i want to power down the dac of adau1701 in self-boot mode when no signal input it and turn it off while signal input. but i have some quest to implemnet it
could you tell me how to implement it ?
You can't turn the DAC on or off without writing directly to a register, so in self-boot mode (with no microcontroller connected), this will not be possible. You could, however, use some kind of noise gate or signal detector to make sure the output is muted when no input signal is present. This will guarantee that no signal is output, but it will not save much power overall.
Noise gate example: http://ez.analog.com/message/7651#7651
Signal detector example: http://ez.analog.com/message/7669#7669
(You can use the logic signal to control other blocks, like a mute block, for example)
thanks for your response. Mute output is not useful for noise of dac. I want to decrease the noise of dac when no
signal input. I think it is a good ideal to let dac go into power down mode, but I can't find a way to implement it .
the adua1701 is not only work in self-boot mode.it maybe run othe modes(eg. connect whit a mcu)
could you give me some other suggestions?
The sigmadsp DACs seem to be very silent.
Can you check the input source? May be the noise is travelling all the way...
Just unplug the input pin and see if the noise disappears.
What is your source anyway?
It's certainly possible to use an MCU in the system to control the ADAU1701. You could have a flag on a GPIO from the ADAU1701 that signals when a signal is absent from the inputs, and the MCU could poll that pin and then mute the DACs via register write when required. However, a software mute should be sufficient. The noise level on the DAC outputs when the input is software-muted should be something like -104 dB referenced to the full scale output level, which results in less than 100 μV (peak) of noise.
the noise of adau1701 is about 100 μV (peak), if i designe a product use it,let the noise signal amplifier 34dB( gain=50) to driver speaker, which results in less than 5mV(peak) of noise from the speaker.the noise is so much and my boss is not interesting,could you give me any way to decrease the noise.
Even if you power down the DAC, there will still be residual thermal noise on the PCB due to environmental factors, and with 34 dB of gain, I bet there would still be a fair bit of noise on the speaker. Therefore, I would recommend another approach: mute the amplifier when there is no input signal detected on the ADAU1701.
Does the amplifier have some kind of mute pin or power-down pin? Perhaps you could use the signal detector in the SigmaDSP to drive a GPIO to the amplifier, so it would mute the amplifier when the input signal is not active.
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