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general description the max2016 dual logarithmic detector/controller is afully integrated system designed for measuring and comparing power, gain/loss, and voltage standing-wave ratio (vswr) of two incoming rf signals. an internal broadband impedance match on the two differential rf input ports allows for the simultaneous monitoring of sig- nals ranging from low frequency to 2.5ghz. the max2016 uses a pair of logarithmic amplifiers to detect and compare the power levels of two rf input signals. the device internally subtracts one power level from the other to provide a dc output voltage that is pro- portional to the power difference (gain). the max2016 can also measure the return loss/vswr of an rf signal by monitoring the incident and reflected power levels associated with any given load. a window detector is easily implemented by using the on-chip comparators, or gate, and 2v reference. this combination of circuitry provides an automatic indication of when the measured gain is outside a programmable range. alarm monitoring can thus be implemented for detecting high-vswr states (such as open or shorted loads). the max2016 operates from a single +2.7v to +5.25v* power supply and is specified over the extended -40? to +85? temperature range. the max2016 is available in a space-saving, 5mm x 5mm, 28-pin thin qfn. applications return loss/vswr measurementsdual-channel rf power measurements dual-channel precision agc/rf power control log ratio function for rf signals remote system monitoring and diagnostics cellular base station, microwave link, radar, and other military applications rf/if power amplifier (pa) linearization features ? complete gain and vswr detector/controller ? dual-channel rf power detector/controller ? low-frequency to 2.5ghz frequency range ? exceptional accuracy over temperature ? high 80db dynamic range ? 2.7v to 5.25v supply voltage range* ? internal 2v reference ? scaling stable over supply and temperaturevariations ? controller mode with error output ? available in 5mm x 5mm, 28-pin thin qfnpackage *see power-supply connection section. max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements ________________________________________________________________ maxim integrated products 1 fa1 1 v cc 2 rfina+ 3 rfina- 4 gnd 5 couth 6 cseth 7 fb1 21 v cc 20 rfinb+ 19 rfinb- 18 gnd 17 coutl 16 csetl 15 cor 8 v cc 9 setd 10 outd 11 v cc 12 fv2 13 fv1 14 fa2 28 outa 27 seta 26 ref 25 setb 24 outb 23 fb2 22 max2016 thin qfn pin configuration ordering information 19-3404; rev 1; 10/06 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available part temp range pin-package pkg code MAX2016ETI -40 c to +85 c 28 thi n qfn - e p *, b ul k t2855-3 MAX2016ETI-t -40 c to +85 c 28 thi n qfn - e p *, t/r t2855-3 MAX2016ETI+d -40 c to +85 c 28 thi n qfn - e p *, l ead fr ee, b ul k t2855-3 MAX2016ETI+td -40 c to +85 c 28 thi n qfn - e p *, l ead fr ee, t/r t2855-3 * ep = exposed pad. + indicates lead-free package. d = dry pack. typical application circuit appears at end of data sheet. downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v cc to gnd .........................................................-0.3v to +5.25v input power differential (rfin_+, rfin_-)......................+23dbm input power single ended (rfin_+ or rfin _-) .............+19dbm all other pins to gnd.................................-0.3v to (v cc + 0.3v) continuous power dissipation (t a = +70?) 28-pin, 5mm x 5mm thin qfn (derate 35.7mw/? above +70?)..................................................................2.8w operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? dc electrical characteristics(v cc = +2.7v to +3.6v, r 1 = r 2 = r 3 = 0 , t a = -40? to +85?, unless otherwise noted. typical values are at v cc = +3.3v, csetl = cseth = v cc , 50 rf system, t a = +25?, unless otherwise noted.) (note 1) parameter symbol conditions min typ max units power supply v s r 6 = 0 2.7 3.3 3.6 supply voltage v s r 6 = 37.4 4.75 5 5.25 v total supply current i cc 43 55 ma measured in each pin 2 and pin 20 16 measured in pin 9 2 supply current measured in pin 12 9 ma input interface input impedance differential impedance at rfina and rfinb 50 resistance at setd 20 input resistance r resistance at seta and setb 40 k detector output source current measured at outa, outb, and outd 4 ma sink current measured at outa, outb, and outd 0.45 ma minimum output voltage measured at outa, outb, and outd 0.5 v maximum output voltage measured at outa, outb, and outd 1.8 v difference output voutd p rfina = p rfinb = -30dbm 1 v outd accuracy ?2 mv comparators output high voltage v oh r load 10k v cc - 10mv v output low voltage v ol r load 10k 10 mv input voltage measured at csetl and cseth gnd to v cc v input bias current csetl and cseth 1 na reference output voltage on pin 25 r load 2k 2v load regulation source 2ma -5 mv downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements _______________________________________________________________________________________ 3 parameter symbol conditions min typ max units rf input frequency range f rf ac-coupled input 2.5 ghz return loss s 11 0.1ghz to 3ghz 20 db large-signal response time p rfin = no signal to 0dbm, ?.5db settling accuracy 100 ns rssi mode?.1ghz rf input power range (note 2) -70 to +10 dbm ?db dynamic range t a = -20? to +85? (note 3) 80 db range center -32 dbm t a = +25? to +85? +0.0083 temperature sensitivity p rfina = p rfinb = -32dbm t a = +25? to -20? -0.0083 db/? slope (note 4) 19 mv/db typical slope variation t a = -20? to +85? -4 ?/? intercept (note 5) -100 dbm typical intercept variation t a = -20? to +85? 0.03 dbm/? rssi mode?.9ghz rf input power range (note 2) -70 to +10 dbm ?db dynamic range t a = -20? to +85? (note 3) 80 db range center -30 dbm t a = +25? to +85? +0.0083 temperature sensitivity p rfina = p rfinb = -30dbm t a = +25? to -20? -0.0083 db/? slope (note 4) 18.1 mv/db typical slope variation t a = -20? to +85? -4 ?/? intercept (note 5) -97 dbm typical intercept variation t a = -20? to +85? 0.02 dbm/? rssi mode?.9ghz rf input power range (note 2) -55 to +12 dbm ?db dynamic range t a = -20? to +85? (note 3) 67 db range center -27 dbm t a = +25? to +85? +0.0125 temperature sensitivity p rfina = p rfinb = -27dbm t a = +25? to -20? -0.0125 db/? slope (note 4) 18 mv/db typical slope variation t a = -20? to +85? -4.8 ?/? intercept (note 5) -88 dbm typical intercept variation t a = -20? to +85? 0.03 dbm/? ac electrical characteristics?uta and outb( typical application circuit , v cc = +2.7v to +3.3v, r 1 = r 2 = r 3 = 0 , t a = -40? to +85?, unless otherwise noted. typical values are at v cc = 3.3v, csetl = cseth = v cc , t a = +25?, unless otherwise noted.) (note 1) downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 4 _______________________________________________________________________________________ parameter symbol conditions min typ max units rssi mode?.17ghz rf input power range (note 2) -52 to +12 dbm ?db dynamic range t a = -20? to +85? (note 3) 64 db range center -25 dbm t a = +25? to +85? +0.0135 temperature sensitivity p rfina = p rfinb = -25dbm t a = +25? to -20? -0.0135 db/? slope (note 4) 17.8 mv/db typical slope variation t a = -20? to +85? -8 ?/? intercept (note 5) -81 dbm typical intercept variation t a = -20? to +85? 0.03 dbm/? rssi mode?.5ghz rf input power range (note 2) -45 to +7 dbm ?db dynamic range t a = -20? to +85? (note 3) 52 db range center -23 dbm t a = +25? to +85? +0.0167 temperature sensitivity p rfina = p rfinb = -23dbm t a = +25? to -20? -0.0167 db/? slope (note 4) 17.8 mv/db typical slope variation t a = -20? to +85? -8 ?/? intercept (note 5) -80 dbm typical intercept variation t a = -20? to +85? 0.03 dbm/? ac electrical characteristics?uta and outb (continued)( typical application circuit , v cc = +2.7v to +3.3v, r 1 = r 2 = r 3 = 0 , t a = -40? to +85?, unless otherwise noted. typical values are at v cc = 3.3v, csetl = cseth = v cc , t a = +25?, unless otherwise noted.) (note 1) ac electrical characteristics?utd( typical application circuit , v cc = +2.7v to +3.3v, r 1 = r 2 = r 3 = 0 , t a = -40? to +85?, unless otherwise noted. typical values are at v cc = 3.3v, csetl = cseth = v cc , t a = +25?, unless otherwise noted.) (note 1) parameter symbol conditions min typ max units outd center point p rfina = p rfinb 1v small-signal envelope bandwidth no external capacitor on pins fv1 and fv2 22 mhz small-signal settling time any 8db change on the inputs,no external capacitor on fv1 and fv2, settling accuracy is ?.5db 150 ns large-signal settling time any 30db change on the inputs, no externalcapacitor on pins fv1 and fv2, settling accuracy is 0.5db 300 ns small-signal rise and fall time any 8db step, no external capacitor on pinsfv1 and fv2 15 ns downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements _______________________________________________________________________________________ 5 parameter symbol conditions min typ max units large-signal rise and fall time any 30db step, no external capacitor onpins fv1 and fv2 35 ns 0.1ghz p rfinb = -32dbm 80 0.9ghz p rfinb = -30dbm 75 1.9ghz p rfinb = -27dbm 60 2.17ghz p rfinb = -25dbm 55 ?db dynamic range 2.5ghz p rfinb = -23dbm 50 db slope f rf = 0.1ghz to 2.5ghz (a-b) -25 mv/db outd voltage deviation p rfina = p rfinb = -30dbm, t a = -20? to +85? ?.25 db 0.1ghz, p rfinb = -32dbm 80 0.9ghz, p rfinb = -30dbm 70 1.9ghz, p rfinb = -27dbm 55 2.17ghz, p rfinb = -25dbm 50 ?db dynamic range overtemperature relative to best-fit curve at +25 c p rfina is swept ; t a = -20? to +85? 2.5ghz, p rfinb = -23dbm 45 db gain measurement balance p rfinb = p rfinb = -50dbm to -5dbm, f rf = 1.9ghz 0.2 db 0.9ghz 90 1.9ghz 65 channel isolation 2.5ghz 55 db ac electrical characteristics?utd (continued)( typical application circuit , v cc = +2.7v to +3.3v, r 1 = r 2 = r 3 = 0 , t a = -40? to +85?, unless otherwise noted. typical values are at v cc = 3.3v, csetl = cseth = v cc , t a = +25?, unless otherwise noted.) (note 1) note 1: the max2016 is tested at t a = +25? and is guaranteed by design for t a = -40? to +85?. note 2: typical minimum and maximum range of the detector at the stated frequency. note 3: dynamic range refers to the range over which the error remains within the ?db range. note 4: the slope is the variation of the output voltage per change in input power. it is calculated by fitting a root-mean-squarestraight line to the data indicated by the rf input power range. note 5: the intercept is an extrapolated value that corresponds to the output power for which the output voltage is zero. it is calcu-lated by fitting a root-mean-square straight line to the data. downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 6 _______________________________________________________________________________________ typical operating characteristics (max2016 ev kit, v cc = 3.3v, r 1 = r 2 = r 3 = 0 , csetl = cseth = v cc , t a = +25?, unless otherwise noted.) differential output voltage vs. a/b difference max2016 toc01 magnitude ratio (db) v outd (v) 30 10 -10 -30 0.5 1.0 1.5 2.0 2.5 0 -50 50 f in = 100mhz p rfinb = -32dbm p rfina is swept t a = -20 c, +25 c, +85 c differential output-voltage error vs. a/b difference max2016 toc02 magnitude ratio (db) error (db) 30 10 -10 -30 -2 -1 0 1 2 3 -3 -50 50 f in = 100mhz p rfinb = -32dbm normalized to dataat +25 c t a = -20 c t a = +85 c differential output voltage vs. a/b difference max2016 toc03 magnitude ratio (db) v outd (v) 30 10 -10 -30 0.5 1.0 1.5 2.0 2.5 0 -50 50 f in = 900mhz p rfinb = -30dbm p rfina is swept t a = -20 c, +25 c, +85 c differential output-voltage error vs. a/b difference max2016 toc04 magnitude ratio (db) error (db) 30 10 -10 -30 -2 -1 0 1 2 3 -3 -50 50 f in = 900mhz p rfinb = -30dbm normalized to dataat +25 c t a = -20 c t a = +85 c differential output voltage vs. a/b difference max2016 toc05 magnitude ratio (db) v outd (v) 20 0 -20 0.5 1.0 1.5 2.0 2.5 0 -40 40 f in = 1900mhz p rfinb = -27dbm p rfina is swept t a = -20 c t a = +25 c t a = +85 c differential output-voltage error vs. a/b difference max2016 toc06 magnitude ratio (db) error (db) 20 0 -20 -2 -1 0 1 2 3 -3 -40 40 f in = 1900mhz p rfinb = -27dbm normalized to dataat +25 c t a = -20 c t a = +85 c downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements _______________________________________________________________________________________ 7 typical operating characteristics (continued) (max2016 ev kit, v cc = 3.3v, r 1 = r 2 = r 3 = 0 , csetl = cseth = v cc , t a = +25?, unless otherwise noted.) differential output-voltage balance max2016 toc11 p rfina (dbm) v outd (v) -15 -30 -45 0.90 0.95 1.00 1.05 1.10 1.150.85 -60 0 f in = 1900mhz p rfina = p rfinb + 5db p rfina = p rfinb - 5db p rfina = p rfinb t a = -20 c t a = +25 c t a = +85 c t a = -20 c t a = +25 c t a = +85 c t a = -20 c t a = +25 c t a = +85 c s 11 magnitude max2016 toc12 frequency (ghz) magnitude (db) 2.5 2.0 1.5 1.0 0.5 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10-60 03 . 0 t a = -20 c t a = +25 c t a = +85 c 20 0 -20 -40 40 max2016 toc09 differential output voltage vs. a/b difference magnitude ratio (db) v outd (v) 0.5 1.0 1.5 2.0 2.5 0 f in = 2500mhz p rfinb = -23dbm p rfina is swept t a = -20 c t a = +25 c t a = +85 c differential output-voltage error vs. a/b difference max2016 toc10 magnitude ratio (db) error (db) 20 0 -20 -2 -1 0 1 2 3 -3 -40 40 f in = 2500mhz p rfinb = -23dbm normalized to dataat +25 c t a = -20 c t a = +85 c 15 -5 -25 -45 35 max2016 toc07 differential output voltage vs. a/b difference magnitude ratio (db) v outd (v) 0.5 1.0 1.5 2.0 2.5 0 f in = 2170mhz p rfinb = -25dbm p rfina is swept t a = -20 c t a = +25 c t a = +85 c differential output-voltage error vs. a/b difference max2016 toc08 magnitude ratio (db) error (db) 20 0 -20 -2 -1 0 1 2 3 -3 -40 40 f in = 2170mhz p rfinb = -25dbm normalized to dataat +25 c t a = -20 c t a = +85 c downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 8 _______________________________________________________________________________________ typical operating characteristics (continued) (max2016 ev kit, v cc = 3.3v, r 1 = r 2 = r 3 = 0 , csetl = cseth = v cc , t a = +25?, unless otherwise noted.) v outa vs. p rfina max2016 toc17 p rfina (dbm) v outa (v) -5 -25 -45 0.5 1.0 1.5 2.0 2.5 0 -65 15 f in = 1900mhz t a = -20 c t a = +25 c t a = +85 c v outa error vs. p rfina max2016 toc18 p rfina (dbm) error (db) -5 -25 -45 -2 -1 0 1 2 3 -3 -65 15 f in = 1900mhz normalized to dataat +25 c t a = -20 c t a = +85 c v outa vs. p rfina max2016 toc13 p rfina (dbm) v outa (v) 0 -20 -40 -60 0.5 1.0 1.5 2.0 2.5 0 -80 20 f in = 100mhz t a = -20 c t a = +25 c t a = +85 c v outa error vs. p rfina max2016 toc14 p rfina (dbm) error (db) 0 -20 -40 -60 -2 -1 0 1 2 3 -3 -80 20 f in = 100mhz normalized to dataat +25 c t a = -20 c t a = +85 c v outa vs. p rfina max2016 toc15 p rfina (dbm) v outa (v) 0 -20 -40 -60 0.5 1.0 1.5 2.0 2.5 0 -80 20 f in = 900mhz t a = -20 c t a = +25 c t a = +85 c v outa error vs. p rfina max2016 toc16 p rfina (dbm) error (db) 0 -15 -30 -45 -60 -2 -1 0 1 2 3 -3 -75 15 f in = 900mhz normalized to dataat +25 c t a = -20 c t a = +85 c downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements _______________________________________________________________________________________ 9 typical operating characteristics (continued) (max2016 ev kit, v cc = 3.3v, r 1 = r 2 = r 3 = 0 , csetl = cseth = v cc , t a = +25?, unless otherwise noted.) v outa vs. p rfina max2016 toc19 p rfina (dbm) v outa (v) 0 -15 -30 -45 0.5 1.0 1.5 2.0 2.5 0 -60 15 f in = 2170mhz t a = -20 c t a = +25 c t a = +85 c v outa error vs. p rfina max2016 toc20 p rfina (dbm) error (db) 0 -15 -30 -45 -2 -1 0 1 2 3 -3 -60 15 f in = 2170mhz normalized to dataat +25 c t a = -20 c t a = +85 c max2016 toc21 0 -15 -30 -45 0.5 1.0 1.5 2.0 2.5 0 -60 15 v outa vs. p rfina p rfina (dbm) v outa (v) f in = 2500mhz t a = -20 c t a = +25 c t a = +85 c -2 -1 0 1 2 3 -3 max2016 toc22 0 -15 -30 -45 -60 15 v outa error vs. p rfina p rfina (dbm) error (db) f in = 2500mhz normalized to dataat +25 c t a = -20 c t a = +85 c downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 10 ______________________________________________________________________________________ detailed description the max2016 dual logarithmic amplifier is designed fora multitude of applications including dual-channel rf power measurements, agc control, gain/loss detection, and vswr monitoring. this device measures rf signals ranging from low frequency to 2.5ghz, and operates from a single 2.7v to 5.25v (using series resistor, r6) power supply. as with its single-channel counterpart (max2015), the max2016 provides unparalleled perfor- mance with a high 80db dynamic range at 100mhz and exceptional accuracy over the extended temperature and supply voltage ranges. the max2016 uses a pair of logarithmic amplifiers to detect and compare the power levels of two rf input signals. the device subtracts one power level from the other to provide a dc output voltage that is proportional to the power difference (gain). the max2016 can alsomeasure the return loss/vswr of an rf signal by moni- toring the incident and reflected power levels associat- ed with any given load. a window detector is easily implemented by using the on-chip comparators, or gate, and 2v reference. this combination of circuitry provides an automatic indica- tion of when the measured gain is outside a program- mable range. alarm monitoring can thus be imple- mented for detecting high-vswr states (such as open or shorted loads). rf inputs (rfina and rfinb) the max2016 has two differential rf inputs. the inputto detector a (rfina) uses the two input ports rfina+ and rfina-, and the input to detector b (rfinb) uses the two input ports rfinb+ and rfinb-. pin description pin name function 1, 28 fa1, fa2 external capacitor input. connecting a capacitor between fa1 and fa2 sets the highpass cutofffrequency corner for detector a (see the input highpass filter section). 2, 9, 12, 20 v cc supply voltage. bypass with capacitors as specified in the typical application circuit . place capacitors as close to each v cc as possible (see the power-supply connections section). 3, 4 rfina+, rfina- differential rf inputs for detector a. requires external dc-blocking capacitors. 5, 17 gnd ground. connect to the pcb ground plane. 6 couth high-comparator output 7 cseth threshold input on high comparator 8 cor comparator or logic output. output of couth ored with coutl. 10 setd set-point input for gain detector 11 outd dc output voltage representing p rfina - p rfinb . this output provides a dc voltage proportional to the difference of the input rf powers on rfina and rfinb. 13, 14 fv2, fv1 video-filter capacitor inputs for outd 15 csetl threshold set input on low comparator 16 coutl low-comparator output 18, 19 rfinb-, rfinb+ differential rf inputs for detector b. requires external dc-blocking capacitors. 21, 22 fb1, fb2 external capacitor input. connecting a capacitor between fb1 and fb2 sets the highpass cutofffrequency corner for detector b (see the input highpass filter section). 23 outb detector b output. this output provides a voltage proportional to the log of the input power ondifferential inputs rfinb+ and rfinb- (rfinb). 24 setb set-point input for detector b 25 ref 2v reference output 26 seta set-point input for detector a 27 outa detector a output. this output provides a voltage proportional to the log of the input power ondifferential inputs rfina+ and rfina- (rfina). ep gnd exposed paddle. ep must connect to the pcb ground plane. downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements ______________________________________________________________________________________ 11 the differential rf inputs allow for the measurement ofbroadband signals ranging from low frequency to 2.5ghz. for single-ended signals, rfina- and rfinb- are ac-coupled to ground. the rf inputs are internally biased and need to be ac-coupled. using 680pf capacitors, as shown in the typical application circuit , results in a 10mhz highpass corner frequency. aninternal 50 resistor between rfina+ and rfina- (as well as rfinb+ and rfinb-) produces a good low-fre-quency to 3.0ghz match. seta, setb, and setd inputs the set_ inputs are used for loop control when thedevice is in controller mode. likewise, these same set_ inputs are used to set the slope of the output sig- nal (mv/db) when the max2016 is in detector mode. the center node of the internal resistor-divider is fed to the negative input of the power detector? internal out- put op amp. reference the max2016 has an on-chip 2v voltage reference.the internal reference output is connected to ref. the output can be used as a reference voltage source for the comparators or other components and can source up to 2ma. outa and outb each out_ is a dc voltage proportional to the rf inputpower level. the change of out_ with respect to the power input is approximately 18mv/db (r 1 = r 2 = 0 ). the input power level can be determined by the followingequation: where p int is the extrapolated intercept point of where the output voltage intersects the horizontal axis. outd outd is a dc voltage proportional to the difference ofthe input rf power levels. the change of the outd with respect to the power difference is -25mv/db (r3 = 0 ). the difference of the input power levels (gain) can be determined by the following equation:where v center is the output voltage, typically 1v, when p rfina = p rfinb . applications information monitoring vswr and return loss the max2016 can be used to measure the vswr of anrf signal, which is useful for detecting the presence or absence of a properly loaded termination, such as an antenna (see figure 1). the transmitted wave from the power amplifier is coupled to rfina and to the anten- na. the reflected wave from the antenna is connected to rfinb through a circulator. when the antenna is missing or damaged, a mismatch in the nominal load pp vv slope rfina rfinb outd center = () p v slope p rfin out int _ _ =+ max2016 csetl coutl v ref logarithmic detector logarithmic detector coutl outd setd 20k rfinb rfina outd transmitter coupler circulator attenuator gnd figure 1. vswr monitoring configuation downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 12 ______________________________________________________________________________________ impedance results, leading to an increase in reflectedpower and subsequent change in the transmission line? vswr. this increase in reflected power is mani- fested by an increase in the voltage at outd. an alarm condition can be set by using the low comparator out- put (coutl) as shown in figure 1. the comparator automatically senses the change in vswr, yielding a logic 0 as it compares outd to a low dc voltage at csetl. csetl, in turn, is set by using the internal refer- ence voltage and an external resistor-divider network. for accurate measurement of signals carrying signifi- cant amplitude modulation, limit the bandwidth of the difference amplifier to be less than the lowest modula- tion frequency. this will minimize the ripple in the outd waveform. this is particularly appropriate if the system-level time delay between the two sense points is significant with respect to the period of modulation. figure 1 illustrates a simple level detector. for window- detector implementation, see the comparator/window detector section. measuring vswr and return loss in figure 2, the two logarithmic amplifiers measure theincident and the reflected power levels to produce two proportional output voltages at outa and outb. since outd is a dc voltage proportional to the difference of outa and outb, return loss (rl) and vswr can be easily calculated within a microprocessor using the following relationships: where return loss (rl) is expressed in decibels, v center is the output voltage (typically 1v) when p rfina = p rfinb , and slope is typically equal to -25mv/db (for r3 = 0 ). vswr can similarly be calculated through the followingrelationship: vswr rlrl = + ?? ?? ?? ?? 110 110 2020 rl p p vv slope rfina rfinb outd center = = () max2016 rfinarfinb gnd adc p in load 4-port directional coupler logarithmic detector logarithmic detector outd setd 20k figure 2. measuring return loss and vswr of a given load downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements ______________________________________________________________________________________ 13 measuring gain the max2016 can be used to measure the gain of anrf block (or combination of blocks) through the imple- mentation outlined in figure 3. as shown, a coupled signal from the input of the block is fed into rfina, while the coupled output is connected to rfinb. the dc output voltage at outd is proportional to the power difference (i.e., gain). the gain of a complete receiver or transmitter lineup can likewise be measured since the max2016 accepts rf signals that range from low frequency to 2.5ghz; see figure 4. the max2016 accurately measures the gain, regardless of the different frequencies present within superheterodyne architectures. for accurate measurement of signals carrying signifi- cant amplitude modulation, limit the bandwidth of the difference amplifier to be less than the lowest modula- tion frequency. this will minimize the ripple in the outd waveform. this is particularly appropriate if the system-level time delay between the two sense points is significant with respect to the period of modulation. max2016 rfina rfinb in logarithmic detector logarithmic detector gnd outd setd 20k coupler coupler rf block out outd figure 3. gain measurement configuration max2016 lna f rf f if rfina rfinb logarithmic detector logarithmic detector coupler lo mixer coupler outd setd 20k out figure 4. conversion gain measurement configuration downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 14 ______________________________________________________________________________________ measuring power (rssi detector mode) in detector mode, the max2016 acts like a receive-sig-nal-strength indicator (rssi), which provides an output voltage proportional to the input power. this is accom- plished by providing a feedback path from outa (outb) to seta (setb) (r1/r2 = 0 ; see figure 5). by connecting set_ directly to out_, the op-amp gainis set to 2v/v due to two internal 20k feedback resis- tors. this provides a detector slope of approximately18mv/db with a 0.5v to 1.8v output range. gain-controller mode the max2016 can be used as a gain controller withinan automatic gain-control (agc) loop. as shown in figure 6, rfina and rfinb monitor the vga? input and output power levels, respectively. the max2016 produces a dc voltage at outd that is proportional tothe difference in these two rf input power levels. an internal op amp compares the dc voltage with a refer- ence voltage at setd. the op amp increases or decreases the voltage at outd until outd equals setd. thus, the max2016 adjusts the gain of the vga to a level determined by the voltage applied to setd. place the nominal signal levels of rfina and rfinb near the middle of their respective dynamic ranges to accommodate the largest range of gain compensation. this is nominally -25dbm to -30dbm. if so selected, the nominal voltage applied to setd will be approximately 1.0v. operate the setd voltage within the range of 0.5v to 1.5v for the greatest accuracy of gain control. max2016 rfin+arfin-a outa in_ gnd r1/r2 20k 20k detectors seta outa rfin+brfin-b outb in_ r1/r2 20k 20k detectors setb outb figure 5. in detector mode (rssi), outa/outb is a dcvoltage proportional to the input power max2016 logarithmic detector logarithmic detector 20k vga gain control input rfina rfinb outd setd vga input vga output set-point dac coupler coupler figure 6. in gain-controller mode, the outd maintains thegain of the vga downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements ______________________________________________________________________________________ 15 power-controller mode the max2016 can also be used as a power detector/controller within an agc loop. figure 7 depicts a sce- nario where the max2016 is employed as the agc cir- cuit. as shown in the figure, the max2016 monitors the output of the pa through a directional coupler. an inter- nal differencing amplifier (figure 5) compares the detected signal with a reference voltage determined by v set_ . the differencing amplifier increases or decreas- es the voltage at out_, according to how closely thedetected signal level matches the v set_ reference. the max2016 maintains the power of the pa to a leveldetermined by the voltage applied to set_. since the logarithmic detector responds to any ampli- tude modulation being carried by the carrier signal, it may be necessary to insert an external lowpass filter between the differencing amplifier output (outa/outb) and the gain-control element to remove this modulation signal. outa and outb slope adjustment the transfer slope function of outa and outb can beincreased from its nominal value by varying resistors r1 and r2 (see the typical application circuit ). the equation controlling the slope is: outd slope adjustment the transfer slope function of outd can be increasedfrom its nominal value by varying resistor r3 (see the typical application circuit ). the equation controlling the slope is: input highpass filters the max2016 integrates a programmable highpass fil-ter on each rf input. the lower cutoff frequency of the max2016 can be decreased by increasing the external capacitor value between fa1 and fa2 or fb1 and fb2. by default, with no capacitor connecting fa1 and fa2 or fb1 and fb2, the lower cutoff frequency is 20mhz. using the following equation determines the lowest operating frequency: where r = 2 . differential output video filter the bandwidth and response time difference of the out-put amplifier can be controlled with the external capaci- tor, c 15 , connected between fv1 and fv2. with no external capacitor, the bandwidth is greater than 20mhz. the following equation determines the bandwidth of the amplifier difference: where r = 1.8k . use a video bandwidth lower than the anticipated low-est amplitude-modulation frequency range to yield the greatest accuracy in tracking the average carrier power for high peak-to-average ratio waveforms. frequency rc = 1 2 frequency rc = 1 2 slope outd mv db rk k = ?? ? ?? ? + ?? ? ?? ? 25 320 20 slope outa or outb mv db rorr k k = ?? ? ?? ? () + ?? ?? ?? ?? 9 124 0 20 max2016 logarithmic detector transmitter set-point dac outa/ outb seta/ setb coupler rfina/ rfinb power amplifier gain-control input lowpass filter 20k 20k figure 7. in power-controller mode, the dc voltage at outa oroutb controls the gain of the pa, leading to a constant output power level ( note: only one controller channel is shown within the figure. since the max2016 is a dual con-troller/detector, the second channel can be easily implemented by using the adjacent set of input and output connections.) downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 16 ______________________________________________________________________________________ comparators/window detectors the max2016 integrates two comparators for use inmonitoring the difference in power levels (gain) of rfina and rfinb. the thresholds of the two compara- tors are set to the voltage applied to the csetl and cseth pins. the output of each comparator can be monitored independently or from the cor output that ors the outputs of the individual comparators. this can be used for a window-detector function. these comparators can be used to trigger hardware interrupts, allowing rapid detection of over-range condi- tions. these comparators are high-speed devices. connect high-value bypass capacitors (0.1?) between each comparator threshold input (csetl and cseth) to ground to provide a solid threshold voltage at high switching speeds. some applications may benefit from the use of hystere- sis in the comparator response. this can be useful for prevention of false triggering in the presence of small noise perturbations in the signal levels, or with signals with large amplitude modulation. to introduce hysteresis into the comparator output, connect a feedback resistor from coutl to cstel. select the value of this resistor, in combination with the resistive-divider values used to set threshold-level csetl, to set the amount of hystere- sis. set the parallel combination of resistors connected to csetl to be less than 10k for best performance. figure 8 illustrates the use of these comparators in a gain-monitoring application. the low comparator has its threshold (csetl) set at a low-gain trip point. if the gain drops below this trip point, the coutl output goes from a logic 0 to a logic 1. the high comparator has its threshold (cseth) set at a high trip point. if the gain exceeds this trip point, the couth output goes from logic 0 to logic 1. the window comparator output (cor) rests a logic 0 if the gain is in the acceptable range, between csetl and cseth. it goes to a logic 1 if the gain is either above or below these limits. power-supply connection the max2016 is designed to operate from a single+2.7v to +3.6v supply. to operate under a higher sup- ply voltage range, a resistor must be connected in series with the power supply and v cc to reduce the voltage delivered to the chip. for a +4.75v to +5.25v supply,use a 37.4 (?%) resistor in series with the supply. layout considerations a properly designed pcb is an essential part of anyrf/microwave circuit. keep rf signal lines as short as possible to reduce losses, radiation, and inductance. for the best performance, route the ground pin traces directly to the exposed pad under the package. the pcb exposed pad must be connected to the ground plane of the pcb. it is suggested that multiple vias beused to connect this pad to the lower level ground max2016 rfina rfinb in logarithmic detector logarithmic detector outd setd coupler coupler rf block out csetl cor cseth 20k figure 8. window comparators monitoring mode. cor goes high if outd drops below csetl or rises above cseth. downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements ______________________________________________________________________________________ 17 max2016 ref seta outa outb setb 2.0v ref log amplifiers log amplifiers v cc rfinb+ rfinb- fb1fb2 fv1 fv2 setd outd cseth couth coutl csetl cor fa2 fa1 rfina- rfina+ gnd exposed pad 20k 50 50 20k 20k 20k 2, 9, 12, 20 5, 17 34 1 28 8 16 15 11 10 13 14 22 21 18 19 24 23 25 27 26 6 7 20k functional diagram planes. this method provides a good rf/thermal con-duction path for the device. solder the exposed pad on the bottom of the device package to the pcb. the max2016 evaluation kit can be used as a reference for board layout. gerber files are available upon request at www.maxim-ic.com. power-supply bypassing proper voltage-supply bypassing is essential for high-frequency circuit stability. bypass each v cc pin with a capacitor as close to the pin as possible ( typical application circuit ). exposed pad rf/thermal considerations the exposed paddle (ep) of the max2016? 28-pin thinqfn-ep package provides two functions. one is a low thermal-resistance path to the die; the second is a low- rf impedance ground connection. the ep must be soldered to a ground plane on the pcb, either directlyor through an array of plated via holes (minimum of four holes to provide ground integrity). downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements 18 ______________________________________________________________________________________ fa1 1 v cc 2 rfina+ 3 rfina- 4 gnd 5 couth 6 cseth 7 fb1 21 v cc 20 rfinb+ 19 rfinb- 18 gnd 17 coutl 16 csetl 15 cor 8 v cc 9 setd 10 outd 11 v cc 12 fv2 13 fv1 14 fa2 28 outa 27 seta 26 ref 25 setb 24 outb 23 fb2 22 max2016 v ref r1 v outa r2 v outb c12 c5 c4 c1 c2 c11 c8 c9 c16 c17 comparatorb c15 a + b r3 c7 c14 v outd v cc v cc v cc v cc v cc v cc v cc v s c18 comparatora rfina rfinb c10 c13 c6 c3 r6 exposed paddle note: comparators are disabled by connecting csetl and cseth to v cc . typical application circuit chip information process: bicmos designation value description c1, c2, c8, c9 680pf microwave capacitors (0402) c3, c6, c10, c13 33pf microwave capacitors (0402) c4, c7, c11, c14 0.1? microwave capacitors (0603) c5, c12, c15, c16, c17 not used capacitors are optional for frequency compensation, bypass c18 10? tantalum capacitor (c case) r1, r2, r3 0 resistors (0402) 0 resistor (1206) for v s = 2.7v to 3.6v r6 37.4 ?% resistor (1206) for v s = 4.75v to 5.25v table 1. component values used in the typical application circuit downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements ______________________________________________________________________________________ 19 package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .) qfn thin.eps downloaded from: http:///
max2016 lf-to-2.5ghz dual logarithmic detector/ controller for power, gain, and vswr measurements maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2006 maxim integrated products is a registered trademark of maxim integrated products, inc. max2016 max2016 package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .) revision history pages changed at rev 1: 1, 5, 10?0 downloaded from: http:///

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