AK4951AEN Datasheet, PDF(47/105 Page) Asahi Kasei Microsystems

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

AK4951AEN Datasheet, PDF (47/105 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/HP/SPK-AMP

◁

[AK4951A]

(5) 4-band Equalizer & 1-band Equalizer after ALC

This block can be used as equalizer or Notch Filter. 4-band equalizers (EQ2~EQ5) are switched ON/OFF

independently by EQ2, EQ3, EQ4 and EQ5 bits. EQ1 bit controls ON/OFF switching of the equalizer after

ALC (EQ1). When the equalizer is OFF, the audio data passes this block by 0dB gain. E1A15-0 bits,

E1B15-0 bits and E1C15-0 bits set the coefficient of EQ1. E2A15-0 bits, E2B15-0 bits and E2C15-0 bits

set the coefficient of EQ2. E3A15-0 bits, E3B15-0 bits and E3C15-0 bits set the coefficient of EQ3.

E4A15-0 bits, E4B15-0 bits and E4C15-0 bits set the coefficient of EQ4. E5A15-0 bits, E5B15-0 bits and

E5C15-0 bits set the coefficient of EQ5. The EQn (n=1, 2, 3, 4 or 5) coefficient must be set when EQn bit

= â0â or PMPFIL bit = â0â. EQn starts operation 4/fs(max) after when EQn = PMPFIL bit = â1â is set.

Each EQ2 ~ 5 blocks have a gain controller (EQ2G ~ EQ5G) independently after the equalizer. EQnG5-0

bits (n = 2~5) setting is reflected by writing â1â to EQCn bit (n = 2~5). EQnG5-0 bits and EQCn bit (n=2~5)

can be set during operation (EQn =PMPFIL bit= â1â).

fs: Sampling Frequency

fo1 ~ fo5: Center Frequency

fb1 ~ fb5: Band width where the gain is 3dB different from the center frequency

K1 ~ K5: Gain (ï1 ï£ Kn < 3)

EQ1: E1A[15:0] bits =A1, E1B[15:0] bits =B1, E1C[15:0] bits =C1

EQ2: E2A[15:0] bits =A2, E2B[15:0] bits =B2, E2C[15:0] bits =C2

EQ3: E3A[15:0] bits =A3, E3B[15:0] bits =B3, E3C[15:0] bits =C3

EQ4: E4A[15:0] bits =A4, E4B[15:0] bits =B4, E4C[15:0] bits =C4

EQ5: E5A[15:0] bits =A5, E5B[15:0] bits =B5, E5C[15:0] bits =C5

(MSB=E1A15, E1B15, E1C15, E2A15, E2B15, E2C15, E3A15, E3B15, E3C15, E4A15, E4B15,

E4C15, E5A15, E5B15, E5C15 ; LSB= E1A0, E1B0, E1C0, E2A0, E2B0, E2C0, E3A0, E3B0,

E3C0, E4A0, E4B0, E4C0, E5A0, E5B0, E5C0)

An = Kn x

tan (ï°fbn/fs)

1 + tan (ï°fbn/fs)

, Bn = cos(2ï° fon/fs) x

, Cn =

1 + tan (ï°fbn/fs)

1 ï tan (ï°fbn/fs)

1 + tan (ï°fbn/fs)

(n = 1, 2, 3, 4, 5)

Transfer Function

H(z) = {1 + G2 x h2(z) + G3 x h3(z) + G4 x h4(z) + G5 x h5(z)} x {1+ h1(z) }

(G2, 3, 4, 5 = 1 or G)

hn (z) = An

1 ï z ï2

1ï Bnz ï1ï Cnz ï2

(n = 1, 2, 3, 4, 5)

The center frequency must be set as below.

0.003 < fon / fs < 0.497

When gain of K is set to âï1â, this equalizer becomes a notch filter. When EQ2 ï¾EQ5 is used as a notch

filter, central frequency of a real notch filter deviates from the above-mentioned calculation, if its central

frequency of each band is near. The control soft that is attached to the evaluation board has functions

that revises a gap of frequency and calculates the coefficient. When its central frequency of each band

is near, the central frequency should be revised and confirm the frequency response.

016001936-E-00

- 47 -

2016/03

▷