Datasheet AD8310 (Analog Devices)

Fast, Voltage-Out, DC to 440 MHz, 95 dB Logarithmic Amplifier AD8310 FEATURES FUNCTIONAL BLOCK DIAGRAM Multistage demodulating logarithmic amplifier AD8310 Voltage output, rise time <15 ns VPOS BAND GAP REFERENCE ENBL SUPPLY 5 8mA 7 ENABLE AND BIASING High current capacity: 25 mA into grounded RL SIX 14.3dB 900MHz BFIN BUFFER 95 dB dynamic range: −91 dBV to +4 dBV 6 INHI AMPLIFIER STAGES INPUT +INPUT 8 Single supply of 2.7 V min at 8 mA typ 1.0k
Ω
MIRROR –INPUT 1 INLO DC to 440 MHz operation, ±0.4 dB linearity 2
μ
A + VOUT 3 /dB 4 OUTPUT – Slope of +24 mV/dB, intercept of −108 dBV NINE DETECTOR CELLS 2 3k
Ω
3k
Ω
Highly stable scaling over temperature SPACED 14.3dB COMM 1k
Ω
COMMON 2 COMM Fully differential dc-coupled signal path COMM INPUT-OFFSET OFLT OFFSET 3 100 ns power-up time, 1 mA sleep current COMPENSATION LOOP FILTER 33pF
001
COMM APPLICATIONS
01084-
Conversion of signal level to decibel form
Figure 1.
Transmitter antenna power measurement Receiver signal strength indication (RSSI) Low cost radar and sonar signal processing Network and spectrum analyzers Signal-level determination down to 20 Hz True-decibel ac mode for multimeters GENERAL DESCRIPTION
The fully differential input offers a moderately high impedance The AD8310 is a complete, dc to 440 MHz demodulating (1 kΩ in parallel with about 1 pF). A simple network can match logarithmic amplifier (log amp) with a very fast voltage mode the input to 50 Ω and provide a power sensitivity of −78 dBm to output, capable of driving up to 25 mA into a grounded load in +17 dBm. The logarithmic linearity is typically within ±0.4 dB under 15 ns. It uses the progressive compression (successive up to 100 MHz over the central portion of the range, but it is detection) technique to provide a dynamic range of up to 95 dB somewhat greater at 440 MHz. There is no minimum frequency to ±3 dB law conformance or 90 dB to a ±1 dB error bound up limit; the AD8310 can be used down to low audio frequencies. to 100 MHz. It is extremely stable and easy to use, requiring no Special filtering features are provided to support this wide range. significant external components. A single-supply voltage of The output voltage runs from a noise-limited lower boundary of 2.7 V to 5.5 V at 8 mA is needed, corresponding to a power 400 mV to an upper limit within 200 mV of the supply voltage consumption of only 24 mW at 3 V. A fast-acting CMOS- for light loads. The slope and intercept can be readily altered compatible enable pin is provided. using external resistors. The output is tolerant of a wide variety Each of the six cascaded amplifier/limiter cells has a small- of load conditions and is stable with capacitive loads of 100 pF. signal gain of 14.3 dB, with a −3 dB bandwidth of 900 MHz. The AD8310 provides a unique combination of low cost, small A total of nine detector cells are used to provide a dynamic size, low power consumption, high accuracy and stability, high range that extends from −91 dBV (where 0 dBV is defined as dynamic range, a frequency range encompassing audio to UHF, the amplitude of a 1 V rms sine wave), an amplitude of about fast response time, and good load-driving capabilities, making ±40 μV, up to +4 dBV (or ±2.2 V). The demodulated output this product useful in numerous applications that require the is accurately scaled, with a log slope of 24 mV/dB and an reduction of a signal to its decibel equivalent. intercept of −108 dBV. The scaling parameters are supply- and temperature-independent. The AD8310 is available in the industrial temperature range of −40°C to +85°C in an 8-lead MSOP package.
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Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION PROGRESSIVE COMPRESSION SLOPE AND INTERCEPT CALIBRATION OFFSET CONTROL PRODUCT OVERVIEW ENABLE INTERFACE INPUT INTERFACE OFFSET INTERFACE OUTPUT INTERFACE USING THE AD8310 BASIC CONNECTIONS TRANSFER FUNCTION IN TERMS OF SLOPE AND INTERCEPT dBV vs. dBm INPUT MATCHING NARROW-BAND MATCHING GENERAL MATCHING PROCEDURE Step 1: Tune Out CIN Step 2: Calculate CO and LO Step 3: Split CO into Two Parts Step 4: Calculate LM SLOPE AND INTERCEPT ADJUSTMENTS INCREASING THE SLOPE TO A FIXED VALUE OUTPUT FILTERING LOWERING THE HIGH-PASS CORNER FREQUENCY OF THE OFFSET COMPENSATION LOOP APPLICATIONS INFORMATION CABLE-DRIVING DC-COUPLED INPUT EVALUATION BOARD DIE INFORMATION OUTLINE DIMENSIONS ORDERING GUIDE