User's Manual

Cinterion
®
EHS8 Hardware Interface Overview Page 14 of 43
EHS8_HIO_v02.770 2014-08-11
Confidential / Preliminary
2 Interface Characteristics
24
2 Interface Characteristics
EHS8 is equipped with an SMT application interface that connects to the external application.
The SMT application interface incorporates the various application interfaces as well as the
RF antenna interface.
2.1 Application Interface
2.1.1 USB Interface
EHS8 supports a USB 2.0 High Speed (480Mbit/s) device interface that is Full Speed (12Mbit/s)
compliant. The USB interface is primarily intended for use as command and data interface and
for downloading firmware.
The external application is responsible for supplying the VUSB_IN line. This line is used for
cable detection only. The USB part (driver and transceiver) is supplied by means of BATT+.
This is because EHS8 is designed as a self-powered device compliant with the “Universal Serial
Bus Specification Revision 2.0”
1
.
1)
All serial (including R
S
) and pull-up resistors for data lines are implemented.
2)
If the USB interface is operated in High Speed mode (480MHz), it is recommended to
take special care routing the data lines USB_DP and USB_DN. Application layout should
in this case implement a differential impedance of 90 ohms for proper signal integrity.
Figure 2: USB circuit
To properly connect the module's USB interface to the external application, a USB 2.0
compatible connector and cable or hardware design is required. Furthermore, the USB modem
driver distributed with EHS8 needs to be installed.
1
. The specification is ready for download on http://www.usb.org/developers/docs/
VBUS
DP
DN
VREG (3V075)
BATT+
USB_DP
2)
lin. reg.
GND
Module
Detection only
VUSB_IN
USB part
1)
RING0
Host wakeup
USB_DN
2)
R
S
R
S
SMT