TLV320AIC10

Did you add a low-pass filter between the output of the AIC10 and the amps? The AIC10 will produce out of band noise (because it is a delta-sigma DAC) which must be filtered with a simple RC low-pass cutting off frequencies above Fs/2

AIC10 already has a low pass filter after sigma delta DAC. Still I need to connect a LP filter externally to the output pins before feeding the signal to pre-amplifier?

If you get noise like you described and it's out of the frequency band that you are interested in, please add a LP filter.

Ok, Fs in my design is 8KHz. So the cutoff frequency becomes 4KHz. Is a LP filter with R = 47KOhm and C = 1 nF OK?

47k and 1nF give you an fc = 3386Hz, which is a bit low. I'd try a 3.9k and 10nF combination (fc = 4080Hz).

Hi,

Tried the low pass experiment. NO improvement. The hissing noise is still existing. I need to mention here that, there are clicks and pops heard when ever call is initiated or dropped. The codec is free running once it is brought out of reset and configured. I mean to say that I am resetting the AMBE2000 vocoder for every call initiation and drop, but NOT the TLV320AIC10 codec.

Please give me a solution for atleast the clicks and pops heard.

Expecting reply asap.

Thanks & Regards,

Srikanth.

Hi,

I am still Trying to improve voice quality in my design. I have also tried the digital loop back options in TLV320AIC10. The following are the experiments i have done -

1. TLV320AIC10 in digital loop back with ADC channel disabled. (i,e Cntrl Reg3 = 0x0683)
   • My observation: Slight, motor booting kind of noise at the speaker driven by OUTP of AIC. Also a hissing sound is heard.
2. TLV320AIC10 in digital loop back with DAC channel disabled. (i.e Cntrl Reg3 = 0x0685)
   • Mt observation: Hissing noise reduced but motor booting sound is heard predominantly. The motor booting noise changing when there's data on DIN....!!!???

I suspect that, there's some thing to do with digital noise which is making its way into the coding and decoding process of AIC.

How to address this issue. What are the cares need to be taken to handle digital noise while using TLV320AIC10.

Please some one help me out.

Thanks & Regards,

Srikanth.

If you use the proper low pass filter on the output and your power supplies are clean (also make sure that the ground return path has as low impedance as possible), the part will not produce audible noise.

I would focus on your power supplies.

Hi Hartl,

Hope you had a look at the description of experiments I had done. I am still waiting to improve the voice quality in our design. Please help me out with this. We have used PCM 3500 earlier, it worked fine; voice quality was good. We are trying TLV320AIC10 for the first time. We are stuck at this voice quality issue.

We are seriously running out of time. Please help us out. 

Expecting a speedy reply.

Thanks & Regards,

Srikanth.

Were you able to check the power supplies?

Hi Hartl,

Ya i checked the power supplies. Did not find any problem. we are using LM2575 along with MIC39100 for 5V and 3.3 V supplies. 

I have debugged the issue and found that, when I replace audio amplifier LM4951 (connected to TLV320AIC10's audio output pins)  with LM386 the background noise and the motor boating noise is NOT found. The motor boating noise is found when LM4951 is coming into picture. The following is the configuration of LM4951:

Ci = 0.1uF, Ri = 20KOhm,  Rf = 43 KOhm, Rc  = 1KOhm, CBypass = 1 uF, Shutdown pin is pulled up to 5V with 10 Ohm resistor.

Note: I have tested LM4951 individually with out connecting AIC. The above mentioned noises were NOT there. Its the combination of AIC and LM4951 thats creating the noises. Can you please suggest me where Iam going wrong.

Thanks & Regards,

Srikanth.