NORA-B1 series - System integration manual
UBX-20027617 - R02
System description
Page 10 of 58
C1-Public
1.5.2
Digital I/O interfaces reference voltage
The digital I/O pins operating voltage is equal to
VDD
, regardless of whether it is connected to an
external source or generated from the high voltage regulator. As noted above, when in high voltage
mode,
VDD
voltage is configured through the VREGHVOUT register in the application core UICR.
1.5.3
USB supply input
If used by the application, apply the VBUS power from the upstream USB host port to the
VBUS
pin.
The USB voltage regulator is an 3.3V LDO regulator used to power the USB subsystem and provide a
reference voltage for the
USB_DP
and
USB_DM
signals.
1.5.4
VDD/VDDH application circuits
The power for NORA-B1 series modules is provided through the
VDD
and
VDDH
pins. The power can
be taken from any of the following sources:
•
Switching Mode Power Supply (SMPS)
•
Low Drop Out (LDO) regulator
•
Battery
An SMPS is the ideal choice when the available primary supply source has a higher value than the
operating supply voltage of the NORA-B1 series modules. The use of SMPS provides the best power
efficiency for the overall application and minimizes the current drawn from the main supply source.
⚠
When using an SMPS source, ensure that the AC voltage ripple at the switching frequency is kept
as low as possible. The layout must be implemented to minimize impact of high frequency ringing.
The use of an LDO linear regulator is convenient for a primary supply with a relatively low voltage
where the typical 85-90% efficiency of the switching regulator leads to minimal current saving. Linear
regulators are not recommended for high voltage step-down, as they dissipate a considerable amount
of energy.
DC-DC efficiency should be evaluated as a tradeoff between active and idle duty cycles of the specific
application. Although some DC-DC conversion can be efficient for extremely light loads, DC-DC
conversion efficiency quickly degrades as the idle current drops below a few milliamps (mA), which
significantly reduces the battery life.
Due to the low current consumption and wide voltage range of NORA-B1, a battery can be used as a
main supply. The capacity of the battery should be selected to match the application. Care should be
taken to ensure that the battery can deliver the peak current required by the module. See the
NORA-B1 series data sheet [1] for the electrical specifications.
Although it is best practice to include decoupling capacitors on the supply rails close to the NORA-B1
series module, the need for additional capacitance is normally dependent on the design of the power
routing in the host system.
1.6
System function interfaces
1.6.1
Module reset
You can reset NORA-B1 by applying a low level on the
nRESET
input pin, which is internally pulled high
to
VDD
. This causes an “external” or “hardware” reset of the module. The current parameter settings
are not saved in the non-volatile memory of the module and a proper network detach is not performed.
