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DNT90 Integration Guide - 08/09/12
Pin
Name
I/O
Description (continued)
24
ADC2
I
ADC input 2. Direct input when the ADC is operating in single-ended mode, positive differential
input relative to ADC0 when the ADC is operating in differential mode.
25
ADC_EXT_
REF
I/O
ADC external reference voltage pin. The voltage at this pin can be used by the ADCs as a refer-
ence for ratiometric measurements. With no external voltage or load applied, this pin presents a
nominal 2.7 V output through a 2.126 K source resistance. A low impedance external reference
voltage in the range of 1.0 to 2.7 V may be applied to this pin as an option.
26
RSVD
-
Reserved pin. Leave unconnected.
27
RSVD
-
Reserved pin. Leave unconnected.
28
GND
-
Connect to the host circuit board ground plane.
29
RSVD
-
Reserved pin. Leave unconnected.
30
GND
-
Connect to the host circuit board ground plane.
6.3 Antenna Connector
Table 6.2.1
A U.FL miniature coaxial connector is provided on both DNT90E 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 DNT90E 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
C i r c u i t B o a r d S t r i p l i n e T r a c e D e t a i l
F o r 5 0 o h m
i m p e d a n c e W
= 1 . 7 5 * H
Figure 6.3.1
Trace Separation from
50 ohm Microstrip
Length of Trace Run
Parallel to Microstrip
100 mil
125 mill
150 mil
200 mil
200 mil
290 mil
250 mil
450 mil
300 mil
650 mil
Table 6.3.2
stripline. Referring to Figure 6.3.1, the width of this stripline depends on the thickness of the circuit board
between the stripline and the groundplane. For FR-4 type circuit board materials (dielectric constant of
4.7), the width of the stripline is equal to 1.75 times the thickness of the circuit board. Note that other cir-
C o p
p e r
S t r i
p l i n
e T r a
c e
C o
p p e
r
G r o
u n d
P l a
n e
F R - 4
P C B
M a t
e r i a
l