AD8310

Features:

Multistage Demodulating Logarithmic Amplifier
Voltage Output, Rise-Time <15 ns
High-Current Capacity: 25 mA into Grounded RL
95 dB Dynamic Range: 91 dBV to +4 dBV
Single Supply of 2.7 V Min at 8 mA Typ
DC-440 MHz Operation, ±0.4 dB Linearity
Slope of 24 mV/dB, Intercept of 108 dBV
Highly Stable Scaling over Temperature
Fully Differential DC-Coupled Signal Path
100 ns Power-Up Time, 1 A Sleep Current




Application

Conversion of Signal Level to Decibel Form
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




Pinout








Specifications

Supply Voltage VS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .7.5 V
Input Power (re 50 ), Single-Ended . . . . . . . . . . . . .. . . . . . . . . . 18 dBm
Differential Drive . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .. . 22 dBm
Internal Power Dissipation . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .200 mW
q_JA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200°C/W
Maximum Junction Temperature . . . . . . . . . . . . . . . . .. . . . . . . . . .. 125°C
Operating Temperature Range . . . . . . . . . . . .. . . . . . . . . 40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . .. . . . . . . . .65°C to +150°C
Lead Temperature Range (Soldering 60 sec) . . . . . . . . .. . . . . . . . . 300°C
*Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may effect device reliability.






Description

The AD8310 is a complete, dc-440 MHz demodulating logarithmic amplifier (log amp) with a very fast voltage-mode output capable of driving up to 25 mA into a grounded load in under 15 ns. It uses the progressive compression (successive detection) technique to provide a dynamic range of up to 95 dB to ±3 dB law-conformance, or 90 dB to a ±1 dB error bound up to 100 MHz. It is extremely stable and easy to use, requiring no significant external components. A single supply voltage of 2.7 V to 5.5 V at 8 mA is needed, corresponding to a power consumption of only 24 mW at 3 V. A fast-acting CMOS-compatible enable pin is provided.

Each of the six cascaded amplifier/limiter cells AD8310 has a small-signal gain of 14.3 dB, with a 3 dB bandwidth of 900 MHz. A total of nine detector cells are used, to provide a dynamic range that extends from 91 dBV (where 0 dBV is defined as the amplitude of a 1 V rms sine wave) that is, an amplitude of about ±40 mV, up to +4 dBV (or ±2.2 V). The demodulated output is accurately scaled, with a log slope of 24 mV/dB and an intercept of 108 dBV; the scaling parameters are supply- and temperatureindependent. The fully-differential input offers a moderately high impedance (1 k in parallel with about 1 pF). A simple network can match the input to 50 and provide a power sensitivity of to 78 dBm to +17 dBm. The logarithmic linearity is typically within ±0.4 dB up to 100 MHz over the central portion of the range, but is somewhat greater at 440 MHz. There is no minimum frequency limit; the AD8310 may be used down to low audio frequencies. Special filtering features are provided to support this wide range.

The output voltage runs AD8310 from a noise-limited lower boundary of 400 mV to an upper limit within 200 mV of the supply voltage for light loads. The slope and intercept can be readily altered using external resistors. The output is tolerant of a wide variety of load conditions and is stable with capacitive loads of 100 pF.

The AD8310 provides a unique combination of low cost, small size, small power consumption, high accuracy and stability, high dynamic range, a frequency range encompassing audio to UHF, fast response time and good load-driving capabilities, making this product useful in numerous applications requiring the reduction of a signal to its decibel equivalent.

The AD8310 is available in the industrial temperature range of 40°C to +85°C, in an 8-lead Mini_SO package.