Analog Devices Inc./Maxim Integrated MAX6138BEXR21+T

Overview

MAX6138BEXR21+T from Maxim Integrated is a precision two-terminal shunt-mode bandgap voltage reference with a fixed reverse breakdown voltage of 2.048V, ±0.2% initial accuracy, 25ppm/°C max temperature coefficient over –40°C to +85°C, 60μA–15mA operating current range, and ultra-low 28μV_RMS wideband noise (10Hz–10kHz). It serves as a stable voltage reference in portable battery-powered systems requiring high accuracy in minimal board space.

For engineers reviewing the MAX6138BEXR21+T datasheet, MAX6138BEXR21+T pinout, MAX6138BEXR21+T application, or MAX6138BEXR21+T equivalent, key selection considerations include its SC70-3 package footprint, shunt-current regulation behavior, no-output-capacitor stability, and compatibility with low-power analog signal chains in space-constrained designs.

Technical Context

The MAX6138BEXR21+T implements a laser-trimmed bandgap core to achieve precise 2.048V reverse breakdown voltage with guaranteed 0.2% initial tolerance and 25ppm/°C max TC across –40°C to +85°C. Its dynamic impedance remains ≤0.8Ω at 1mA/120Hz, enabling stable regulation under varying load and supply conditions.

It operates as a two-terminal shunt device-Pin 1 (+) and Pin 2 (–) form the reference terminals, while Pin 3 is NC (must float or tie to Pin 2). No external capacitor is required for stability, and it maintains performance with any capacitive load, simplifying layout in ADC reference, sensor biasing, and portable power-monitoring circuits.

Key Specifications

Pinout & Package

Package: SC70-3 (1.8mm × 1.8mm, 0.95mm height), RoHS-compliant, thermal pad not present. Pin 3 is No Connect and must be left floating or tied to Pin 2 per datasheet requirement.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM4040C20IDCKR and ADR3420ARJZ-R7, the MAX6138BEXR21+T delivers optimal balance of SC70-3 size, 0.2% accuracy, 25ppm/°C TC, and zero-capacitor stability-making it the preferred choice for space-constrained, battery-operated 12–14-bit measurement systems where layout simplicity and long-term reliability are prioritized.

Availability

MAX6138BEXR21+T is available at Aetrix Electronics and suitable for portable medical devices, industrial process transmitters, battery management systems, and precision data loggers requiring stable component supply with consistent parametric performance across production lots.

Supply support for MAX6138BEXR21+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, medical, and communications applications.

The MAX6138 series targets high-accuracy, space-constrained voltage reference needs in portable and battery-powered equipment-emphasizing ultra-small packaging, low-noise operation, and capacitor-free stability without sacrificing initial accuracy or thermal drift performance.

FAQ

What is the exact output voltage tolerance and temperature coefficient specification for MAX6138BEXR21+T?

The MAX6138BEXR21+T has a nominal reverse breakdown voltage of 2.048V with ±0.2% initial accuracy (i.e., 2.0439V to 2.0521V at +25°C) and a guaranteed maximum temperature coefficient of 25ppm/°C over the –40°C to +85°C operating range. These values are production-tested and specified in the Electrical Characteristics table for the MAX6138_21 variant in the official Maxim Integrated datasheet Rev 3.

Can MAX6138BEXR21+T operate without an external output capacitor?

Yes, the MAX6138BEXR21+T is explicitly designed to operate stably without any external output capacitor and remains stable with arbitrary capacitive loads-including 1µF ceramic bypass caps. This eliminates BOM components and layout constraints, making it ideal for direct connection to ADC reference inputs or op-amp supplies where capacitor aging or ESR variation could degrade accuracy.

What are the absolute maximum ratings for shunt current and power dissipation in MAX6138BEXR21+T?

The MAX6138BEXR21+T allows a maximum reverse shunt current of 20mA and a forward current of 10mA. At +70°C ambient, its continuous power dissipation is rated at 174mW in the SC70-3 package, derating by 2.17mW/°C above that temperature. Exceeding these limits risks permanent damage or accelerated long-term drift beyond the specified 120ppm/1000h.

How is Pin 3 configured on MAX6138BEXR21+T, and what happens if it's left unconnected?

Pin 3 of the MAX6138BEXR21+T is designated N.C. (No Connect) and must either be left floating or connected directly to Pin 2 (cathode). Leaving it unconnected is acceptable and does not impair function; however, connecting it to Pin 2 provides a robust ESD discharge path and avoids potential leakage through stray capacitance-both configurations are validated in the datasheet's Pin Description section.

Does MAX6138BEXR21+T support operation at the extremes of its –40°C to +85°C temperature range with full parameter guarantees?

Yes, all key electrical parameters-including output voltage accuracy, temperature coefficient, dynamic impedance, and noise-are fully guaranteed over the entire –40°C to +85°C operating temperature range per the datasheet's Electrical Characteristics tables for MAX6138_21. The 25ppm/°C TC guarantee covers worst-case drift across this full span, and minimum operating current remains ≤65μA even at –40°C.