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Tetus

Pop noise on analog output

Question

Hi,

When start and stop Analog Discovery 2, a pop noise on analog output.
It will appear few ms from FDwfDeviceOpen or FDwfDeviceClose function call.
Since the noise voltage is + 3/-1.5V, it will exceed 1Vpp of the maximum absolute rating of the connected instrument.
How can I reduce pop noise?

Thanks,

 

Popnoise.png

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Hello,

This noise is caused by DAC startup, output buffer positive and negative supply asymmetric charge/discharge.

Use external divider or buffer circuit to reduce or remove this noise.

Edited by attila

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Hi Tetus,

I have a similar issue with this 'pop' damaging external circuitry. One solution is to use an opamp or buffer with a positive enable pin in between the AnalogDiscovery and your other components. You can then use the digital IO on the AnalogDiscovery to enable the opamp after this 'pop' has occurred. You can also disable the opamp before turning off the analog channels. However, this same pop occurs when the USB cable is disconnected from the AnalogDiscovery, so you will have to ensure that this cannot happen. 

 

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Hello,

I tried several mute circuits.
Since analog discovery internal power supply is disabled at start-up, it requires an external for op-amp.
The relay circuit may be simpler.

mute.png

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