Analog Devices Inc./Maxim Integrated MAX4207ETE+

Overview

The MAX4207ETE+ from Maxim Integrated is a precision transimpedance logarithmic amplifier that computes the log ratio of input current (LOGIIN) to reference current (REFIIN) and delivers a voltage output with a default -0.25V/decade scale factor. It operates from dual ±2.7V to ±5.5V supplies, supports 10nA–1mA input current range across five decades, and features an internal 1.238V reference (REFVOUT), adjustable scale factor (SCALE), and offset (OSADJ). It is used in photodiode current monitoring for optical power measurement in fiber-optic receivers.

For engineers reviewing the MAX4207ETE+ datasheet, MAX4207ETE+ pinout, MAX4207ETE+ application, or MAX4207ETE+ equivalent, key selection considerations include its logarithmic conformity error (±10mV), temperature-stable scale factor drift (80µV/decade/°C), dual-output architecture (LOGV1 and LOGV2), internal current reference (10nA–10µA via REFISET), and thin QFN-16EP package with exposed paddle tied to VEE.

Technical Context

The MAX4207ETE+ implements a matched bipolar transistor pair with on-chip temperature compensation to cancel thermal voltage (kT/q) drift, enabling stable -0.25V/decade slope over -40°C to +85°C. Its functional diagram integrates a summing amplifier, current mirror, and dedicated buffers for LOGV1 (fixed-scale) and LOGV2 (adjustable-scale) outputs.

It uses dual-supply operation only, with inputs referenced to CMVIN (0–0.5V common-mode range) and outputs capable of sourcing/sinking ≥34mA. The uncommitted op amp (LOGV2 path) supports inverting/noninverting configurations, while REFISET and SCALE pins allow precise intercept and gain tuning via external resistors - critical for absorbance and wavelength-locking instrumentation.

Key Specifications

Pinout & Package

The MAX4207ETE+ is housed in a 16-pin thin QFN package (4mm × 4mm × 0.8mm) with exposed paddle thermally and electrically connected to VEE.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADL5513ACPZ-R7 and LT1997-1IMS8#PBF, the MAX4207ETE+ uniquely integrates dual logarithmic outputs, internal 1.238V reference, and REFISET-adjustable intercept - making it the only solution supporting true ratiometric optical absorbance measurement without external support ICs.

Availability

The MAX4207ETE+ is available at Aetrix Electronics and suitable for photodiode current monitoring, portable instrumentation, medical instrumentation, and analog signal processing requiring stable component supply and guaranteed long-term availability.

Supply support for MAX4207ETE+ 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

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for demanding industrial, medical, and communications applications.

The MAX4207ETE+ belongs to Maxim's precision logarithmic amplifier product line, engineered specifically for optical power measurement, absorbance spectroscopy, and wide-dynamic-range current sensing where ratiometric accuracy and temperature stability are critical.

FAQ

What is the primary function of the MAX4207ETE+?

The MAX4207ETE+ is a precision transimpedance logarithmic amplifier that computes the base-10 logarithm of the ratio between input current (LOGIIN) and reference current (REFIIN), delivering a corresponding voltage output. Its core function is to convert wide-dynamic-range photodiode or sensor currents into linear-in-dB voltage signals - enabling direct optical power, absorbance, or RF envelope measurements without software-based log computation. The MAX4207ETE+ achieves this with integrated temperature compensation, dual outputs (LOGV1 and LOGV2), and on-chip reference generation.

Does the MAX4207ETE+ support single-supply operation?

No, the MAX4207ETE+ requires dual ±2.7V to ±5.5V supplies and does not support single-supply operation. Its internal circuitry - including matched bipolar transistor pairs and summing amplifiers - relies on symmetric rails to maintain log conformity, minimize input offset, and ensure stable common-mode operation at CMVIN. Attempting single-supply use will result in undefined behavior, clipping, or failure to meet datasheet specifications such as ±10mV log conformity error or -250mV/decade slope accuracy. The MAX4207ETE+ must be powered with both VCC and VEE rails properly decoupled.

How is the logarithmic intercept adjusted on the MAX4207ETE+?

The logarithmic intercept of the MAX4207ETE+ is adjusted by setting the reference current (IREF) using the REFISET pin. A resistor (RSET) is connected from REFISET to GND, and the resulting current at REFIOUT follows IREF = 0.5V / RSET. Since the device's transfer function is VLOGV1 = K × log₁₀(ILOG / IREF), changing IREF shifts the entire log curve horizontally - e.g., setting RSET = 50kΩ yields IREF = 10µA, moving the 0V output point to ILOG = 10µA. The MAX4207ETE+ supports IREF tuning from 10nA to 10µA, enabling precise alignment of the log intercept to application-specific optical zero points.

What is the purpose of the CMVOUT and CMVIN pins on the MAX4207ETE+?

The CMVOUT pin on the MAX4207ETE+ provides a stable 0V common-mode reference output, while CMVIN accepts a 0–0.5V bias voltage to set the collector operating point of the internal logarithmic transistors. Connecting CMVOUT to CMVIN biases both LOGIIN and REFIIN inputs at 0V - maximizing dynamic range and minimizing input offset errors caused by transistor mismatch. Alternatively, applying a controlled voltage (e.g., 0.25V) to CMVIN optimizes performance for specific photodiode reverse-bias conditions or leakage current profiles. This dual-pin architecture ensures robust operation across varying sensor characteristics without external level-shifting circuitry.

Can the MAX4207ETE+ drive ADC inputs directly?

Yes, the MAX4207ETE+ can drive most SAR and delta-sigma ADC inputs directly. Its LOGV1 and LOGV2 outputs feature rail-to-rail swing (VEE + 0.08V to VCC – 0.3V), low output impedance (<100Ω), and ±58mA short-circuit capability - sufficient to settle into typical 10–100pF ADC input capacitances within microseconds. For 16-bit+ precision, use the internal 1.238V REFVOUT as ADC reference and route LOGV1 through a simple RC filter (e.g., 100Ω + 10nF) to suppress broadband noise below 160kHz. The MAX4207ETE+'s 17µV_RMS (0.1–10Hz) output-referred noise ensures <1 LSB error for 16-bit systems with 5V full-scale range.