5 MHz500 MHz 100 dB Demodulating a Logarithmic Amplifier with Limiter Output AD8309 FEATURES FUNCTIONAL BLOCK DIAGRAM Complete Multistage Log-Limiting IF Amplifier SIX STAGES TOTAL GAIN 72dB TYP GAIN 18dB 100 dB Dynamic Range: 78 dBm to +22 dBm (Re 50 V) Stable RSSI Scaling Over Temperature and Supplies: INHI LMHI 12dB 12dB 12dB LIM 20 mV/dB Slope, 95 dBm Intercept INLO LMLO 60.4 dB RSSI Linearity up to 200 MHz BIAS LADR ATTEN LMDR CTRL Programmable Limiter Gain and Output Current 4 3 DET DET DET DET Differential Outputs to 10 mA, 2.4 V p-p I-V VLOG Overall Gain 100 dB, Bandwidth 500 MHz TEN DETECTORS SPACED 12dB FLTR Constant Phase (Typical 680 ps Delay Skew) Single Supply of +2.7 V to +6.5 V at 16 mA Typical GAIN BAND-GAP SLOPE INTERCEPT ENBL Fully Differential Inputs, R = 1 kV, C = 2.5 pF BIAS REFERENCE BIAS TEMP COMP IN IN 500 ns Power-Up Time, <1 mA Sleep Current APPLICATIONS Receivers for Frequency and Phase Modulation Very Wide Range IF and RF Power Measurement Receiver Signal Strength Indication (RSSI) Low Cost Radar and Sonar Signal Processing Instrumentation: Network and Spectrum Analyzers PRODUCT DESCRIPTION The overall dynamic range for this combination extends from The AD8309 is a complete IF limiting amplifier, providing both 91 dBV (78 dBm at the 50 W level) to a maximum permissible an accurate logarithmic (decibel) measure of the input signal value of +9 dBV, using a balanced drive of antiphase inputs each (the RSSI function) over a dynamic range of 100 dB, and a of 2 V in amplitude, which would correspond to a sine wave programmable limiter output, useful from 5 MHz to 500 MHz. power of +22 dBm if the differential input were terminated in 50 W . The slope of the RSSI output is closely controlled to It is easy to use, requiring few external components. A single 20 mV/dB, while the intercept is set to 108 dBV (95 dBm supply voltage of +2.7 V to +6.5 V at 16 mA is needed, corre- re 50 W ). These scaling parameters are determined by a band- sponding to a power consumption of under 50 mW at 3 V, plus gap voltage reference and are substantially independent of tem- the limiter bias current, determined by the application and perature and supply. The logarithmic law conformance is typically typically 2 mA, providing a limiter gain of 100 dB when using within 0.4 dB over the central 80 dB of this range at any fre- 200 W loads. A CMOS-compatible control interface can enable quency between 10 MHz and 200 MHz, and is degraded only the AD8309 within about 500 ns and disable it to a standby slightly at 500 MHz. current of under 1 m A. The RSSI response time is nominally 67 ns (10%90%). The The six cascaded amplifier/limiter cells in the main path have a averaging time may be increased without limit by the addition of small signal gain of 12.04 dB ( 4), with a 3 dB bandwidth of an external capacitor. The full output of 2.34 V at the maximum 850 MHz, providing a total gain of 72 dB. The programmable input of +9 dBV can drive any resistive load down to 50 W and output stage provides a further 18 dB of gain. The input is fully this interface remains stable with any value of capacitance on differential and presents a moderately high impedance (1 kW in the output. parallel with 2.5 pF). The input-referred noise-spectral-density, when driven from a terminated 50 W , source is 1.28 nV/ Hz, The AD8309 is fabricated on an advanced complementary equivalent to a noise figure of 3 dB. The sensitivity of the bipolar process using silicon-on-insulator isolation techniques AD8309 can be raised by using an input matching network. and is available in the industrial temperature range of 40 C to +85 C, in a 16-lead TSSOP package. Each of the main gain cells includes a full-wave detector. An additional four detectors, driven by a broadband attenuator, are used to extend the top end of the dynamic range by over 48 dB. REV. B Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or Tel: 781/329-4700 World Wide Web Site: (V = +5 V, T = +258C, unless otherwise noted) AD8309SPECIFICATIONS S A 1 1 Parameter Conditions Min Typ Max Units INPUT STAGE (Inputs INHI, INLO) 2 Maximum Input Differential Drive, p-p 3.5 4V +9 dBV Equivalent Power in 50 W Terminated in 52.3 W +22 dBm Noise Floor Terminated 50 W Source 1.28 nV/ Hz Equivalent Power in 50 W 500 MHz Bandwidth 78 dBm Input Resistance From INHI to INLO 800 1000 1200 W Input Capacitance From INHI to INLO 2.5 pF DC Bias Voltage Either Input 1.725 V LIMITING AMPLIFIER (Outputs LMHI, LMLO) Usable Frequency Range 5 500 MHz At Limiter Output R = R = 50 W to 10 dB Point 875 MHz LOAD LIM Phase Variation at 100 MHz Over Input Range 60 dBm to +10 dBm 3 Degrees Limiter Output Current Nominally 400 mV/R 0110 mA LIM Versus Temperature 40 C T +85 C 0.008 %/ C A 3 Input Range 78 +9 dBV Equivalent dBm 65 +22 dBm Maximum Output Voltage At Either LMHI or LMLO, wrt VPS2 1 1.25 V Rise/Fall Time (10%90%) R 50 W , 40 W R 400 W 0.4 ns LOAD LIM LOGARITHMIC AMPLIFIER (Output VLOG) 3 dB Error Dynamic Range From Noise Floor to Maximum Input 100 dB Transfer Slope 5 MHz f 200 MHz 18 20 22 mV/dB < +85 C 17 20 23 mV/dB Over Temperature 40 C < T A Intercept (Log Offset) 5 MHz f 200 MHz 116 108 100 dBV Equivalent dBm (re 50 W ) 103 95 87 dBm +85 C 117 108 99 dBV Over Temperature 40 C T A Equivalent dBm (re 50 W ) 104 95 86 dBm Temperature Sensitivity 0.009 dB/ C Linearity Error (Ripple) Input from 83 dBV (70 dBm) to +7 dBV (+20 dBm) 0.4 dB Output Voltage Input = 91 dBV (78 dBm) V = +5 V, +2.7 V 0.34 V S Input = +9 dBV (+22 dBm) V = +5 V 2.34 2.75 V S Input = +9 dBV (+22 dBm) V = +2.75 V 2.10 V S Minimum Load Resistance, R 40 50 W L Maximum Sink Current To Ground 0.75 1.0 1.25 mA Output Resistance 0.3 W Small-Signal Bandwidth 3.5 MHz Output Settling Time to 1% Large Scale Input, +3 dBV (+16 dBm), 50 W , C 100 pF 120 220 ns R L L Rise/Fall Time (10%90%) Large Scale Input, +3 dBV (+16 dBm), R 50 W , C 100 pF 67 100 ns L L POWER INTERFACES Supply Voltage, V 2.7 5 6.5 V POS Quiescent Current Zero-Signal, LMDR Open 13 16 20 mA Over Temperature 40 C < T < +85 C 111623 mA A Disable Current 40 C < T < +85 C 0.01 4 m A A Additional Bias for Limiter R = 400 W (See Text) 1.4 1.6 mA LIM Logic Level to Enable Power HI Condition, 40 C < T < +85 C 1.8 V V A POS Input Current when HI 3 V at ENBL, 40 C < T < +85 C4060 m A A Logic Level to Disable Power LO Condition, 40 C < T < +85 C 0.5 1 V A NOTES 1 Minimum and maximum specified limits on parameters that are guaranteed but not tested are six sigma values. 2 The input level is specified in dBV since logarithmic amplifiers respond strictly to voltage, not power. 0 dBV corresponds to a sinusoidal single-frequency input of 1 V rms. A power level of 0 dBm (1 mW) in a 50 W termination corresponds to an input of 0.2236 V rms. Hence, the relationship between dBV and dBm is a fixed offset of +13 dBm in the special case of a 50 W termination. 3 Due to the extremely high Gain Bandwidth Product of the AD8309, the output of either LMHI or LMLO will be unstable for levels below 78 dBV (65 dBm, re 50 W ). Specifications subject to change without notice. 2 REV. B