www.RFM.com
© 2010-2012 by RF Monolithics, Inc.
Technical s1.678.684.2000
E-mail:
Page 31 of 80
DNT90 Integration Guide - 08/09/12
D N T
5 0 0
cuit board traces should be spaced away from the stripline to prevent signal coupling, as shown in Table
6.3.2. The stripline trace should be kept short to minimize its insertion loss.
6.4 Power Supply and Input Voltages
DNT90E radio modules can operate from an unregulated DC input (Pad 19) in the range of 3.3 to 5.5 V
with a maximum ripple of 5% over the temperature range of -40 to 85 °C.
Applying AC, reverse DC, or a
DC voltage outside the range given above can cause damage and/or create a fire and safety hazard. Fur-
ther, care must be taken so logic inputs applied to the radio stay within the voltage range of 0 to 3.3 V.
Signals applied to the analog inputs must be in the range of 0 to ADC_EXT_REF (Pad/Pin 25). Applying a
voltage to a logic or analog input outside of its operating range can damage the DNT90E module.
6.5 ESD and Transient Protection
The DNT90EC and DNT90EP circuit boards are electrostatic discharge (ESD) sensitive. ESD precautions
must be observed when handling and installing these components. Installations must be protected from
electrical transients on the power supply and I/O lines. This is especially important in outdoor installations,
and/or where connections are made to sensors with long leads.
Inadequate transient protection can result
in damage and/or create a fire and safety hazard.
6.6 Interfacing to 5 V Logic Systems
All logic signals including the serial ports on the DNT90E are 3.3 V signals. To interface to 5 V signals,
the resistor divider network shown in Figure 3.7.1 below must be placed between the 5 V signal outputs
and the DNT90E signal inputs. The output voltage swing of the DNT90E 3.3 V signals is sufficient to
drive 5 V logic inputs.
5 V
L o g i c
6.7 Mounting and Enclosures
Figure 6.6.1
DNT90EC radio modules are mounted by reflow soldering them to a host circuit board. DNT90EP
modules are mounted by plugging their pins into a set of mating connectors on the host circuit board.
Refer to Sec- tion 8.3 and/or the DNT90E Data Sheet for DNT90EP connector details.
DNT90E enclosures must be made of plastics or other materials with low RF attenuation to avoid compro-
mising antenna performance where antennas are internal to the enclosure. Metal enclosures are not suit-
able for use with internal antennas as they will block antenna radiation and reception. Outdoor enclosures
must be water tight, such as a NEMA 4X enclosure.
DNT90
2 .
2
K
4 .
3
K