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| Philips Semiconductors Product specification Low-voltage mixer FM IF system SA676 DESCRIPTION The SA676 is a low-voltage monolithic FM IF system incorporating a mixer/oscillator, two limiting intermediate frequency amplifiers, quadrature detector, logarithmic received signal strength indicator (RSSI), voltage regulator and audio and RSSI op amps. The SA676 is available in a 20-pin SSOP (shrink small outline package). The SA676 was designed for cordless telephone applications in which efficient and economic integrated solutions are required and yet high performance is desirable. Although the product is not targeted to meet the stringent specifications of high performance cellular equipment, it will exceed the needs for analog cordless phones. The minimal amount of external components and absence of any external adjustments makes for a very economical solution. PIN CONFIGURATION DK Package RF IN+ 1 RF IN- DECOUPLING 2 OSCOUT 3 OSCIN 4 RSSI OUT 5 VCC 6 AUDIO FEEDBACK 7 AUDIO OUT 8 RSSI FEEDBACK 9 QUADRATURE IN 10 20 MIXER OUT 19 IF AMP DECOUPLING 18 IF AMP IN 17 IF AMP DECOUPLING 16 IF AMP OUT 15 GND 14 LIMITER IN 13 LIMITER DECOUPLING 12 LIMITER DECOUPLING 11 LIMITER OUT FEATURES * Low power consumption: 3.5mA typical at 3V * Mixer input to >100MHz * Mixer conversion power gain of 17dB at 45MHz * XTAL oscillator effective to 100MHz (L.C. oscillator or external oscillator can be used at higher frequencies) SR00514 Figure 1. Pin Configuration * 102dB of IF Amp/Limiter gain * 2MHz IF amp/limiter small signal bandwidth * Temperature compensated logarithmic Received Signal Strength Indicator (RSSI) with a 70dB dynamic range * Audio output internal op amp * RSSI output internal op amp * Internal op amps with rail-to-rail outputs * ESD protection: Human Body Model 2kV Robot Model 200V * Low external component count; suitable for crystal/ceramic/LC filters APPLICATION * Cordless phones ORDERING INFORMATION DESCRIPTION 20-Pin Plastic Shrink Small Outline Package (Surface-mount) TEMPERATURE RANGE -40 to +85C ORDER CODE SA676DK DWG # SOT266-1 BLOCK DIAGRAM 20 19 18 17 16 15 14 13 12 11 IF AMP MIXER RSSI LIMITER QUAD OSCILLATOR +- VREG E B -+ AUDIO 1 2 3 4 5 6 7 8 9 10 SR00515 Figure 2. Block Diagram 1993 Dec 15 6-129 853-1726 11659 Philips Semiconductors Product specification Low-voltage mixer FM IF system SA676 ABSOLUTE MAXIMUM RATINGS SYMBOL VCC TSTG TA JA Single supply voltage Storage temperature range Operating ambient temperature range Thermal impedance DK package PARAMETER RATING 7 -65 to +150 -40 to +85 117 UNITS V C C C/W DC ELECTRICAL CHARACTERISTICS VCC = +3V, TA = 25C; unless otherwise stated. LIMITS SYMBOL VCC ICC PARAMETER Power supply voltage range DC current drain TEST CONDITIONS MIN 2.7 3.5 SA676 TYP MAX 7.0 5.0 V mA UNITS AC ELECTRICAL CHARACTERISTICS TA = 25C; VCC = +3V, unless otherwise stated. RF frequency = 45MHz; +14.5dBV RF input step-up; IF frequency = 455kHz; R17 = 2.4k and R18 = 3.3k; RF level = -45dBm; FM modulation = 1kHz with 5kHz peak deviation. Audio output with de-emphasis filter and C-message weighted filter. Test circuit Figure 3. The parameters listed below are tested using automatic test equipment to assure consistent electrical characteristics. 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. SYMBOL PARAMETER TEST CONDITIONS LIMITS MIN TYP 100 100 7.0 f1 = 45.0; f2 = 45.06MHz Input RF level = -52dBm Matched 14.5dBV step-up 50 source RF input resistance RF input capacitance Mixer output resistance IF section IF amp gain Limiter gain AM rejection Audio level SINAD sensitivity THD S/N Total harmonic distortion Signal-to-noise ratio IF RSSI output, R9 = 2k1 RSSI range IF input impedance IF output impedance Limiter input impedance Limiter output impedance Limiter output voltage Pin 18 Pin 16 Pin 14 Pin 11 Pin 11 1.3 1.3 No modulation for noise IF level = -110dBm IF level = -50dBm 50 source 50 source 30% AM 1kHz Gain of two IF level -110dBm 60 44 58 50 120 17 -55 60 0.5 1.7 70 1.5 0.3 1.5 0.3 130 .90 2.2 dB dB dB mV dB dB dB V V dB k k k k mVRMS (Pin 20) 1.25 Single-ended input 10 -10 17 +2.5 8 3.0 1.5 4.0 MAX UNITS Mixer/Osc section (ext LO = 220mVRMS) fIN fOSC Input signal frequency Crystal oscillator frequency Noise figure at 45MHz Third-order input intercept point (50 source) Conversion power gain MHz MHz dB dBm dB dB k pF k 1993 Dec 15 6-130 Philips Semiconductors Product specification Low-voltage mixer FM IF system SA676 AC ELECTRICAL CHARACTERISTICS SYMBOL RF/IF section (int LO) System SINAD sensitivity PARAMETER (Continued) TEST CONDITIONS MIN RF level = -114dBm LIMITS TYP 12 MAX dB UNITS NOTE: 1. The generator source impedance is 50, but the SA676 input impedance at Pin 18 is 1500. As a result, IF level refers to the actual signal that enters the SA676 input (Pin 18) which is about 21dB less than the "available power" at the generator. CIRCUIT DESCRIPTION The SA676 is an IF signal processing system suitable for second IF systems with input frequency as high as 100MHz. The bandwidth of the IF amplifier and limiter is at least 2MHz with 90dB of gain. The gain/bandwidth distribution is optimized for 455kHz, 1.5k source applications. The overall system is well-suited to battery operation as well as and high quality products of all types. The input stage is a Gilbert cell mixer with oscillator. Typical mixer characteristics include a noise figure of 7.0dB, conversion gain of 17dB, and input third-order intercept of -10dBm. The oscillator will operate in excess of 100MHz in L/C tank configurations. Hartley or Colpitts circuits can be used up to 100MHz for xtal configurations. The output impedance of the mixer is a 1.5k resistor permitting direct connection to a 455kHz ceramic filter. The input resistance of the limiting IF amplifiers is also 1.5k. With most 455kHz ceramic filters and many crystal filters, no impedance matching network is necessary. The IF amplifier has 44dB of gain and 5.5MHz bandwidth. The IF limiter has 58dB of gain and 4.5MHz bandwidth. To achieve optimum linearity of the log signal strength indicator, there must be a 12dB(v) insertion loss between the first and second IF stages. If the IF filter or interstage network does not cause 12dB(v) insertion loss, a fixed or variable resistor or an L pad for simultaneous loss and impedance matching can be added between the first IF output (Pin 16) and the interstage network. The overall gain will then be 90dB with 2MHz bandwidth. The signal from the second limiting amplifier goes to a Gilbert cell quadrature detector. One port of the Gilbert cell is internally driven by the IF. The other output of the IF is AC-coupled to a tuned quadrature network. This signal, which now has a 90 phase relationship to the internal signal, drives the other port of the multiplier cell. The demodulated output of the quadrature drives an internal op amp. This op amp can be configured as a unity gain buffer, or for simultaneous gain, filtering, and 2nd-order temperature compensation if needed. It can drive an AC load as low as 10k with a rail-to-rail output. A log signal strength indicator completes the circuitry. The output range is greater than 70dB and is temperature compensated. This signal drives an internal op amp. The op amp is capable of rail-to-rail output. It can be used for gain, filtering, or 2nd-order temperature compensation of the RSSI, if needed. NOTE: dB(v) = 20log VOUT/VIN 1993 Dec 15 6-131 Philips Semiconductors Product specification Low-voltage mixer FM IF system SA676 C26 R18 3.3k R17 2.4k FLT1 C23 C21 FLT2 C18 C17 C15 20 19 18 17 16 15 14 13 12 11 IF AMP MIXER LIMITER RSSI QUAD OSCILLATOR +- VREG -+ 1 C1 2 3 4 5 6 7 R11 10k 8 9 10 C9 C12 C8 L1 C2 C7 C10 C5 L2 45MHz INPUT C6 X1 C19 390pF R10 10k C27 2.2F R19 11k IFT1 C14 RSSI OUTPUT VCC AUDIO SA676DK Demoboard Application Component List C1 C2 C5 C6 C7 C8 C9 C10 C12 C14 C15 C17 C18 C19 C21 51pF NPO Ceramic 220pF NPO Ceramic 100nF +10% Monolithic Ceramic 5-30pF trim cap 1nF Ceramic 10.0pF NPO Ceramic 100nF +10% Monolithic Ceramic 10F Tantalum (minimum) * 2.2F +10% Tantalum 100nF +10% Monolithic Ceramic 10pF NPO Ceramic 100nF +10% Monolithic Ceramic 100nF +10% Monolithic Ceramic 390pF +10% Monolithic Ceramic 100nF +10% Monolithic Ceramic C23 C26 C27 FLT 1 FLT 2 IFT 1 L1 L2 X1 R5 R10 R11 R17 R18 R19 100nF +10% Monolithic Ceramic 100nF +10% Monolithic Ceramic 2.2F Tantalum Ceramic Filter Murata SFG455A3 or equiv Ceramic Filter Murata SFG455A3 or equiv 330H TOKO 303LN-1130 330nH Coilcraft UNI-10/142-04J08S 0.8H nominal TOKO 292CNS-T1038Z 44.545MHz Crystal ICM4712701 Not Used in Application Board (see Note 8, pg 8) 8.2k +5% 1/4W Carbon Composition 10k +5% 1/4W Carbon Composition 2.4k +5% 1/4W Carbon Composition 3.3k +5% 1/4W Carbon Composition 11k +5% 1/4W Carbon Composition SR00516 * NOTE: This value can be reduced when a battery is the power source. Figure 3. SA676 45MHz Application Circuit 1993 Dec 15 6-132 Philips Semiconductors Product specification Low-voltage mixer FM IF system SA676 RF GENERATOR 45MHz SA676 DEMOBOARD RSSI AUDIO VCC (+3) DE-EMPHASIS FILTER DC VOLTMETER C-MESSAGE SCOPE HP339A DISTORTION ANALYZER SR00517 Figure 4. SA676 Application Circuit Test Set Up NOTES: 1. C-message: The C-message and de-emphasis filter combination has a peak gain of 10 for accurate measurements. Without the gain, the measurements may be affected by the noise of the scope and HP339A analyzer. The de-emphasis filter has a fixed -6dB/Octave slope between 300Hz and 3kHz. 2. Ceramic filters: The ceramic filters can be 30kHz SFG455A3s made by Murata which have 30kHz IF bandwidth (they come in blue), or 16kHz CFU455Ds, also made by Murata (they come in black). All specifications and testing are done with the wideband filter. 3. RF generator: Set your RF generator at 45.000MHz, use a 1kHz modulation frequency and a 6kHz deviation if you use 16kHz filters, or 8kHz if you use 30kHz filters. 4. Sensitivity: The measured typical sensitivity for 12dB SINAD should be 0.45V or -114dBm at the RF input. 5. Layout: The layout is very critical in the performance of the receiver. We highly recommend our demo board layout. 6. RSSI: The smallest RSSI voltage (i.e., when no RF input is present and the input is terminated) is a measure of the quality of the layout and design. If the lowest RSSI voltage is 500mV or higher, it means the receiver is in regenerative mode. In that case, the receiver sensitivity will be worse than expected. 7. Supply bypass and shielding: All of the inductors, the quad tank, and their shield must be grounded. A 10-15F or higher value tantalum capacitor on the supply line is essential. A low frequency ESR screening test on this capacitor will ensure consistent good sensitivity in production. A 0.1F bypass capacitor on the supply pin, and grounded near the 44.545MHz oscillator improves sensitivity by 2-3dB. 8. R5 can be used to bias the oscillator transistor at a higher current for operation above 45MHz. Recommended value is 22k, but should not be below 10k. 1993 Dec 15 6-133 Philips Semiconductors Product specification Low-voltage mixer FM IF system SA676 mA 6 VCC = 7V 5 VCC = 5V ICC (mA) 4 VCC = 3V 3 VCC = 2.7V 2 -55 -35 -15 5 25 45 65 85 105 125 C TEMPERATURE (C) SR00518 Figure 5. ICC vs Temperature and Supply Voltage 18.00 17.75 2.7V 17.50 CONVERSION GAIN (dB) 3V 17.25 7.0V 17.00 16.75 16.50 16.25 16.00 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 TEMPERATURE (C) SR00519 Figure 6. Conversion Gain vs Temperature and Supply Voltage 1993 Dec 15 6-134 Philips Semiconductors Product specification Low-voltage mixer FM IF system SA676 20 10 0 RF = 45MHz IF = 455kHz -10 IF OUTPUT POWER (dBm) -20 -30 -40 FUND PRODUCT 3rd ORDER PRODUCT -50 -60 -70 *50 INPUT -80 -66 -56 -46 -36 -26 -16 -6 4 14 24 34 RF* INPUT LEVEL (dBm) SR00520 Figure 7. Mixer Third Order Intercept and Compression 5 AUDIO 0 -5 -10 VCC = 3V RF = 45MHz -20 DECIBELS (dB) -25 -30 -35 -40 -45 -50 -55 -60 -65 -125 NOISE -115 -105 -95 -85 -75 RF LEVEL (dBm) -65 -55 -45 -35 -25 THD + NOISE AM REJECTION DEVIATION = 5kHz AUDIO LEVEL = 117.6mVRMS SR00521 Figure 8. Sensitivity vs RF Level (+25C) 1993 Dec 15 6-135 Philips Semiconductors Product specification Low-voltage mixer FM IF system SA676 2.1 2.0 1.9 1.8 1.7 1.6 1.5 VOLTAGE (V) 1.4 1.3 1.2 1.1 +85C 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 -125 -115 -105 -95 -85 -75 -65 -55 -45 +27C -40C RF LEVEL (dBm) SR00522 Figure 9. RSSI vs RF Level and Temperature - VCC = 3V V 300 250 VCC = 7V 200 mV RMS VCC = 5V 150 VCC = 3V 100 VCC = 2.7V 50 0 -55 -35 -15 5 25 45 65 85 105 125 C SR00523 Figure 10. Audio Output vs Temperature and Supply Voltage 1993 Dec 15 6-136 |
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