TLV320AIC3120: Common Mode setting in audio codec TLV320AIC3120

AMIT SHARMA2

Part Number: TLV320AIC3120

What should be CM setting in Audio codec TLV320AIC3120 if i am using MIC_LP pin for mic connection?What roll will feed forward resistance will play if i select 10K,20K or 40K?

over 8 years ago

0 Luis Fernando Rodriguez S. over 8 years ago

TI__Guru* 84915 points

Hi, Amit,

The input CM level is fixed at 1.35V. The resistors 10K, 20K and 40K only affects the PGA gain as mentioned in the datasheet:

www.ti.com/.../tlv320aic3120.pdf

So, even if the resistor is modified, the common-mode voltage will be always 1.35V (you may measure this value at the analog inputs). The PGA gain will be affected by the selected resistors.

Best regards,
Luis Fernando Rodríguez S.

0 AMIT SHARMA2 over 8 years ago in reply to Luis Fernando Rodriguez S.

Intellectual 470 points

thanks Luis for reply

What will happen if i will not connect unused(floating) mic input to CM internally. This is option available in TLV320AIC3120 by programming codec internal resistor.

Also there is option not to connect CM to MIC PGA . Is there ant application note for highlighting concept of CM?

regards

AMIT

0 Luis Fernando Rodriguez S. over 8 years ago in reply to AMIT SHARMA2

TI__Guru* 84915 points

Hi, Amit,

The unused (floating) mic inputs can be routed to the CM internally. This is recommended to reduce noise at the analog inputs. So, it is suggested to connect the unused analog inputs to a 0.47uF capacitor to GND. Additionally, the unused analog inputs can be routed to the CM internally for noise immunity.

Regarding the CM connection to MIC PGA, this connection is required when a single-ended input is used. The analog inputs require of a common-mode voltage in order to avoid a negative voltage at the analog inputs. Basically, this CM voltage would avoid any damage at the analog inputs due to negative level.

Best regards,
Luis Fernando Rodríguez S.

0 AMIT SHARMA2 over 8 years ago in reply to Luis Fernando Rodriguez S.

Intellectual 470 points

thanks

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TLV320AIC3120: Common Mode setting in audio codec TLV320AIC3120