UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
135 of 1269
NXP Semiconductors
UM10503
Chapter 11: LPC43xx Clock Generation Unit (CGU)
11.8.4 PLL0AUDIO settings for audio applications
11.8.4.1 Using the fractional divider
shows typical divider settings for the audio PLL0 with the fractional divider active.
To use the fractional divider, follow these steps:
1. Set bit SEL_EXT = 0 and PLLFRACT_REQ = 1 in the PLL0AUDIO_CTRL register
(
).
2. Calculate NDEC, PDEC, and PLLFRACT_CTRL for the output frequency Fout.
3. Write the calculated NDEC and PDEC values to the PLL0AUDIO_NP_DIV register.
4. Write the calculated PLLFRACT_CTRL value to the PLL0AUDIOFRAC register.
Table 94.
PLL0 (for USB) settings for 480 MHz output clock
Fclkin [MHz]
PLL0USB_MDIV
PLL0USB_NP_DIV
1
0x073E 56C9
0x0030 2062
2
0x073E 2DAD
0x0030 2062
3 0x0B3E
34B1
0x0030
2062
4 0x0E3E
7777
0x0030
2062
5
0x0D32 6667
0x0030 2062
6 0x0B2A
2A66
0x0030
2062
8
0x0820 6AAA
0x0030 2062
10
0x071A 7FAA
0x0030 2062
12
0x0616 7FFA
0x0030 2062
15
0x0512 3FFF
0x0030 2062
16
0x0410 1FFF
0x0030 2062
20
0x040E 03FF
0x0030 2062
24
0x030C 00FF
0x0030 2062
Table 95.
PLL0AUDIO divider settings for 12 MHz input
Fs [kHz]
Fout [MHz]
Fcco [MHz] Error [Hz]
NDEC
PDEC PLL0AUDIO_NP_DIV
PLLF0RACT_CTRL
128Fs
192
24.576
540.672
1
514
29
0x0000201d
0x16872b
96
12.288
417.792
1
1
3
0x00001003
0x1a1cac
88.2
11.2896
338.688
1
0
24
0x00000018
0x070e56
64
8.192
344.064
1
0
30
0x0000001e
0x072b02
48
6.144
307.2
1
1
6
0x00001006
0x133333
44.1
5.6448
282.24
1
1
6
0x00001006
0x11a3d7
256Fs
192
49.152
491.52
11
514
5
0x00002005
0x147ae1
96
24.576
540.672
1
514
29
0x0000201d
0x16872b
88.2
22.5792
451.584
1
1
14
0x0000100e
0x1c3958
64
16.384
360.448
1
1
29
0x0000101d
0x16872b