Analog Devices Inc./Maxim Integrated MAX4039ETB+T

Overview

The MAX4039ETB+T from Maxim Integrated is a dual, rail-to-rail operational amplifier with integrated 1.232V buffered voltage reference, operating from +1.8V to +3.6V supply and consuming only 5.3µA total supply current (typ) at VDD = 3.6V. It features ultra-low input bias current (±100pA max over temperature), 25mV rail-to-rail output swing into 5kΩ, and is optimized for precision sensor signal conditioning in single- or two-cell battery-powered systems such as pH meters and potentiostats.

For engineers reviewing the MAX4039ETB+T datasheet, MAX4039ETB+T pinout, MAX4039ETB+T application, or MAX4039ETB+T equivalent, key selection criteria include its dual-amplifier + reference integration, guaranteed operation down to +1.8V, ±100pA input bias current limit over full temperature range, 5.3µA total quiescent current, and TDFN-EP package compatibility with space-constrained portable instrumentation.

Technical Context

The MAX4039ETB+T integrates two independent low-power op amps and a buffered 1.232V reference in a single 10-pin TDFN package. Its BiCMOS process enables rail-to-rail output swing within 25mV of rails into 5kΩ while maintaining ±100pA input bias current across –40°C to +85°C.

The reference delivers 100µA sourcing / 20µA sinking capability with ±0.5% initial accuracy and ≤120ppm/°C tempco, eliminating need for external bypass capacitors. Amplifiers are unity-gain stable and support capacitive loads up to 5000pF without oscillation.

Key Specifications

Pinout & Package

The MAX4039ETB+T is housed in a 3mm × 3mm × 0.8mm, 10-pin TDFN-EP package with exposed paddle (EP) internally connected to VSS. The EP must be soldered to VSS or left unconnected; routing traces beneath it is not recommended.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-op-amp-with-reference applications.

Compared with MAX4038ETA-T, the MAX4039ETB+T saves board space and calibration complexity via integrated reference but trades off reference voltage flexibility. Compared with LTC2050CMS8#PBF, it achieves >200× lower supply current at the expense of higher input voltage noise and absence of zero-drift architecture.

Availability

MAX4039ETB+T is available at Aetrix Electronics and suitable for pH meters, potentiostats, remote sensor amplifiers, and portable medical instrumentation requiring stable component supply across industrial and medical design cycles.

Supply support for MAX4039ETB+T 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 and mixed-signal ICs for battery-powered, sensor, and industrial applications.

The MAX4036–MAX4039 product line targets ultra-low-power electrochemical measurement systems, integrating micropower op amps and buffered references to simplify potentiostat and high-impedance sensor front ends.

FAQ

What is the minimum supply voltage required for reliable operation of the MAX4039ETB+T?

The MAX4039ETB+T requires a minimum supply voltage of +1.8V for guaranteed operation, as specified in the Electrical Characteristics table under "Supply Voltage Range" for MAX4037/MAX4039 variants. Operation below +1.8V may result in degraded reference accuracy, reduced output swing, or failure to meet PSRR and line regulation specifications. The +1.4V minimum applies only to MAX4036/MAX4038 (no reference) versions.

Can the MAX4039ETB+T reference output drive a 100kΩ load while maintaining accuracy?

Yes, the MAX4039ETB+T reference output maintains ±0.5% accuracy over temperature when sourcing up to 100µA or sinking up to 20µA. A 100kΩ load draws only 12.32nA from the 1.232V reference, well within the 100µA sourcing capability. Load regulation is specified at 0.003%/µA, so error remains <0.04% - negligible for most precision applications.

Does the MAX4039ETB+T require an external bypass capacitor on the REF pin?

No, the MAX4039ETB+T reference does not require an external bypass capacitor on the REF pin. The datasheet explicitly states "No External Reference Bypass Capacitor Required" in the Features list and confirms this in the Applications Information section. The internal buffer is designed for stability with capacitive loads up to 250pF, and typical operation is verified without added capacitance.

How does the input bias current of the MAX4039ETB+T affect high-impedance pH electrode measurements?

The MAX4039ETB+T's maximum input bias current of ±100pA over –40°C to +85°C introduces <1mV error across a typical 10MΩ pH electrode source impedance. This is well within the ±0.01pH accuracy requirement of clinical-grade meters. Combined with rail-to-rail output swing, it enables full 0–14 pH range digitization using a 3V supply and 12-bit ADC without level-shifting circuitry.

Is the exposed paddle (EP) on the MAX4039ETB+T's TDFN package electrically connected, and how should it be handled?

Yes, the exposed paddle (EP) on the MAX4039ETB+T's TDFN package is internally connected to VSS. The datasheet specifies that it must be soldered to the VSS pad on the PCB or left unconnected - it must never be floated or tied to another potential. Proper thermal and electrical connection to VSS improves thermal dissipation and reduces noise coupling; routing signal traces beneath the EP is discouraged due to risk of parasitic coupling.