EVA-8M and EVA-M8 series - Hardware Integration Manual
UBX-16010593 - R06
Design-in
Page 8 of 47
Early Production Information
LDOs generate stabilized voltages for the Core and RF domains of the chip respectively. The current
at
VCC
depends heavily on the current state of the system and is in general very dynamic.
☞
Do not add any series resistance (< 0.2
Ω
) to the
VCC
supply, as it will generate input voltage noise
due to the dynamic current conditions.
☞
The equipment must be supplied by an external limited power source in compliance with the clause
2.5 of the standard IEC 60950-1.
2.1.1.2
I/O supply voltage (VCC_IO)
The digital I/Os of the EVA-8M / EVA-M8 series GNSS modules can be supplied with a separate voltage
from the host system connected to the
VCC_IO
pin of the module. The wide range of
VCC_IO
allows
seamless interfacing to standard logic voltage levels. However, in most applications
VCC_IO
and
VCC
share the same voltage level and are tied together.
VCC_IO
supplies also the RTC and the backup RAM
(BBR) during normal operation.
The EVA-8M / EVA-M8 series GNSS modules come in two different IO voltage range flavors:
1.
EVA-M8Q with IO voltage from 2.7 V to 3.6 V
2.
EVA-M8M and EVA-8M with the wider range from 1.65 V to 3.6 V. The level should be set
according to section 2.2.5.
☞
VCC_IO
must be supplied in order for the system to boot.
☞
When running the firmware from the external SQI Flash most of the
VCC_IO
current is consumed
by the SQI bus.
2.1.1.3
Backup power supply (V_BCKP)
In the event of a power failure at
VCC_IO
, the backup domain is supplied by
V_BCKP
.
☞
If no backup supply is available, connect
V_BCKP
to
VCC_IO
.
☞
Avoid high resistance on the
V_BCKP
line: During the switch from main supply to backup supply,
a short current adjustment peak can cause high voltage drop on the pin with possible
malfunctions.
☞
If the “single crystal” feature is enabled (which derives the RTC frequency from the main clock),
the
V_BCKP
pin also supplies the clock domain if there is a power failure at
VCC_IO
, meaning that
the
V_BCKP
current will also be higher. Ensure that the capacity of the backup battery chosen
meets your requirements. EVA-M8Q module uses TCXO oscillator and does not support the
“single crystal” feature. For more information about “single crystal” feature see section 2.4.2
2.1.1.4
USB interface power supply
VDD_USB
supplies I/Os of the USB interface. If the USB interface is being used, the system can be
either self-powered, i.e. powered independently from the USB bus, or it can be bus-powered, i.e.
powered through the USB connection. In bus-powered mode, the system supply voltages need to be
generated from the USB supply voltage VBUS.
☞
If the USB interface is not used, the
VDD_USB
pin must be connected to GND.
2.1.2
Power management configuration
Depending on the application, the power supply schematic will differ. Some examples are shown in the
following sections:
•
Single supply voltage for
VCC
and
VCC_IO
, no backup supply
see Appendix, Figure 13
•
Separate supply voltages for
VCC
,
VCC_IO
and
V_BCKP
see Appendix, Figure 14
•
Single supply voltage for
VCC
and
VCC_IO
, use of a backup supply
see Appendix, Figure 16
