HSMS-286C-TR1 Avago Technologies US Inc., HSMS-286C-TR1 Datasheet - Page 10

• Manufacturer Part Number: HSMS-286C-TR1
• Description: DETECTOR DIODE,SOT-323
• Manufacturer: Avago Technologies US Inc.

Specifications of HSMS-286C-TR1

• Rohs Compliant: NO
• Diode Type: Schottky - 1 Pair Series Connection
• Voltage - Peak Reverse (max): 4V
• Capacitance @ Vr, F: 0.25pF @ 0V, 1MHz
• Package / Case: SC-70-3, SOT-323-3
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Max: -
• Power Dissipation (max): -
• Resistance @ If, F: -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Input return loss, shown in
Figure 23, exhibits wideband
match.
Figure 23. Input Return Loss.
Voltage Doublers
To this point, we have restricted
our discussion to single diode
detectors. A glance at Figure 9,
however, will lead to the
suggestion that the two types of
single diode detectors be
combined into a two diode
voltage doubler
a full wave rectifier). Such a
detector is shown in Figure 24.
Figure 24. Voltage Doubler Circuit.
Such a circuit offers several
advantages. First the voltage
outputs of two diodes are added
in series, increasing the overall
value of voltage sensitivity for the
network (compared to a single
diode detector). Second, the RF
impedances of the two diodes are
added in parallel, making the job
of reactive matching a bit easier.
Such a circuit can easily be
realized using the two series
diodes in the HSMS-286C.
RF IN
-10
-15
-20
-5
0
5.6
NETWORK
Z-MATCH
5.7
FREQUENCY (GHz)
[4]
(known also as
5.8
VIDEO OUT
5.9
6.0
The “Virtual Battery”
The voltage doubler can be used
as a virtual battery, to provide
power for the operation of an I.C.
or a transistor oscillator in a tag.
Illuminated by the CW signal from
a reader or interrogator, the
Schottky circuit will produce
power sufficient to operate an I.C.
or to charge up a capacitor for a
burst transmission from an
oscillator. Where such virtual
batteries are employed, the bulk,
cost, and limited lifetime of a
battery are eliminated.
Temperature Compensation
The compression of the detector’s
transfer curve is beyond the
scope of this data sheet, but some
general comments can be made.
As was given earlier, the diode’s
video resistance is given by
where T is the diode’s tempera-
ture in °K.
As can be seen, temperature has a
strong effect upon R
will in turn affect video band-
width and input RF impedance.
A glance at Figure 6 suggests that
the proper choice of bias current
in the HSMS-286x series can
minimize variation over
temperature.
The detector circuits described
earlier were tested over tempera-
ture. The 915 MHz voltage
doubler using the HSMS-286C
series produced the output
voltages as shown in Figure 25.
The use of 3 µA of bias resulted in
the highest voltage sensitivity, but
at the cost of a wide variation
over temperature. Dropping the
bias to 1 µA produced a detector
R
V
=
8.33 x 10
I
S
+ I
V
b
, and this
-5
nT
with much less temperature
variation.
A similar experiment was con-
ducted with the HSMS-286B
series in the 5.8 GHz detector.
Once again, reducing the bias to
some level under 3 µA stabilized
the output of the detector over a
wide temperature range.
It should be noted that curves
such as those given in Figures 25
and 26 are highly dependent upon
the exact design of the input
impedance matching network.
The designer will have to experi-
ment with bias current using his
specific design.
Figure 25. Output Voltage vs.
Temperature and Bias Current in the
915 MHz Voltage Doubler using the
HSMS-286C.
Figure 26. Output Voltage vs.
Temperature and Bias Current in the
5.80 GHz Voltage Detector using the
HSMS-286B Schottky.
120
100
35
25
15
80
60
40
5
10
-55
-55
-35
-35
1.0 µA
10 µA
3.0 µA
0.5 µA
TEMPERATURE (°C)
-15
3.0 µA
1.0 µA
10 µA
0.5 µA
TEMPERATURE (°C)
-15
INPUT POWER = – 30 dBm
INPUT POWER = –30 dBm
5
5
25
25
45
45
65
65
85
85