HSMS-286ASERIES [ETC]
Surface Mount Microwave Schottky Detector Diodes in SOT-323 (SC-70) (155K in pdf) ; 表面贴装肖特基微波检波二极管，采用SOT -323 （ SC - 70 ） （以PDF 155K ）\n
| 型号： | HSMS-286ASERIES |
| 厂家： | 
ETC |
| 描述： | Surface Mount Microwave Schottky Detector Diodes in SOT-323 (SC-70) (155K in pdf)
|
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Surface Mount Microwave
Schottky Detector Diodes in
SOT-323 (SC-70)
Technical Data
HSMS-285A Series
HSMS-286A Series
Features
Package Lead Code
Identification
( Top View)
Description
Hewlett-Packard’s HSMS-285A
family of zero bias Schottky detector
diodes and the HSMS-286A family of
DC biased detector diodes have been
designed and optimized for use from
915 MHz to 5.8 GHz. They are ideal
for RF/ID and RF Tag, cellular and
other consumer applications
• Surface Mount SOT-323
Package
• High Detection Sensitivity:
Up to 50 mV/µW at 915 MHz
Up to 35 mV/µW at 2.45 GHz
Up to 25 mV/µW at 5.80 GHz
SERIES
SINGLE
B
C
• Low Flicker Noise:
COMMON
ANODE
COMMON
CATHODE
requiring small and large signal
detection, modulation, RF to DC
conversion or voltage doubling.
-162 dBV/Hz at 100 Hz
• Low FIT ( Failure in Time)
Rate*
Available in various package
• Tape and Reel Options
Available
E
F
configurations, these two families of
detector diodes provide low cost
solutions to a wide variety of design
problems. Hewlett-Packard’s
manufacturing techniques assure
that when two diodes are mounted
into a single SOT-323 package, they
are taken from adjacent sites on the
wafer, assuring the highest possible
degree of match.
* For more information see the
Surface Mount Schottky
Reliability Data Sheet.
DC Electrical Specifications, TC = +25°C, Single Diode
Part
Number
HSMS-
Package
Marking
Code[1]
Maximum Forward
Voltage V
Typical
Capacitance CT
( pF)
Lead
Code
F
Configuration
( mV)
285B
285C
286B
286C
286E
286F
P0
P2
T0
T2
T3
T4
B
C
B
C
E
F
Single[2]
150
250
250
350
0.30
Series Pair [2,3]
Single[4]
0.25
Series Pair [2,3]
Common Anode[2,3]
Common Cathode[2,3]
Test Conditions
IF = 0.1 mA IF = 1.0 mA V = 0.5V to -1.0V
R
f = 1 MHz
Notes:
1. Package marking code is laser marked.
2. ∆VF for diodes in pairs is 15.0 mV maximum at 1.0 mA.
3. ∆CT for diodes in pairs is 0.05 pF maximum at -0.5 V.
2
RF Electrical Parameters, TC = +25oC, Single Diode
Sensitivity
Typical Tangential
TSS ( dBm) @ f =
γ
Typical Video
Part
Number
Typical Voltage Sensitivity
( mV/µW) @ f =
Resistance R ( KΩ)
v
HSMS-
915 MHz 2.45 GHz 5.8 GHz 915 MHz 2.45 GHz 5.8 GHz
-57 -56 -55 40 30 22
285B
285C
8.0
5.0
Test
Conditions
Video Bandwidth = 2 MHz
Zero Bias
Power in = 40 dBm
RL = 100 LW, Zero Bias
50 35 25
286B
286C
286E
286F
-57
-56
-55
Test
Conditions
Video Bandwidth = 2 MHz
Power in = –40 dBm
RL = 100 KΩ, Ib = 5 µA
Ib = 5 µA
Absolute Maximum Ratings, Ta = 25ºC, Single Diode
ESD WARNING: Handling
Precautions Should Be Taken
To Avoid Static Discharge.
Symbol
Parameter
Unit
Absolute Maximum[1]
HSMS-285x HSMS-286x
PIV
TJ
Peak Inverse Voltage
Junction Temperature
Storage Temperature
Operating Temperature
Thermal Resistance [2]
V
°C
2.0
150
4.0
150
TSTG
TOP
θjc
°C
-65 to 150
-65 to 150
150
-65 to 150
-65 to 150
150
°C
°C/W
Notes:
1. Operation in excess of any one of these conditions may result in
permanent damage to the device.
2. TC = +25°C, where TC is defined to be the temperature at the pack-
age pins where contact is made to the circuit board.
Equivalent Circuit Model
HSMS-285B, HSMS-286B
Singles
SPICE Parameters
Parameter
Units
V
HSMS-285A
HSMS-286A
7.0
0.08 pF
BV
CJO
EG
IBV
IS
3.8
0.18
pF
eV
A
0.18
0.69
0.69
R
3 x 10E -4
3 x 10E -6
1.06
10E -5
5 x 10E -8
1.08
2 nH
j
A
R
S
N
RS
Ω
25
5.0
PB (V )
V
0.35
0.65
J
PT (XTI)
M
2
2
0.18 pF
0.5
0.5
RS = series resistance (see Table of SPICE parameters)
8.33 X 10-5 nT
Rj
=
Ib + Is
where
Ib = externally applied bias current in amps
Is = saturation current (see table of SPICE parameters)
T = temperature, °K
n = identity factor (see table of SPICE parameters)
3
Typical Parameters, Single Diode
100
100
10
100
I
(left scale)
F
TA = +85°C
TA = +25°C
TA = –55°C
10
1
10
1
10
0.1
0.01
.1
∆V (right scale)
F
.01
1
0.05
1
0.25
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
– FORWARD VOLTAGE (V)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0.10
0.15
0.20
V
FORWARD VOLTAGE (V)
FORWARD VOLTAGE (V)
F
Figure 1. +25°C Forward Current vs.
Forward Voltage, HSMS-285A Series.
Figure 2. Forward Current vs. Forward Figure 3. Forward Voltage Match,
Voltage at Temperature, HSMS-286A
Series.
HSMS-286C, E and F Pairs.
10000
30
10,000
R
= 100 KΩ
L
R
= 100 KΩ
20 µA
5 µA
L
915 MHz
10 µA
1000
100
10
10
2.45 GHz
915 MHz
1000
100
2.45 GHz
Frequency = 2.45 GHz
Fixed-tuned FR4 circuit
5.8 GHz
1
10
1
5.8 GHz
R
= 100 KΩ
L
1
DIODES TESTED IN FIXED-TUNED
FR4 MICROSTRIP CIRCUITS.
DIODES TESTED IN FIXED-TUNED
FR4 MICROSTRIP CIRCUITS.
0.3
0.3
-50
-50
-40
-30
-20
-10
0
-40
-30
–40
–30
–20
–10
0
10
POWER IN (dBm)
POWER IN (dBm)
POWER IN (dBm)
Figure 4. +25°C Output Voltage vs.
Figure 5. +25°C Expanded Output
Voltage vs. Input Power. See Figure 4.
Figure 6. Dynamic Transfer
Characteristic as a Function of DC Bias,
HSMS-286A.
Input Power, HSMS-285A Series at Zero
Bias, HSMS-286A Series at 3 µA Bias.
3.1
40
35
FREQUENCY = 2.45 GHz
2.9
P
R
= -40 dBm
= 100 KΩ
IN
L
2.7
2.5
2.3
30
25
2.1
1.9
20
1.7
1.5
1.3
1.1
0.9
Input Power =
15
10
–30 dBm @ 2.45 GHz
Data taken in fixed-tuned
FR4 circuit
MEASUREMENTS MADE USING A
FR4 MICROSTRIP CIRCUIT.
R
= 100 KΩ
L
5
0
10 20 30 40 50 60 70 80 90 100
.1
1
10
100
TEMPERATURE (°C)
BIAS CURRENT (µA)
Figure 7. Voltage Sensitivity as a
Function of DC Bias Current, ꢀ
HSMS-286A.
Figure 8. Output Voltage vs.
Temperature, HSMS-285A Series.
4
Applications Information
Introduction
8.33 X 10-5 n T
Rj = –––––––––––– = RV – Rs
IS + Ib
(with high values of IS, suitable for
zero bias applications) are realized
on p-type silicon. Such diodes
suffer from higher values of RS
than do the n-type. Thus, p-type
diodes are generally reserved for
detector applications (where very
high values of RV swamp out high
RS) and n-type diodes are used for
mixer applications (where high
L.O. drive levels keep RV low).
Hewlett-Packard’s family of
HSMS-285A zero bias Schottky
diodes have been developed
specifically for low cost, high
volume detector applications
where bias current is not available.
The HSMS-286A family of DC
Schottky diodes have been
developed for low cost, high
volume detector applications
where stability over temperature is
an important design consideration.
0.026
= ––––– at 25°C
IS + Ib
where
n = ideality factor (see table of
SPICE parameters)
T = temperature in °K
IS = saturation current (see
table of SPICE parameters)
Ib = externally applied bias
current in amps
Measuring Diode Parameters
The measurement of the five
elements which make up the
equivalent circuit for a packaged
Schottky diode (see Figure 10) is a
complex task. Various techniques
are used for each element. The
task begins with the elements of
the diode chip itself.
IS is a function of diode barrier
height, and can range from
picoamps for high barrier diodes
to as much as 5 µA for very low
barrier diodes.
Schottky Barrier Diode
Characteristics
Stripped of its package, a Schottky
barrier diode chip consists of a
metal-semiconductor barrier
formed by deposition of a metal
layer on a semiconductor. The
most common of several different
types, the passivated diode, is
shown in Figure 9, along with its
equivalent circuit.
The Height of the Schottky
Barrier
The current-voltage characteristic
of a Schottky barrier diode at
room temperature is described by
the following equation:
C
P
L
R
V
P
R
S
R
S
V - IRS
METAL
I = IS (exp
(
––––––
0.026
)
- 1)
C
J
PASSIVATION
PASSIVATION
N-TYPE OR P-TYPE EPI LAYER
R
FOR THE HSMS-285A or HSMS-286A SERIES
On a semi-log plot (as shown in
the HP catalog) the current graph
will be a straight line with inverse
slope 2.3 X 0.026 = 0.060 volts per
cycle (until the effect of RS is seen
in a curve that droops at high
current). All Schottky diode curves
have the same slope, but not
necessarily the same value of
current for a given voltage. This is
determined by the saturation
current, IS, and is related to the
barrier height of the diode.
j
SCHOTTKY JUNCTION
C
j
C
L
= 0.08 pF
= 2 nH
= 0.18 pF
= 25 Ω
P
P
N-TYPE OR P-TYPE SILICON SUBSTRATE
C
R
R
J
S
V
CROSS-SECTION OF SCHOTTKY
BARRIER DIODE CHIP
EQUIVALENT
CIRCUIT
= 9 KΩ
Figure 10. Equivalent Circuit of a
Schottky Diode.
Figure 9. Schottky Diode Chip.
RS is the parasitic series resistance
of the diode, the sum of the
bondwire and leadframe
RS is perhaps the easiest to
measure accurately. The V-I curve
is measured for the diode under
forward bias, and the slope of the
curve is taken at some relatively
high value of current (such as
5 mA). This slope is converted into
a resistance Rd.
resistance, the resistance of the
bulk layer of silicon, etc. RF
energy coupled into RS is lost as
heat —it does not contribute to
the rectified output of the diode.
CJ is parasitic junction capacitance
of the diode, controlled by the
thickness of the epitaxial layer and
the diameter of the Schottky
contact. Rj is the junction
Through the choice of p-type or
n-type silicon, and the selection of
metal, one can tailor the
characteristics of a Schottky
diode. Barrier height will be
altered, and at the same time CJ
and RS will be changed. In general,
very low barrier height diodes
0.026
RS = Rd – ––––––
If
RV and CJ are very difficult to
measure. Consider the impedance
of CJ = 0.16 pF when measured at
1 MHz — it is approximately 1 MΩ.
resistance of the diode, a function
of the total current flowing
through it.
5
For a well designed zero bias
Schottky, RV is in the range of 5 to
25 KΩ, and it shorts out the
linear analysis program having the Of interest in the design of the
five element equivalent circuit
with RV, CJ and RS fixed. The
video portion of the circuit is the
diode’s video impedance —the
other four elements of the equiv-
alent circuit disappear at all
reasonable video frequencies. In
general, the lower the diode’s
junction capacitance. Moving up to optimizer can then adjust the
a higher frequency enables the
measurement of the capacitance,
but it then shorts out the video
resistance. The best measurement
technique is to mount the diode in
series in a 50 Ω microstrip test
circuit and measure its insertion
loss at low power levels (around
-20 dBm) using an HP8753C
network analyzer. The resulting
display will appear as shown in
Figure 11.
values of LP and CP until the
calculated S11 matches the
measured values. Note that
extreme care must be taken to de- video impedance, the better the
embed the parasitics of the 50 Ω
design.
test fixture.
DC BIAS
Detector Circuits
L
1
When DC bias is available,
Schottky diode detector circuits
can be used to create low cost RF
and microwave receivers with a
sensitivity of -55 dBm to
Z-MATCH
NETWORK
VIDEO
OUT
RF
IN
-10
-57 dBm.[1] Moreover, since
external DC bias sets the video
impedance of such circuits, they
display classic square law
0.16 pF
50 Ω
-15
DC BIAS
50 Ω
-20
L
1
response over a wide range of
input power levels[2,3]. These
circuits can take a variety of
forms, but in the most simple case
they appear as shown in Figure 12.
This is the basic detector circuit
used with the HSMS-286A family
of diodes.
Z-MATCH
NETWORK
VIDEO
OUT
RF
IN
-25
50 Ω 9 KΩ
-30
50 Ω
-35
-40
Figure 12. Basic Detector
Circuits.
3
10
100
1000 3000
FREQUENCY (MHz)
The situation is somewhat more
complicated in the design of the
RF impedance matching network,
which includes the package
inductance and capacitance
(which can be tuned out), the
series resistance, the junction
capacitance and the video
resistance. Of these five elements
of the diode’s equivalent circuit,
the four parasitics are constants
and the video resistance is a
function of the current flowing
through the diode.
Figure 11. Measuring CJ and RV.
Where DC bias is not available, a
zero bias Schottky diode is used to
replace the conventional Schottky
in these circuits, and bias choke L1
is eliminated. The circuit then is
reduced to a diode, an RF
impedance matching network and
(if required) a DC return choke
and a capacitor. This is the basic
detector circuit used with the
HSMS-285A family of diodes.
At frequencies below 10 MHz, the
video resistance dominates the
loss and can easily be calculated
from it. At frequencies above 300
MHz, the junction capacitance sets
the loss, which plots out as a
straight line when frequency is
plotted on a log scale. Again,
calculation is straightforward.
LP and CP are best measured on
the HP8753C, with the diode
terminating a 50 Ω line on the
input port. The resulting tabulation
of S11 can be put into a microwave
In the design of such detector
circuits, the starting point is the
equivalent circuit of the diode, as
shown in Figure 10.
[1]
Hewlett-Packard Application Note 923, Schottky Barrier Diode Video Detectors.
Hewlett-Packard Application Note 986, Square Law and Linear Detection.
Hewlett-Packard Application Note 956-5, Dynamic Range Extension of Schottky Detectors.
[2]
[3]
6
26,000
constraints and cost limitations,
but certain general design
principals exist for all types.[5]
Design work begins with the RF
impedance of the HSMS-285A
wide microstrip line is used to
mount the lead of the diode’s
SOT-323 package. A shorted shunt
stub of length <λ/4 provides the
necessary shunt inductance and
RV ≈ ––––––
IS + Ib
where
IS = diode saturation current
in µA
series, which is given in Figure 13. simultaneously provides the return
Note that the impedance of the
HSMS-286A series is very similar
when bias current is set to 3 µA.
circuit for the current generated in
the diode. The impedance of this
circuit is given in Figure 15.
Ib = bias current in µA
Saturation current is a function of
the diode’s design,[4] and it is a
constant at a given temperature.
For the HSMS-285A series, it is
typically 3 to 5 µA at 25°C. For the
medium barrier HSMS-2860 family,
saturation current at room
temperature is on the order of
50 nA.
5
2
0.2
0.6
1
1 GHz
2
3
Together, saturation and (if used)
bias current set the detection
sensitivity, video resistance and
input RF impedance of the
4
5
6
FREQUENCY (GHz): 0.9-0.93
Schottky detector diode. Since no
external bias is used with the
HSMS-285A series, a single
Figure 13. RF Impedance of the
HSMS-285A Series at -40 dBm.
Figure 15. Input Impedance.
The input match, expressed in
terms of return loss, is given in
Figure 16.
transfer curve at any given
915 MHz Detector Circuit
frequency is obtained, as shown in
Figure 4. Where bias current is
used, some tradeoff in sensitivity
and square law dynamic range is
seen, as shown in Figure 6 and
described in reference [3].
Figure 14 illustrates a simple
impedance matching network for a
915 MHz detector.
0
65nH
-5
RF
INPUT
VIDEO
OUT
WIDTH = 0.050"
LENGTH = 0.065"
-10
-15
-20
The most difficult part of the
design of a detector circuit is the
input impedance matching
network. For very broadband
detectors, a shunt 60 Ω resistor
will give good input match, but at
the expense of detection
100 pF
WIDTH = 0.015"
LENGTH = 0.600"
TRANSMISSION LINE
DIMENSIONS ARE FOR
MICROSTRIP ON
0.032" THICK FR-4.
0.9
0.915
0.93
FREQUENCY (GHz)
Figure 14. 915 MHz Matching
Network for the HSMS-285A
Series at Zero Bias or the
sensitivity.
Figure 16. Input Return Loss.
HSMS-286A Series at 3 µA Bias.
When maximum sensitivity is
required over a narrow band of
frequencies, a reactive matching
network is optimum. Such net-
works can be realized in either
lumped or distributed elements,
depending upon frequency, size
As can be seen, the band over
A 65 nH inductor rotates the
which a good match is achieved is
more than adequate for 915 MHz
RFID applications.
impedance of the diode to a point
on the Smith Chart where a shunt
inductor can pull it up to the
center. The short length of 0.065"
[4]
Hewlett-Packard Application Note 969, An Optimum Zero Bias Schottky Detector Diode.
[5]
Hewlett-Packard Application Note 963, Impedance Matching Techniques for Mixers and Detectors.
7
HSMS-285A
RF
INPUT
VIDEO
OUT
#2-56 TAP
0.40 MIN.,
4 PLACES
WIDTH = 0.017"
LENGTH = 0.436"
1.000
0.900
100 pF
WIDTH = 0.078"
LENGTH = 0.165"
0.670
TRANSMISSION LINE
DIMENSIONS ARE FOR
MICROSTRIP ON
0.330
0.100
0.00 REF.
0.032" THICK FR-4.
0.00 REF.
#2-56 TAP
THROUGH,
4 PLACES
MATERIAL:
0.250" H.H.
BRASS PLATE
Figure 17. 2.45 GHz Matching
Network for the HSMS-285A
Series.
Figure 19. Mounting Plate.
0.094" THROUGH, 4 PLACES
FREQUENCY (GHz): 2.3-2.6
FINISHED
BOARD
SIZE IS
Figure 21. Input Impedance.
HSMS-2850
1.00" X 1.00".
MATERIAL IS
1/32" FR-4
EPOXY/
0
-5
RF IN
VIDEO OUT
FIBERGLASS,
1 OZ. COPPER
BOTH SIDES.
NOTE THAT
THE BACK SIDE
OF THE BOARD
IS A GROUND
PLANE.
H
H
-10
-15
-20
0.030" PLATED THROUGH HOLE,
3 PLACES
CHIP CAPACITOR, 20 TO 100 pF
Figure 20. Test Detector.
Figure 18. Physical Realization.
2.45 GHz Detector Circuit
Two SMA connectors (E.F.
Johnson 142-0701-631 or
equivalent), a high-Q capacitor
(ATC 100A101MCA50 or
equivalent), miscellaneous
hardware and an HSMS-285B are
added to create the test circuit
shown in Figure 20.
2.3
2.45
2.6
At 2.45 GHz, the RF impedance of
the HSMS-285A series is closer to
the line of constant susceptance
which passes through the center of
the chart, resulting in a design
which is realized entirely in
distributed elements — see
Figure 17.
FREQUENCY (GHz)
Figure 22. Input Return Loss.
impedance to the diode at
2.45 GHz. The temptation will be
to adjust the circuit elements to
achieve an ideal single frequency
match, as illustrated in Figure 23.
The calculated input impedance
for this network is shown in
Figure 21.
In order to save cost (at the
expense of having a larger circuit),
an open circuit shunt stub could
be substituted for the chip
capacitor. On the other hand, if
space is at a premium, the long
series transmission line at the
input to the diode can be replaced
with a lumped inductor.
This does indeed result in a very
good match at midband, as shown
in Figure 24.
The corresponding input match is
shown in Figure 22. As was the
case with the lower frequency
design, bandwidth is more than
adequate for the intended RFID
application. Note that this same
design applies to the HSMS-286A
series when it is used with 3 to
5 µA of external bias.
However, bandwidth is narrower
and the designer runs the risk of a
shift in the midband frequency of
his circuit if there is any small
deviation in circuit board or diode
characteristics due to lot-to-lot
variation or change in temper-
ature. The matching technique
illustrated in Figure 21 is much
less sensitive to changes in diode
and circuit board processing.
A possible physical realization of
such a network is shown in
Figure 18.
A word of caution to the designer
is in order. A glance at Figure 21
will reveal the fact that the circuit
does not provide the optimum
This board is mounted on the
brass or aluminum mounting plate
shown in Figure 19.
8
HSMS-285A SERIES
VIDEO
OUT
5.8 GHz Detector Circuit
A possible design for a 5.8 GHz
detector is given in Figure 25.
Voltage Doublers
RF
INPUT
To this point, we have restricted
our discussion to single diode
detectors. A glance at Figure 12,
however, will lead to the
suggestion that the two types of
single diode detectors be
combined into a two diode voltage
doubler[6] (known also as a full
wave rectifier). Such a detector is
shown in Figure 28.
WIDTH = 0.016"
LENGTH = 0.037"
20 pF
WIDTH = 0.045"
LENGTH = 0.073"
As was the case at 2.45 GHz, the
circuit is entirely distributed
element, both low cost and
compact. Input impedance for this
network is given in Figure 26.
TRANSMISSION LINE
DIMENSIONS ARE FOR
MICROSTRIP ON
0.032" THICK FR-4.
Figure 25. 5.8 GHz Matching
Network for the HSMS-285A
Series at Zero Bias or the
Input return loss, shown in
Figure 27, exhibits wideband
match.
HSMS-286A Series at 3 µA Bias.
Z-MATCH
NETWORK
VIDEO OUT
RF IN
Figure 28. Voltage Doubler
Circuit.
2.45 GHz
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-285C or the
HSMS-286C.
FREQUENCY (GHz): 2.3-2.6
FREQUENCY (GHz): 5.6-6.0
Figure 23. Input Impedance.
Modified 2.45 GHz Circuit.
Figure 26. Input Impedance.
0
-5
0
-5
The “Virtual Battery”
-10
-15
-20
-10
-15
-20
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
2.3
2.45
2.6
5.6
5.7
5.8
5.9
6.0
FREQUENCY (GHz)
FREQUENCY (GHz)
Figure 27. Input Return Loss.
Figure 24. Input Return Loss.
Modified 2.45 GHz Circuit.
oscillator. Where such virtual
batteries are employed, the bulk,
cost, and limited lifetime of a
battery are eliminated.
[6]
Hewlett-Packard Application Note 956-4, Schottky Diode Voltage Doubler.
9
Flicker Noise
which can be expressed as
20 log10 dBV/Hz
A similar experiment was con-
ducted with the HSMS-286B 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 tempera-
ture range.
Reference to Figure 5 will show
that there is a junction of metal,
silicon, and passivation around the
rim of the Schottky contact. It is in
this three-way junction that flicker
noise[7] is generated. This noise
can severely reduce the sensitivity
of a crystal video receiver utilizing
a Schottky detector circuit if the
video frequency is below the noise
corner. Flicker noise can be
v
Thus, for a diode with RV = 9 KΩ,
the noise voltage is 12.2 nV/Hz or
-158 dBV/Hz. On the graph of
Figure 26, -158 dBV/Hz would
replace the zero on the vertical
scale to convert the chart to one of such as those given in Figures 30
absolute noise voltage vs.
frequency.
It should be noted that curves
and 31 are highly dependent upon
the exact design of the input
impedance matching network.
The designer will have to experi-
The compression of the detector’s ment with bias current using his
transfer curve is beyond the scope specific design.
of this data sheet, but some
substantially reduced by the
Temperature Compensation
elimination of passivation, but
such diodes cannot be mounted in
non-hermetic packages. p-type
silicon Schottky diodes have the
least flicker noise at a given value
of external bias (compared to n-
type silicon or GaAs). At zero bias,
such diodes can have extremely
low values of flicker noise. For the
HSMS-285A series, the noise
general comments can be made.
As was given earlier, the diode’s
video resistance is given by
120
INPUT POWER = –30 dBm
3.0 µA
100
80
-5
8.33 X 10 nT
R = ––––––––––––
V
IS + Ib
1.0 µA
10 µA
temperature ratio is given in
Figure 29.
where T is the diode’s tempera-
ture in °K.
60
40
15
0.5 µA
As can be seen, temperature has a
strong effect upon RV, and this
will in turn affect video bandwidth
and input RF impedance. A glance
at Figure 7 suggests that the
proper choice of bias current in
the HSMS-286A series can mini-
mize variation over temperature.
-55 -35 -15
5
25 45
65 85
10
5
TEMPERATURE (°C)
Figure 30. Output Voltage vs.
Temperature and Bias Current in the
915 MHz Voltage Doubler using the
HSMS-286C.
0
-5
10
35
100
1000
10000
100000
INPUT POWER = –30 dBm
The detector circuits described
earlier were tested over tempera-
ture. The 915 MHz voltage doubler
using the HSMS-286C series pair
produced the output voltages as
shown in Figure 30. The use of
3 µA of bias resulted in the highest
voltage sensitivity, but at the cost
of a wide variation over tempera-
ture. Dropping the bias to 1 µA
produced a detector with much
less temperature variation.
FREQUENCY (Hz)
3.0 µA
Figure 29. Typical Noise
Temperature Ratio.
25
10 µA
1.0 µA
Noise temperature ratio is the
quotient of the diode’s noise
power (expressed in dBV/Hz)
divided by the noise power of an
ideal resistor of resistance R = RV.
15
5
0.5 µA
-55 -35 -15
5
25 45
65 85
TEMPERATURE (°C)
For an ideal resistor R, at 300°K,
the noise voltage can be computed
from
Figure 31. Output Voltage vs.
Temperature and Bias Current in the
5.80 GHz Voltage Detector using the
HSMS-286B Schottky.
v = 1.287 X 10-10 √R volts/Hz
[7]
Hewlett-Packard Application Note 965-3, Flicker Noise in Schottky Diodes.
10
Diode Burnout
reflow type of surface mount
assembly process.
0.026
Any Schottky junction, be it an RF
diode or the gate of a MESFET, is
relatively delicate and can be
burned out with excessive RF
power. Many crystal video
receivers used in RFID (tag)
applications find themselves in
poorly controlled environments
where high power sources may be
present. Examples are the areas
around airport and FAA radars,
nearby ham radio operators, the
vicinity of a broadcast band
transmitter, etc. In such
environments, the Schottky diodes
of the receiver can be protected by
a device known as a limiter
diode.[8] Formerly available only in
radar warning receivers and other
high cost electronic warfare
applications, these diodes have
been adapted to commercial and
consumer circuits.
After ramping up from room
temperature, the circuit board
with components attached to it
(held in place with solder paste)
passes through one or more
preheat zones. The preheat zones
increase the temperature of the
board and components to prevent
thermal shock and begin evaporat-
ing solvents from the solder paste.
The reflow zone briefly elevates
the temperature sufficiently to
produce a reflow of the solder.
0.07
0.035
0.016
Figure 32. PCB Pad Layout
( dimensions in inches) .
SMT Assembly
Reliable assembly of surface
mount components is a complex
process that involves many
material, process, and equipment
factors, including: method of
heating (e.g., IR or vapor phase
reflow, wave soldering, etc.)
circuit board material, conductor
thickness and pattern, type of
solder alloy, and the thermal
conductivity and thermal mass of
components. Components with a
low mass, such as the SOT-323
package, will reach solder reflow
temperatures faster than those
with a greater mass.
The rates of change of tempera-
ture for the ramp-up and cool-
down zones are chosen to be low
enough to not cause deformation
of the board or damage to compo-
nents due to thermal shock. The
maximum temperature in the
reflow zone (T ) should not
MAX
Hewlett-Packard offers a complete
line of surface mountable PIN
limiter diodes. Most notably, our
HSMP-4820 (SOT-23) can act as a
very fast (nanosecond) power-
sensitive switch when placed
between the antenna and the
Schottky diode, shorting out the
RF circuit temporarily and
exceed 235 °C.
These parameters are typical for a
surface mount assembly process
for HP SOT-323 diodes. As a
general guideline, the circuit board
and components should be exposed
only to the minimum temperatures
and times necessary to achieve a
uniform reflow of solder.
HP’s SOT-323 diodes have been
qualified to the time-temperature
profile shown in Figure 33. This
profile is representative of an IR
reflecting the excessive RF energy
back out the antenna.
250
200
TMAX
Assembly Instructions
SOT-323 PCB Footprint
A recommended PCB pad layout
for the miniature SOT-323 (SC-70)
package is shown in Figure 32
(dimensions are in inches). This
layout provides ample allowance
for package placement by auto-
mated assembly equipment
150
Reflow
Zone
100
Preheat
Zone
Cool Down
Zone
50
0
without adding parasitics that
could impair the performance.
0
60
120
180
240
300
TIME (seconds)
Figure 33. Surface Mount Assembly Profile.
[8]
Hewlett-Packard Application Note 1050, Low Cost, Surface Mount Power Limiters.
11
Package Dimensions
Outline SOT-323 ( SC-70, 3 Lead)
1.30 (0.051)
REF.
2.20 (0.087)
2.00 (0.079)
1.35 (0.053)
1.15 (0.045)
0.650 BSC (0.025)
0.425 (0.017)
TYP.
2.20 (0.087)
1.80 (0.071)
0.10 (0.004)
0.00 (0.00)
0.30 REF.
0.20 (0.008)
0.10 (0.004)
1.00 (0.039)
0.80 (0.031)
0.25 (0.010)
0.15 (0.006)
10°
0.30 (0.012)
0.10 (0.004)
DIMENSIONS ARE IN MILLIMETERS (INCHES)
Part Number Ordering Information
No. of
Part Number
HSMS-285A-TR1[1]
HSMS-285A-BLK[1]
HSMS-286A-TR1[2]
HSMS-286A-BLK
Devices
3000
100
Container
7" Reel
antistatic bag
7" Reel
3000
100
antistatic bag
Notes:
1. “A” = B or C only
2. “A” = B, C, E or F
Device Orientation
REEL
TOP VIEW
4 mm
END VIEW
8 mm
CARRIER
TAPE
##
##
##
##
USER
FEED
DIRECTION
Note: “##” represents Package Marking Code.
COVER TAPE
Tape Dimensions and Product Orientation
For Outline SOT-323 ( SC-70 3 Lead)
P
P
D
2
P
0
E
F
W
C
D
1
t
(CARRIER TAPE THICKNESS)
T (COVER TAPE THICKNESS)
t
1
K
8° MAX.
5° MAX.
0
A
B
0
0
www.hp.com/go/rf
DESCRIPTION
SYMBOL
SIZE (mm)
SIZE (INCHES)
CAVITY
LENGTH
WIDTH
DEPTH
PITCH
A
B
K
P
D
2.24 ± 0.10
2.34 ± 0.10
1.22 ± 0.10
4.00 ± 0.10
1.00 + 0.25
0.088 ± 0.004
0.092 ± 0.004
0.048 ± 0.004
0.157 ± 0.004
0.039 + 0.010
0
0
0
For technical assistance or the location of
your nearest Hewlett-Packard sales office,
distributor or representative call:
BOTTOM HOLE DIAMETER
1
0
Americas/Canada: 1-800-235-0312 or
408-654-8675
PERFORATION
DIAMETER
PITCH
POSITION
D
P
E
1.55 ± 0.05
4.00 ± 0.10
1.75 ± 0.10
0.061 ± 0.002
0.157 ± 0.004
0.069 ± 0.004
Far East/Australasia: Call your local HP
sales office.
CARRIER TAPE WIDTH
THICKNESS
W
8.00 ± 0.30
0.315 ± 0.012
t
0.255 ± 0.013 0.010 ± 0.0005
5.4 ± 0.10 0.205 ± 0.004
0.062 ± 0.001 0.0025 ± 0.00004
1
Japan: (81 3) 3335-8152
COVER TAPE
WIDTH
TAPE THICKNESS
C
T
t
Europe: Call your local HP sales office.
DISTANCE
CAVITY TO PERFORATION
(WIDTH DIRECTION)
F
3.50 ± 0.05
0.138 ± 0.002
Data subject to change.
Copyright © 1998 Hewlett-Packard Co.
CAVITY TO PERFORATION
(LENGTH DIRECTION)
P
2
2.00 ± 0.05
0.079 ± 0.002
Obsoletes 5965-8838E
Printed in U.S.A.
5966-4282E (3/98)
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