DC Offset

RG16114

Other Parts Discussed in Thread: TLV320AIC3101, TLV320ADC3101

Greetings,

I have a design with TLV320AIC3101. Everything works great but I notice some DC offset in the signal. Is there a way to reduce or eliminate this DC offset.

BR and Thanks in Advance
Robert

over 15 years ago

0 VikasThawani over 15 years ago

TI__Expert 4205 points

Hi RG

Yes the DC offset can be removed by using the Programmable High pass filter for both the channels. Please refer to registers 12, 107 on page0 and Registers 65-76 on page1 of the datasheet of TLV320AIC3101 for more details.

0 RG16114 over 15 years ago in reply to VikasThawani

Prodigy 50 points

Hi Vikas,

Thank you for your quick answer.

However, I screwed up as I wrote incorrect part number. I am using TLV320ADC3101 and NOT the codec version of this part. The ADC version does not have those registers you mentioned. As I out of luck with DC offset issue in ADC part?

Best regards
Robert

0 VikasThawani over 15 years ago in reply to RG16114

TI__Expert 4205 points

Hi RG

There is a first order IIR filter available to remove the dc component of the signal efficiently. Refer to page 36-37 of the datasheet of TLV320ADC3101 for details. The registers used to configure the coefficients are available in Page4 Reg8-13 and Reg 72-77.

0 RG16114 over 15 years ago in reply to VikasThawani

Prodigy 50 points

Thanks Vikas,

Now I have to figure out the coefficients. Any pointers for calculating co-efficients.

Regards
Robert

0 VikasThawani over 15 years ago in reply to RG16114

TI__Expert 4205 points

Hi RG,

For calculating coefficients for IIR filter, you need to know which prototype of filter is being used like Butterworth, Chebyshev. Then you need to take the analog prototype of that filter and apply Bilinear transformation, convert it to digital filter with the known parameters of Cut-off frequency, gain, sampling frequency etc. Compare it with the IIR filter transfer function in datasheet and calculate the coefficients.

0 J- over 15 years ago in reply to VikasThawani

TI__Mastermind 46195 points

RG,

You can also use the biquad calculator http://focus.ti.com/docs/toolsw/folders/print/coefficient-calc.html or the control software http://www.ti.com/litv/zip/slac248.

With the tools above, you can use the biquad sections, or with a slight modification, you could convert the coefficients for the half-biquad section (i.e. first order filter). Refer to the datasheet for the transfer functions of both structures.

Regards,

J-

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DC Offset