Surface Mount Microwave Schottky Detector Diodes Technical Data HSMS-286x Series Features * Surface Mount SOT-23/ SOT-143 Packages SOT-23/SOT-143 Package Lead Code Identification (top view) * Miniature SOT-323 and SOT-363 Packages SINGLE 3 SERIES 3 * High Detection Sensitivity: up to 50 mV/W at 915 MHz up to 35 mV/W at 2.45 GHz up to 25 mV/W at 5.80 GHz 1 1 * Low FIT (Failure in Time) Rate* * Tape and Reel Options Available * Matched Diodes for Consistent Performance * Better Thermal Conductivity for Higher Power Dissipation * Lead-free Option Available * For more information see the Surface Mount Schottky Reliability Data Sheet. 2 COMMON ANODE 3 1 * 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 #0 #3 #2 2 COMMON CATHODE 3 2 1 #4 2 UNCONNECTED PAIR 3 4 1 #5 2 SOT-323 Package Lead Code Identification (top view) SINGLE 3 SERIES 3 1 1 B 2 COMMON ANODE 3 1 E 2 C 2 COMMON CATHODE 3 1 F 2 Description Agilent'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. Available in various package configurations, this family of detector diodes provides low cost solutions to a wide variety of design problems. Agilent'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. 2 SOT-363 Package Lead Code Identification (top view) UNCONNECTED TRIO 6 5 4 6 5 4 1 2 3 1 2 3 1 2 3 K BRIDGE QUAD 6 5 1 2 P 4 6 3 1 L 2 4 R 6 5 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. RING QUAD 5 PLx HIGH ISOLATION UNCONNECTED PAIR Pin Connections and Package Marking 3 SOT-23/SOT-143 DC Electrical Specifications, TC = +25C, Single Diode Part Number HSMS- Package Marking Code[1] Lead Code Configuration 2860 2862 2863 2864 2865 T0 T2 T3 T4 T5 0 2 3 4 5 Single Series Pair [2,3] Common Anode [2,3] Common Cathode [2,3] Unconnected Pair [2,3] Forward Voltage VF (mV) 250 Min. Test Conditions Typical Capacitance CT (pF) 350 Max. IF = 1.0 mA 0.30 VR = 0 V, f = 1 MHz Notes: 1. Package marking code is in white. 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. SOT-323/SOT-363 DC Electrical Specifications, TC = +25C, Single Diode Part Number HSMS- Package Marking Code[1] 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 [2,3] Common Anode [2,3] Common Cathode [2,3] High Isolation Unconnected Pair Unconnected Trio Bridge Quad Ring Quad Forward Voltage VF (mV) 250 Min. Test Conditions Notes: 1. Package marking code is laser marked. 2. VF for diodes in trios and quads is 15.0 mV maximum at 1.0 mA. 3. CT for diodes in trios and quads is 0.05 pF maximum at -0.5V. 350 Max. IF = 1.0 mA Typical Capacitance CT (pF) 0.25 VR = 0 V, f = 1 MHz 3 RF Electrical Specifications, TC = +25C, 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 (mV/ W) @ f = 915 MHz 2.45 GHz 5.8 GHz 50 Video Bandwidth = 2 MHz Ib = 5 A 35 25 Power in = -40 dBm RL = 100 K, Ib = 5 A Typical Video Resistance RV (K) 5.0 Ib = 5 A Absolute Maximum Ratings, TC = +25C, Single Diode Symbol Parameter Unit 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 C/W 500 150 jc Thermal Resistance[2] Notes: 1. Operation in excess of any one of these conditions may result in permanent damage to the device. 2. TC = +25C, where TC is defined to be the temperature at the package pins where contact is made to the circuit board. ESD WARNING: Handling Precautions Should Be Taken To Avoid Static Discharge. 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 1 E-5 IS A 5 E -8 N 1.08 RS 6.0 PB (VJ) V 0.65 PT (XTI) 2 M 0.5 5 FORWARD CURRENT (A) 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 A 1000 5 A 100 Frequency = 2.45 GHz Fixed-tuned FR4 circuit 10 POWER IN (dBm) Figure 4. +25C Expanded Output Voltage vs. Input Power. See Figure 3. -20 0 -10 RL = 100 K 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 A 2.45 GHz 5.8 GHz 1 10,000 915 MHz 10 915 MHz Figure 3. +25C Output Voltage vs. Input Power, 3 A Bias. Figure 2. Forward Voltage Match. RL = 100 K VOLTAGE OUT (mV) RL = 100 K 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 = -55C TA = +25C TA = +85C 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 K 5 .1 1 10 100 BIAS CURRENT (A) Figure 6. Voltage Sensitivity as a Function of DC Bias Current. 6 Applications Information Introduction Agilent'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 25C 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 A 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 Agilent 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 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 A. See Figure 10. 2 0.2 0.6 5 1 1 GHz 2 3 4 [1] Agilent Application Note 923, Schottky Barrier Diode Video Detectors. Agilent Application Note 986, Square Law and Linear Detection. [3] Agilent Application Note 956-5, Dynamic Range Extension of Schottky Detectors. [4] Agilent Application Note 956-4, Schottky Diode Voltage Doubler. [5] Agilent 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 A 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 </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 Agilent. 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 A Bias. FREQUENCY (GHz): 2.3-2.6 Figure 19. Input Impedance. Modified 2.45 GHz Circuit. Figure 17. Input Impedance, 3 A 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 A Bias. 2.6 10 RETURN LOSS (dB) 0 -5 -10 -15 -20 5.6 5.7 5.8 5.9 6.0 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. 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 with much less temperature variation. 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 A 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 OUTPUT VOLTAGE (mV) The "Virtual Battery" 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 A of bias resulted in the highest voltage sensitivity, but at the cost of a wide variation over temperature. Dropping the bias to 1 A produced a detector 3.0 A 100 80 1.0 A 10 A 60 40 -55 0.5 A -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) Input return loss, shown in Figure 23, exhibits wideband match. 3.0 A 25 10 A 1.0 A 15 0.5 A 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 150C 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 100C/W, and the chip thermal resistance for these three families of diodes is approximately 40C/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) jc + Ta n = ideality factor T = temperature in K Rs = diode series resistance Equation (1). where Tj = junction temperature Ta = diode case temperature jc = thermal resistance Vf If = DC power dissipated PRF = RF power dissipated Note that jc, the thermal resistance from diode junction to the foot of the leads, is the sum of two component resistances, jc = pkg + chip Equation (2). and IS (diode saturation current) is given by 2 n Is = I 0 T ) (298 - 4060 e 1 ( 1T - 298 ) Agilent 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] Agilent 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 0.07 0.035 0.016 Figure 33. PCB Pad Layout (dimensions in inches). 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. Agilent'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 235C. These parameters are typical for a surface mount assembly process for Agilent 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 0.026 250 TMAX 0.035 0.016 Figure 34. PCB Pad Layout (dimensions in inches). 200 TEMPERATURE (C) 0.075 150 Reflow Zone 100 Preheat Zone Cool Down Zone 50 0 0 60 120 180 TIME (seconds) Figure 35. Surface Mount Assembly Profile. 240 300 14 Part Number Ordering Information Part Number HSMS-286x-TR2* No. of Devices 10000 Container 13" Reel HSMS-286x-TR1* HSMS-286x-BLK * 3000 100 7" Reel 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. Package Dimensions Outline 23 (SOT-23) 1.02 (0.040) 0.89 (0.035) Outline SOT-323 (SC-70 3 Lead) 0.54 (0.021) 0.37 (0.015) PACKAGE MARKING CODE (XX) DATE CODE (X) PACKAGE MARKING CODE (XX) 1.30 (0.051) REF. 2.20 (0.087) 2.00 (0.079) XXX DATE CODE (X) 3 1.40 (0.055) 1.20 (0.047) XXX 2.65 (0.104) 2.10 (0.083) 1.35 (0.053) 1.15 (0.045) 2 1 0.650 BSC (0.025) 0.60 (0.024) 0.45 (0.018) 2.04 (0.080) 1.78 (0.070) 0.425 (0.017) TYP. 2.20 (0.087) 1.80 (0.071) TOP VIEW 0.10 (0.004) 0.00 (0.00) 0.152 (0.006) 0.066 (0.003) 3.06 (0.120) 2.80 (0.110) 1.02 (0.041) 0.85 (0.033) 0.30 REF. 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) 0.20 (0.008) 0.10 (0.004) 0.69 (0.027) 0.45 (0.018) 0.10 (0.004) 0.013 (0.0005) DIMENSIONS ARE IN MILLIMETERS (INCHES) SIDE VIEW END VIEW DIMENSIONS ARE IN MILLIMETERS (INCHES) Outline 143 (SOT-143) Outline SOT-363 (SC-70 6 Lead) 0.92 (0.036) 0.78 (0.031) DATE CODE (X) 2 PACKAGE MARKING CODE (XX) 1.30 (0.051) REF. 2.20 (0.087) 2.00 (0.079) XXX DATE CODE (X) 1 PACKAGE MARKING CODE (XX) 1.40 (0.055) 1.20 (0.047) XXX 4 2.65 (0.104) 2.10 (0.083) 1.35 (0.053) 1.15 (0.045) 3 0.60 (0.024) 0.45 (0.018) 2.04 (0.080) 1.78 (0.070) 0.650 BSC (0.025) 0.54 (0.021) 0.37 (0.015) 3.06 (0.120) 2.80 (0.110) 0.425 (0.017) TYP. 2.20 (0.087) 1.80 (0.071) 0.15 (0.006) 0.09 (0.003) 0.10 (0.004) 0.00 (0.00) 0.30 REF. 1.04 (0.041) 0.85 (0.033) 0.10 (0.004) 0.013 (0.0005) 0.69 (0.027) 0.45 (0.018) 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) DIMENSIONS ARE IN MILLIMETERS (INCHES) 0.20 (0.008) 0.10 (0.004) 15 Device Orientation For Outlines SOT-23, -323 REEL TOP VIEW END VIEW 4 mm CARRIER TAPE 8 mm USER FEED DIRECTION ABC For Outline SOT-143 TOP VIEW ABC ABC For Outline SOT-363 END VIEW TOP VIEW 4 mm ABC ABC Note: "AB" represents package marking code. "C" represents date code. COVER TAPE 8 mm ABC END VIEW 4 mm ABC 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 8C MAX ANGLE FOR SOT-363 (SC70-6 LEAD) An 10C MAX www.agilent.com/semiconductors For product information and a complete list of distributors, please go to our web site. For technical assistance call: Americas/Canada: +1 (800) 235-0312 or (916) 788-6763 Europe: +49 (0) 6441 92460 China: 10800 650 0017 Hong Kong: (65) 6756 2394 India, Australia, New Zealand: (65) 6755 1939 Japan: (+81 3) 3335-8152(Domestic/International), or 0120-61-1280(Domestic Only) Korea: (65) 6755 1989 Singapore, Malaysia, Vietnam, Thailand, Philippines, Indonesia: (65) 6755 2044 Taiwan: (65) 6755 1843 Data subject to change. Copyright (c) 2004 Agilent Technologies, Inc. Obsoletes 5988-0970EN March 24, 2004 5989-0480EN