User's Manual

LE940B6 Hardware User Guide

1VV0301331 Rev. 1.8 - 2017-03-15

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8.1. USB Port

The LE940B6 module includes a Universal Serial Bus (USB) transceiver, which operates at USB

high-speed (480Mbits/sec). It can also operate with USB full-speed hosts (12Mbits/sec).

It is compliant with the USB 2.0 specification and can be used for control and data transfers as

well as for diagnostic monitoring and firmware update.

NOTE:

With the LE940B6 module, firmware updates by the host are only possible via USB and not

possible via UART. The reason is that Telit considers it impractical to transfer firmware binaries

exceeding 100Mb via UART.

The USB port is typically the main interface between the LE940B6 module and OEM hardware.

NOTE:

The USB_D+ and USB_D- signals have a clock rate of 480 MHz. The signal traces must be routed

carefully. Minimize trace lengths, number of vias, and capacitive loading. The impedance value

should be as close as possible to 90 Ohms differential.

The pull-up, pull-down and series resistors on pins USB_D+ and USB_D- as required by the USB

2.0 specification are included inside the module.

Table 25 lists the USB interface signals.

Table 25: USB Interface Signals

Signal Pad

No.

Usage

USB_VBUS A18 Power and cable detection for the internal USB transceiver.

Acceptable input voltage range 2.5V – 5.5V @ max 5 mA consumption

USB_D- F19 Minus (-) line of the differential, bi-directional USB signal to/from the

peripheral device

USB_D+ D19 Plus (+) line of the differential, bi-directional USB signal to/from the

peripheral device

NOTE:

USB_VBUS input power is internally used to detect the USB port and start the enumeration

process. It is not used for supplying power to the internal LE940B6 USB HW block.