LPC55S6X datasheet(103/128 Pages) NXP

номер детали	LPC55S6X

подробное описание детали	32-bit Arm Cortex짰-M33; M33 coprocessor, TrustZone, PowerQuad, CASPER, 320 KB SRAM; 640 KB flash, USB HS,Flexcomm Interface, SDIO, 32-bit counter/ timers,SCTimer/PWM, PLU, 16-bit 1.0 Msamples/sec ADC,Comparator, Temperature Sensor, AES, PUF, SHA, CRC, RNG

PDF	128 Pages

Scroll/Zoom	100%

производитель	NXP [NXP Semiconductors]

домашняя страница	http://www.nxp.com

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103 / 128 page

LPC55S6x

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 1.9 — 10 February 2020

103 of 128

NXP Semiconductors

LPC55S6x

32-bit ARM Cortex-M33 microcontroller

For best results, it is very critical to select a matching crystal for the on-chip oscillator.

Load capacitance (CL), series resistance (RS), and drive level (DL) are important

parameters to consider while choosing the crystal. After selecting the proper crystal, the

external load capacitor CX1 and CX2 values can also be generally determined by the

following expression:

CX1 = CX2 = 2CL  (CPad + CParasitic)

Where:

CL - Crystal load capacitance

CPad - Pad capacitance of the XTAL32K_P and XTAL32K_N pins (~3 pF).

CParasitic – Parasitic or stray capacitance of external circuit.

Although CParasitic can be ignored in general, the actual board layout and placement of

external components influences the optimal values of external load capacitors. Therefore,

it is recommended to fine tune the values of external load capacitors on actual hardware

board to get the accurate clock frequency. For fine tuning, output the RTC Clock to one of

the GPIOs and optimize the values of external load capacitors for minimum frequency

deviation.

13.3.1 RTC Printed Circuit Board (PCB) design guidelines

• Connect the crystal and external load capacitors on the PCB as close as possible to

the oscillator input and output pins of the chip.

• The length of traces in the oscillation circuit should be as short as possible and must

not cross other signal lines.

• Ensure that the load capacitors CX1, CX2, and CX3, in case of third overtone crystal

usage, have a common ground plane.

• Loops must be made as small as possible to minimize the noise coupled in through

the PCB and to keep the parasitics as small as possible.

• Lay out the ground (GND) pattern under crystal unit.

• Do not lay out other signal lines under crystal unit for multi-layered PCB.

Fig 24. RTC oscillator components

aaa-0181472-x

LPC

XTAL32K_P

XTAL32K_N

CX2

CX1

XTAL

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