LPC4088 datasheet(105/123 Pages) NXP

105 / 123 page

LPC408X_7X

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Objective data sheet

Rev. 1 — 17 September 2012

105 of 123

NXP Semiconductors

LPC408x/7x

32-bit ARM Cortex-M4 microcontroller

In slave mode the input clock signal should be coupled by means of a capacitor of 100 pF

(Figure 37), with an amplitude between 200 mV(RMS) and 1000 mV(RMS). This

corresponds to a square wave signal with a signal swing of between 280 mV and 1.4 V.

The XTALOUT pin in this configuration can be left unconnected.

External components and models used in oscillation mode are shown in Figure 38 and in

Table 33 and Table 34. Since the feedback resistance is integrated on chip, only a crystal

and the capacitances CX1 and CX2 need to be connected externally in case of

fundamental mode oscillation (the fundamental frequency is represented by L, CL and

RS). Capacitance CP in Figure 38 represents the parallel package capacitance and should

not be larger than 7 pF. Parameters FOSC, CL, RS and CP are supplied by the crystal

manufacturer.

Fig 38. Oscillator modes and models: oscillation mode of operation and external crystal

model used for CX1/CX2 evaluation

Table 33.

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

002aah274

LPC40xx

XTALIN

XTALOUT

CX2

CX1

XTAL

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