TLV320AIC3204: Volume become smaller as single end input change to differential input

Hi, Daniel,

If the input is changed from Single-ended to differential mode and same input signals are provided, there is an expected reduction on the amplitude of the read signal assuming the settings are correct. Can you please provide more details of the input signals provided to IN2L and IN2R in both single-ended and differential mode?. Also, having the register configuration would help to identify a problem with the input routing. From the schematic, IN2L and IN2R appear to be provided from a Stereo source, is this right?. How is the input signal architecture adjusted for differential mode?.

Best Regards,

  -Diego Meléndez López
   Audio Applications Engineer

Dear Diego,

Thanks for your help.

Correct my input signal description. Our input source is a pure analog L/R RCA (P19) or stereo (P18), not a differential signal.

When we input L or R only, the sound is very loud. But as we input L+R, the volume becomes small.

Attached the schematic. Please kindly help.

Also, How to set register to choose ADC to DAC directly route, and don't route through 0~-30dB mixer(MAL/MAR)? (as below picture)

Is the setting "IN2R/L input is weakly driven to common mode" and "IN2R/L is not routed to any MICPGA"?

Thanks

Hi, Daniel,

Thanks for the clarification. This issue seems strange, in general, there should be changes on the amplitude of the output signal regardless the mix, assuming the same levels are provided. Do you make any change on the register configuration when mixing L+R?. What is the process to make the mix on system-level and codec-level?. Have you verified that the input signal amplitude is constant during both test cases?.

In order to directly connect ADC and DAC, you need to enable the audio loopback (Page 0, Register 29, Bit D4). Please keep in mind that doing this will disconnect the ADC/DAC from the digital audio interface. Settings you mention are used for different purposes.

Best Regards,

  -Diego Meléndez López
   Audio Applications Engineer

Dear Diago,

Thanks for your help.

As you can see our schematic, we only use only HPL for speaker out；LOR/LOL for headphone out. And IN2L/IN2R analog in.

Question1:

Page1 0x34 write  0x10---no SPK out

Page1 0x36 also write  0x10---then SPK out

But we can get HP out if only route IN2R or IN2L to Right MICPGA or Left MICPGA.

Page1 0x34 write  0x10---HP out

Page1 0x36 write  0x10---HP out

Page1 0x37 write  0x10 or 0x01---HP out

Question2:

When mute in the beginning, then unmute, the sound would become very small.

We need to re-write Page1 0x17 and 0x18 to get back the normal volume.

We dump the register log, please kindly help to give us some suggestion to fix these two questions.

Thanks

3204 register.TXT

Hi, Daniel,

From the information you shared, it seems the issue could be related to the routing of the input pins to the PGA. You are connecting IN2L and IN2R to the same PGA (left), which is correct when providing an input in differential mode, but for a Stereo single-ended application (as yours)  this is not correct. You need to route left input to the positive terminal of the PGA, while connecting the negative terminal to the common mode. Same applies for right channel. Can you please try this?. Connecting a stereo pair in differential mode would affect the signal quality and also, may cause a reduction on the amplitude because of the differentiation of the signals. 

Best Regards,

  -Diego Meléndez López
   Audio Applications Engineer