EVA-7M - Hardware Integration Manual
UBX-12003235 - R05
Production Information
Design-in
Page 8 of 42
2.1.1.1
Main supply voltage (VCC)
During operation, the EVA-7M 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.
2.1.1.2
I/O supply voltage (VCC_IO)
The digital I/Os of the EVA-7M 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.
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 RTC frequency is derived 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.
2.1.1.4
USB interface power supply
V_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
V_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 12
•
Separate supply voltages for
VCC
,
VCC_IO
and
V_BCKP
see Appendix, Figure 13
•
Single supply voltage for
VCC
and
VCC_IO
, use of a backup supply
see Appendix, Figure 15
For description of the different operating modes see the
