MAX-7 / NEO-7 - Hardware Integration Manual
UBX-13003704
-
R09
Production Information
Design
Page
15 of 52
3
Design
3.1
Design checklist
Designing-in a u-blox 7 module is easy, especially when based on a u-blox reference design. Nonetheless, it pays
to do a quick sanity check of the design. This section lists the most important items for a simple design check.
The design checklist can also help to avoid an unnecessary PCB respin and achieve the best possible
performance. Follow the design checklists when developing any u-blox 7 GNSS applications. This can
significantly reduce development time and costs.
3.1.1
Schematic checklist
If required, does your schematic allow for using different module variants? See the u-blox website
(www.u-blox.com) to compare the available features of u-blox 7 GNSS modules.
Plan the use of a second interface (Test points on UART, DDC or USB) for firmware updates or as a
service connector.
Power supply requirements
GNSS positioning modules require a stable power supply. In selecting a strategy to achieve a clean and
stable power supply, any resistance in the
VCC
supply line can negatively influence performance.
Consider the following points:
Wide power lines or even power planes are preferred.
Avoid resistive components in the power line (e.g. narrow power lines, coils, resistors, etc.).
Placing a filter or other source of resistance at
VCC
can create significantly longer acquisition times.
For ground plane design, see section 3.3.3.
Are all power supplies (
VCC
, VDD_USB) within the specified range? (See the data sheet:
NEO-7
[1] or
MAX-7
Compare the peak supply current consumption of your u-blox 7 module
with the specification of the
power supply. (See the data sheet
for more information.)
At the module input, use low ESR capacitors that can deliver the required current/charge for switching
from backup mode to normal operation.
Backup battery
Use of valid time and the GNSS orbit data at startup will improve the GNSS performance i.e. enables hot
starts, warm starts and the AssistNow Autonomous process as well as AssistNow Offline. To make use of
these features connect a battery to V_BCKP to continue supplying the backup domain in case of power
failure at
VCC_IO
.
If no backup supply voltage is available, connect the
V_BCKP
pin to
VCC_IO
(or to
VCC
if not avaiable).
3.1.2
Layout checklist
See section 3.3.
Is the GNSS module located according to the recommendation?
Has the grounding concept been followed?
Has the micro strip been kept as short as possible?
Add a ground plane underneath the GNSS module to reduce interference.
For improved shielding, add as many vias as possible around the micro strip, around the serial
communication lines, underneath the GNSS module etc.
Have appropriate EOS/ESD/EMI protection measures been included? This is especially important for
designs including cellular modules.
