ADAU1373BCBZ-R7 datasheet(64/296 Pages) AD

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ADAU1373

Rev. 0 | Page 64 of 296

Worked Examples

The following examples illustrate how to calculate the coefficients

for the desired peak and low-pass/high-pass shelving filter.

Low-Pass Shelving Filter

If Band 6 is intended to operate as a low-pass shelving filter and

the cutoff frequency of the filter is 80 Hz, peak gain is 6 dB, and

input signal sampling frequency is 48 kHz, the coefficients are

as follows:

)

(

= 1.995262314968880

)

48000

cos(

))

48000

sin(

(

−

= 0.989582475318754

)

(

)

(

−

= 1.005184084865251

)

(

)

(

−

= −0.984398390453503

p2 = 0

d1 = α = 0.989582475318754

d2 = 0

Transfer the coefficients to integer numbers:

p0 = round(1.005184084865251 × 8192) = 8234

p1 = round(−0.984398390453503 × 8192) = −8064

p2 = 0

d1 = round(0.989582475318754 × 8192) = 8107

d2 = 0

Represent the integer coefficients by 16-bit, twos

complement hexadecimal values:

p0 = 16-bit 0x202A

p1 = 16-bit 0xE080

p2 = 16-bit 0x0000

d1 = 16-bit 0x1FAB

d2 = 16-bit 0x0000

Therefore, the registers representing EQ1 coefficients

should be set as follows:

EQ6 COEF0M = 8’0x20, EQ6 COEF0L = 8’0x2A;

EQ6 COEF1M = 8’0xE0, EQ6 COEF1L = 8’0x80;

EQ6 COEF2M = 8’0x1F, EQ6 COEF2L = 8’0xAB

Peak Filter

If Band 1 is intended to operate as a peak filter with a filter center

frequency of 240 Hz, the bandwidth is 120 Hz, peak gain is 6 dB,

and the input signal sampling frequency is 48KHz, then the

coefficients are as follows:

)

(

= 1.995262314968880

)

4800

120

cos(

))

48000

120

sin(

(

−

= 0.984414127416097

)

48000

240

cos(

= 0.999506560365732

)

(

)

(

−

= 1.007756015814333

p1 = −(1 + α) × β = −1.983434938834828

p2 =

)

(

)

(

−

= 0.976658111601764

d1 = (1 + α) × β = 1.983434938834828

d2 = − α = −0.984414127416097

Transfer the coefficients to integer numbers:

p0 = round(1.007756015814333 × 8192) = 8256

p1 = round(−1.983434938834828 × 8192) = −16248

p2 = round(0.976658111601764 × 8192) = 8000

d1 = round(1.983434938834828 × 8192) = 16248

d2 = round(−0.984414127416097 × 8192) = −8064

Represent the integer coefficients by 16-bit, twos

complement hexadecimal values:

p0 = 16-bit 0x2040

p1 = 16-bit 0x1F40

p2 = 16-bit 0x1F41

d1 = 16-bit 0x3F78

d2 = 16-bit 0xE080

Therefore, the registers representing EQ1 coefficients

should be set as follows:

EQ1 COEF0M = 8’0x20, EQ1 COEF0L = 8’0x40;

EQ1 COEF1M = 8’0x1F, EQ1 COEF1L = 8’0x40;

EQ1 COEF2M = 8’0x1F, EQ1 COEF2L = 8’0x41;

EQ1 COEF3M = 8’0x3F, EQ1 COEF3L = 8’0x78;

EQ1 COEF4M = 8’0xE0, EQ1 COEF4L = 8’0x80

ADAU1373BCBZ-R7 Datasheet(PDF) 64 Page - Analog Devices

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