Analog Devices Inc./Maxim Integrated MAX6138CEXR12+T

Overview

MAX6138CEXR12+T from Maxim Integrated is a precision two-terminal shunt-mode bandgap voltage reference with a fixed reverse breakdown voltage of 1.2205 V, ±0.5% initial accuracy, 25 ppm/°C max temperature coefficient, and 60 µA to 15 mA operating current range. It delivers stable reference performance in space-constrained portable systems such as battery-powered instrumentation and low-power ADC/DAC biasing circuits.

For engineers reviewing the MAX6138CEXR12+T datasheet, MAX6138CEXR12+T pinout, MAX6138CEXR12+T application, or MAX6138CEXR12+T equivalent, key selection criteria include its SC70-3 package footprint, no-output-capacitor requirement, low 28 µV_RMS noise (10 Hz–10 kHz), and guaranteed stability with capacitive loads across -40°C to +85°C.

Technical Context

The MAX6138CEXR12+T implements a laser-trimmed bandgap core to achieve precise 1.2205 V reverse breakdown voltage with minimal thermal drift. Its two-terminal architecture eliminates need for external feedback components and enables direct integration into high-side or low-side shunt regulator topologies.

It operates as a passive voltage sink: reverse current (cathode-to-anode) between 60 µA and 15 mA sets the regulated voltage across its terminals, while dynamic impedance remains ≤0.8 Ω at 1 mA-ensuring tight regulation under varying load and supply conditions without external compensation.

Key Specifications

Pinout & Package

MAX6138CEXR12+T uses the 3-pin SC70-3 surface-mount package (1.8 mm × 1.8 mm), 50% smaller than comparable SOT23 devices. Pin 3 is NC (no connection) and must be left floating or tied to Pin 2.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar shunt voltage reference applications.

Compared with LM4040C12IDCKR and ADR3412ARJZ-R7, MAX6138CEXR12+T offers the smallest footprint among 1.2 V shunt references, balanced 0.5% accuracy for cost-sensitive industrial designs, and guaranteed stability without output capacitance-making it optimal for miniaturized, capacitor-free, and medium-precision applications.

Availability

MAX6138CEXR12+T is available at Aetrix Electronics and suitable for portable medical sensors, battery-powered data loggers, and industrial field transmitters requiring stable component supply, consistent parametric performance, and long-term manufacturing continuity.

Supply support for MAX6138CEXR12+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, mixed-signal, and power management ICs for demanding industrial, automotive, and communications applications.

The MAX6138 series targets space- and power-constrained systems requiring high-accuracy, low-drift, two-terminal shunt references-specifically optimized for portable instrumentation, sensor interfaces, and compact data acquisition modules.

FAQ

What is the exact output voltage tolerance of the MAX6138CEXR12+T?

The MAX6138CEXR12+T has a guaranteed initial accuracy of ±0.5% at +25°C, corresponding to a reverse breakdown voltage range of 1.2144 V to 1.2266 V. This tolerance is laser-trimmed and specified across the full -40°C to +85°C operating temperature range, making MAX6138CEXR12+T suitable for applications where moderate precision is required without post-production calibration.

Can MAX6138CEXR12+T operate without an external output capacitor?

Yes, MAX6138CEXR12+T is explicitly designed to operate stably without any external output capacitor. Its internal architecture ensures unconditional stability even with capacitive loads up to 1 µF, eliminating the need for additional BOM components and simplifying layout-especially beneficial in ultra-compact or conformally coated designs where capacitor placement is impractical.

What is the minimum shunt current required for regulation in MAX6138CEXR12+T?

The MAX6138CEXR12+T requires a minimum shunt current of 60 µA to maintain regulation at +25°C, with a worst-case specification of 67 µA at +85°C per the datasheet's electrical characteristics table. Maintaining ≥60 µA across all operating conditions ensures the device remains in reverse breakdown and delivers its specified 1.2205 V output; falling below this risks loss of regulation and increased output drift.

How does the temperature coefficient of MAX6138CEXR12+T compare to other shunt references?

MAX6138CEXR12+T guarantees a maximum temperature coefficient of 25 ppm/°C over -40°C to +85°C-significantly tighter than legacy parts like LM4040 (100 ppm/°C) and competitive with mid-tier alternatives. While higher-precision options such as ADR3412 offer 10 ppm/°C, MAX6138CEXR12+T strikes a balance between drift performance, cost, and SC70 packaging, delivering predictable ±0.25 mV total drift across its full temperature range.

Is Pin 3 of MAX6138CEXR12+T functional or optional?

Pin 3 of MAX6138CEXR12+T is designated N.C. (No Connection) and has no internal function. The datasheet explicitly states it must be left floating or connected to Pin 2 (the cathode/negative terminal); neither configuration affects electrical performance. This design choice preserves compatibility with standard SC70-3 land patterns while enabling mechanical stabilization via optional tie-down-no circuit impact results from either choice.