LPC1767 View Datasheet(PDF) - Philips Electronics
Part Name
Description
MFG CO.
'LPC1767' PDF : 66 Pages View PDF
NXP Semiconductors
LPC1769/68/67/66/65/64
32-bit ARM Cortex-M3 microcontroller
VDD
USB_UP_LED
LPC17xx
VDD
USB_CONNECT
USB_D+
33 Ω
USB_D−
33 Ω
VBUS
VSS
D+
D−
VBUS
USB-B
connector
Fig 27. LPC1769/68/66/65/64 USB device port configuration
002aad943
14.2 XTAL1 input
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
Ci = 100 pF. To limit the input voltage to the specified range, choose an additional
capacitor to ground Cg which attenuates the input voltage by a factor Ci/(Ci + Cg). In slave
mode, a minimum of 200 mV (RMS) is needed. For more details see the LPC17xx User
manual.
LPC1xxx
XTAL1
Ci
Cg
100 pF
002aae835
Fig 28. Slave mode operation of the on-chip oscillator
14.3 XTAL and RTCX Printed Circuit Board (PCB) layout guidelines
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 Cx1, Cx2, and Cx3 in 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 Cx1 and Cx2 should be chosen smaller
accordingly to the increase in parasitics of the PCB layout.
LPC1769_68_67_66_65_64_4
Product data sheet
Rev. 04 — 1 February 2010
© NXP B.V. 2010. All rights reserved.
59 of 66
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