EVA-M8E - Hardware Integration Manual
UBX-15028542 - R05
Contents
Page 8 of 44
Production Information
2.1.1.1
Main supply voltage (VCC)
During operation, the EVA-M8E module is supplied through the
VCC
pin. It makes use of an internal
DC/DC converter for improved power efficiency. In a following step, built-in 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-M8E module 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.
☞
VCC_IO
must be supplied in order for the system to boot.
☞
Because of running the firmware from the external SQI Flash, most of the VDD_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 Real-Time Clock see section 2.4
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 14
•
Separate supply voltages for
VCC
,
VCC_IO
and
V_BCKP
see Appendix, Figure 15
