AIC26 Low pass filter

ronnym

I am using the AIC26 for an audio app. I am using the left and right high power outputs in a capacitorless bridge mode. It works fine with no spectral shaping using the example in the data sheet.

I have attempted to use the Biquad filter calculator to create a Butterworth 1st order low pass filter at 3.6KHz. I put the calculated numbers into the associated registers, but get no output. Am I writing the wrong registers, or wrong numbers? The filter is activated, and I even tried inverting the right channel numbers.

Any help would be greatly appreciated.

over 8 years ago

0 Dominik Hartl11 over 8 years ago

TI__Guru 51346 points

Please provide the BQ values in hexadecimal and the register write sequence.

0 ronnym over 8 years ago in reply to Dominik Hartl11

Expert 1835 points

TIBQ filter app;

Butterworth 1 Fc 3628

Gain 0.0

Text Filter

Left channel:

N0 0x6F95

N1 0x6F95

D1 0xA0D5

All other filter registers 0x00

On right channel, N0 and N1 are the negative of the left per AIC26 text.

Thanks.

0 Dominik Hartl11 over 8 years ago in reply to ronnym

TI__Guru 51346 points

You can't set all other to zero because if you set N3, N4 and N5 to zero, the transfer function will be zero (see page 23, product of the two biquads with the N3,N4,N5,D4,D5 BQ2 being zero). If you only want to use one biquad, set N3 = 32767 and the rest of the BQ2 coefficients to zero.

0 ronnym over 8 years ago

Expert 1835 points

Thank you. Hopefully, that's what I needed.

0 ronnym over 8 years ago in reply to ronnym

Expert 1835 points

I plugged in those values, and got a screaming white noise. Not a low pass filter effect at all... Some subtle nuance escapes me.
The filter software said set N0, N1, and D1. I tried setting N3 to 32767. Still no luck.

0 Dominik Hartl11 over 8 years ago

TI__Guru 51346 points

Please attach the complete register write sequence.

Audio

Audio forum

AIC26 Low pass filter