LIMIT ON ADAU1701
Hello!
"Hello everyone. I have a question about limiting on the ADAU1701. I'm working with an input board on an active speaker. I’ve tried feeding it the highest signal I have — a 1kHz sine wave at 3Vrms (through the XLR input of the board).
This ADAU1701 board is using opamps for both input and output. I measured the waveforms at the output (after going through the ADAU1701 and the opamps), and they look like in the image below:
Yellow = ADC1
Pink = ADC0
Sine output (DAC==> OPAMP).
How is this possible? When I try to replicate it in SigmaStudio myself, the signal gets clipped..."
Audio Signal Processors
software
sigmastudio
SigmaDSP Audio Processors
AUTO LIMIT
adau1701
SigmaStudio v4.7
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Hello dangquangtin,
First, I suggest you use an internal oscillator as a signal source because it has a known level and use that to validate the output. You are running the output differential so that is a little more tricky. The DAC output is a voltage that is centered on the common mode voltage. Now you are getting the difference but I noticed a feedback path from the output of the OpAmp and the next stage goes to ground and there is no coupling cap until afterwards.
Also, I think you have a gain of almost 4x on the diff amp?
The inputs for the ADC is a current input not a voltage input. What you are doing is way wrong and you made no mention of what value the ADC_RES is? This is the resistor that sets the current for full scale. This is detailed in the datasheet.
I suggest you have a look at our eval board for some hints.
Dave T
Hello DaveThib,
Thank you for your response. I'd like to add that this is not my design — it's from an audio company, and it has been working very well for many years. For the ADC_RES, I'm using an 18K resistor.
DQ.TIN
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