datasheet

datasheet
HSMS-286x Series
Surface Mount Microwave
Schottky Detector Diodes
Data Sheet
Description
Features
Avago’s HSMS-286x 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
applications as well as large signal detection,
modulation, RF to DC conversion or voltage doubling.
• Surface Mount SOT-23/SOT-143 Packages
• Miniature SOT-323 and SOT-363 Packages
• 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
• Low FIT (Failure in Time) Rate*
• Tape and Reel Options Available
• Unique Configurations in Surface Mount SOT-363
Package
– increase flexibility
– save board space
– reduce cost
• HSMS-286K Grounded Center Leads Provide up to
10 dB Higher Isolation
• Matched Diodes for Consistent Performance
• Better Thermal Conductivity for Higher Power
Dissipation
• Lead-free Option Available
Available in various package configurations, this family
of detector diodes provides low cost solutions to a wide
variety of design problems. Avago’s manufacturing
techniques assure that when two or more diodes are
mounted into a single surface mount package, they are
taken from adjacent sites on the wafer, assuring the
highest possible degree of match.
Pin Connections and Package Marking
6
PLx
1
2
3
5
* For more information see the Surface Mount Schottky
Reliability Data Sheet.
4
Notes:
1. Package marking provides orientation and identification.
2. The first two characters are the package marking code.
The third character is the date code.
SOT-323 Package Lead Code Identification
(top view)
SINGLE
SERIES
3
SOT-23/SOT-143 Package Lead Code
Identification (top view)
SINGLE
3
SERIES
3
1
1
#0
2
COMMON
ANODE
3
#2
1
B
2
COMMON
ANODE
3
2
COMMON
CATHODE
3
3
1
E
2
1
#3
2
1
#4
UNCONNECTED
PAIR
3
4
1
#5
2
COMMON
CATHODE
3
1
F
2
SOT-363 Package Lead Code Identification
(top view) HIGH ISOLATION
UNCONNECTED
UNCONNECTED PAIR
1
C
TRIO
6
5
4
6
5
1
2
3
1
2
4
2
K
BRIDGE
QUAD
6
5
1
2
4
6
3
1
L
3
RING
QUAD
5
4
2
P
2
R
3
2
SOT-23/SOT-143 DC Electrical Specifications, TC = +25°C, Single Diode
Part
Number
HSMS-
Package
Marking
Code
Lead
Code
2860
2862
2863
2864
2865
T0
T2
T3
T4
T5
0
2
3
4
5
Configuration
Single
Series Pair [1,2]
Common Anode [1,2]
Common Cathode [1,2]
Unconnected Pair [1,2]
Test Conditions
Forward Voltage
VF (mV)
250 Min.
350 Max.
IF = 1.0 mA
Typical
Capacitance
CT (pF)
0.30
VR = 0 V, f = 1 MHz
Notes:
1. ∆VF for diodes in pairs is 15.0 mV maximum at 1.0 mA.
2. ∆CT for diodes in pairs is 0.05 pF maximum at –0.5 V.
SOT-323/SOT-363 DC Electrical Specifications, TC = +25°C, Single Diode
Part
Number
HSMS-
Package
Marking
Code
Lead
Code
286B
286C
286E
286F
286K
T0
T2
T3
T4
TK
B
C
E
F
K
286L
286P
286R
TL
TP
ZZ
L
P
R
Configuration
Single
Series Pair [1,2]
Common Anode [1,2]
Common Cathode [1,2]
High Isolation
Unconnected Pair
Unconnected Trio
Bridge Quad
Ring Quad
Test Conditions
Notes:
1. ∆VF for diodes in pairs is 15.0 mV maximum at 1.0 mA.
2. ∆CT for diodes in pairs is 0.05 pF maximum at –0.5 V.
Forward Voltage
VF (mV)
250 Min.
350 Max.
IF = 1.0 mA
Typical
Capacitance
CT (pF)
0.25
VR = 0 V, f = 1 MHz
3
RF Electrical Specifications, TC = +25°C, Single Diode
Part
Number
HSMS2860
2862
2863
2864
2865
286B
286C
286E
286F
286K
286L
286P
286R
Typical Tangential Sensitivity
TSS (dBm) @ f =
915 MHz
2.45 GHz
5.8 GHz
– 57
Test
Conditions
– 56
– 55
Typical Voltage Sensitivity g
(mV/µW) @ f =
915 MHz
2.45 GHz
5.8 GHz
50
Video Bandwidth = 2 MHz
Ib = 5 µA
35
Power in = –40 dBm
RL = 100 KΩ, Ib = 5 µA
Absolute Maximum Ratings, TC = +25°C, Single Diode
Symbol
Parameter
Unit
25
Absolute
Maximum[1]
SOT-23/143
SOT-323/363
PIV
Peak Inverse Voltage
V
4.0
4.0
TJ
Junction Temperature
°C
150
150
TSTG
Storage Temperature
°C
-65 to 150
-65 to 150
TOP
Operating Temperature
°C
-65 to 150
-65 to 150
θ jc
Thermal Resistance[2]
°C/W
500
150
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 package pins
where contact is made to the circuit board.
Typical Video
Resistance
RV (KΩ)
5.0
Ib = 5 µA
Attention:
Observe precautions for
handling electrostatic
sensitive devices.
ESD Machine Model (Class A)
ESD Human Body Model (Class 0)
Refer to Avago Application Note A004R:
Electrostatic Discharge Damage and Control.
4
Equivalent Linear Circuit Model,
Diode chip
Rj
RS
Cj
RS = series resistance (see Table of SPICE parameters)
C j = junction capacitance (see Table of SPICE parameters)
Rj =
8.33 X 10-5 nT
Ib + Is
where
Ib = externally applied bias current in amps
Is = saturation current (see table of SPICE parameters)
T = temperature, °K
n = ideality factor (see table of SPICE parameters)
Note:
To effectively model the packaged HSMS-286x product,
please refer to Application Note AN1124.
SPICE Parameters
Parameter
Units
Value
BV
V
7.0
CJ0
pF
0.18
EG
eV
0.69
IBV
A
1E-5
IS
A
5 E -8
N
1.08
RS
Ω
6.0
PB (VJ)
V
0.65
PT (XTI)
2
M
0.5
5
FORWARD CURRENT (µA)
1
.1
.01
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
IF (left scale)
10
∆VF (right scale)
1
0.05
FORWARD VOLTAGE (V)
0.10
0.15
0.20
30
1000
2.45 GHz
100
10
DIODES TESTED IN FIXED-TUNED
FR4 MICROSTRIP CIRCUITS.
0.1
-50
VOLTAGE OUT (mV)
5.8 GHz
1
-30
10 µA
1000
5 µA
100
Frequency = 2.45 GHz
Fixed-tuned FR4 circuit
10
POWER IN (dBm)
Figure 4. +25°C Expanded Output
Voltage vs. Input Power. See Figure 3.
-20
0
-10
RL = 100 KΩ
35
30
25
20
Input Power =
–30 dBm @ 2.45 GHz
Data taken in fixed-tuned
FR4 circuit
15
10
1
–40
-30
40
DIODES TESTED IN FIXED-TUNED
FR4 MICROSTRIP CIRCUITS.
-40
-40
POWER IN (dBm)
20 µA
2.45 GHz
5.8 GHz
1
10,000
915 MHz
10
915 MHz
Figure 3. +25°C Output Voltage vs.
Input Power, 3 µA Bias.
Figure 2. Forward Voltage Match.
RL = 100 KΩ
VOLTAGE OUT (mV)
RL = 100 KΩ
FORWARD VOLTAGE (V)
Figure 1. Forward Current vs.
Forward Voltage at Temperature.
0.3
-50
1
0.25
10000
OUTPUT VOLTAGE (mV)
FORWARD CURRENT (mA)
TA = –55°C
TA = +25°C
TA = +85°C
10
10
VOLTAGE OUT (mV)
100
100
FORWARD VOLTAGE DIFFERENCE (mV)
Typical Parameters, Single Diode
–30
–20
–10
0
10
POWER IN (dBm)
Figure 5. Dynamic Transfer
Characteristic as a Function of DC Bias.
RL = 100 KΩ
5
.1
1
10
100
BIAS CURRENT (µA)
Figure 6. Voltage Sensitivity as a
Function of DC Bias Current.
6
Applications Information
Introduction
Avago’s HSMS-286x family of
Schottky detector diodes has been
developed specifically for low
cost, high volume designs in two
kinds of applications. In small
signal detector applications
(Pin < -20 dBm), this diode is used
with DC bias at frequencies above
1.5 GHz. At lower frequencies, the
zero bias HSMS-285x family
should be considered.
In large signal power or gain
control applications
(Pin > -20 dBm), this family is used
without bias at frequencies above
4 GHz. At lower frequencies, the
HSMS-282x family is preferred.
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 7, along
with its equivalent circuit.
;;
METAL
PASSIVATION
N-TYPE OR P-TYPE EPI
RS
PASSIVATION
LAYER
SCHOTTKY JUNCTION
Cj
Rj
N-TYPE OR P-TYPE SILICON SUBSTRATE
CROSS-SECTION OF SCHOTTKY
BARRIER DIODE CHIP
EQUIVALENT
CIRCUIT
Figure 7. Schottky Diode Chip.
RS is the parasitic series
resistance of the diode, the sum of
the bondwire and leadframe
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. R j is the junction
resistance of the diode, a function
of the total current flowing
through it.
8.33 X 10-5 n T
R j = –––––––––––– = R V – R s
IS + I b
0.026
= ––––– at 25°C
IS + I b
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
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.
The Height of the Schottky
Barrier
The current-voltage characteristic
of a Schottky barrier diode at
room temperature is described by
the following equation:
V - IR
I = IS (exp ––––––S - 1)
0.026
(
is determined by the saturation
current, IS, and is related to the
barrier height of the diode.
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 (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 small signal
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) and
DC biased detectors.
Measuring Diode Linear
Parameters
The measurement of the many
elements which make up the
equivalent circuit for a packaged
Schottky diode is a complex task.
Various techniques are used for
each element. The task begins
with the elements of the diode
chip itself. (See Figure 8).
)
On a semi-log plot (as shown in
the Avago 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
RV
RS
Cj
Figure 8. Equivalent Circuit of a
Schottky Diode Chip.
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
7
high value of current (such as
5 mA). This slope is converted
into a resistance Rd.
0.026
RS = Rd – ––––––
If
For n-type diodes with relatively
low values of saturation current,
C j is obtained by measuring the
total capacitance (see AN1124).
Rj, the junction resistance, is
calculated using the equation
given above.
In the design of such detector
circuits, the starting point is the
equivalent circuit of the diode. Of
interest in the design of the video
portion of the circuit is the diode’s
video impedance — the other
elements of the equivalent circuit
disappear at all reasonable video
frequencies. In general, the lower
the diode’s video impedance, the
better the design.
DC BIAS
L1
The characterization of the
surface mount package is too
complex to describe here — linear
equivalent circuits can be found in
AN1124.
RF
IN
Z-MATCH
NETWORK
DC BIAS
Detector Circuits
(small signal)
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
-57 dBm.[1] Moreover, since
external DC bias sets the video
impedance of such circuits, they
display classic square law
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 9.
This is the basic detector circuit
used with the HSMS-286x family
of diodes.
Output voltage can be virtually
doubled and input impedance
(normally very high) can be
halved through the use of the
voltage doubler circuit[4].
VIDEO
OUT
L1
RF
IN
Z-MATCH
NETWORK
VIDEO
OUT
Figure 9. Basic Detector Circuits.
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 the elements of the
diode’s equivalent circuit, the
parasitics are constants and the
video resistance is a function of
the current flowing through the
diode.
RV = Rj + RS
The sum of saturation current and
bias current sets the detection
sensitivity, video resistance and
input RF impedance of the
Schottky detector diode. Where
bias current is used, some
tradeoff in sensitivity and square
law dynamic range is seen, as
shown in Figure 5 and described
in reference [3].
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
sensitivity.
When maximum sensitivity is
required over a narrow band of
frequencies, a reactive matching
network is optimum. Such networks can be realized in either
lumped or distributed elements,
depending upon frequency, size
constraints and cost limitations,
but certain general design
principals exist for all types.[5]
Design work begins with the RF
impedance of the HSMS-286x
series when bias current is set to
3 µA. See Figure 10.
2
0.2
0.6
5
1
1 GHz
2
3
4
[1]
Avago Application Note 923, Schottky Barrier Diode Video Detectors.
Avago Application Note 986, Square Law and Linear Detection.
[3] Avago Application Note 956-5, Dynamic Range Extension of Schottky Detectors.
[4] Avago Application Note 956-4, Schottky Diode Voltage Doubler.
[5] Avago Application Note 963, Impedance Matching Techniques for Mixers and Detectors.
[2]
6
5
Figure 10. RF Impedance of the
Diode.
8
915 MHz Detector Circuit
Figure 11 illustrates a simple
impedance matching network for
a 915 MHz detector.
0.094" THROUGH, 4 PLACES
The input match, expressed in
terms of return loss, is given in
Figure 13.
FINISHED
BOARD
SIZE IS
1.00" X 1.00".
MATERIAL IS
1/32" FR-4
EPOXY/
FIBERGLASS,
1 OZ. COPPER
BOTH SIDES.
0
VIDEO
OUT
WIDTH = 0.050"
LENGTH = 0.065"
100 pF
WIDTH = 0.015"
LENGTH = 0.600"
TRANSMISSION LINE
DIMENSIONS ARE FOR
MICROSTRIP ON
0.032" THICK FR-4.
Figure 11. 915 MHz Matching
Network for the HSMS-286x Series
at 3 µA Bias.
RETURN LOSS (dB)
65nH
RF
INPUT
-5
-10
0.030" PLATED THROUGH HOLE,
3 PLACES
-15
Figure 15. Physical Realization.
-20
0.9
0.915
0.93
FREQUENCY (GHz)
Figure 13. Input Return Loss.
A 65 nH inductor rotates the
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"
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
simultaneously provides the
return circuit for the current
generated in the diode. The
impedance of this circuit is given
in Figure 12.
As can be seen, the band over
which a good match is achieved is
more than adequate for 915 MHz
RFID applications.
The HSMS-282x family is a better
choice for 915 MHz applications—
the foregoing discussion of a
design using the HSMS-286B is
offered only to illustrate a design
approach for technique.
RF
INPUT
VIDEO
OUT
WIDTH = 0.017"
LENGTH = 0.436"
100 pF
WIDTH = 0.078"
LENGTH = 0.165"
TRANSMISSION LINE
DIMENSIONS ARE FOR
MICROSTRIP ON
0.032" THICK FR-4.
2.45 GHz Detector Circuit
At 2.45 GHz, the RF impedance 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 14.
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.
A possible physical realization of
such a network is shown in
Figure 15, a demo board is
available from Avago.
HSMS-2860
Figure 14. 2.45 GHz Matching
Network.
RF IN
VIDEO OUT
FREQUENCY (GHz): 0.9-0.93
Figure 12. Input Impedance.
CHIP CAPACITOR, 20 TO 100 pF
Figure 16. Test Detector.
9
Two SMA connectors (E.F.
Johnson 142-0701-631 or equivalent), a high-Q capacitor
(ATC 100A101MCA50 or equivalent), miscellaneous hardware
and an HSMS-286B are added to
create the test circuit shown in
Figure 16.
A word of caution to the designer
is in order. A glance at Figure 17
will reveal the fact that the circuit
does not provide the optimum
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 19.
The calculated input impedance
for this network is shown in
Figure 17.
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 temperature. The matching technique
illustrated in Figure 17 is much
less sensitive to changes in diode
and circuit board processing.
5.8 GHz Detector Circuit
A possible design for a 5.8 GHz
detector is given in Figure 21.
2.45 GHz
RF
INPUT
VIDEO
OUT
WIDTH = 0.016"
LENGTH = 0.037"
20 pF
WIDTH = 0.045"
LENGTH = 0.073"
Figure 21. 5.8 GHz Matching Network
for the HSMS-286x Series at 3 µA
Bias.
FREQUENCY (GHz): 2.3-2.6
Figure 19. Input Impedance. Modified
2.45 GHz Circuit.
Figure 17. Input Impedance,
3 µA Bias.
The corresponding input match is
shown in Figure 18. As was the
case with the lower frequency
design, bandwidth is more than
adequate for the intended RFID
application.
RETURN LOSS (dB)
0
-5
This does indeed result in a very
good match at midband, as shown
in Figure 20.
-5
-10
-15
-20
2.3
-10
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 22.
0
RETURN LOSS (dB)
FREQUENCY (GHz): 2.3-2.6
2.45
2.6
FREQUENCY (GHz)
-15
-20
2.3
Figure 20. Input Return Loss.
Modified 2.45 GHz Circuit.
FREQUENCY (GHz): 5.6-6.0
Figure 22. Input Impedance.
2.45
FREQUENCY (GHz)
Figure 18. Input Return Loss,
3 µA Bias.
2.6
10
-5
-10
-15
-20
5.6
5.7
5.8
5.9
6.0
FREQUENCY (GHz)
Temperature Compensation
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[4] (known also as
a full wave rectifier). Such a
detector is shown in Figure 24.
RF IN
Z-MATCH
NETWORK
VIDEO OUT
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.
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
RV =
8.33 x 10-5 nT
IS + I b
A similar experiment was conducted 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 experiment with bias current using his
specific design.
120
INPUT POWER = –30 dBm
where T is the diode’s temperature in °K.
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 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 temperature. 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
3.0 µA
100
80
1.0 µA
10 µA
60
40
-55
0.5 µA
-35
-15
5
25
45
65
85
TEMPERATURE (°C)
Figure 25. Output Voltage vs.
Temperature and Bias Current in the
915 MHz Voltage Doubler using the
HSMS-286C.
35
INPUT POWER = – 30 dBm
OUTPUT VOLTAGE (mV)
RETURN LOSS (dB)
0
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.
with much less temperature
variation.
OUTPUT VOLTAGE (mV)
The “Virtual Battery”
Input return loss, shown in
Figure 23, exhibits wideband
match.
3.0 µA
25
10 µA
1.0 µA
15
0.5 µA
5
-55
-35
-15
5
25
45
65
85
TEMPERATURE (°C)
Figure 26. Output Voltage vs.
Temperature and Bias Current in the
5.80 GHz Voltage Detector using the
HSMS-286B Schottky.
11
Six Lead Circuits
3
4
6
5
4
2
1
2
3
The differential detector is often
used to provide temperature
compensation for a Schottky
detector, as shown in Figures 27
and 28.
1
HSMS-286K
SOT-363
HSMS-2865
SOT-143
bias
Figure 29. Comparing Two Diodes.
matching
network
differential
amplifier
Figure 27. Differential Detector.
The HSMS-286K, with leads 2 and
5 grounded, offers some isolation
from RF coupling between the
diodes. This product is used in a
differential detector as shown in
Figure 30.
detector Vs
diode
PA
detector Vs
diode
PA
to differential
amplifier
to differential
amplifier
HSMS-2865
HSMS-286K
reference diode
reference diode
Figure 28. Conventional Differential
Detector.
Figure 30. High Isolation
Differential Detector.
These circuits depend upon the
use of two diodes having matched
Vf characteristics over all
operating temperatures. This is
best achieved by using two
diodes in a single package, such
as the SOT-143 HSMS-2865 as
shown in Figure 29.
In order to achieve the maximum
isolation, the designer must take
care to minimize the distance
from leads 2 and 5 and their
respective ground via holes.
Isolation between the two diodes
can be obtained by using the
HSMS-286K diode with leads 2
and 5 grounded. The difference
between this product and the
conventional HSMS-2865 can be
seen in Figure 29.
5000
OUTPUT VOLTAGE (mV)
In high power differential detectors, RF coupling from the
detector diode to the reference
diode produces a rectified voltage
in the latter, resulting in errors.
Tests were run on the HSMS-282K
and the conventional HSMS-2825
pair, which compare with each
other in the same way as the
HSMS-2865 and HSMS-286K, with
the results shown in Figure 31.
RF diode
Vout
1000
Square law
response
HSMS-2825
ref. diode
10
37 dB
1
0.5
-35
HSMS-282K
ref. diode
47 dB
-25
-15
Such differential detector circuits
generally use single diode
detectors, either series or shunt
mounted diodes. The voltage
doubler offers the advantage of
twice the output voltage for a
given input power. The two
concepts can be combined into
the differential voltage doubler,
as shown in Figure 32.
bias
differential
amplifier
matching
network
Figure 32. Differential Voltage
Doubler, HSMS-286P.
Frequency = 900 MHz
100
The line marked “RF diode, Vout”
is the transfer curve for the
detector diode — both the
HSMS-2825 and the HSMS-282K
exhibited the same output
voltage. The data were taken over
the 50 dB dynamic range shown.
To the right is the output voltage
(transfer) curve for the reference
diode of the HSMS-2825, showing
37 dB of isolation. To the right of
that is the output voltage due to
RF leakage for the reference
diode of the HSMS-282K, demonstrating 10 dB higher isolation
than the conventional part.
-5
5
15
INPUT POWER (dBm)
Figure 31. Comparing HSMS-282K
with HSMS-2825.
Here, all four diodes of the
HSMS-286P are matched in their
Vf characteristics, because they
came from adjacent sites on the
wafer. A similar circuit can be
realized using the HSMS-286R
ring quad.
12
Other configurations of six lead
Schottky products can be used to
solve circuit design problems
while saving space and cost.
Thermal Considerations
The obvious advantage of the
SOT-363 over the SOT-143 is
combination of smaller size and
two extra leads. However, the
copper leadframe in the SOT-323
and SOT-363 has a thermal
conductivity four times higher
than the Alloy 42 leadframe of the
SOT-23 and SOT-143, which
enables it to dissipate more
power.
The maximum junction temperature for these three families of
Schottky diodes is 150°C under
all operating conditions. The
following equation, equation 1,
applies to the thermal analysis of
diodes:
Package thermal resistance for
the SOT-323 and SOT-363 package is approximately 100°C/W,
and the chip thermal resistance
for these three families of diodes
is approximately 40°C/W. The
designer will have to add in the
thermal resistance from diode
case to ambient — a poor choice
of circuit board material or heat
sink design can make this number
very high.
Equation (1) would be straightforward to solve but for the fact that
diode forward voltage is a function of temperature as well as
forward current. The equation,
equation 3, for Vf is:
11600 (Vf – If Rs)
nT
e
–1
If = IS
Equation (3).
Diode Burnout
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.[6] Formerly
available only in radar warning
receivers and other high cost
electronic warfare applications,
these diodes have been adapted to
commercial and consumer
circuits.
where
T j = (V f I f + PRF) θ jc + Ta
n = ideality factor
T = temperature in °K
Rs = diode series resistance
Equation (1).
where
Tj = junction temperature
Ta = diode case temperature
θ jc = thermal resistance
Vf If = DC power dissipated
PRF = RF power dissipated
Note that θjc, the thermal resistance from diode junction to the
foot of the leads, is the sum of
two component resistances,
θjc = θpkg + θchip
Equation (2).
and IS (diode saturation current)
is given by
2
n
Is = I 0
T
)
(298
– 4060
e
1
( 1T – 298
)
Avago offers a complete line of
surface mountable PIN limiter
diodes. Most notably, our HSMP4820 (SOT-23) or HSMP-482B
(SOT-323) 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 reflecting the
excessive RF energy back out the
antenna.
Equation (4).
Equations (1) and (3) are solved
simultaneously to obtain the
value of junction temperature for
given values of diode case
temperature, DC power dissipation and RF power dissipation.
[6]
Avago Application Note 1050, Low Cost, Surface Mount Power Limiters.
13
Assembly Instructions
SMT Assembly
SOT-323 PCB Footprint
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
packages, will reach solder
reflow temperatures faster than
those with a greater mass.
A recommended PCB pad layout
for the miniature SOT-323 (SC-70)
package is shown in Figure 33
(dimensions are in inches).
0.026
0.079
0.039
0.022
Dimensions in inches
Figure 33. Recommended PCB Pad
Layout for Avago’s SC70 3L/SOT-323
Products.
A recommended PCB pad layout
for the miniature SOT-363 (SC-70
6 lead) package is shown in
Figure 34 (dimensions are in
inches). This layout provides
ample allowance for package
placement by automated assembly equipment without adding
parasitics that could impair the
performance.
Avago’s diodes have been qualified to the time-temperature
profile shown in Figure 35. This
profile is representative of an IR
reflow type of surface mount
assembly process.
preheat zones. The preheat zones
increase the temperature of the
board and components to prevent
thermal shock and begin evaporating solvents from the solder
paste. The reflow zone briefly
elevates the temperature sufficiently to produce a reflow of the
solder.
The rates of change of temperature for the ramp-up and cooldown zones are chosen to be low
enough to not cause deformation
of the board or damage to components due to thermal shock. The
maximum temperature in the
reflow zone (TMAX) should not
exceed 235°C.
These parameters are typical for a
surface mount assembly process
for Avago 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.
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
250
TMAX
0.026
0.079
0.039
TEMPERATURE (°C)
200
150
Reflow
Zone
100
Preheat
Zone
Cool Down
Zone
50
0.018
Dimensions in inches
Figure 34. Recommended PCB Pad
Layout for Avago’s SC70 6L/SOT-363
Products.
0
0
60
120
180
TIME (seconds)
Figure 35. Surface Mount Assembly Profile.
240
300
14
Package Dimensions
Outline 23 (SOT-23)
Outline SOT-323 (SC-70 3 Lead)
e1
e2
e1
E
E
E1
XXX
E1
XXX
e
L
B
e
C
L
D
B
DIMENSIONS (mm)
C
DIMENSIONS (mm)
D
A
A1
Notes:
XXX-package marking
Drawings are not to scale
SYMBOL
A
A1
B
C
D
E1
e
e1
e2
E
L
MIN.
0.79
0.000
0.37
0.086
2.73
1.15
0.89
1.78
0.45
2.10
0.45
A
MAX.
1.20
0.100
0.54
0.152
3.13
1.50
1.02
2.04
0.60
2.70
0.69
A1
Notes:
XXX-package marking
Drawings are not to scale
Outline 143 (SOT-143)
SYMBOL
A
A1
B
C
D
E1
e
e1
E
L
MIN.
MAX.
0.80
1.00
0.00
0.10
0.15
0.40
0.10
0.20
1.80
2.25
1.10
1.40
0.65 typical
1.30 typical
1.80
2.40
0.425 typical
Outline SOT-363 (SC-70 6 Lead)
e2
DIMENSIONS (mm)
e1
B1
E
HE
SYMBOL
E
D
HE
A
A2
A1
Q1
e
b
c
L
E
E1
XXX
e
L
B
e
D
C
DIMENSIONS (mm)
D
A
A1
Notes:
XXX-package marking
Drawings are not to scale
MIN.
MAX.
1.15
1.35
1.80
2.25
1.80
2.40
0.80
1.10
0.80
1.00
0.00
0.10
0.10
0.40
0.650 BCS
0.15
0.30
0.10
0.20
0.10
0.30
SYMBOL
A
A1
B
B1
C
D
E1
e
e1
e2
E
L
MIN.
0.79
0.013
0.36
0.76
0.086
2.80
1.20
0.89
1.78
0.45
2.10
0.45
MAX.
1.097
0.10
0.54
0.92
0.152
3.06
1.40
1.02
2.04
0.60
2.65
0.69
Q1
A1
A2
b
e
c
A
L
15
For Outlines SOT-23, -323
Device Orientation
REEL
TOP VIEW
END VIEW
4 mm
CARRIER
TAPE
8 mm
USER
FEED
DIRECTION
ABC
ABC
ABC
Note: "AB" represents package marking code.
"C" represents date code.
COVER TAPE
For Outline SOT-143
For Outline SOT-363
TOP VIEW
END VIEW
TOP VIEW
4 mm
END VIEW
4 mm
ABC
ABC
ABC
ABC
8 mm
ABC
Note: "AB" represents package marking code.
"C" represents date code.
8 mm
ABC
ABC
ABC
ABC
Note: "AB" represents package marking code.
"C" represents date code.
16
Tape Dimensions and Product Orientation
For Outline SOT-23
P
P2
D
E
P0
F
W
D1
t1
Ko
9° MAX
13.5° MAX
8° MAX
B0
A0
DESCRIPTION
SYMBOL
SIZE (mm)
SIZE (INCHES)
CAVITY
LENGTH
WIDTH
DEPTH
PITCH
BOTTOM HOLE DIAMETER
A0
B0
K0
P
D1
3.15 ± 0.10
2.77 ± 0.10
1.22 ± 0.10
4.00 ± 0.10
1.00 + 0.05
0.124 ± 0.004
0.109 ± 0.004
0.048 ± 0.004
0.157 ± 0.004
0.039 ± 0.002
PERFORATION
DIAMETER
PITCH
POSITION
D
P0
E
1.50 + 0.10
4.00 ± 0.10
1.75 ± 0.10
0.059 + 0.004
0.157 ± 0.004
0.069 ± 0.004
CARRIER TAPE
WIDTH
THICKNESS
W
t1
8.00 +0.30 –0.10
0.229 ± 0.013
0.315 +0.012 –0.004
0.009 ± 0.0005
DISTANCE
BETWEEN
CENTERLINE
CAVITY TO PERFORATION
(WIDTH DIRECTION)
F
3.50 ± 0.05
0.138 ± 0.002
CAVITY TO PERFORATION
(LENGTH DIRECTION)
P2
2.00 ± 0.05
0.079 ± 0.002
For Outline SOT-143
P
D
P2
P0
E
F
W
D1
t1
K0
9° MAX
9° MAX
A0
B0
DESCRIPTION
SYMBOL
SIZE (mm)
SIZE (INCHES)
CAVITY
LENGTH
WIDTH
DEPTH
PITCH
BOTTOM HOLE DIAMETER
A0
B0
K0
P
D1
3.19 ± 0.10
2.80 ± 0.10
1.31 ± 0.10
4.00 ± 0.10
1.00 + 0.25
0.126 ± 0.004
0.110 ± 0.004
0.052 ± 0.004
0.157 ± 0.004
0.039 + 0.010
PERFORATION
DIAMETER
PITCH
POSITION
D
P0
E
1.50 + 0.10
4.00 ± 0.10
1.75 ± 0.10
0.059 + 0.004
0.157 ± 0.004
0.069 ± 0.004
CARRIER TAPE
WIDTH
THICKNESS
W
t1
8.00 +0.30 –0.10
0.254 ± 0.013
0.315+0.012 –0.004
0.0100 ± 0.0005
DISTANCE
CAVITY TO PERFORATION
(WIDTH DIRECTION)
F
3.50 ± 0.05
0.138 ± 0.002
CAVITY TO PERFORATION
(LENGTH DIRECTION)
P2
2.00 ± 0.05
0.079 ± 0.002
Tape Dimensions and Product Orientation
For Outlines SOT-323, -363
P
P2
D
P0
E
F
W
C
D1
t1 (CARRIER TAPE THICKNESS)
Tt (COVER TAPE THICKNESS)
K0
An
A0
DESCRIPTION
B0
SYMBOL
SIZE (mm)
SIZE (INCHES)
CAVITY
LENGTH
WIDTH
DEPTH
PITCH
BOTTOM HOLE DIAMETER
A0
B0
K0
P
D1
2.40 ± 0.10
2.40 ± 0.10
1.20 ± 0.10
4.00 ± 0.10
1.00 + 0.25
0.094 ± 0.004
0.094 ± 0.004
0.047 ± 0.004
0.157 ± 0.004
0.039 + 0.010
PERFORATION
DIAMETER
PITCH
POSITION
D
P0
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
CARRIER TAPE
WIDTH
THICKNESS
W
t1
8.00 ± 0.30
0.254 ± 0.02
0.315 ± 0.012
0.0100 ± 0.0008
COVER TAPE
WIDTH
TAPE THICKNESS
C
Tt
5.4 ± 0.10
0.062 ± 0.001
0.205 ± 0.004
0.0025 ± 0.00004
DISTANCE
CAVITY TO PERFORATION
(WIDTH DIRECTION)
F
3.50 ± 0.05
0.138 ± 0.002
CAVITY TO PERFORATION
(LENGTH DIRECTION)
P2
2.00 ± 0.05
0.079 ± 0.002
FOR SOT-323 (SC70-3 LEAD)
An
8°C MAX
ANGLE
FOR SOT-363 (SC70-6 LEAD)
An
10°C MAX
Part Number Ordering Information
Part Number
No. of
Devices
Container
HSMS-286x-TR2*
HSMS-286x-TR1*
10000
3000
13" Reel
7" Reel
HSMS-286x-BLK *
100
antistatic bag
where x = 0, 2, 3, 4, 5, B, C, E, F, K, L, P or R for
HSMS-286x.
* For lead-free option, the part number will have the
character “G” at the end, eg. HSMS-286x-TR2G for a
10,000 lead-free reel.
For product information and a complete list of distributors, please go to our web site:
www.avagotech.com
Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies, Limited
in the United States and other countries.
Data subject to change. Copyright © 2006 Avago Technologies, Limited. All rights reserved.
Obsoletes 5989-2495EN
5989-4023EN August 22, 2006
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