LPC2939 NXP Semiconductors, LPC2939 Datasheet - Page 88

• Manufacturer Part Number: LPC2939
• Description: The LPC2939 combine an ARM968E-S CPU core with two integrated TCM blocksoperating at frequencies of up to 125 MHz, Full-speed USB 2
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2939_3
Product data sheet
10.4 XIN_OSC input
10.5 XIN_OSC Printed-Circuit Board (PCB) layout guidelines
The input voltage to the on-chip oscillators is limited to 1.8 V. If the oscillator is driven by a
clock in slave mode, it is recommended that the input be coupled through a capacitor with
C
capacitor to ground C
slave mode, a minimum of 200 mV RMS is needed. For more details see the LPC29xx
User manual UM10316.
The crystal should be connected on the PCB as close as possible to the oscillator input
and output pins of the chip. Take care that the load capacitors C
case of third overtone crystal usage, have a common ground plane. The external
components must also be connected to the ground plain. Loops must be made as small
as possible, in order to keep the noise coupled in via the PCB as small as possible. Also
parasitics should stay as small as possible. Values of C
smaller accordingly to the increase in parasitics of the PCB layout.
Fig 39. Slave mode operation of the on-chip oscillator
i
= 100 pF. To limit the input voltage to the specified range, choose an additional
All information provided in this document is subject to legal disclaimers.
g
which attenuates the input voltage by a factor C
Rev. 03 — 7 April 2010
XIN_OSC
C i
100 pF
ARM9 microcontroller with CAN, LIN, and USB
LPC29xx
002aae730
C g
x1
and C
x2
x1
should be chosen
and C
LPC2939
i
© NXP B.V. 2010. All rights reserved.
/ (C
x2
, and C
i
+ C
g
). In
x3
88 of 99
in