LEA-5, NEO-5, TIM-5H - Hardware Integration Manual
GPS.G5-MS5-09027-A2
Released
Hardware description
Page 10 of 68
specification) for a short time. In order to define a battery capacity for specific applications the sustained power
figure shall be used.
When switching from backup mode to normal operation u-blox 5 modules must charge the internal
capacitors in the core domain. This can result in certain situations result in a significant current draw. For
low power applications using Power Save and backup modes it is important that the power supply or
low ESR capacitors at the module input can deliver this current/charge.
1.3.1.2
V_BCKP - –ackup battery
In case of a power failure on pin
VCC
, the real-time clock and backup RAM are supplied through pin
V_BCKP
.
This enables the u-blox 5 receiver to recover from a power failure with either a Hotstart or a Warmstart
(depending on the duration of
VCC
outage) and to maintain the configuration settings. If no backup battery is
connected, the receiver performs a Coldstart at power up.
If no backup battery available connect the V_BCKP pin to GND (or VCC).
As long as
VCC
is supplied to the u-blox 5 receiver, the backup battery is disconnected from the RTC and the
backup RAM in order to avoid unnecessary battery drain (see Figure 2). Power to RTC and BBR is supplied from
VCC
in this case.
VCC
V_BCKP
Voltage
Supervisor
Module Voltage Supply
RTC and Battery Backup RAM (BBR)
J1
Figure 2: Backup Battery and Voltage
1.3.1.3
VDD_USB - –SB interface power supply (LEA-5, NEO-5)
VDD_USB
supplies the I/Os of the USB interface. If the USB interface is not used, the
VDD_USB
pin must be
connected to GND. For more information regarding the correct handling of
VDD_USB
see section 1.5.2.1
1.3.2
Operating modes
u-blox 5 modules with FW 6.00 have 2 continuous operating modes (Maximum Performance and Eco) and 1
intermittent operating mode (Power Save mode). Maximum Performance mode freely uses the acquisition
engine, resulting in the best possible TTFF, while Eco mode optimizes the use of the acquisition engine to deliver
lower current consumption. At medium to strong signals, there is almost no difference for acquisition and
tracking performance in these modes.
1.3.2.1
Maximum Performance mode
In Maximum Performance mode, u-blox 5 receivers use the acquisition engine at full performance to search for
all possible satellites until the Almanac is completely downloaded.
As a consequence, tracking current consumption level will be achieved when:
A valid GPS position is fixed
Almanac is entirely downloaded
Ephemeris for all satellites in view are valid
