OM11077 NXP Semiconductors, OM11077 Datasheet - Page 54

• Manufacturer Part Number: OM11077
• Description: MODULE DIMM LPC2478 ARM7
• Manufacturer: NXP Semiconductors

Specifications of OM11077

• Accessory Type: Module Card
• For Use With/related Products: ARM-57TS-LPC2478
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 568-4742

NXP Semiconductors
UM10237_4
User manual
3.2.12 Procedure for determining PLL settings
M = (F
N = (2 × M × F
F
Allowed values for M:
At higher oscillator frequencies, in the MHz range, values of M from 6 through 512 are
allowed. This supports the entire useful range of both the main oscillator and the IRC.
For lower frequencies, specifically when the RTC is used to clock the PLL, a set of 65
additional M values have been selected for supporting baud rate generation, CAN/USB
operation, and attaining even MHz frequencies. These values are shown in
Table 51.
PLL parameter determination can be simplified by using a spreadsheet available from
NXP. To determine PLL parameters by hand, the following general procedure may be
used:
1. Determine if the application requires use of the USB interface. The USB requires a
2. Choose the desired processor operating frequency (cclk). This may be based on
IN
= (F
50% duty cycle clock of 48 MHz within a very small tolerance, which means that F
must be an even integer multiple of 48 MHz (i.e. an integer multiple of 96 MHz), within
a very small tolerance.
processor throughput requirements, need to support a specific set of UART baud
rates, etc. Bear in mind that peripheral devices may be running from a lower clock
frequency than that of the processor (see
and
a multiple of the desired cclk frequency, bearing in mind the requirement for USB
support in [1] above, and that lower values of F
12085
13733
15381
16479
19775
21973
4272
5127
6042
6750
7324
8057
9613
CCO
CCO
Section 4–3.4 “Power control” on page
Additional Multiplier Values for use with a Low Frequency Clock Input
× N) / (2 × F
× N) / (2 × M)
IN
) / F
CCO
Rev. 04 — 26 August 2009
IN
10254
12207
13916
15564
17578
20508
23071
4395
5188
6075
6836
7425
8100
)
Low Frequency PLL Multipliers
Chapter 4: LPC24XX Clocking and power control
10376
12817
14099
15625
18127
20599
23438
4578
5400
6104
6866
7690
8545
Section 4–3.3 “Clock dividers” on page 57
60). Find a value for F
CCO
result in lower power dissipation.
10986
13184
14420
15869
20874
23804
18311
4725
5493
6409
6958
7813
8789
UM10237
CCO
© NXP B.V. 2009. All rights reserved.
that is close to
Table 4–51
11719
13672
14648
16113
19226
21149
24170
4807
5859
6592
7050
7935
9155
54 of 792
CCO