DA7217 Datasheet, PDF(46/171 Page) Dialog Semiconductor

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DA7217 Datasheet, PDF (46/171 Pages) Dialog Semiconductor – Ultra-Low Power Stereo Codec

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DA7217

Ultra-Low Power Stereo Codec

x[n]

Z-1

y[n]

Z-1

KEY

z-1 = Delay of one unit (input to output)

an = Feed-forward coefficients (range +2 to -2)

bn = Feedback coefficients (range +2 to -2)

Figure 21: Single Biquad Filter Stage

Each of the five biquad stages has five 16-bit coefficients a0, a1, a2, b1 and b2 as shown in

Figure 21. For the five stages the coefficients are numbered a00, a01 and so on as shown in Figure

22.

The filter sections are implemented using a direct form one architecture which implements the

transfer function shown in Figure 21:

H (z)

ï½

ï« a1zï1

ï« a2 zï2 ï« a3z ï 3 ï«

1ï b1zï1 ï b2 zï2

a4z

ï4

x[n]

a00

Z-1

a01

Z-1

a02

a10

Z-1

b01

a11

Z-1

b02

a12

a20

Z-1

b11

a21

Z-1

b12

a22

a30

Z-1

b21

a31

Z-1

b22

a32

a40

Z-1

b31

a41

Z-1

b32

a42

y[n]

Z-1

b41

Z-1

b42

Figure 22: Cascade of Five Biquad Filter Stages

The biquad filters in both left and right channels share the same set of coefficients.

Each of the coefficients is stored using two 8-bit registers in a dedicated address space. All of the

coefficients are programmed by first writing the coefficient data value to

OUT_1_BIQ_5STAGE_DATA and then the coefficient address to OUT_1_BIQ_5STAGE_ADDR. The

address location for each of the coefficients is described in Table 38.

Each of the 16-bit coefficients are twoâs complement values that can be programmed in the range of

-2 (0x8000) to +2 (0x7FFF(0)). Checks should be made to ensure that the pre-programmed

coefficients result in a stable transfer filter function.

The full numeric range of the coefficients is -2 to +1.999938964843750.

Datasheet

CFR0011-120-00

Revision 2.5

46 of 171

01 Sep 2016

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