EVA-M8E - Hardware Integration Manual
UBX-15028542 - R05
Contents
Page 11 of 44
Production Information
The interface can be used either in “self powered” or “bus powered” mode. The required mode can be
configured using the UBX-CFG-USB message. Also, the vendor ID, vendor string, product ID and
product string can be changed.
In order to get the 90
Ω
differential impedance in between the
USB_DM
and
USB_DP
data line, a 27
Ω
series resistor (R1, R2) must be placed into each data line (
USB_DM
and
USB_DP
).
Module
VDD_USB
LDO
VDD_USB
R4
USB_DP
USB_DM
R5
C24
C23
D2
VBUS
DP
DM
GND
US
B D
evi
ce Co
nn
ec
to
r
U1
EN
R11
EN
Figure 2: USB interface
Name
Component Function
Comments
U1
LDO
Regulates VBUS (4.4 …5.25
V) down to a voltage of 3.3 V).
Almost no current requirement (~1 mA) if the GNSS receiver is
operated as a USB self-powered device, but if bus-powered LDO (U1)
must be able to deliver the maximum current of ~100 mA.
C24,C23 Capacitors
Required according to the specification of LDO U1
D2
Protection
diodes
Protect circuit from
overvoltage / ESD when
connecting.
Use low capacitance ESD protection such as ST Microelectronics
USBLC6-2.
R4, R5
Serial
termination
resistors
Establish a full-speed driver
impedance of 28…44
Ω
A value of 27
Ω
is recommended.
R11
Resistor
Ensures defined signal at
VDD_USB
when VBUS is not
connected / powered
100 k
Ω
is recommended for USB self-powered setup. For bus-powered
setup R8 is not required.
Table 2: Summary of USB external components
See Appendix A.5 and Appendix A.6 for reference schematics for self- and bus-powered operation.
☞
If the USB interface is not used, connect
VDD_USB
to GND.
2.2.6
SQI Flash memory
An external SQI (Serial Quad Interface) Flash memory is mandatory and connected to the EVA-M8E
SQI interface, which provides the following functionalities:
•
Run firmware out of the SQI Flash and have the possibility to update the firmware
•
Store the current configuration permanently
•
Save data logging results
•
Hold AssistNow Offline and AssistNow Autonomous data
☞
An SQI Flash must be connected when firmware update is a prime requirement.
☞
The EVA-M8E module needs to make use of a dedicated flash firmware with an external SQI Flash
memory. The voltage level of the SQI interface follows the
VCC_IO
level. Therefore, the SQI Flash
must be supplied with the same voltage as
VCC_IO
of the EVA-M8E. It is recommended to place a
decoupling capacitor (C4) close to the supply pin of the SQI Flash.
☞
Make sure that the SQI Flash supply range matches the voltage supplied at
VCC_IO
.
