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hsms-285x series surface mount zero bias schottky detector diodes data sheet sot-23/sot-143 package lead code identification (top view) description avagos hsms-285x family of zero bias schottky detector diodes has been designed and optimized for use in small signal (p in < -20 dbm) applications at frequencies below 1.5 ghz. they are ideal for rf/id and rf tag applications where primary (dc bias) power is not available. important note: for detector applications with input power levels greater than C20 dbm, use the hsms-282x series at frequencies below 4.0 ghz, and the hsms-286x series at frequencies above 4.0 ghz. the hsms-285x series is not recommended for these higher power level applications. available in various package configurations, these detec- tor diodes provide low cost solutions to a wide variety of design problems. avagos manufacturing techniques assure that when two diodes are mounted into a single package, they are taken from adjacent sites on the wafer, assuring the highest possible degree of match. sot-323 package lead code identification (top view) features surface mount sot-23/sot-143 packages miniature sot-323 and sot-363 packages high detection sensitivity: up to 50 mv/ w at 915 mhz low flicker noise: -162 dbv/hz at 100 hz 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. sot-363 package lead code identification (top view) unconnected pair #5 series #2 single #0 12 3 12 34 12 3 series c single b 12 3 12 3 bridge quad p unconnected trio l 123 654 123 654 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. pin connections and package marking notes: 1. package marking provides orientation and identification. 2. see electrical specifications for appropriate package marking. plx 1 2 3 6 5 4
2 sot-23/sot-143 dc electrical specifications, t c = +25 c, single diode maximum part package maximum reverse typical number marking lead forward voltage leakage, capacitance hsms- code code configuration v f (mv) ir ( a) c t (pf) 2850 p0 0 single 150 250 175 0.30 2852 p2 2 series pair [1,2] 2855 p5 5 unconnected pair [1,2] test i f = 0.1 ma i f = 1.0 ma vr=2v v r = ?.5 v to ?.0v conditions f = 1 mhz notes: 1. ? v f for diodes in pairs is 15.0 mv maximum at 1.0 ma. 2. ? c t for diodes in pairs is 0.05 pf maximum at 0.5 v. rf electrical specifications, t c = +25 c, single diode part number typical tangential sensitivity typical voltage sensitivity typical video hsms- tss (dbm) @ f = 915 mhz g (mv/ w) @ f = 915 mhz resistance rv (k ? ) 2850 57 40 8.0 2852 2855 285b 285c 285l 285p test video bandwidth = 2 mhz power in = 40 dbm conditions zero bias r l = 100 k ? , zero bias zero bias sot-323/sot-363 dc electrical specifications, t c = +25 c, single diode maximum part package maximum reverse typical number marking lead forward voltage leakage, capacitance hsms- code code configuration v f (mv)ir ( a) c t (pf) 285b p0 b single 150 250 175 0.30 285c p2 c series pair 285l pl l unconnected trio 285p pp p bridge quad test i f = 0.1 ma i f = 1.0 ma vr=2v v r = 0.5 v to 1.0v conditions f = 1 mhz notes: 1. ? v f for diodes in pairs is 15.0 mv maximum at 1.0 ma. 2. ? c t for diodes in pairs is 0.05 pf maximum at 0.5 v.
3 equivalent linear circuit model hsms-285x chip spice parameters parameter units hsms-285x b v v 3.8 c j0 pf 0.18 e g ev 0.69 i bv a3 e-4 i s a3 e-6 n 1.06 r s ? 25 p b (v j ) v 0.35 p t (xti) 2 m 0.5 absolute maximum ratings, t c = +25 c, single diode symbol parameter unit absolute maximum [1] sot-23/143 sot-323/363 p iv peak inverse voltage v 2.0 2.0 t j junction temperature c 150 150 t stg storage temperature c -65 to 150 -65 to 150 t op operating temperature c -65 to 150 -65 to 150 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. t c = +25 c, where t c 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. c j r j r s r j = 8.33 x 10 -5 nt i b + i s where i b = externally applied bias current in amps i s = 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-285x product, please refer to application note an1124. r s = series resistance (see table of spice parameters) c j = junction capacitance (see table of spice parameters)
4 typical parameters, single diode figure 1. typical forward current vs. forward voltage. figure 2. +25 c output voltage vs. input power at zero bias. figure 3. +25 c expanded output voltage vs. input power. see figure 2. figure 4. output voltage vs. temperature. i f ?forward current (ma) 0 0.01 v f ?forward voltage (v) 0.8 1.0 100 1 0.1 0.2 1.8 10 1.4 0.4 0.6 1.2 1.6 voltage out (mv) -50 0.1 power in (dbm) -30 -20 10000 10 1 -40 0 100 -10 1000 r l = 100 k ? diodes tested in fixed-tuned fr4 microstrip circuits. 915 mhz voltage out (mv) -50 0.3 power in (dbm) -30 10 1 -40 30 r l = 100 k ? 915 mhz diodes tested in fixed-tuned fr4 microstrip circuits. output voltage (mv) 0 0.9 temperature ( c) 40 50 3.1 2.1 1.5 10 100 2.5 80 20 30 70 90 60 1.1 1.3 1.7 1.9 2.3 2.7 2.9 measurements made using a fr4 microstrip circuit. frequency = 2.45 ghz p in = -40 dbm r l = 100 k ?
5 applications information introduction avagos hsms-285x family of schottky detector diodes has been developed specifically for low cost, high volume designs in small signal (p in < -20 dbm) applica- tions at frequencies below 1.5 ghz. at higher frequencies, the dc biased hsms-286x family should be considered. in large signal power or gain con- trol applications (p in > -20 dbm), the hsms-282x and hsms-286x products should be used. the hsms-285x zero bias diode is not designed for large signal designs. 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 5, along with its equivalent circuit. figure 5. schottky diode chip. r s 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 r s is lost as heat it does not contribute to the rectified output of the diode. c j is parasitic junction capaci- tance 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 nt r j = CCCCCCCCCCCC = r v C r s i s + i b 0.026 = CCCCC at 25 c i s + i b where n = ideality factor (see table of spice parameters) t = temperature in k i s = saturation current (see table of spice parameters) i b = externally applied bias current in amps i s 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 s i = i s (exp ( CCCCCC ) - 1) 0.026 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 r s 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, i s , 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 charac- teristics of a schottky diode. barrier height will be altered, and at the same time c j and r s will be changed. in general, very low barrier height diodes (with high values of i s , suitable for zero bias applications) are realized on p-type silicon. such diodes suffer from higher values of r s than do the n-type. thus, p-type diodes are generally reserved for small signal detector applications (where very high values of r v swamp out high r s ) and n-type diodes are used for mixer applications (where high l.o. drive levels keep r v low). measuring diode parameters the measurement of the five elements which make up the low frequency equivalent circuit for a packaged schottky diode (see figure 6) is a complex task. various techniques are used for each element. the task begins with the elements of the diode chip itself. l p r s r v c j c p for the hsms-285x series c p = 0.08 pf l p = 2 nh c j = 0.18 pf r s = 25 ? r v = 9 k ? figure 6. equivalent circuit of a schottky diode. r s is perhaps the easiest to measure accurately. the v-i curve is measured for the diode under forward bias, and the slope of the r s r j c j metal schottky junction passivation passivation n-type or p-type epi layer n-type or p-type silicon substrate cross-section of schottky barrier diode chip equivalent circuit
6 curve is taken at some relatively high value of current (such as 5 ma). this slope is converted into a resistance r d . 0.026 r s = r d C CCCCCC i f r v and c j are very difficult to measure. consider the impedance of c j = 0.16 pf when measured at 1 mhz it is approximately 1m ? . for a well designed zero bias schottky, r v is in the range of 5 to 25 k ? , and it shorts out the junction capacitance. moving up to 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 ? 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 7. insertion loss (db) 3 -40 frequency (mhz) -10 -25 3000 -20 10 1000 100 -35 -30 -15 50 ? 50 ? 0.16 pf 50 ? 50 ? 9 k ? figure 7. measuring c j and r v . 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. l p and c p are best measured on the hp8753c, with the diode terminating a 50 ? line on the input port. the resulting tabula- tion of s 11 can be put into a microwave linear analysis program having the five element equivalent circuit with r v , c j and r s fixed. the optimizer can then adjust the values of l p and c p until the calculated s 11 matches the measured values. note that extreme care must be taken to de-embed the parasitics of the 50 ? test fixture. detector circuits 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] these circuits can take a variety of forms, but in the most simple case they appear as shown in figure 8. this is the basic detector circuit used with the hsms-285x family of diodes. in the design of such detector circuits, the starting point is the equivalent circuit of the diode, as shown in figure 6. of interest in the design of the video portion of the circuit is the diodes video impedance the other four elements of the equiv- alent circuit disappear at all reasonable video frequencies. in general, the lower the diodes video impedance, the better the design. video out rf in z-match network video out z-match network rf in 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 diodes equivalent circuit, the four parasitics are constants and the video resistance is a function of the current flowing through the diode. 26,000 r v CCCCCC i s + i b where i s = diode saturation current in a i b = bias current in a saturation current is a function of the diodes design, [2] and it is a constant at a given temperature. for the hsms-285x series, it is typically 3 to 5 a at 25 c. saturation current sets the detec- tion sensitivity, video resistance and input rf impedance of the zero bias schottky detector diode. [1] avago application note 923, schottky barrier diode video detectors. [2] avago application note 969, an optimum zero bias schottky detector diode. figure 8. basic detector circuits.
7 since no external bias is used with the hsms-285x series, a single transfer curve at any given frequency is obtained, as shown in figure 2. 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 net- works 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. [3] design work begins with the rf impedance of the hsms-285x series, which is given in figure 9. 1 ghz 2 3 4 5 6 0.2 0.6 1 2 5 figure 9. rf impedance of the hsms-285x series at -40 dbm. 915 mhz detector circuit figure 10 illustrates a simple impedance matching network for a 915 mhz detector. 65nh 100 pf video out rf input width = 0.050" length = 0.065" width = 0.015" length = 0.600" transmission line dimensions are for microstrip on 0.032" thick fr-4. figure 10. 915 mhz matching network for the hsms-285x series at zero bias. 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 diodes sot-323 package. a shorted shunt stub of length < /4 provides the necessary shunt inductance and simultaneously provides the return circuit for the current gen- erated in the diode. the imped- ance of this circuit is given in figure 11. frequency (ghz): 0.9-0.93 figure 11. input impedance. the input match, expressed in terms of return loss, is given in figure 12. return loss (db) 0.9 -20 frequency (ghz) 0.915 0 -10 -15 0.93 -5 figure 12. input return loss. as can be seen, the band over which a good match is achieved is more than adequate for 915 mhz rfid applications. voltage doublers to this point, we have restricted our discussion to single diode detectors. a glance at figure 8, however, will lead to the sugges- tion that the two types of single diode detectors be combined into a two diode voltage doubler [4] (known also as a full wave recti- fier). such a detector is shown in figure 13. video out z-match network rf in figure 13. 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. [3] avago application note 963, impedance matching techniques for mixers and detectors. [4] avago application note 956-4, schottky diode voltage doubler. [5] avago application note 965-3, flicker noise in schottky diodes.
8 such a circuit can easily be realized using the two series di- odes in the hsms-285c. flicker noise 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 [5] 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 substantially reduced by the 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-285x series, the noise temperature ratio is given in figure 14. noise temperature ratio (db) frequency (hz) 15 10 5 0 -5 10 100 1000 10000 100000 figure 14. typical noise temperature ratio. noise temperature ratio is the quotient of the diodes noise power (expressed in dbv/hz) di- vided by the noise power of an ideal resistor of resistance r = r v . for an ideal resistor r, at 300 k, the noise voltage can be com- puted from v = 1.287 x 10 -10 r volts/hz which can be expressed as 20 log 10 v dbv/hz thus, for a diode with r v = 9 k ? , the noise voltage is 12.2 nv/hz or -158 dbv/hz. on the graph of figure 14, -158 dbv/hz would replace the zero on the vertical scale to convert the chart to one of absolute noise voltage vs. frequency. 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 receiv- ers used in rfid (tag) applica- tions 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 trans- mitter, etc. in such environments, the schottky diodes of the receiver can be protected by a de- vice known as a limiter diode. [6] formerly available only in radar warning receivers and other high cost electronic warfare applica- tions, these diodes have been adapted to commercial and consumer circuits. avago 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 reflecting the excessive rf energy back out the antenna. assembly instructions sot-323 pcb footprint a recommended pcb pad layout for the miniature sot-323 (sc-70) package is shown in figure 15 (dimensions are in inches). this layout provides ample allowance for package placement by auto- mated assembly equipment without adding parasitics that could impair the performance. figure 16 shows the pad layout for the six-lead sot-363. 0.026 0.039 0.079 0.022 dimensions in inches figure 15. recommended pcb pad layout for avago s sc70 3l/sot-323 products. 0.026 0.079 0.018 0.039 dimensions in inches figure 16. recommended pcb pad layout for avago's sc70 6l/sot-363 products. [6] avago application note 1050, low cost, surface mount power limiters.
9 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 packages, will reach solder reflow temperatures faster than those with a greater mass. time (seconds) t max temperature ( c) 0 0 50 100 150 200 250 60 preheat zone cool down zone reflow zone 120 180 240 300 figure 17. surface mount assembly profile. avagos diodes have been quali- fied to the time-temperature profile shown in figure 17. this profile is representative of an ir reflow type of surface mount assembly process. 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 evapo- rating solvents from the solder paste. the reflow zone briefly elevates the temperature suffi- ciently to produce a reflow of the solder. 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 max ) 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. part number ordering information no. of part number devices container hsms-285x-tr2* 10000 13" reel hsms-285x-tr1* 3000 7" reel hsms-285x-blk * 100 antistatic bag where x = 0, 2, 5, b, c, l and p for hsms-285x. for lead-free option, the part number will have the character "g" at the end, eg. hsms-285x-tr2g for a 10,000 lead-free reel.
10 package dimensions outline 23 (sot-23) outline 143 (sot-143) e b e2 e1 e1 c e xxx l d a a1 notes: xxx-package marking drawings are not to scale dimensions (mm) min. 0.79 0.000 0.37 0.086 2.73 1.15 0.89 1.78 0.45 2.10 0.45 max. 1.20 0.100 0.54 0.152 3.13 1.50 1.02 2.04 0.60 2.70 0.69 symbol a a1 b c d e1 e e1 e2 e l e b e2 b1 e1 e1 c e xxx l d a a1 notes: xxx-package marking drawings are not to scale dimensions (mm) 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 symbol a a1 b b1 c d e1 e e1 e2 e l e outline sot-363 (sc-70 6 lead) outline sot-323 (sc-70 3 lead) e he d e a1 b a a2 q1 l c dimensions (mm) min. 1.15 1.80 1.80 0.80 0.80 0.00 0.10 0.15 0.10 0.10 max. 1.35 2.25 2.40 1.10 1.00 0.10 0.40 0.30 0.20 0.30 symbol e d he a a2 a1 q1 e b c l 0.650 bcs e b e1 e1 c e xxx l d a a1 notes: xxx-package marking drawin g s are not to scale dimensions (mm) min. 0.80 0.00 0.15 0.10 1.80 1.10 1.80 max. 1.00 0.10 0.40 0.20 2.25 1.40 2.40 symbol a a1 b c d e1 e e1 e l 1.30 typical 0.65 typical 0.425 typical
11 device orientation user feed direction cover tape carrier tape reel for outline sot-143 for outlines sot-23, -323 note: "ab" represents package marking code. "c" represents date code. end vie w 8 mm 4 mm top view abc abc abc abc end vie w 8 mm 4 mm top view note: "ab" represents package marking code. "c" represents date code. abc abc abc abc for outline sot-363 note: "ab" represents package marking code. "c" re p resents date code. end vie w 8 mm 4 mm top view abc abc abc abc
12 tape dimensions and product orientation for outline sot-23 9 max a 0 p p 0 d p 2 e f w d 1 ko 8 max b 0 13.5 max t1 description symbol size (mm) size (inches) length width depth pitch bottom hole diameter a 0 b 0 k 0 p d 1 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 cavity diameter pitch position d p 0 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 perforation width thickness w t1 8.00 + 0.30 0.10 0.229 0.013 0.315 + 0.012 0.004 0.009 0.0005 carrier tape cavity to perforation (width direction) cavity to perforation (length direction) f p 2 3.50 0.05 2.00 0.05 0.138 0.002 0.079 0.002 distance between centerline for outline sot-143 w f e p 2 p 0 d p d 1 description symbol size (mm) size (inches) length width depth pitch bottom hole diameter a 0 b 0 k 0 p d 1 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 cavity diameter pitch position d p 0 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 perforation width thickness w t1 8.00 + 0.30 0.10 0.254 0.013 0.315+ 0.012 0.004 0.0100 0.0005 carrier tape cavity to perforation (width direction) cavity to perforation (length direction) f p 2 3.50 0.05 2.00 0.05 0.138 0.002 0.079 0.002 distance a 0 9 max 9 max t 1 b 0 k 0
tape dimensions and product orientation for outlines sot-323, -363 p p 0 p 2 f w c d 1 d e a 0 an t 1 (carrier tape thickness) t t (cover tape thickness) an b 0 k 0 description symbol size (mm) size (inches) length width depth pitch bottom hole diameter a 0 b 0 k 0 p d 1 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 cavity diameter pitch position d p 0 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 perforation width thickness w t 1 8.00 0.30 0.254 0.02 0.315 0.012 0.0100 0.0008 carrier tape cavity to perforation (width direction) cavity to perforation (length direction) f p 2 3.50 0.05 2.00 0.05 0.138 0.002 0.079 0.002 distance for sot-323 (sc70-3 lead) an 8 c max for sot-363 (sc70-6 lead) 10 c max angle width tape thickness c t t 5.4 0.10 0.062 0.001 0.205 0.004 0.0025 0.00004 cover tape 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 5989-2494en 5989-4022en august 14, 2006

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