LPC55S2X datasheet(39/132 Pages) NXP

39 / 132 page

LPC55S2x/LPC552x

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Product data sheet

Rev. 2.1 — 6 August 2021

39 of 132

NXP Semiconductors

LPC55S2x/LPC552x

32-bit ARM Cortex-M33 microcontroller

6.1.1 Termination of unused pins

Table 4 shows how to terminate pins that are not used in the application. In many cases,

unused pins should be connected externally or configured correctly by software to

minimize the overall power consumption of the part.

Unused pins with GPIO function should be configured as outputs set to LOW with their

internal pull-up disabled. To configure a GPIO pin as output and drive it LOW, select the

GPIO function in the IOCON register, select output in the GPIO DIR register, and write a 0

to the GPIO PORT register for that pin. Disable the pull-up in the pin’s IOCON register.

In addition, it is recommended to configure all GPIO pins that are not bonded out on

smaller packages as outputs driven LOW with their internal pull-up disabled.

[1]

I = Input, IA = Inactive (no pull-up/pull-down enabled), PU = Pull-Up enabled

Table 4.

Termination of unused pins

Default

state[1]

Recommended termination of unused pins

RESET

I; PU

The RESET pin can be left unconnected if the application does not use it.

all PIOn_m (not open-drain) I; PU

Can be left unconnected if driven LOW and configured as GPIO output with pull-up

or pull-down disabled by software.

PIOn_m (I2C open-drain)

Can be left unconnected if driven LOW and configured as GPIO output by software.

XTAL32K_P

Connect to ground. When grounded, the RTC oscillator is disabled.

XTAL32K_N

Can be left unconnected.

XTAL32M_P

Connect to ground. When grounded, the RTC oscillator is disabled.

XTAL32M_N

Can be left unconnected.

VREFP

Tie to VBAT_DCDC.

VREFN

Tie to VSS.

VDDA

Tie to VBAT_DCDC.

VSSA

Tie to VSS.

USBn_DP

Can be left unconnected.

USBn_DM

Can be left unconnected.

USBn_3V3

Tie to VBAT_DCDC. If not using USB and using 1.8 V supply, USBn_3V3 can be

connected to 1.8 V.

USB1_VBUS

Can be left unconnected.

USBn_VSS

Tie to VSS.

LPC55S2X Datasheet(PDF) 39 Page - NXP Semiconductors

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