NORA-W30 series - System integration manual
UBX-22021119 - R02
Module integration
Page 13 of 52
C1-Public
•
GPIO input
•
Timers
NORA-W30 can be awakened from deep sleep mode by the following sources:
•
Power-down event
•
Real-time clock
•
Key press
•
Low-power timers
•
GPIO input
2.4
Power management
2.4.1
SPS, digital I/O and system supply (VDD)
NORA-W30 series have a single power supply input
–
VDD
–
which is also the I/O voltage reference.
Nominal voltage is 3.3 VDC ±10%.
2.4.2
Power supply configuration
The RTL8720DF within NORA-W30 series can be configured for operating the MCU cores in switch
mode power supply (SMPS, or SPS) or low drop-out (LDO) linear mode. Default is SPS. LDO may be
selected by changing the strapping, though is not recommended for normal operation. See also
2.4.3
VDD application circuits
The power for NORA-W30 series modules is applied through the
VDD
pins. These supplies are taken
from either of the following sources:
•
Switch Mode Power Supply (SMPS)
•
Low dropout linear regulator (LDO)
An SMPS is the ideal design choice when the available primary supply source is significantly higher
than the operating supply voltage of the module. This offers the best power efficiency for the
application design and minimizes the amount of current drawn from the main supply source.
⚠
When taking VDD supplies from an SMPS make sure that the AC ripple voltage is kept as low as
possible at the switching frequency. Design layouts should focus on minimizing the impact of any
high-frequency ringing.
Use an LDO linear regulator for primary VDD supplies that have a relatively low voltage. As LDO
regulators dissipate power linearly related to the step-down voltage, LDOs are not recommended for
step down of high voltages.
DC-DC efficiency should be regarded as a trade-off between the active and idle duty cycles of an
application. Although some DC-DC devices achieve high efficiency at light loads, these efficiencies
typically degrade as soon as the idle current drops below a few milliamps. This can have a negative
impact on the life of a battery.
If decoupling capacitors are needed on the supply rails, it is best practice to position these as close as
possible to the NORA-W30 series module. The power routing of some host system designs makes
decoupling capacitance unnecessary.
For electrical specifications, see also the appropriate NORA-W30 series data sheet
