TLV320AIC3104-Q1: Output is clipping when LOP/M output-control set >= 6dB

Anthony Armbruster

Part Number: TLV320AIC3104-Q1
Other Parts Discussed in Thread: TLV320AIC3104

I have setup the audio codec as described within 'TLV320AIC3104 Programming Made Easy', and the differential outputs clip when LOP/M output-control set >= 6dB. For our power, AVDD, DRVDD, and IOVDD are powered by 3.3V, and DVDD is powered by 1.8V. We are using the following register settings, which primarily follow 'TLV320AIC3104 Programming Made Easy'.

// I2S, 16bit

{static_cast<Reg>(0x09),0x00},

// Route Left data to Left DAC, Route Right data to Right DAC

{static_cast<Reg>(0x07),0x0A},

// Power up Left and Right DAC’s

{static_cast<Reg>(0x25),0xC0},

// Unmute digital volume controls, set gain to 0 dB

{static_cast<Reg>(0x2B),0x00},

{static_cast<Reg>(0x2C),0x00},

// Route DAC outputs to line out and associated gain

{static_cast<Reg>(0x52),0x80},

{static_cast<Reg>(0x5C),0x80},

// Power up line out ± (differential), set gain +9dB

{static_cast<Reg>(0x56),0x99}, //or 0x09 for 0dB

{static_cast<Reg>(0x5D),0x99}, //or 0x09 for 0dB

// Sample rate 16k

{static_cast<Reg>(0x02),0x44},

Why, with standard settings, are the outputs clipped when the amplifier is set >= 6dB?
Also, when set to 0dB, I only get 3.7V peak-peak, and I believe that this should be closer to 4.0V per the data sheet. Why would that be?

I have attached screenshots of both 0dB and 9dB.

over 1 year ago

0 pdjuandi over 1 year ago

TI__Mastermind 29745 points

Hi,

With 6dB or higher i.e. +9dB your output is exceeding the FS 4Vpp so you are seeing the clipped signal.

On 0dB gain setting, are you sending 0 dBFS and what load condition?

Regards.

0 Anthony Armbruster over 1 year ago in reply to pdjuandi

Prodigy 10 points

I am sending a full scaled sine wave over I2S, so I believe that this is considered 0 dBFS.
The outputs are the differential line-out pairs, which are high impedance. I have tried with no load, and also connecting it to a class-d amp, and in both cases the output signal was the same.

Does this mean that the amplifier gain is not intended to be used for signals that are full scale? You stated that I am "exceeding the FS 4Vpp so you are seeing the clipped signal", where/how is that documented?