Murata Electronics North America DNT900 Manual Do Utilizador
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DNT900 - 11/05/08
3.5 Interfacing to 5 V Logic Systems
All logic signals including the serial ports on the DNT900 are 3.3 V signals. To interface to 5 V signals, the
resistor divider network shown below must be placed between the 5 V signal outputs and the DNT900
signal inputs. The output voltage swing of the DNT900 3.3 V signals is sufficient to drive 5 V logic inputs.
resistor divider network shown below must be placed between the 5 V signal outputs and the DNT900
signal inputs. The output voltage swing of the DNT900 3.3 V signals is sufficient to drive 5 V logic inputs.
5V
Logic
DNT500
2.2K
4.3K
Figure 3.5.1
3.6 Power-On Reset Requirements
The DNT900 has an internal reset circuit that generates and maintains the DNT900 in a reset state until
the power supply voltage reaches 3.3 volts for 100 milliseconds. This reset circuit protects the radio and
non-volatile memory from brown-out voltage conditions. If devices that communicate with the DNT900
have shorter reset periods, an allowance must be made to allow the DNT900 to come out of reset. Com-
mands and data sent before the DNT900 is out of reset will be ignored.
the power supply voltage reaches 3.3 volts for 100 milliseconds. This reset circuit protects the radio and
non-volatile memory from brown-out voltage conditions. If devices that communicate with the DNT900
have shorter reset periods, an allowance must be made to allow the DNT900 to come out of reset. Com-
mands and data sent before the DNT900 is out of reset will be ignored.
3.7 Mounting and Enclosures
DNT900C radio modules are mounted by reflow soldering them to a host circuit board. DNT900P mod-
ules are mounted by plugging their pins into a set of mating connectors on the host circuit board. Refer to
the DNT900 Data Sheet for DNT900P connector details.
ules are mounted by plugging their pins into a set of mating connectors on the host circuit board. Refer to
the DNT900 Data Sheet for DNT900P connector details.
DNT900 radio module enclosures must be made of plastics or other materials with low RF attenuation to
avoid compromising antenna performance. Metal enclosures are not suitable as they will block antenna
radiation and reception. Outdoor enclosures must be water tight, such as a NEMA 4X enclosure.
avoid compromising antenna performance. Metal enclosures are not suitable as they will block antenna
radiation and reception. Outdoor enclosures must be water tight, such as a NEMA 4X enclosure.
3.8 Connecting Antennas
A U.FL miniature coaxial connector is provided on both DNT900 configurations for connection to the
RFIO port. A short U.FL coaxial cable can be used to connect the RFIO port directly to an antenna. In this
case the antenna should be mounted firmly to avoid stressing the U.FL coaxial cable due to antenna
mounting flexure. Alternately, a U.FL coaxial jumper cable can be used to connect the DNT900 module to
RFIO port. A short U.FL coaxial cable can be used to connect the RFIO port directly to an antenna. In this
case the antenna should be mounted firmly to avoid stressing the U.FL coaxial cable due to antenna
mounting flexure. Alternately, a U.FL coaxial jumper cable can be used to connect the DNT900 module to
a U.FL connector on the host circuit board. The connection between the host circuit board U.FL connector
and the antenna or antenna connector on the host circuit board should be implemented as a 50 ohm
stripline. The design details of the stripline are covered in the DNT900 Data Sheet.
and the antenna or antenna connector on the host circuit board should be implemented as a 50 ohm
stripline. The design details of the stripline are covered in the DNT900 Data Sheet.