Specifications

XT55 Hardware Interface Description
Confidential / Preliminary
s
mo b i l e
XT55_hd_v00.02 Page 73 of 116 17.03.2004
4.4 Power supply of the XT55 GPS part
The power supply for the GPS part of the XT55 module has to be a single voltage source of
V
CC
=3.3V ± 5%. It must be able to provide sufficient current of 250 mA.
GPS_VCC:
Two GPS_VCC pins of the board-to-board connector are dedicated to connect the power
supply voltage, five GND pins shared with the GSM/GPRS part of the XT55 module are
recommended for grounding; see Figure 42 for details.
GPS_V_ANT:
This pin is reserved for an external DC power supply for active antenna.
The antenna bias for an external active antenna can be provided in two way to pin
GPS_V_ANT.
The GPS_V_ANT input voltage should be chosen according to the antenna to be used.
In order to use a 5V active GPS antenna, the GPS_V_ANT has to be connected to 5V
external power supply respectively.
The other possibility is available when you connect the GPS_VCC_RF output (which
provides 3.0V) to GPS_V_ANT, so that an antenna with 3.0V supply voltage can be used.
GPS_VCC_RF:
This pin is an output which provide +3.0 V DC, and can be connected to the GPS_V_ANT, to
supply the connected GPS antenna. In Trickle Power and Push-To-Fix modes,
GPS_VCC_RF is switched off during the sleep mode.
4.5 General purpose input/output
Several I/O’s (GPS_GPIO0, GPS_GPIO1, GPS_GPIO3, GPS_GPIO5, GPS_GPIO6,
GPS_GPIO7, GPS_GPIO10, GPS_GPIO13, GPS_GPIO14, GPS_GPIO15) of the CPU are
connected to the hardware interface connector of the XT55 GPS receiver. They are reserved
for customer specific applications.
For example:
· For realization a SPI-Bus
· For realization an antenna indication.
Not all of these pins are supported by the current GPS firmware.