LPC2478 NXP Semiconductors, LPC2478 Datasheet - Page 84

• Manufacturer Part Number: LPC2478
• Description: NXP Semiconductors designed the LPC2478 microcontroller, powered by theARM7TDMI-S core, to be a highly integrated microcontroller for a wide range ofapplications that require advanced communications and high quality graphic displays
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2478
Product data sheet
14.5 XTAL and RTCX Printed Circuit Board (PCB) layout guidelines
14.6 Standard I/O pin configuration
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
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
accordingly to the increase in parasitics of the PCB layout.
Figure 30
The default configuration for standard I/O pins is input with pull-up enabled. The weak
MOS devices provide a drive capability equivalent to pull-up and pull-down resistors.
Fig 30. Standard I/O pin configuration with analog input
•
•
•
•
as digital output
as analog input
as digital input
pin configured
pin configured
pin configured
Digital output driver
Digital input: Pull-up enabled/disabled
Digital input: Pull-down enabled/disabled
Analog input (for ADC input channels)
driver
shows the possible pin modes for standard I/O pins with analog input function:
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 12 September 2011
analog input
data input
output
output enable
pull-down enable
pull-up enable
select analog input
x1
Single-chip 16-bit/32-bit microcontroller
and C
x2
should be chosen smaller
V
DD
weak
pull-up
weak
pull-down
x1
, C
x2
, and C
LPC2478
© NXP B.V. 2011. All rights reserved.
V
ESD
DD
ESD
V
SS
x3
in case of
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PIN