LPC55S2X datasheet(102/132 Pages) NXP

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NXP Semiconductors

LPC55S2x/LPC552x

32-bit Arm Cortex®-M33 microcontroller

• Ensure that the load capacitors 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.

13.5 Suggested USB full-speed interface solutions

The USB device can be connected to the USB as self-powered device (see Figure 30) or bus-powered device

(see Figure 31).

The USB_VBUS pin is 5 V tolerant only when VDD is applied and at operating voltage level. Therefore, if the

USB_VBUS function is connected to the USB connector and the device is self-powered, the USB_VBUS pin

must be protected for situations when

VDD = 0 V.

If VDD is always at operating level while VBUS = 5 V, the USB_VBUS pin can be connected directly to the

VBUS pin on the USB connector.

For such USB applications, the internal pull-down on the GPIO/VBUS pad must be enabled on pins P0_22 or

P1_11 when attaching/de-attaching in the USB application. Enable the internal pull-downs with user software.

For USB ISP mode, the internal resistor pull-down is not enabled on the P0_22 pin where the VBUS pin can be

floating. USB enumeration may still occur when VBUS is not connected.

For systems where VDD can be 0 V and VBUS is directly applied to the VBUS pin, precautions must be taken

to reduce the voltage to below 3.6 V, which is the maximum allowable voltage on the USB_VBUS pin in this

case.

One method is to use a voltage divider to connect the USB_VBUS pin to the VBUS on the USB connector. The

voltage divider ratio should be such that the USB_VBUS pin is greater than 0.7 VDD to indicate a logic HIGH

while below the 3.6 V allowable maximum voltage.

For the following operating conditions:

VBUSmax = 5.25 V

VDD = 3.6 V

The voltage divider should provide a reduction of 3.6 V/5.25 V or ~0.686 V.

LPCxxxx

VBAT_DCDC/VBAT_

PMU/VDD/USB_3V3

1.5 κΩ

USB-B

connector

USB_DP

USB_DM

USB_VBUS

VSS

RS = 33 Ω

USB

USB_CONNECT

D+

D-

Figure 30. USB interface on a self-powered device where USB_VBUS = 5 V

LPC55S2X_LPC552X

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

Data sheet

Rev. 2.3 — 29 August 2024

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