WM8955BL Wolfson Microelectronics, WM8955BL Datasheet - Page 30

• Manufacturer Part Number: WM8955BL
• Description: Stereo DAC
• Manufacturer: Wolfson Microelectronics

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WM8955BL
The PLL frequency ratio R = f
(2Eh):
N = int (R)
K = int (2
Example:
MCLK = 12MHz required clock = 12.288MHz
R should be chosen to ensure 5<N<13. There is a divide by 4 and selectable divide by 2 after the
PLL which should be set to meet this requirement. Enabling the divide by 2 sets the required f
12.288MHz = 98.304MHz.
R = 98.304/12 = 8.192
N = intR = 8
K = int (2
Table 20 PLL Frequency Ratio Control
The PLL performs best when f
are shown below.
Table 21 PLL Frequency Examples
(MHz)
MCLK
11.91
11.91
19.68
19.68
14.4
14.4
19.2
19.2
19.8
19.8
R44 (2Ch)
PLL Control (1)
R45 (2Dh)
PLL Control (2)
R46 (2Eh)
PLL Control (3)
R59 (3Bh)
12
12
13
13
24
24
26
26
27
27
REGISTER
ADDRESS
22
22
DESIRED
OUTPUT
(R-N))
x (8.192-8)) = 805306 = C49BAh.
11.2896
11.2896
11.2896
11.2896
11.2896
11.2896
11.2896
11.2896
11.2896
11.2896
12.288
12.288
12.288
12.288
12.288
12.288
12.288
12.288
12.288
12.288
(MHz)
8:5
3:0
8:0
8:0
BIT
90.3168
90.3168
90.3168
90.3168
90.3168
90.3168
90.3168
90.3168
90.3168
90.3168
7
98.304
98.304
98.304
98.304
98.304
98.304
98.304
98.304
98.304
98.304
(MHz)
F2
2
/f
2
1
is around 90MHz. Its stability peaks at N=8. Some example settings
(see Figure 17) can be set using K and N in registers 44 (2Ch) to 46
N
K [21:18]
K [17:9]
K [8:0]
KEN
LABEL
MCLK
DIV2
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
OUT
DIV2
PLL
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
DEFAULT
1BAh
1000
0011
024h
0
7.5833
8.2539
7.5264
6.9474
7.5618
6.8267
9.1785
9.9902
9.1229
9.9297
7.5264
6.9474
7.5618
6.6901
7.2818
8.192
6.272
9.408
10.24
8.192
R
Integer part of PLL input/output
frequency ratio. Use values greater
than 5 and less than 13.
Fractional part of PLL input/output
frequency ratio (treat as one 22-digit
binary number)
0: Fractional part (K) disabled
1: K enabled
(Hex)
F2
A
7
8
7
8
6
7
6
6
9
9
9
9
9
7
8
6
7
6
7
DESCRIPTION
PD Rev 4.1 February 2007
1A1CAC
3CA2F4
3CA2F4
2C2B30
25545C
103FF6
21B089
34E818
3B8023
21B089
12089E
23F548
116872
3F6017
7DDCA
23F548
C49BA
C49BA
F5C28
B6D22
(Hex)
K
Production Data
2
= 8x
30