QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 747 LOG-LINEAR RF/IF DETECTOR LT5537 DESCRIPTION Demonstration circuit 747 is a log-linear RF/IF detector featuring the LT®5537. The LT5537 is a wide dynamic range RF/IF log detector, operational from below 10MHz to 1000MHz. The lower limit of the operating frequency range can be extended to near DC by the use of an external capacitor. The input dynamic range at 200MHz with ±3dB nonlinearity is 90dB (from –76dBm to 14dBm, single- ended 50Ω input). The detector output voltage slope is normally 20mV/dB, and the typical temperature coefficient is 0.01dB/°C at 200MHz. Design files for this circuit board are available. Call the LTC factory. LTC is a trademark of Linear Technology Corporation Table 1. Typical Performance Summary (VCC = 3V, ENBL = 3V, TA = 25°C, unless otherwise noted. Test circuit shown in Figure 1.) PARAMETER CONDITION VALUE Supply Voltage 2.7V to 5.25V Supply Current 13.5mA Shutdown Current ENBL Voltage ENBL Input Current ENBL = Low 500µA Low, Chip Disabled 0.3V max High, Chip Enabled 1.0V min VENBL = 0V 0µA VENBL = 3V 100µA RF/IF Input DC Common Mode Voltage (VCC – 0.4) V Small-Signal Impedance Measured at 200MHz 1.73kΩ // 1.45pF Output Start Voltage No Input Signal Present 0.4V Response Time Input from –30dBm to 0dBm, CLOAD = 2.5pF 110ns Baseband Modulation Bandwidth Output Load Capacitance = 2.5pF 6MHz Input Frequency Range Operation at lower frequency is possible. See LT5537 datasheet. 10MHz to 1GHz 50Ω Termination Maximum Input Power for Monotonic Output 200MHz 14.0dBm 600MHz 11.6dBm 1GHz 9.4dBm f = 10MHz Linear Dynamic Range ±3dB Error 88.8dB ±1dB Error 72.5dB Slope R1 = 33k (The output slope is adjustable using R1.) 19.6mV/dB Intercept VOUT = 0V, extrapolated -97dBm Sensitivity Sensitivity can be improved by as much as 10dB by using a narrowband input matching network. See LT5537 datasheet. -76.7dBm Temperature Coefficient PIN = -20dBm -0.007dB/°C 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 747 LOG-LINEAR RF/IF DETECTOR f = 100MHz Linear Dynamic Range ±3dB Error 90.5dB ±1dB Error 82.8dB Slope R1 = 33k (The output slope is adjustable using R1.) 20.3mV/dB Intercept VOUT = 0V, extrapolated -95dBm Sensitivity Sensitivity can be improved by as much as 10dB by using a narrowband input matching network. See LT5537 datasheet. -77dBm Temperature Coefficient PIN = -20dBm -0.004dB/°C ±3dB Error 90.3dB ±1dB Error 83.5dB Slope R1 = 33k (The output slope is adjustable using R1.) 21.2mV/dB Intercept VOUT = 0V, extrapolated -94dBm Sensitivity Sensitivity can be improved by as much as 10dB by using a narrowband input matching network. See LT5537 datasheet. -76.4dBm Temperature Coefficient PIN = -20dBm 0.010dB/°C ±3dB Error 88.2dB f = 200MHz Linear Dynamic Range f = 400MHz Linear Dynamic Range ±1dB Error 70.8dB Slope R1 = 33k (The output slope is adjustable using R1.) 23.1mV/dB Intercept VOUT = 0V, extrapolated -91dBm Sensitivity Sensitivity can be improved by as much as 10dB by using a narrowband input matching network. See LT5537 datasheet. -75.3dBm Temperature Coefficient PIN = -20dBm 0.019dB/°C ±3dB Error 85.8dB ±1dB Error 72.5dB Slope R1 = 33k (The output slope is adjustable using R1.) 25.2mV/dB Intercept VOUT = 0V, extrapolated -89dBm Sensitivity Sensitivity can be improved by as much as 10dB by using a narrowband input matching network. See LT5537 datasheet. -74.1dBm Temperature Coefficient PIN = -20dBm 0.026dB/°C ±3dB Error 63.5dB f = 600MHz Linear Dynamic Range f = 1GHz Linear Dynamic Range ±1dB Error 51.7dB Slope R1 = 33k (The output slope is adjustable using R1.) 31.4mV/dB Intercept VOUT = 0V, extrapolated -80dBm Sensitivity Sensitivity can be improved by as much as 10dB by using a narrowband input matching network. See LT5537 datasheet. -69.2dBm Temperature Coefficient PIN = -20dBm 0.031dB/°C 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 747 LOG-LINEAR RF/IF DETECTOR QUICK START PROCEDURE Demonstration circuit 747 is easy to set up to evaluate the performance of the LT5537. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 5. Connect signal generator’s output to demo board INPUT port (SMA connector J1) via coaxial cable. A 3dB attenuator may be inserted to improve input match. 1. Connect voltmeter’s negative (-) lead to demo board GND test point (E4 or E5). 6. 2. Connect voltmeter’s positive (+) lead to the demo board OUTPUT test point (E2). Using a jumper cable, connect demo board VCC test point (E3) to ENBL test point (E1). Now the detector is enabled (on) and is ready for measurement. 3. Connect DC power supply’s negative (-) output to demo board GND test point (E4 or E5). 4. Connect DC power supply’s positive (+) output (2.7V to 5.25V) to demo board VCC test point (E3). NOTE: Do not exceed 5.5V, the absolute maximum supply voltage. NOTE: Make sure that the power is not applied to ENBL before it is applied to VCC. The voltages on the ENBL test point must never exceed VCC + 0.2V. 7. Apply RF input signal and measure OUTPUT DC voltages. NOTE: Do not exceed +22dBm, the absolute maximum RF input power. Figure 1. Proper Measurement Equipment Setup 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 747 LOG-LINEAR RF/IF DETECTOR 4