Dear Sir/Mdm,
I'm working on this system with capacitive coupled inputs to IN1R and IN1L. 0.1uF caps are used. These ic inputs are then routed to MICPGA.
When I attach the external audio input device before powering up my system(includes AIC3206), the audio path works fine.
However if I power up my system and then connect the external audio input device, the audio path does not go thru and I heard a 'rushing'(wideband?) noise in the path.
The audio path does not recover on its own.
The following are my findings thus far:
1. Setting Page 0 Register 0x51 to 0x00 and then to 0xC0 will recover the audio path. My objective is to power on-off the ADC.
2. With my system powered up, setting Page 1 Register 0x39 to 0x00 and 0x37 to 0x00 to disconnect ic inputs from the MICPGA inputs. Connect the external audio device followed by setting Register 0x39 to 0x10 and 0x37 to 0x40 respective to connect the ic inputs to MICPGA will also be ok, the audio path will be ok. My objective was to further confirm that issue was highly connected to these input pins.
3. While checking Page 0 Register 42 0x2A ADC Saturation Sticky Flag, before and after connecting the external audio device, I find that flag shows that ADC Overflow after the external audio connector is applied.
4. the external audio device is a microphone, when the symptom arise, if blow hard into the microphone(loud noise into microphone), the audio path will also recover.
While I have been successful in resolving this issue by reducing the ground difference between External Audio Device and the AIC3206, I would like to understand more from the CODEC IC perspective.
Q. Is it possible ADC Overflow will result in the symptom described? If yes, is it possible that CODEC IC settings can either provide increased immunity against such input levels OR even mask the effect of the ADC Overflow Status?
Thanks n rgds, setoh.
