AMY-6M - Hardware Integration Manual
UBX-17021971 – R07
Design-in
Page 28 of 57
2.8
Active antenna supervisor
u-blox 6 firmware supports an active antenna supervisor circuit, which can be connected to AMY-6M via pins
PIO08/EXTINT1, PIO17, and PIO18. The external components shown in Figure 25 detect whether an active
antenna is connected, i.e. if the DC supply current exceeds a threshold defined by R34, R38, and R39, or if a
short circuit of the antenna supply has occurred. It will shut down the antenna via transistor T31 if it’s not
needed or if a short circuit has been detected.
o p t io n al
V _ A N T
A M Y - 6 M
PIO 0 8 / EX T IN T 1
R 3 4
PIO 1 7
PIO 1 8
R 3 8
R 3 9
R 3 0
R 3 1
t o an t en n a in p u t
U 3 2 .1
U 3 2 .2
V _ A N T
V D D _ IO
V D D _ IO
T 3 1
U 3 1
Figure 25: Active antenna supervisor circuit
Equation 1 Calculation of antenna supervisor current (I
ANT
)
Equation 1 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. See
u-blox 6
Receiver Description including Protocol Specification
Table 7 shows the functions of the antenna supervisor pins.
Table 7: Assignments of the antenna supervisor function
Function
Input/Output
Pin
Antenna off
Output
PIO17
Antenna detection
Input
PIO8/EXTINT1
Antenna short circuit detection
Input
PIO18
