far so good. The point is that I cannot really see from the datasheet is pulling the /RST pin low - either after POR or on the fly - should have this effect. Was it just luck or is the /RST pin designed to inhibit DAC operation as per my observation. Maybe I'm blind but again, I cannot see this from the datasheet.

Appreciate any confirmation.

Thanks
Mark

  • 0
    TI__Guru 52683 points

    Hi Mark,

    In this case, the /RST will prevent the output from sourcing any current, and it will keep the configuration registers in their default state (or really the rising edge of /RST will allow the registers to be initialized).

    I think your startup/reset plan is reasonable and should accomplish what you want.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 140 points

    Hi Paul

    Yes, that is exactly in line with my observation and is exactly what I needed to happen in the DAC (so that I can safely mute the audio output). 

    If it is not in there, it could be a good thing to have in the datasheet in a future revision.

    Thanks

    Mark