LPC1313 datasheet(52/62 Pages) NXP

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LPC1311_13_42_43

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Product data sheet

Rev. 3 — 10 August 2010

52 of 62

NXP Semiconductors

LPC1311/13/42/43

32-bit ARM Cortex-M3 microcontroller

11.3 XTAL 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.

Table 19.

Recommended values for CX1/CX2 in oscillation mode (crystal and external

components parameters) low frequency mode

Fundamental oscillation

frequency FOSC

Crystal load

capacitance CL

Maximum crystal

series resistance RS

External load

capacitors CX1, CX2

1 MHz - 5 MHz

10 pF

< 300

18 pF, 18 pF

20 pF

< 300

39 pF, 39 pF

30 pF

< 300

57 pF, 57 pF

5 MHz - 10 MHz

10 pF

< 300

18 pF, 18 pF

20 pF

< 200

39 pF, 39 pF

30 pF

< 100

57 pF, 57 pF

10 MHz - 15 MHz

10 pF

< 160

18 pF, 18 pF

20 pF

< 60

39 pF, 39 pF

15 MHz - 20 MHz

10 pF

< 80

18 pF, 18 pF

Table 20.

Recommended values for CX1/CX2 in oscillation mode (crystal and external

components parameters) high frequency mode

Fundamental oscillation

frequency FOSC

Crystal load

capacitance CL

Maximum crystal

series resistance RS

External load

capacitors CX1, CX2

15 MHz - 20 MHz

10 pF

< 180

18 pF, 18 pF

20 pF

< 100

39 pF, 39 pF

20 MHz - 25 MHz

10 pF

< 160

18 pF, 18 pF

20 pF

< 80

39 pF, 39 pF

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