AMY-5M - Hardware Integration Manual
GPS.G5-MS5-08207-A3
Preliminary
Design-in
Page 27 of 54
Equation 2 Calculation of antenna supervisor current (I
ANT
)
Equation 2 shows the calculation of the antenna supervisor current I
ANT
. In case antenna supply voltage V_ANT
exceeds VDD_IO, open drain buffers U32 (e.g. Fairchild NC7WZ07) and resistors R31 and R30 are required to
maintain control on T31 as well as to avoid leakage currents into the internal pull-ups of pins PIO8/EXTINT1 and
PIO18.
R34 serves as a current limiter in case of a short circuit.
The three I/Os used for the Antenna Supervisor function are assigned using protocol messages.
Table 5 shows the functions of the antenna supervisor pins.
Function
Input/Output
Pin
Antenna off
Output
PIO17
Antenna detection
Input
PIO8/EXTINT1
Antenna short circuit detection
Input
PIO18
Table 5: Assignments of the antenna supervisor function
2.7
Design-in checklist
2.7.1
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 0 (Power
Management).
Use a dual power supply for optimal power consumption and performance.
For USB devices: Is the voltage VDDUSB within the specified range? Do you have a Bus or Self powered
setup?
Compare the peak current consumption of AMY-5M with the specification of your power supply.
GPS receivers require a stable power supply. Avoid series resistance in your power supply line to minimize
the voltage ripple on V_DCDC and VDD_3V
(<50mVpp).
Backup battery
For achieving a minimal Time To First Fix (TTFF) after a power down, make sure to connect a backup battery
to V_BCKP, and use an RTC.