EVA-8M and EVA-M8 series - Hardware Integration Manual
UBX-16010593 - R06
Design-in
Page 18 of 47
Early Production Information
Safe Boot Mode is used in production to program the SQI Flash. It is recommended to have the
possibility to pull the
SAFEBOOT_N
pin “low” when the module starts up. This can be provided using
an externally connected test point or via a host CPUs digital I/O port.
2.7
System Reset (RESET_N)
The EVA-8M / EVA-M8 series GNSS modules provide a
RESET_N
pin to reset the system. The
RESET_N
is an input-only with internal pull-up resistor. It must be at low level for at least 10 ms to
make sure
RESET_N
is detected. It is used to reset the system. Leave
RESET_N
open for normal
operation. The
RESET_N
complies with the
VCC_IO
level and can be actively driven high.
☞
RESET_N
should be only used in critical situations to recover the system. The Real-Time Clock
(RTC) will also be reset and thus immediately afterwards the receiver cannot perform a Hot Start.
☞
In reset state, the module consumes a significant amount of current. It is therefore recommended
to use
RESET_N
only as a reset signal and not as an enable/disable.
2.8
Design-in checklist
2.8.1
General considerations
Check power supply requirements and schematic:
Is the power supply voltage within the specified range? See how to connect power in Section 2.1.
For USB devices: Is the voltage
VDD_USB
voltage within the specified range? Do you have a Bus
or Self powered setup?
Compare the peak current consumption of EVA-8M / EVA-M8 series GNSS modules with the
specification of your power supply.
GNSS receivers require a stable power supply. Avoid series resistance in your power supply line
(the line to
VCC
) to minimize the voltage ripple on
VCC
.
Backup battery
For achieving a minimal Time To First Fix (TTFF) after a power down (warm starts, hot starts),
make sure to connect a backup battery to
V_BCKP
, and use an RTC. If not used, make sure
V_BCKP
is connected to
VCC_IO
.
Antenna/ RF input
The total noise figure including external LNA (or the LNA in the active antenna) should be around
1 dB.
With the EVA-8M / EVA-M8 series GNSS module, an external LNA is mandatory if no active
antenna is used to achieve the performance values as written in the
EVA-M8 Data Sheet [1] and
the
EVA-8M Data Sheet [2] .
Make sure the antenna is not placed close to noisy parts of the circuitry and not facing noisy
parts. (e.g. micro-controller, display, etc.)
To optimize performance in environments with out-band jamming/interference sources, use an
additional SAW filter.
☞
For more information dealing with interference issues see the
GPS Antenna Application Note [4]
Schematic
Inner pins of the package must all be connected to GND.
2.8.2
Schematic design-in for EVA-8M / EVA-M8 series GNSS modules
For a minimal design with the EVA-8M / EVA-M8 series GNSS modules, the following functions and
pins need to be considered:
•
Connect the power supply to
VCC
,
VCC_IO
and
V_BCKP
.
