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philips semiconductors sa604a high performance low power fm if system product specification replaces data of december 15, 1994 1997 nov 07 rf communications products ic17 data handbook
philips semiconductors product specification sa604a high performance low power fm if system 2 1997 nov 07 853-1431 18663 description the sa604a is an improved monolithic low-power fm if system incorporating two limiting intermediate frequency amplifiers, quadrature detector, muting, logarithmic received signal strength indicator, and voltage regulator. the sa604a features higher if bandwidth (25mhz) and temperature compensated rssi and limiters permitting higher performance application compared with the sa604. the sa604a is available in a 16-lead so (surface-mounted miniature) package. features ? low power consumption: 3.3ma typical ? temperature compensated logarithmic received signal strength indicator (rssi) with a dynamic range in excess of 90db ? two audio outputs - muted and unmuted ? low external component count; suitable for crystal/ceramic filters ? excellent sensitivity: 1.5 m v across input pins (0.22 m v into 50 w matching network) for 12db sinad (signal to noise and distortion ratio) at 455khz ? sa604a meets cellular radio specifications pin configuration d package if amp decoupling 1 2 3 4 5 6 7 8 9 10 11 12 13 14 16 15 gnd mute input rssi output mute audio output unmute audio output quadrature input if amp input if amp decoupling if amp output gnd limiter input limiter decoupling limiter decoupling limiter v cc sr00311 figure 1. pin configuration applications ? cellular radio fm if ? high performance communications receivers ? intermediate frequency amplification and detection up to 25mhz ? rf level meter ? spectrum analyzer ? instrumentation ? fsk and ask data receivers ordering information description temperature range order code dwg # 16-pin plastic small outline (so) package (surface-mount) -40 to +85 c sa604ad sot109-1 absolute maximum ratings symbol parameter rating units v cc single supply voltage 9 v t stg storage temperature range -65 to +150 c t a operating ambient temperature range sa604a 40 to +85 c q ja thermal impedance d package 90 c/w
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 3 block diagram 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 signal voltage if amp limiter regulator strength gnd v cc gnd mute quad det limiter sr00312 figure 2. block diagram dc electrical characteristics v cc = +6v, t a = 25 c; unless otherwise stated. limits symbol parameter test conditions sa604a units min typ max v cc power supply voltage range 4.5 8.0 v i cc dc current drain 2.5 3.3 4.0 ma mute switch input threshold (on) (off) 1.7 1.0 v v
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 4 ac electrical characteristics typical reading at t a = 25 c; v cc = 6v, unless otherwise stated. if frequency = 455khz; if level = -47dbm; fm modulation = 1khz with 8khz peak deviation. audio output with c-message weighted filter and de-emphasis capacitor. test circuit figure 3. the param eters listed below are tested using automatic test equipment to assure consistent electrical characterristics. the limits do not represent the ultimate performance limits of the device. use of an optimized rf layout will improve many of the listed parameters. limits symbol parameter test conditions sa604a units min typ max input limiting -3db test at pin 16 -92 dbm/50 w am rejection 80% am 1khz 30 34 db recovered audio level 15nf de-emphasis 80 175 260 mv rms recovered audio level 150pf de-emphasis 530 mv rms thd total harmonic distortion -34 -42 db s/n signal-to-noise ratio no modulation for noise 73 db rf level = -118dbm 0 160 650 mv rssi output 1 rf level = -68dbm 1.9 2.65 3.1 v rf level = -18dbm 4.0 4.85 5.6 v rssi range r 4 = 100k (pin 5) 90 db rssi accuracy r 4 = 100k (pin 5) 1.5 db if input impedance 1.4 1.6 k w if output impedance 0.85 1.0 k w limiter input impedance 1.4 1.6 k w unmuted audio output resistance 58 k w muted audio output resistance 58 k w note: 1. sa604 data sheets refer to power at 50 w input termination; about 21db less power actually enters the internal 1.5k input. sa604 (50) sa604a (1.5k)/sa605 (1.5k -97dbm -118dbm -47dbm -68dbm +3dbm -18dbm the sa605 and sa604a are both derived from the same basic die. the sa605 performance plots are directly applicable to the sa60 4a.
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 5 if input gnd rssi audio data gnd gnd off on v cc signetics ne604a test ckt m u t e 100nf + 80 20% 63v k1000025v ceramic 455khz ceramic filter murata sfg455a3 100nf + 10% 50v 100nf + 10% 50v 455khz (ce = 180pf) toko rmc 2a6597h 51 w + 1% 1/4w metal film 150pf + 2% 100v n1500 ceramic 6.8 m f + 20% 25v tantalum 1nf + 10% 100v k2000-y5p ceramic 15nf + 10% 50v 100nf + 10% 50v c1 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12 f1 f2 r1 100nf +10% 50v 100nf + 10% 50v 100nf +10% 50v 10pf + 2% 100v npo ceramic r2 r3 r4 1500 w + 1% 1/4w metal film 1500 w + 5% 1/8w carbon composition 100k w + 1% 1/4w metal film 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 ne604a test circuit sa604a input q = 20 loaded mute input rssi output audio output data output c 5 c 3 c 6 s 1 c 10 c 8 f 2 c 12 c 9 f 1 c 7 c 11 r 1 r 2 r 3 c 4 c 1 c 2 r 4 if input gnd rssi audio data gnd gnd off on v cc signetics ne604a test ckt m u t e v cc sr00313 figure 3. sa604a test circuit
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 6 16 15 14 13 11 10 9 8 7 6 5 4 3 2 1 12 42k gnd 42k 700 7k 1.6k 40k 700 35k 1.6k 40k 2k 4.5k 2k 8k full wave rect. voltage/ current converter volt reg volt reg mute quad det band gap volt gnd 80k 55k 55k 40k 40k 80k 80k full wave rect. v ee v cc v cc v cc sr00314 figure 4. equivalent circuit
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 7 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 ne604a test circuit sa604a mute audio rssi data 8765 4 3 2 1 sa602 +6v 100nf 10nf 47pf 22pf 100nf 5.6pf 44.545 3rd overture xtal sfg455a3 out out cmsg filter 455khz q=20 sfg455a3 +6v 4v 10pf 3v 2v 1v 0 20 40 60 80 10 100 1k 10k 100k 120 100 80 60 40 20 audio out `c' message weighted ne604a if input ( m v) (1500 w ) (0db ref = recovered audio for +8khz peak deviation (db) audio rssi (volts) thd + noise am (80% mod) noise ne602 rf input (dbm) (50 w ) 0.1 m f 0.1 m f 0.1 m f 0.1 m f 0.1 m f 22pf 1nf 0.5 to 1.3 m h 5.5 m h 6.8 m f 0.21 to 0.28 m h 100k 0.1 m f sr00315 figure 5. typical application cellular radio (45mhz to 455khz) circuit description the sa604a is a very high gain, high frequency device. correct operation is not possible if good rf layout and gain stage practices are not used. the sa604a cannot be evaluated independent of circuit, components, and board layout. a physical layout which correlates to the electrical limits is shown in figure 3. this configuration can be used as the basis for production layout. the sa604a is an if signal processing system suitable for if frequencies as high as 21.4mhz. the device consists of two limiting amplifiers, quadrature detector, direct audio output, muted audio output, and signal strength indicator (with output characteristic). the sub-systems are shown in figure 4. a typical application with 45mhz input and 455khz if is shown in figure 5. if amplifiers the if amplifier section consists of two log-limiting stages. the first consists of two differential amplifiers with 39db of gain and a small signal bandwidth of 41mhz (when driven from a 50 w source). the output of the first limiter is a low impedance emitter follower with 1k w of equivalent series resistance. the second limiting stage consists of three differential amplifiers with a gain of 62db and a small signal ac bandwidth of 28mhz. the outputs of the final differential stage are buffered to the internal quadrature detector. one of the outputs is available at pin 9 to drive an external quadrature capacitor and l/c quadrature tank. both of the limiting amplifier stages are dc biased using feedback. the buffered output of the final differential amplifier is fed back to the input through 42k w resistors. as shown in figure 4, the input impedance is established for each stage by tapping one of the feedback resistors 1.6k w from the input. this requires one additional decoupling capacitor from the tap point to ground. because of the very high gain, bandwidth and input impedance of the limiters, there is a very real potential for instability at if frequencies above 455khz. the basic phenomenon is shown in figure 8. distributed feedback (capacitance, inductance and radiated fields)
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 8 42k 15 16 1 1.6k 40k v+ 700 14 7k sr00316 figure 6. first limiter bias 11 12 10 40k 80k 8 40k v+ 9 42k sr00317 figure 7. second limiter and quadrature detector bpf bpf sr00318 figure 8. feedback paths a. terminating high impedance filters with transformation to low impedance b. low impedance termination and gain reduction bpf high impedance low impedance high impedance bpf bpf resistive loss into bpf bpf a sr00319 figure 9. practical termination
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 9 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 sa604a 430 430 sr00320 figure 10. crystal input filter with ceramic interstage filter forms a divider from the output of the limiters back to the inputs (including rf input). if this feedback divider does not cause attenuation greater than the gain of the forward path, then oscillation or low level regeneration is likely. if regeneration occurs, two symptoms may be present: (1)the rssi output will be high with no signal input (should nominally be 250mv or lower), and (2) the demodulated output will demonstrate a threshold. above a certain input level, the limited signal will begin to dominate the regeneration, and the demodulator will begin to operate in a anormalo manner. there are three primary ways to deal with regeneration: (1) minimize the feedback by gain stage isolation, (2) lower the stage input impedances, thus increasing the feedback attenuation factor, and (3) reduce the gain. gain reduction can effectively be accomplished by adding attenuation between stages. this can also lower the input impedance if well planned. examples of impedance/gain adjustment are shown in figure 9. reduced gain will result in reduced limiting sensitivity. a feature of the sa604a if amplifiers, which is not specified, is low phase shift. the sa604a is fabricated with a 10ghz process with very small collector capacitance. it is advantageous in some applications that the phase shift changes only a few degrees over a wide range of signal input amplitudes. stability considerations the high gain and bandwidth of the sa604a in combination with its very low currents permit circuit implementation with superior performance. however, stability must be maintained and, to do that, every possible feedback mechanism must be addressed. these mechanisms are: 1) supply lines and ground, 2) stray layout inductances and capacitances, 3) radiated fields, and 4) phase shift. as the system if increases, so must the attention to fields and strays. however, ground and supply loops cannot be overlooked, especially at lower frequencies. even at 455khz, using the test layout in figure 3, instability will occur if the supply line is not decoupled with two high quality rf capacitors, a 0.1 m f monolithic right at the v cc pin, and a 6.8 m f tantalum on the supply line. an electrolytic is not an adequate substitute. at 10.7mhz, a 1 m f tantalum has proven acceptable with this layout. every layout must be evaluated on its own merit, but don't underestimate the importance of good supply bypass. at 455khz, if the layout of figure 3 or one substantially similar is used, it is possible to directly connect ceramic filters to the input and between limiter stages with no special consideration. at frequencies above 2mhz, some input impedance reduction is usually necessary. figure 9 demonstrates a practical means. as illustrated in figure 10, 430 w external resistors are applied in parallel to the internal 1.6k w load resistors, thus presenting approximately 330 w to the filters. the input filter is a crystal type for narrowband selectivity. the filter is terminated with a tank which transforms to 330 w . the interstage filter is a ceramic type which doesn't contribute to system selectivity, but does suppress wideband noise and stray signal pickup. in wideband 10.7mhz ifs the input filter can also be ceramic, directly connected to pin 16. in some products it may be impractical to utilize shielding, but this mechanism may be appropriate to 10.7mhz and 21.4mhz if. one of the benefits of low current is lower radiated field strength, but lower does not mean non-existent. a spectrum analyzer with an active probe will clearly show if energy with the probe held in the proximity of the second limiter output or quadrature coil. no specific recommendations are provided, but mechanical shielding should be considered if layout, bypass, and input impedance reduction do not solve a stubborn instability. the final stability consideration is phase shift. the phase shift of the limiters is very low, but there is phase shift contribution from the quadrature tank and the filters. most filters demonstrate a large phase shift across their passband (especially at the edges). if the quadrature detector is tuned to the edge of the filter passband, the combined filter and quadrature phase shift can aggravate stability. this is not usually a problem, but should be kept in mind. quadrature detector figure 7 shows an equivalent circuit of the sa604a quadrature detector. it is a multiplier cell similar to a mixer stage. instead of mixing two different frequencies, it mixes two signals of common frequency but different phase. internal to the device, a constant amplitude (limited) signal is differentially applied to the lower port of the multiplier. the same signal is applied single-ended to an external capacitor at pin 9. there is a 90 phase shift across the plates of this capacitor, with the phase shifted signal applied to the upper port of the multiplier at pin 8. a quadrature tank (parallel l/c network) permits frequency selective phase shifting at the if frequency. this quadrature tank must be returned to ground through a dc blocking capacitor. the loaded q of the quadrature tank impacts three fundamental aspects of the detector: distortion, maximum modulated peak deviation, and audio output amplitude. typical quadrature curves are illustrated in figure 12. the phase angle translates to a shift in the multiplier output voltage.
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 10 thus a small deviation gives a large output with a high q tank. however, as the deviation from resonance increases, the non-linearity of the curve increases (distortion), and, with too much deviation, the signal will be outside the quadrature region (limiting the peak deviation which can be demodulated). if the same peak deviation is applied to a lower q tank, the deviation will remain in a region of the curve which is more linear (less distortion), but creates a smaller phase angle (smaller output amplitude). thus the q of the quadrature tank must be tailored to the design. basic equations and an example for determining q are shown below. this explanation includes first-order effects only. frequency discriminator design equations for sa604a v out sr00321 figure 11. v o = c s c p + c s 1 + w 1 s + q 1 s 2 () 1 w 1 v in (1a) l(c p + c s ) where w 1 = 1 (1b) q 1 = r (c p + c s ) w 1 (1c) from the above equation, the phase shift between nodes 1 and 2, or the phase across c s will be: f = v o - v in = (2) t g -1 w 1 w q 1 w 2 () w 1 1 figure 12 is the plot of f vs. w () w 1 it is notable that at w = w 1 , the phase shift is p 2 and the response is close to a straight line with a slope of df dw = w 1 2q 1 the signal v o would have a phase shift of w 1 2q 1 w p 2 with respect to the v in . sin (3) w if v in = a sin w t ? v o = a w t + p 2 w 1 2q 1 multiplying the two signals in the mixer, and low pass filtering yields: sin (4) w v in ? v o = a 2 sin w t w t + p 2 w 1 2q 1 after low pass filtering cos (5) w ? v out = p 2 w 1 2q 1 1 2 a 2 = 1 2 a 2 sin w w 1 2q 1 () (6) v out 2q 1 2q 1 w 1 w 1 + dw = w w 1 () for 2q 1 w w 1 << p 2 which is discriminated fm output. (note that dw is the deviation frequency from the carrier w 1 . ref. krauss, raab, bastian; solid state radio eng.; wiley, 1980, p. 311. example: at 455khz if, with + 5khz fm deviation. the maximum normalized frequency will be 455 + 5khz 455 = 1.010 or 0.990 go to the f vs. normalized frequency curves (figure 12) and draw a vertical straight line at = 1.01. w w 1 the curves with q = 100, q = 40 are not linear, but q = 20 and less shows better linearity for this application. too small q decreases the amplitude of the discriminated fm signal. (eq. 6) ? choose a q = 20 the internal r of the 604a is 40k. from eq. 1c, and then 1b, it results that c p + c s = 174pf and l = 0.7mh. a more exact analysis including the source resistance of the previous stage shows that there is a series and a parallel resonance in the phase detector tank. to make the parallel and series resonances close, and to get maximum attenuation of higher harmonics at 455khz if, we have found that a c s = 10pf and c p = 164pf (commercial values of 150pf or 180pf may be practical), will give the best results. a variable inductor which can be adjusted around 0.7mh should be chosen and optimized for minimum distortion. (for 10.7mhz, a value of c s = 1pf is recommended.) audio outputs two audio outputs are provided. both are pnp current-to-voltage converters with 55k w nominal internal loads. the unmuted output is always active to permit the use of signaling tones in systems such as cellular radio. the other output can be muted with 70db typical attenuation. the two outputs have an internal 180 phase difference. the nominal frequency response of the audio outputs is 300khz. this response can be increased with the addition of external resistors from the output pins to ground in parallel with the internal 55k resistors, thus lowering the output time constant. singe the output structure is a current-to-voltage converter (current is driven into the resistance, creating a voltage drop), adding external parallel resistance also has the effect of lowering the output audio amplitude and dc level. this technique of audio bandwidth expansion can be effective in many applications such as sca receivers and data transceivers. because the two outputs have a 180 phase relationship, fsk demodulation can be accomplished by applying the two output
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 11 differentially across the inputs of an op amp or comparator. once the threshold of the reference frequency (or ano-signalo condition) has been established, the two outputs will shift in opposite directions (higher or lower output voltage) as the input frequency shifts. the output of the comparator will be logic output. the choice of op amp or comparator will depend on the data rate. with high if frequency (10mhz and above), and wide if bandwidth (l/c filters) data rates in excess of 4mbaud are possible. rssi the areceived signal strength indicatoro, or rssi, of the sa604a demonstrates monotonic logarithmic output over a range of 90db. the signal strength output is derived from the summed stage currents in the limiting amplifiers. it is essentially independent of the if frequency. thus, unfiltered signals at the limiter inputs, spurious products, or regenerated signals will manifest themselves as rssi outputs. an rssi output of greater than 250mv with no signal (or a very small signal) applied, is an indication of possible regeneration or oscillation. in order to achieve optimum rssi linearity, there must be a 12db insertion loss between the first and second limiting amplifiers. with a typical 455khz ceramic filter, there is a nominal 4db insertion loss in the filter. an additional 6db is lost in the interface between the filter and the input of the second limiter. a small amount of additional loss must be introduced with a typical ceramic filter. in the test circuit used for cellular radio applications (figure 5) the optimum linearity was achieved with a 5.1k w resistor from the output of the first limiter (pin 14) to the input of the interstage filter. with this resistor from pin 14 to the filter, sensitivity of 0.25 m v for 12db sinad was achieved. with the 3.6k w resistor, sensitivity was optimized at 0.22 m v for 12db sinad with minor change in the rssi linearity. any application which requires optimized rssi linearity, such as spectrum analyzers, cellular radio, and certain types of telemetry, will require careful attention to limiter interstage component selection. this will be especially true with high if frequencies which require insertion loss or impedance reduction for stability. at low frequencies the rssi makes an excellent logarithmic ac voltmeter. for data applications the rssi is effective as an amplitude shift keyed (ask) data slicer. if a comparator is applied to the rssi and the threshold set slightly above the no signal level, when an in-band signal is received the comparator will be sliced. unlike fsk demodulation, the maximum data rate is somewhat limited. an internal capacitor limits the rssi frequency response to about 100khz. at high data rates the rise and fall times will not be symmetrical. the rssi output is a current-to-voltage converter similar to the audio outputs. however, an external resistor is required. with a 91k w resistor, the output characteristic is 0.5v for a 10db change in the input amplitude. additional circuitry internal to the sa604a are voltage and current regulators which have been temperature compensated to maintain the performance of the device over a wide temperature range. these regulators are not accessible to the user. 200 175 150 125 100 75 50 25 0 0.95 0.975 1.0 1.025 1.05 f q = 100 q = 80 q = 60 q = 20 q = 10 sr00322 figure 12. phase vs normalized if frequency 1 1 1
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 12 so16: plastic small outline package; 16 leads; body width 3.9 mm sot109-1
philips semiconductors product specification sa604a high performance low power fm if system 1997 nov 07 13 philips semiconductors and philips electronics north america corporation reserve the right to make changes, without notice, in the products, including circuits, standard cells, and/or software, described or contained herein in order to improve design and/or performanc e. philips semiconductors assumes no responsibility or liability for the use of any of these products, conveys no license or title under a ny patent, copyright, or mask work right to these products, and makes no representations or warranties that these products are free from patent, copy right, or mask work right infringement, unless otherwise specified. applications that are described herein for any of these products are for illustrative purposes only. philips semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. life support applications philips semiconductors and philips electronics north america corporation products are not designed for use in life support appl iances, devices, or systems where malfunction of a philips semiconductors and philips electronics north america corporation product can reasonab ly be expected to result in a personal injury. philips semiconductors and philips electronics north america corporation customers using or sel ling philips semiconductors and philips electronics north america corporation products for use in such applications do so at their own risk and agree to fully indemnify philips semiconductors and philips electronics north america corporation for any damages resulting from such improper use or sale. this data sheet contains preliminary data, and supplementary data will be published at a later date. philips semiconductors reserves the right to make changes at any time without notice in order to improve design and supply the best possible product. philips semiconductors 811 east arques avenue p.o. box 3409 sunnyvale, california 940883409 telephone 800-234-7381 definitions data sheet identification product status definition objective specification preliminary specification product specification formative or in design preproduction product full production this data sheet contains the design target or goal specifications for product development. specifications may change in any manner without notice. this data sheet contains final specifications. philips semiconductors reserves the right to make changes at any time without notice, in order to improve design and supply the best possible product. ? copyright philips electronics north america corporation 1997 all rights reserved. printed in u.s.a.

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