
NXP Semiconductors
LPC2921/2923/2925
ARM9 microcontroller with CAN, LIN, and USB
 NXP B.V. 2010.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: salesaddresses@nxp.com
Date of release: 14 April 2010
Document identifier: LPC2921_23_25_3
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’. 
6.15 
Power, Clock, and Reset control SubSystem 
(PCRSS). . . . . . . . . . . . . . . . . . . . . . . . . . . . .  40
Clock description  . . . . . . . . . . . . . . . . . . . . . .  41
Clock Generation Unit (CGU0). . . . . . . . . . . .  42
6.15.2.1 Functional description. . . . . . . . . . . . . . . . . . .  42
6.15.2.2 PLL functional description  . . . . . . . . . . . . . . .  45
6.15.2.3 Pin description . . . . . . . . . . . . . . . . . . . . . . . .  46
6.15.3 
Clock generation for USB (CGU1) . . . . . . . . .  47
6.15.3.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . .  47
6.15.4 
Reset Generation Unit (RGU). . . . . . . . . . . . .  47
6.15.4.1 Functional description. . . . . . . . . . . . . . . . . . .  48
6.15.4.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . .  48
6.15.5 
Power Management Unit (PMU). . . . . . . . . . .  49
6.15.5.1 Functional description. . . . . . . . . . . . . . . . . . .  49
6.16 
Vectored interrupt controller . . . . . . . . . . . . . .  51
6.16.1 
Functional description. . . . . . . . . . . . . . . . . . .  51
6.16.2 
Clock description  . . . . . . . . . . . . . . . . . . . . . .  52
7 
Limiting values. . . . . . . . . . . . . . . . . . . . . . . . .  53
8 
Static characteristics. . . . . . . . . . . . . . . . . . . .  55
8.1 
Power consumption . . . . . . . . . . . . . . . . . . . .  60
8.2 
Electrical pin characteristics . . . . . . . . . . . . . .  61
9 
Dynamic characteristics . . . . . . . . . . . . . . . . .  64
9.1 
Dynamic characteristics: I/O and CLK_OUT 
pins, internal clock, oscillators, PLL, and 
CAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  64
9.2 
USB interface . . . . . . . . . . . . . . . . . . . . . . . . .  66
9.3 
Dynamic characteristics: I
2
C-bus interface. . .  67
9.4 
Dynamic characteristics: SPI . . . . . . . . . . . . .  68
9.5 
Dynamic characteristics: flash memory and 
EEPROM . . . . . . . . . . . . . . . . . . . . . . . . . . . .  69
9.6 
Dynamic characteristics: ADC1/2  . . . . . . . . .  70
10 
Application information. . . . . . . . . . . . . . . . . .  70
10.1 
Operating frequency selection . . . . . . . . . . . .  70
10.2 
Suggested USB interface solutions . . . . . . . .  71
10.3 
SPI signal forms . . . . . . . . . . . . . . . . . . . . . . .  72
10.4 
XIN_OSC input. . . . . . . . . . . . . . . . . . . . . . . .  74
10.5 
XIN_OSC Printed Circuit Board (PCB) 
layout guidelines. . . . . . . . . . . . . . . . . . . . . . .  74
11 
Package outline . . . . . . . . . . . . . . . . . . . . . . . .  75
12 
Soldering of SMD packages . . . . . . . . . . . . . .  76
12.1 
Introduction to soldering . . . . . . . . . . . . . . . . .  76
12.2 
Wave and reflow soldering . . . . . . . . . . . . . . .  76
12.3 
Wave soldering. . . . . . . . . . . . . . . . . . . . . . . .  76
12.4 
Reflow soldering. . . . . . . . . . . . . . . . . . . . . . .  77
13 
Abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . .  79
14 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . .  79
15 
Revision history. . . . . . . . . . . . . . . . . . . . . . . .  80
16 
Legal information. . . . . . . . . . . . . . . . . . . . . . .  81
6.15.1 
6.15.2 
16.1 
16.2 
16.3 
16.4 
17 
18 
Data sheet status. . . . . . . . . . . . . . . . . . . . . .  81
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . .  81
Disclaimers  . . . . . . . . . . . . . . . . . . . . . . . . . .  81
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . .  82
Contact information . . . . . . . . . . . . . . . . . . . .  82
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  83