Analog Devices Inc. AD8309ARU

Overview

AD8309ARU from Analog Devices is a 5 MHz–500 MHz demodulating logarithmic amplifier with limiter output, delivering 100 dB dynamic range (–78 dBm to +22 dBm), 20 mV/dB RSSI slope, and differential limiter outputs up to 2.4 V_p-p. It serves as an IF signal processor in RF receivers for simultaneous RSSI measurement and hard limiting.

For engineers reviewing the AD8309ARU datasheet, AD8309ARU pinout, AD8309ARU application, or AD8309ARU equivalent, this device is selected for wide-dynamic-range IF power detection, phase/frequency demodulation support, stable temperature-invariant RSSI scaling, and low-power single-supply operation (2.7 V to 6.5 V, 16 mA typical).

Technical Context

The AD8309ARU integrates six cascaded 12.04 dB gain stages (850 MHz –3 dB bandwidth) plus a programmable 18 dB limiter stage, achieving 100 dB total gain and 500 MHz usable bandwidth. Its logarithmic response uses ten detectors-six in the main path and four driven via broadband attenuator-to extend dynamic range beyond 48 dB at the top end.

Input is fully differential (1 kΩ || 2.5 pF), referenced to internal band-gap voltage for stable 20 mV/dB slope and –95 dBm intercept across –40°C to +85°C. The limiter supports programmable output current (0–10 mA) and exhibits <±3° phase variation over –60 dBm to +10 dBm at 100 MHz.

Key Specifications

Pinout & Package

AD8309ARU is housed in a 16-lead TSSOP package (RU-16) with exposed paddle (grounded via pins 3, 6, 11, 14). The package supports standard surface-mount assembly and thermal dissipation via paddle soldering.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar logarithmic amplifier applications.

Compared with LT5537IMS#TRPBF and MAX2016ETX+, the AD8309ARU uniquely combines 100 dB dynamic range, integrated limiter with differential outputs, and temperature-stable RSSI scaling in a single 16-lead TSSOP-making it optimal for dual-function IF signal processors in 5–500 MHz receivers.

Availability

AD8309ARU is available at Aetrix Electronics and suitable for RF receiver design, instrumentation-grade power measurement, and radar signal conditioning requiring stable component supply across industrial temperature ranges.

Supply support for AD8309ARU includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD8309ARU belongs to Analog Devices' precision logarithmic amplifier product line, engineered specifically for wide-dynamic-range RF/IF signal processing in communications, test equipment, and defense electronics.

FAQ

What is the maximum input level the AD8309ARU can handle without damage?

The AD8309ARU has an absolute maximum differential input level of +26 dBm (re 50 Ω), per its Absolute Maximum Ratings. Operation above +22 dBm (the specified maximum usable input) risks compression-induced measurement error but remains within safe operating limits until the +26 dBm threshold. For reliable long-term performance, inputs should be kept ≤+22 dBm with proper termination and layout practices to avoid reflections.

How does the AD8309ARU achieve stable RSSI slope over temperature?

The AD8309ARU achieves stable 20 mV/dB RSSI slope using an on-chip band-gap voltage reference that drives both the logarithmic scaling circuitry and intercept calibration. This reference is trimmed and thermally compensated during manufacturing, resulting in a measured temperature coefficient of only –0.009 dB/°C across –40°C to +85°C-verified in Figure 10 of the datasheet.

Can the AD8309ARU limiter output drive a 50 Ω load directly?

Yes-the AD8309ARU limiter outputs (LMHI/LMLO) are designed to drive 50 Ω loads directly. With RLIM = 400 Ω, the limiter delivers up to 10 mA output current into 50 Ω, producing a 2.4 V_p-p differential swing. Layout best practices (symmetrical traces, ground plane, matched length) are required to preserve phase integrity and minimize skew below 680 ps.

What is the role of the FLTR pin (Pin 10) on the AD8309ARU?

The FLTR pin on the AD8309ARU connects to an external capacitor that sets the low-pass filter pole for the VLOG output. Adding capacitance (e.g., 27 pF to 3300 pF) reduces RSSI bandwidth from 3.5 MHz down to sub-Hz levels, enabling averaging of pulsed or noisy RF inputs. The pin is internally connected to the VLOG buffer's feedback node-no series resistor is needed.

Is the AD8309ARU pin-compatible with earlier revisions like AD8309ARU-REEL7?

Yes-the AD8309ARU, AD8309ARU-REEL, and AD8309ARU-REEL7 share identical pinout, electrical specifications, and thermal characteristics. The suffixes denote packaging only: bulk (AD8309ARU), 13″ tape-and-reel (AD8309ARU-REEL), and 7″ tape-and-reel (AD8309ARU-REEL7). All operate across –40°C to +85°C and use the RU-16 TSSOP footprint.