wm8350 Wolfson Microelectronics plc, wm8350 Datasheet - Page 56

• Manufacturer Part Number: wm8350
• Description: Wolfson Audioplus? Stereo Codec With Power Management
• Manufacturer: Wolfson Microelectronics plc

WM8350
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The field FLL_RATE controls internal functions within the FLL; it is recommended that only the default
setting be used for this parameter. FLL_RSP_RATE controls the internal loop gain and should be set
to the recommended value.
The FLL output frequency is directly determined from FLL_RATIO, FLL_OUTDIV and the real number
represented by FLL_N and FLL_K. The field FLL_N is an integer (LSB = 1); FLL_K is the fractional
portion of the number (MSB = 0.5). The fractional portion is only valid when enabled by the field
FLL_FRAC. It is recommended that FLL_FRAC is enabled at all times.
The FLL frequency is determined according to the following equation:
F
according to the desired output F
Table 16 Choice of FLL_OUTDIV
Note that the output frequencies that do not lie within the ranges quoted above cannot be guaranteed
across the full range of device operating temperatures.
Once F
recommendations in Table 17. The value of N.K can then be determined using the equation above.
FLL_REF_FREQ should be set as described in Table 17.
For best performance, FLL Fractional Mode should always be used. Therefore, if the calculations
yield an integer value of N.K, then it is recommended to adjust FLL_RATIO in order to obtain a non-
integer value of N.K.
The register fields that control the FLL are described in Table 17. Example settings for a variety of
reference frequencies and output frequencies are shown in Table 18.
VCO
R42 (2Ah)
FLL Control 1
REGISTER
ADDRESS
OUTPUT FREQUENCY F
must be in the range 90-100 MHz. The value of FLL_OUTDIV should be selected as follows
2.8125 MHz - 3.125 MHz
5.625 MHz - 6.25 MHz
11.25 MHz - 12.5 MHz
VCO
22.5 MHz - 25 MHz
F
F
has been determined, the value of FLL_RATIO should be selected in accordance with the
OUT
VCO
= (F
= (F
REF
VCO
10:8
BIT
15
14
x N.K x FLL_RATIO)
/ FLL_OUTDIV)
FLL_ENA
FLL_OSC_EN
A
FLL_OUTDIV
[2:0]
OUT
LABEL
OUT
.
4h (divide by 32)
3h (divide by 16)
2h (divide by 8)
1h (divide by 4)
FLL_OUTDIV
DEFAULT
010
0
0
Digital Enable for FLL
0 = disabled
1 = enabled
Note that FLL_OSC_ENA must be
enabled before enabling FLL_ENA.
Analogue Enable for FLL
0 = FLL disabled
1 = FLL enabled
Note that FLL_OSC_ENA must be
enabled before enabling FLL_ENA.
F
000 = F
001 = F
010 = F
011 = F
100 = F
101 = Reserved
110 = Reserved
OUT
clock divider
VCO
VCO
VCO
VCO
VCO
/ 2
/ 4
/ 8
/ 16
/ 32
DESCRIPTION
PD, June 2009, Rev 4.1
Production Data
56