u-blox AMY-5M, Руководство по интеграции оборудования

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AMY-5M - Hardware Integration Manual Objective Specification Design-In
GPS.G5-MS5-08207 u-blox proprietary Page 23
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2.4.3 SAFEBOOT_N
Design a test point to access SAFEBOOT_N in the PCB design.
2.4.4 RTC
The RTC crystal is optional as it is only required in stand-alone applications where hot or warm starts are
enabled. In these cases, actual time is maintained in the RTC and Ephemeris and other last known data is kept in
the backup RAM. In A-GPS based systems, the RTC is not required and coarse or fine time information is
available from the network. If neither backup RAM nor RTC are required, V_BCKP should be connected to GND.
If the RTC is not used, its input XTAL_IN should be connected to GND and the output XTAL_OUT must be left
open.
As an alternative to the RTC, a 32 kHz signal can be supplied from an external source (e.g. from the host system)
into XTAL_IN. This is a core domain signal, its high level must not exceed VDD_B. (1.2V!)
2.5 Increasing Jamming Immunity
In the case of a large out-of-band jamming signal, caused by a wireless transmitter close to the GPS antenna for
instance, an alternative configuration can be used, which still allows taking advantage of the integrated LNA.
This is illustrated in Figure 13: A single-ended SAW Filter F2 can be placed at the RF_IN pin.
f
GPS
=1575.42MHz
SAW Filter
F2
AMY-5
RF_IN
Figure 13: Alternative Configuration for large out-of-band jamming signals
2.6 Design-In Checklist
2.6.1 Schematic Design-In Checklist for u-blox 5
Designing-in an AMY-5M GPS receiver is easy especially when a design is based on the reference design in the
Hardware Integration Manual. 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 Layout Design-In Checklist also helps to avoid an
unnecessary respin of the PCB and helps to achieve the best possible performance.
It is highly recommended to follow the Design-In Checklist when developing any u-blox 5 GPS
applications. This can significantly reduce development time and costs.
Have you chosen the optimal module?
AMY-5M modules have been intentionally designed to allow GPS receivers to be optimally tailored to specific
applications. Changing between the different variants is easy.
Check Power Supply Requirements and Schematic:
Is the power supply within the specified range? See how to connect power in Section 2.1 (Power
Management).
Use a dual power supply for optimal power consumption and performance.