Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver DESCRIPTION SA637 FEATURES The SA637 is a low-voltage high performance monolithic digital system with high-speed RSSI incorporating a mixer, oscillator with buffered output, two limiting intermediate frequency amplifiers, fast logarithmic received signal strength indicator (RSSI), voltage regulator, RSSI op amp and power down pin. The SA637 is available in SSOP (shrink small outline package). The SA637 was designed for portable digital communication applications and will function down to 2.7V. The limiter amplifier has differential outputs with 2MHz small signal bandwidth. The RSSI output has access to the feedback pin. This enables the designer to level adjust the outputs or add filtering. PIN CONFIGURATION • VCC = 2.7 to 5.5V • Low power receiver (3.8mA @ 3V) • Power down mode (ICC = 110µA) • Fast RSSI rise and fall times • Extended RSSI range with temperature DK Packages 20 MIXER OUTPUT 19 IF AMP DECOUP 18 IF AMP IN RFIN 1 RFIN 2 OSC E 3 17 IF AMP DECOUP 16 IF AMP OUT OSC B 4 compensation • RSSI op amp • 2MHz limiter small signal bandwidth • 455kHz filter matching (1.5kΩ) • Differential limiter output • Oscillator buffer • SSOP-20 package OSC 5 BUFFER 6 V 15 GND CC RSSI 7 14 LIMITER IN 13 LIMITER DECOUP 12 LIMITER DECOUP 11 LIM OUT (+) RSSI 8 FEEDBACK POWER 9 DOWN LIM OUT (-) 10 APPLICATIONS • ADC (American Digital Cellular) • Digital receiver systems • Cellular radio ORDERING INFORMATION DESCRIPTION TEMPERATURE RANGE ORDER CODE DWG # -40 to +85°C SA637DK 1563 20-Pin Plastic Shrink Small Outline Package (Surface-mount) BLOCK DIAGRAM 20 19 18 17 16 15 14 13 12 11 GND IF AMP LIMITER MIXER FAST RSSI OSCILLATOR + – + E 1 October 27, 1993 POWER DOWN – 2 3 B 4 VCC 5 6 2 7 8 9 10 853-1718 11205 Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver SA637 ABSOLUTE MAXIMUM RATINGS SYMBOL PARAMETER VCC Supply voltage VIN Voltage applied to any other pin TSTG TA RATING UNITS -0.3 to +6.0 V -0.3 to (VCC + 0.3) V Storage temperature range -65 to +150 Operating ambient temperature range -40 to +85 NOTE: Thermal impedance (θJA) = 117°C/W °C °C DC ELECTRICAL CHARACTERISTICS VCC = +3V, TA = 25°C; unless otherwise stated. SYMBOL PARAMETER TEST CONDITIONS LIMITS MIN VCC Power supply voltage range ICC DC current drain TYP 2.7 Pin 9 = HIGH or OPEN UNITS MAX 5.5 V 3.8 4.5 mA VCC = 4.7V 4.4 5.5 mA Standby Pin 9 = LOW 0.11 0.5 mA Input current Pin 9 = LOW -10 10 µA Pin 9 = HIGH -10 10 µA Pin 9 = LOW 0 0.3VCC µA Pin 9 = HIGH 0.7VCC VCC µA Input level tON Power up time tOFF Power down time RSSI valid (10% to 90%) 10 µs RSSI invalid (90% to 10%) 5 µs AC ELECTRICAL CHARACTERISTICS TA = 25°C; VCC = +3V, unless otherwise stated. RF frequency = 90MHz; RF input step-up = +14.5dBV; IF frequency = 455kHz; RF level = -68dBm. Test circuit Figure 1. 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 UNITS MAX Mixer/Osc section fIN fOSC Input signal frequency 200 MHz Crystal oscillator frequency 200 MHz Matched input and output 6.2 dB Input matched to 50Ω source -17 dBm -27 dBm NF Noise figure at 90MHz TOI Third-order input intercept point P1dB Input 1dB compression point Conversion power gain Matched 50Ω 7 dB 2.5 kΩ RIN Mixer input resistance CIN Mixer input capacitance 2.2 pF ROUT Mixer output resistance 1.87 kΩ Buffered LO output level LO = 447mVP-P, 1kΩ AC load 100 300 500 mVP-P IF section IFBW IF amp power gain 50Ω source 36 Limiter power gain 50Ω source 60 dB 2.5 MHz IF amp bandwidth October 27, 1993 3 dB Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver SA637 AC ELECTRICAL CHARACTERISTICS (Continued) SYMBOL PARAMETER TEST CONDITIONS RF RSSI output LIMITS UNITS MIN TYP MAX RF level = -118dBm .01 0.2 .65 V RF level = -68dBm .4 0.9 1.7 V RF level = -28dBm 1.0 1.7 2.3 RSSI range 90 RSSI accuracy RSSI ripple V dB ±1.5 dB 30 mVP-P RSSI speed No interstage filter 2.5 µs With interstage filter 22 µs No interstage filter 10 µs With interstage filter 50 µs IF input impedance 1.5 kΩ IF output impedance 1.5 kΩ Limiter input impedance 1.5 kΩ Rise time RSSI speed Fall time Limiter output impedance (Pin 10, Pin 11) 200 Ω Limiter output signal level (Pin 10, Pin 11) 1.5kΩ AC load 280 mVP-P 1.27 V Differential output matching ±6 mV Differential output offset ±30 mV Limiter output DC level CIRCUIT DESCRIPTION Mixer The mixer has a balanced input and is capable of being driven single-ended. The input impedance is 2.5kΩ in parallel with a 2.2pF cap at 90MHz RF. The mixer output can drive a 1500Ω ceramic filter at 455kHz or 600kHz directly without any matching required. The mixer conversion power gain is 7dB when both input and output are matched and optimum LO level is used to drive the internal mixer core. overall bandwidth is limited to 2MHz. The input and output impedance of the IF amplifier and the input impedance of the IF limiter are set to 1500Ω (match to 455kHz filter). A second filter is connected between the IF amplifier and the limiter for improved channel selectivity and reduced instability. This ceramic filter provides 3dB interstage insertion loss which results in optimal RSSI linearity. The overall gain can be reduced if desired by adding an external attenuator after the IF amplifier. The differential limiter outputs (Pins 10 and 11) are available for demodulator circuits. Oscillator and Buffer The on-board oscillator supplies the signal for the mixer down-conversion. The internally biased transistor can be configured as a Colpitts or Butler overtone crystal oscillator. The transistor’s bias current can be increased if desired by adding a shunt resistor from Pin 3 to ground. The oscillator’s buffered output (Pin 5) can be used as a feedback signal to lock the oscillator to an appropriate reference. RSSI The received signal strength indicator provides a linear voltage indication of the received signal strength in dB for a range in excess of 90dB. The response time to a change in input signal is less than a few microseconds and the delay is kept to a minimum because of the use of a minimum phase shift circuit. Because of the speed of the RSSI circuit, the RSSI rise and fall time may, in practice, be dominated by the IF Amplifier and IF Limiter The IF strip provides more than 95dB of power gain for the down converted signal. Its October 27, 1993 4 bandwidth of the external bandpass filter that is placed between the mixer and the IF, and the external filter placed between the IF amplifier and limiter. Since the RSSI function requires the signal to propagate through the whole IF strip, and the rise and fall time of the filters are inversely proportional to their bandwidth, there is a trade-off between channel selectivity and RSSI response. A possible solution is to use a second SA637 with wider band external filters for faster RSSI response. The RSSI curve is temperature compensated and in addition is designed for improved consistency from unit to unit. The RSSI circuit drives an on-chip low power op amp with rail-to-rail output which can be connected as a unity gain RSSI buffer or a gain stage or even a comparator. DC Power Supply The IC is designed for operation between 2.7 and 5.5V. A power supply dependent biasing scheme is used in the mixers to benefit from the large headroom available at higher VCCs. Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver SA637 PERFORMANCE CHARACTERISTICS Supply Current vs Temperature and Supply Voltage Power Down Supply Current vs Temperature and Supply Voltage 8.00 POWER DOWN SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 7.00 6.00 5.5V 5.00 3V 4.00 2.7V 3.00 2.00 1.00 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 0.50 0.45 0.40 0.35 0.30 5.5V 0.25 0.20 3V 0.15 0.10 2.7V 0.05 0.00 -50 -40 -30 -20 -10 90 TEMPERATURE (°C) 20 30 40 50 60 70 80 90 Mixer Third Order Input Intercept Point vs Temperature and Supply Voltage 10.00 THIRD-ORDER INTERCEPT POINT (dBm) -10.00 9.00 MIXER GAIN (dB) 10 TEMPERATURE (°C) Mixer Power Gain vs Temperature and Supply Voltage 8.00 5.5V 7.00 3V 2.7V 6.00 5.00 4.00 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 -12.00 -14.00 5.5V 3V -16.00 2.7V -18.00 -20.00 -22.00 -24.00 90 -50 -40 -30 -20 -10 TEMPERATURE (°C) 0 10 20 30 40 50 60 70 80 90 TEMPERATURE (°C) Oscillator Buffer Output Level vs Temperature and Supply Voltage Mixer Third Order Intercept and Compression vs Input Power – Vcc=3V, T=25°C 0.50 0 0.45 -10 -20 0.40 5.5V 0.35 OUTPUT POWER (dBm) MIXER GAIN (dB) 0 3V 0.30 2.7V 0.25 0.20 0.15 0.10 -30 -40 -50 -60 -70 -80 0.05 -90 0.00 -100 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 -50 90 October 27, 1993 -45 -40 -35 -30 -25 INPUT POWER (dBm) TEMPERATURE (°C) 5 -20 -15 -10 Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver SA637 PERFORMANCE CHARACTERISTICS (cont.) IF Power Gain vs Temperature and Supply Voltage Limiter Power Gain vs Temperature and Supply Voltage 65.00 40.00 38.00 63.00 5.5V 5.5V 36.00 IF GAIN (dB) IF GAIN (dB) 3V 2.7V 34.00 3V 61.00 2.7V 59.00 57.00 32.00 55.00 30.00 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 -50 -40 -30 -20 -10 90 0 TEMPERATURE (°C) 10 20 30 40 50 60 70 Limiter Output (+) Level vs Temperature and Supply Voltage 90 Limiter Output (–) Level vs Temperature and Supply Voltage 400.00 400.00 5.5V 350.00 5.5V 350.00 3V 300.00 LIMITER OUTPUT (–) (mVp-p) LIMITER OUTPUT (+) (mVp-p) 80 TEMPERATURE (°C) 2.7V 250.00 200.00 150.00 100.00 50.00 3V 300.00 2.7V 250.00 200.00 150.00 100.00 50.00 0.00 0.00 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 -50 -40 -30 -20 -10 90 0 10 20 30 40 50 60 70 80 90 TEMPERATURE (°C) TEMPERATURE (°C) RSSI vs RF Level and Supply Voltage – Temperature = 25°C RSSI vs RF Level and Temperature – VCC = 3V 2.50 2.50 2.25 2.25 2.00 2.00 1.75 1.75 RSSI (V) RSSI (V) 5.5V 1.50 1.25 1.00 1.50 1.25 0.75 -40C 0.50 +85C 0.25 0.00 -120 -110 -100 -90 0.25 -80 -70 -60 -50 -40 -30 -20 -10 0.00 -120 -110 -100 -90 0 -80 -70 -60 -50 -40 -30 RF LEVEL (dBm) RF LEVEL (dBm) October 27, 1993 2.7V 1.00 0.75 0.50 3V 6 -20 -10 0 Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver SA637 PIN FUNCTIONS PIN PIN DC V No. MNEMONIC 1 RF IN PIN PIN DC V No. MNEMONIC EQUIVALENT CIRCUIT EQUIVALENT CIRCUIT +1.40 VREF 6 6 2.5k VCC 2.5k +3.00 BANDGAP 1 2 RF 2 BYPASS +1.40 VCC RSSI 7 OSC 3 E OUT +0.20 + 7 — 18k +1.79 4 MIX VCC 3 OSC 4 B +2.56 150µA RSSI 8 FEEDBACK +0.20 8 — + OSC 5 BUFFER +1.79 R POWER 9 DOWN 5 9 R 150µA October 27, 1993 +2.00 7 Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver SA637 PIN FUNCTIONS (continued) PIN PIN DC V No. MNEMONIC EQUIVALENT CIRCUIT PIN PIN DC V No. MNEMONIC EQUIVALENT CIRCUIT 10 LIMITER OUT IF +1.25 16 11 11 +1.28 DECOUP 16 6.6k IF AMP +1.28 17 DECOUP +1.28 14 18 LIMITER 13 1.31k 8.8k LIMITER 12 AMP OUT COUPLING IF 1.5k +1.28 18 AMP IN 1.5k +1.28 50µA 50µA 12 17 13 19 LIMITER 14 IN IF AMP +1.28 19 DECOUP +1.28 1.87k 20 MIXER 15 GND October 27, 1993 0 20 8 OUT +2.03 Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver SA637 48dB PAD PAD 32.2dB PAD 48dB PAD 32.2dB PAD LIMITER OUT (+) R49 R29 R47 R48 R32 R28 C29 R27 C20 R35 R37 R33 R34 R31 C27 C33 C30 R38 SW9 FLT1 SW8 SW7 20 19 FLT2 C28 C26 18 SW6 17 16 15 C31 14 C32 13 IF AMP 12 11 LIMITER MIXER FAST RSSI OSCILLATOR RSSI BUFFER LO BUFF + – 1 2 3 4 5 6 RSSI FB + – 7 8 9 10 C1 R16 C22 R50 C6 C2 C4 C5 C11 C21 R20 L2 R17 R2 C3 R14 R13 R51 C12 R1 R4 RF IN R45 R3 OSC OUT LO IN VCC RSSI PWD LIMITER OUT (–) Automatic Test Circuit Component List C1 C2 C3 C4 C5 C6 C11 C20 C21 C26 10nF 91pF 620pF 100nF 100nF 10nF 100nF 100nF 100nF 100nF C27 C28 C29 C30 C31 C32 C33 R1 R2 R3 100nF 100nF 100nF 100nF 100nF 100nF 100nF 249Ω 60.4Ω 60.4Ω R4 R13 R14 R16 R17 R20 R27 R28 R29 R31 49.9Ω 10kΩ 10kΩ 10kΩ 1kΩ 10kΩ 13.7kΩ 1.68kΩ 49.9Ω 1kΩ Figure 1. SA637 Automatic Test Circuit October 27, 1993 9 R32 R33 R34 R35 R38 R39 R45 R47 R48 R49 49.9Ω 13.7kΩ 1.68kΩ 49.9Ω 1kΩ 49.9Ω 49.9Ω 2.43kΩ 39.2kΩ 49.9Ω R32 R50 R51 L2 49.9Ω 1kΩ 49.9Ω 62nH Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver SA637 FLT1 20 19 FLT2 C4 C3 18 17 16 15 C5 14 C6 13 IF AMP C11 12 11 LIMITER MIXER RSSI RSSI BUFF OSCILLATOR +– 5 7 R5 1 2 3 4 6 L1 C8 C1 C9 L3 RF INPUT C2 * 9 10 * C13 R2 R9 * R4 L5 * R7 * R6 * X1 R3 C14 8 R1 C7 C12 * RSSI FB L4 LO + – BUFF * C10 C15 R8 L2 * OSC OUT VCC RSSI POWER LIMITER DOWN OUT(–) LIMITER OUT(+) Component List C1 C2 C3 C4 5-30pF 5-30pF 0.1µF 0.1µF C5 C6 C7 C8 0.1µF 0.1µF 10pF 0.1µF C9 C10 C11 C12 C13 C14 C15 0.1µF 1.0µF 0.1µF 68pF 0.1µF 0.1µF 1000pF R1 R2 R3 R4 R5 R6 R7 R8 R9 OPEN 0Ω (short) 1kΩ 1.0kΩ 2.0kΩ 51Ω 100Ω 100Ω OPEN L1 L2 L3 L4 L5 FLT1 FLT2 X1 0.15µH PM20-R15M 0.15µH PM20-R15M 0.47µH PM20-R47M OPEN OPEN 455kHz SFGCC 455BX-TC 455kHz SFGCC 455BX-TC 82.705MHz CTS XTAL 020-3249-042 * NOTE: These components are optional and depend on user matching requirements. Pads are provided on the demo board. R2 and R9 set the RSSI buffer gain. For unity gain short R2 (Pin 7 to Pin 8) and leave R9 open. Figure 2. SA637 Application Circuit October 27, 1993 10 Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver RF GENERATOR 83.16MHz SA637 SA637 DEMO BOARD RSSI LIMITER OUTPUT VCC = 3V SPECTRUM ANALYZER DC VOLTMETER Figure 3. SA637 Application Circuit Test Set Up NOTES: 1. Carrier-to-Noise (C/N): Connect a spectrum analyzer to Pin 10 or 11; set your RF generator to 83.16MHz or 455kHz above your LO frequency, modulation off; set the spectrum analyzer resolution bandwidth to 300Hz; and adjust your RF input level until the C/N = 26dB. Use video averaging. Assure that LIMOUT(+) and LIMOUT(–) are matched symetrically. 2. Ceramic filters: The ceramic filter can be SFGCC455BX-TC made by Murata which has 30kHz IF bandwidth. 3. Sensitivity: The measured typical sensitivity for 12dB SINAD should be 0.45µV or -114dBm at the RF input. 4. Layout: The layout is very critical in the performance of the receiver. We highly recommend our demo board layout. 5. 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. 6. Supply bypass and shielding: All of the inductors, the quad tank, and their shield must be grounded. A 0.1µF bypass capacitor on the supply pin improves sensitivity. October 27, 1993 11 Philips Semiconductors RF Communications Products Product specification Low-voltage digital IF receiver October 27, 1993 SA637 12