NXP Semiconductors LPC55S0x Instruction Manual

1 Introduction

This document guides the hardware engineers to design and test their

LPC55(S)xx processor-based designs. The document provides information

about board layout recommendations and design checklists to ensure first

pass success and avoid any board bring-up problems.

This guide is released with the relevant device-specific hardware

documentation such as data sheets, reference manuals, and application notes

available on nxp.com.

2 LPC55(S)xx family comparison

All LPC55Sxx/LPC55xx family is based on Arm ® Cortex® -M33 core, with

PowerQuad Accelerator and CASPER Accelerator. The S in the middle

of part name means this part provides more security features, such as

TrustZone Support.

Table 1. LPC55Sxx family core features

Family Core

frequency

Dual

core

Power

Quad

CASPER

LPC55S0x/LPC550x 96 MHz — — YES

LPC55S1x/LPC551x 150 MHz — — YES

LPC55S2x/LPC552x 150 MHz YES YES YES

LPC55S6x/LPC556x 150 MHz YES YES YES

Table 2. LPC55Sxx/LPC55xx peripherals

Family Flexcomm 50 MHz HS-

SPI

HS USB FS USB CAN FD SDIO

LPC55S0x/LPC550x 8 1 — — 1—

LPC55S1x/LPC551x 8 1 1 1 1 —

LPC55S2x/LPC552x 8 1 1 1 —1

LPC55S6x/LPC556x 8 1 1 1 —1

Contents

1 Introduction......................................1

2 LPC55(S)xx family comparison.......1

3 Power supply...................................2

3.1 Introduction.................................. 2

3.2 Bulk and decoupling capacitors... 5

4 Clock circuitry..................................6

4.1 Introduction.................................. 6

4.2 Crystal oscillator...........................7

4.3 RTC oscillator.............................. 8

4.4 Common suggestions for the PCB

layout of oscillator circuit............10

5 Boot mode configurations............. 10

5.1 Boot mode selection.................. 11

6 Debug and programing interface...12

6.1 Debug connector pinouts...........14

7 Communication modules...............14

7.1 CAN interface for CAN-FD module

...................................................14

8 Analog........................................... 15

8.1 ADC impedance.........................15

9 Recommendations........................ 16

9.1 Pin descriptions..........................16

9.2 Termination of unused pins....... 17

9.3 PCB............................................18

9.4 General board layout guidelines

...................................................18

10 References....................................23

11 Revision history.............................23

AN13033

Hardware Design Guidelines for LPC55(S)xx Microcontrollers

Rev. 0 — 30 October 2020 Application Note

Table 3. LPC55Sxx/LPC55xx Timers

Family CTimer SCT MRT WWDT Code

WDT

RTC OS-Timer

LPC55S0x/LPC550x 5 1 1 1 1 1 1

LPC55S1x/LPC551x 5 1 1 1 1 1 1

LPC55S2x/LPC552x 5 1 1 1 —1 1

LPC55S6x/LPC556x 5 1 1 1 —1 1

Table 4. LPC55Sxx/LPC55xx analog peripherals

Family 16 bit ADC Comparator 12 bit DAC

LPC55S0x/LPC550x 1 (10ch)/2 Msps 1 (5 inputs) —

LPC55S1x/LPC551x 1 (10ch)/2 Msps 1 (5 inputs) —

LPC55S2x/LPC552x 1 (10ch)/1 Msps 1 (5 inputs) —

LPC55S6x/LPC556x 1 (10ch)/1 Msps 1 (5 inputs) —

Table 5. LPC55Sxx/LPC55xx packages

Family HVQFN 48 HVQFN 64 HTQFP 64 VFBGA 98 HLQFP

100

HLQFP

144

VBGA 196

LPC55S0x/LPC550x / /

LPC55S1x/LPC551x / / /

LPC55S2x/LPC552x / / /

LPC55S6x/LPC556x / / /

For details, see the latest version of the Datasheet and User Manuel on www.nxp.com.

3 Power supply

3.1 Introduction

LPC55Sxx series requires single 1.8 to 3.6 V operation voltage supply.

LPC55S0x/LPC550x, LPC55S1x/LPC551x, LPC55S2x/LPC552x and LPC55S6x/LPC556x internal core’s voltage are supplied

by internal DC/DC regulator, this DC/DC regulator needs external inductance and two or three capacitors. For details, see

Using

the DCDC feature

(document AN12325).

NXP Semiconductors

Power supply

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 2 / 24

Figure 1. Using internal DC/DC converter

The power and ground pins are described in subsequent sections.

NXP Semiconductors

Power supply

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 3 / 24

Figure 2. Power supply pins

The capacitors in Figure 2 is only for reference.

NOTE

Table 6. Power domains and decoupling capacitors

Power

domain Description Voltage

Bulk/Bypass capacitor for domain Decoupling

capacitor

per pin

CharacteristicsPackage

HTQFP64 VFBGA98 HLFP100

USB0_3V3 USB0 Analog 3.3

V supply 3.3 V 10 uF 10 uF 10 uF 0.1 uF X7R Ceramic

USB1_3V3 USB1 Analog 3.3

V supply 3.3 V 10 uF 10 uF 10 uF 0.1 uF X7R Ceramic

VDD Single power supply

powering I/Os 1.8 - 3.3 V 10 uF 10 uF 10 uF 0.1 uF X7R Ceramic

Table continues on the next page...

NXP Semiconductors

Power supply

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 4 / 24

Table 6. Power domains and decoupling capacitors (continued)

Power

domain Description Voltage

Bulk/Bypass capacitor for domain Decoupling

capacitor

per pin

CharacteristicsPackage

HTQFP64 VFBGA98 HLFP100

VBAT_DCD

Supply of DCDC output

— 22 uF + 100 nF + 47 pF X7R Ceramic

VBAT_PMU

Core supply. For

applications with DCDC

converter, VDD_PMU

and FB are tied at

PCB level.

VDD_PMU Core supply

VDDA Analog supply voltage 1.8 - 3.6 V 10 uF 10 uF 10 uF 0.1 uF X7R ceramic

VREFP ADC positive reference

0.985 -

VDDA

10 uF 10 uF 10 uF 0.1 uF X7R Ceramic

VREFN ADC

negative reference

VSS, VSSA and VREFN must be shorted to GND at package level.

USB0_VSS USB0 analog 3.3

V ground

GND

USB1_VSS USB1 analog 3.3

V ground

VSS Ground

VSS_DCDC Star

ground connections

VSS_PMU Star

ground connections

VSSA Analog ground

FB Feedback node

LX DCDC power

stage output

3.2 Bulk and decoupling capacitors

The effectiveness of the bulk/bypass and the de-coupling capacitors depends on the optimum placement and connection type.

The bulk capacitors are used for a local power supply to the power pin, near the decoupling capacitors and as close as possible

to the assigned reference voltage pin. Decoupling capacitors make the current loop between supply, MCU and reference ground

as short as possible to reduce high frequency transients and noises. Therefore,

• All decoupling capacitors should be placed as close as possible to each of their respective power supply pin.

• The ground side of the decoupling capacitor should have a via to the pad which goes directly down to the internal ground

plane.

NXP Semiconductors

Power supply

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 5 / 24

• The route distance between the capacitors to the power plane should be as short as possible.

Figure 3. Bulk and decoupling capacitor connection

4 Clock circuitry

4.1 Introduction

The LPC55S1x/2x/6x has the following clock sources:

• Internal Free Running Oscillator (FRO). This oscillator provides a selectable 96 MHz output, and a 12 MHz output (divided

down from the selected higher frequency) that can be used as a system clock. The FRO is trimmed to +/- 2% accuracy

over the entire voltage and temperature range.

• 32 kHz Internal Free Running Oscillator FRO. The FRO is trimmed to +/- 2% accuracy over the entire voltage and

temperature range.

• Internal low power oscillator (FRO 1 MHz) trimmed to +/- 15% accuracy over the entire voltage and temperature range.

• Crystal oscillator with an operating frequency of 16 MHz or 32 MHz. Option for external clock input (bypass mode) for

clock frequencies of up to 24 MHz.

• Crystal oscillator with 32.768 kHz operating frequency. Option for external clock input (bypass mode) for clock frequencies

of up to 100 kHz.

• PLL0 and PLL1 allow CPU operation up to the maximum CPU rate without the need for a high-frequency external clock.

PLL0 and PLL1 can run from the internal FRO 12 MHz output, the external oscillator, internal FRO 1 MHz output, or the

32.768 kHz RTC oscillator.

• Clock output function with divider to monitor internal clocks.

• Frequency measurement unit for measuring the frequency of any on-chip or off-chip clock signal.

For external crystal oscillator and RTC oscillator, LPC55Sxx have capacitor bank feature. It means that the

stabilizing capacitors can be unsoldered on both 32 K and 16 MHz XTAL. We also suggest users to keep the two

stabilizing capacitors as DNP/Do Not Populate on PCB.

NOTE

NXP Semiconductors

Clock circuitry

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 6 / 24

4.2 Crystal oscillator

In the crystal oscillator circuit, only the crystal (XTAL) and the capacitances, CX1 and CX2, need to be connected externally on

XTAL32M_P and XTAL32M_N pins, as shown in Figure 4. In bypass mode, an external clock (maximum frequency of up to 24 MHz)

can also be connected to XTAL32M_P if XTAL32M_N is left open. External [0 – VH] square signal can be applied on the XTAL32M_P

pin from 0 V to 850 mV.

Figure 4. Reference oscillator circuit

Table 7. Components of the oscillator circuit

Symbol Description

XTAL Quartz crystal/ceramic resonator

CX1 Stabilizing capacitor

CX2 Stabilizing capacitor

For best results, it is very critical to select a matching crystal for the on-chip oscillator. Load Capacitance (CL), Resistance Series

(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:

Where:

NXP Semiconductors

Clock circuitry

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 7 / 24

• CL: Crystal load capacitance

• CPad: Pad capacitance of the XTAL32M_P and XTAL32M_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. The load capacitors are dependent on the specifications of

the crystal and on the board capacitance. It is recommended to have the crystal manufacturer evaluate the crystal on the PCB.

4.2.1 Crystal 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 and CX2, 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 parasitic 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.

4.3 RTC oscillator

In the RTC oscillator circuit, only the 32.768 kHz crystal (XTAL) and the capacitances, CX1 and CX2, need to be connected

externally on XTAL32K_P and XTAL32K_N, as shown in Figure 5.

In bypass mode, an external clock (maximum frequency of up to 100 kHz) can also be connected to XTAL32K_P if XTAL32K_N is

left open. External [0 – VH] square signal can be applied on the XTAL32K_P pin with 1.1 V +/-10%

An external signal below 1.0 V or above 1.2 V cannot be applied.

NXP Semiconductors

Clock circuitry

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 8 / 24

Figure 5. Reference oscillator circuit

For best results, it is very critical to select a matching crystal for the on-chip oscillator. Load Capacitance (CL), Resistance Series

(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:

Where:

• CL: Crystal load capacitance

• CPad: Pad capacitance of the XTAL32K_P and XTAL32K_N pins (~3 pF)

• CPrasitic: 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.

4.3.1 RTC 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.

NXP Semiconductors

Clock circuitry

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 9 / 24

• 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 GND pattern under crystal unit.

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

4.4 Common suggestions for the PCB layout of oscillator circuit

The crystal oscillator is an analog circuit and must be designed carefully and according to the analog-board layout rules:

• It is recommended to send the PCB to the crystal manufacturer to determine the negative oscillation margin as well as

the optimum regarding CXTAL and CEXTAL capacitors. The datasheet includes recommendations for the tank capacitors

CXTAL and CEXTAL. These values together with the expected PCB, pin, etc. stray capacity values should be used as an

initial point.

• The crystal or resonator oscillator is sensitive to stray capacitance and noise from other signals. It should be placed away

from high-frequency devices and traces in order to avoid and reduce the capacitive coupling between the XTAL and

EXTAL pins and their PCB traces.

• The main oscillation loop current is flowing between the crystal and the load capacitors. This signal path (Oscillator to

CEXTAL to CXTAL to Oscillator) should be kept as short and symmetric tracing as possible. Hence, both the capacitor's

ground connections should be direct always to the closer VSS pin using the cooper-pour ground plane and several vias to

the ground internal layer in the PCB are mandatory.

• The EXTAL and XTAL pins should only be connected to required oscillator components and must not be connected to any

other devices.

Figure 6 shows the recommended placement and routing for the oscillator layout.

Figure 6. Suggested crystal oscillator layout

5 Boot mode configurations

NXP Semiconductors

Boot mode configurations

Hardware Design Guidelines for LPC55(S)xx Microcontrollers, Rev. 0, 30 October 2020

Application Note 10 / 24

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