User's Manual Part 1

MC75 Hardware Interface Description

Strictly confidential / Draft

MC75_V00.190a Page 43 of 91 15.02.2005

3.9 USB Interface

MC75 supports a USB 2.0 Full Speed (12 Mbit/s) device interface. It is primarily intended for

use as command and data interface and for downloading firmware.

The USB I/O-pins are capable of driving the signal at min 3.0V. They are 5V I/O compliant.

To properly connect the module’s USB interface to the host a USB 2.0 compatible connector

is required. Furthermore, the USB modem driver delivered with MC75 must be installed as

described below.

The USB host is responsible for supplying, across the VUSB_IN line, power to the module’s

USB interface, but not to other MC75 interfaces. This is because MC75 is designed as a self-

powered device compliant with the “Universal Serial Bus Specification Revision 2.0”

MCU

USB

Transceiver

lin.

Regulator

PSU

Baseband controller

GSM module

Host

22Ohms

1.5kOhms

USB_DP

USB_DN

VUSB_IN

5V3V

D+

D-

VBUS

GND

80 pole board-to-board connector

Figure 14: USB circuit

The specification is ready for download on http://www.usb.org/developers/docs/