TWL1103T-Q1: Wrong output

Hi Izik, 

This is a continuation of an existing thread, please continue the thread here and allow time for Codec expert to comment.

Thanks,

Yes this is the same issue as the existing thread, I just couldn't attach the slides in the original thread

Looking forward for your comments 

Thanks 

Have you tried enabling the PCM Loopback mode in register 01?

It looks like you are providing input from MIC1 and wanted to send output to EAR2.

Have you verified just the PCMO (TX path)? Once that's correct then you try the loopback or provide input to PCMI for the RX path.

We didn't try the loopback mode. Yes we are providing input from MIC1 and want to send output to EAR2.Is our registers configuration and schematic correct? 

We didn't test the TX path. Please explain what can be accomplished following your recommendations on loopback mode. 

What type of signal can we expect on the EAR2 output when we inject 1kHz sine wave to MIC1 input? 

TX is like an ADC, you send input from MIC and the output in digital on PCMO.

For RX (DAC) input from PCMI and output to EAR.

Your configuration enabling both paths, but do you provide data for the DAC on PCMI?

Loopback mode is to take PCMO and pass it back to DAC input so your EAR should produce the 1KHz tone from your MIC input.

Sorry but your comments are not clear. 

Our application is to send 1kHz analog sine wave to input MIC1 and to have digitized signal output on EAR2. Does our configuration valid for this purpose or do we need to enable loop back mode in order support our application? 

You configure the device to enable both the TX and RX and that's fine, but for EAR output (DAC/RX path) you need the digital input which is from PCMI pin.

Did you provide the digital data in your setup through PCMI? 

Now for TX or MIC path, the digitized output is sent out through PCMO. So if you provide 1KHz sine wave you should see on PCMO the digitized output, put a probe on PCMO and check the data.

I don't know what you intend to do with the PCMO data in your host system/setup, but the EAR has no output because there's no PCMI data.

Set the loopback mode and check your PCMO and PCMI on the scope and listen through EAR output.

We connected PCMO to PCMI and we got the attached at EAR20. 

Please advise if this is the correct signal shape when the input is 1kHz sin wave. Please also review our connections, as the input is single ended to mic1p

Thanks twl_cont.pptx

Now you have output on EAR20, so this confirmed you were not sending any data to PCMI.

The EAR output should be the tone you sent, sinewave 1KHz, did you connect externally or use the loopback register?

My suggestion, check your PCMO with audio analyzer based on the A-Law mode and see you see the 1KHz tone.

Hi, we don't have audio analyzer available. I suspect that the pcmo signal is distorted because of the connections of the TWL1103T. Can you please review our schematic? 

Did we use the correct termination for the unused MIC1N? 

Feedback on your schematic:

• MIC1 or MIC2 are differential inputs, refer to figure 7 of datasheet for typical connection, so connect it as differential.
• If MIC2 is not used place 0.47nF cap to gnd.
• Do you have typical load on EAR output say 32 ohm?

Regards.

I couldn't find the recommended value for Rmic. Could you please advise? 

We cannot provide differential input to MIC1. What would you recommend to do? 

MIC2 is not used. Should we connect it also to MBIAS via Rmic resistor? or just terminate with 0.47nF cap to gnd? 

I will advise tomorrow about the load value for EAR output. 

Thanks and regards

Ok if you can't provide differential, try the following:

• change R257 and R168 to 0 Ohm
• place a 1uF cap on the EAR20 output before connecting to the EAR20 load (32 Ohm)

I see on your scope capture of the EAR20 output, it has DC and that might distort the output.

Hi 

If you could also refer to recommended value for Rmic resistor

Is the 1uF cap on the EAR20 connected in series or shunt? 

It would be best if you can mark all the corrections on our drawing.

Thanks

I don't know your MIC, if you don't need the bias then you don't need Rmic.

1uF in series on EAR20.