LPC1547JBD48 datasheet(85/99 Pages) NXP

85 / 99 page

LPC15XX

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Product data sheet

Rev. 1 — 19 February 2014

85 of 99

NXP Semiconductors

LPC15xx

32-bit ARM Cortex-M3 microcontroller

Remark: When a bus-powered circuit as shown in Figure 45 is used or, for a self-powered

device, when the VBUS pin is not connected, configure the PIO0_3/USB_VBUS pin for

GPIO (PIO0_3) in the IOCON block. This ties the VBUS signal HIGH internally.

14.1.1 USB Low-speed operation

The USB device controller can be used in low-speed mode supporting 1.5 Mbit/s data

exchange with a USB host controller.

Remark: To operate in low-speed mode, change the board connections as follows:

1. Connect USB_DP to the D- pin of the connector.

2. Connect USB_DM to the D+ pin of the connector.

External 10

Ω resistors are recommended in low-speed mode to reduce over-shoots and

accommodate for 5 m cable length required for USB-IF testing.

14.2 XTAL input and crystal oscillator component selection

The input voltage to the on-chip oscillators is limited to 1.8 V. If the oscillator is driven by a

clock in slave mode, it is recommended that the input be coupled through a capacitor with

Ci = 100 pF. To limit the input voltage to the specified range, choose an additional

capacitor to ground Cg which attenuates the input voltage by a factor Ci/(Ci + Cg). In slave

mode, a minimum of 200 mV(RMS) is needed.

Fig 45. USB interface on a bus-powered device

REGULATOR

VBUS

LPC1xxx

VDD

1.5 kΩ

aaa-010821

USB-B

connector

USB_DP

USB_DM

VSS

RS = 33 Ω

USB

USB_CONNECT

LPC1547JBD48 Datasheet(PDF) 85 Page - NXP Semiconductors