Analog Devices Inc./Maxim Integrated MAX6138AEXR33+T

Overview

MAX6138AEXR33+T from Maxim Integrated is a precision two-terminal shunt-mode bandgap voltage reference with a fixed reverse breakdown voltage of 3.3000 V, ±0.1% initial accuracy, 25 ppm/°C max temperature coefficient over –40°C to +85°C, 60 µA to 15 mA operating current range, and ultra-low 50 µV_RMS wideband noise (10 Hz to 10 kHz). It serves as a stable voltage reference in high-accuracy ADC/DAC biasing and portable power management circuits.

For engineers reviewing the MAX6138AEXR33+T datasheet, MAX6138AEXR33+T pinout, MAX6138AEXR33+T application, or MAX6138AEXR33+T equivalent, key selection criteria include guaranteed 0.1% initial tolerance at 3.3 V, SC70-3 package compatibility with space-constrained PCB layouts, stability without output capacitance, and low dynamic impedance (≤0.8 Ω) across full load current range.

Technical Context

The MAX6138AEXR33+T implements a laser-trimmed bandgap core in BiCMOS process to deliver precise 3.3 V reference under reverse-biased operation. Its two-terminal architecture requires only an external series resistor for current setting, eliminating need for supply regulation or feedback loops.

It maintains stable regulation across 60 µA–15 mA shunt current while exhibiting ≤1.0 mV voltage change per mA in low-current region and ≤8.0 mV/mA above 1 mA - enabling predictable performance in varying load and supply conditions typical of battery-powered sensor nodes and industrial data acquisition systems.

Key Specifications

Pinout & Package

The MAX6138AEXR33+T is housed in a 3-pin SC70 surface-mount package (1.8 mm × 1.8 mm, 0.95 mm height), with pin 3 designated as no-connect (N.C.) - 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 TLVH431AIDBZR and ADR3433ARJZ-R7, the MAX6138AEXR33+T uniquely combines 0.1% accuracy, 25 ppm/°C guarantee, 60 µA minimum current, and SC70-3 footprint - making it optimal for space- and power-sensitive precision analog systems where fixed 3.3 V is required.

Availability

MAX6138AEXR33+T is available at Aetrix Electronics and suitable for portable medical sensors, industrial data acquisition modules, and automotive cabin electronics requiring stable component supply with guaranteed long-term availability and RoHS-compliant sourcing.

Supply support for MAX6138AEXR33+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 family delivers high-accuracy, low-noise shunt voltage references in ultra-small SC70 packages - engineered specifically for space-constrained, battery-operated, and metrology-grade systems needing stable fixed-voltage references without external capacitors.

FAQ

What is the guaranteed initial accuracy of the MAX6138AEXR33+T?

The MAX6138AEXR33+T is specified with ±0.1% initial accuracy at +25°C, meaning its 3.3000 V nominal output falls within 3.2967 V to 3.3033 V when measured under standard test conditions. This grade ('A') is laser-trimmed during production and documented in the Electrical Characteristics table for MAX6138_33 (3.3 V variant). The accuracy remains valid across the full –40°C to +85°C operating range per guaranteed temperature coefficient specification.

Does the MAX6138AEXR33+T require an external output capacitor for stability?

No, the MAX6138AEXR33+T does not require an external output capacitor. Its internal design ensures unconditional stability with capacitive loads ranging from 0 to at least 1 µF, as confirmed in the Applications Information section and Typical Operating Characteristics (output impedance vs. frequency plots). This eliminates capacitor-related aging, leakage, and layout complexity - a key advantage over many competing shunt references.

What are the absolute maximum ratings for shunt current in the MAX6138AEXR33+T?

The MAX6138AEXR33+T has an absolute maximum reverse current rating of 20 mA, as stated in the Absolute Maximum Ratings table. While functional operation is guaranteed from 60 µA to 15 mA, exceeding 20 mA risks permanent damage. Designers must size the series resistor (RS) to ensure ISHUNT stays below this limit under worst-case conditions - e.g., maximum supply voltage and minimum load current - per the equation provided in the Applications Information section.

How does the MAX6138AEXR33+T compare to the LM4040 in terms of size and precision?

The MAX6138AEXR33+T is explicitly described as "a higher precision device in a smaller package than the LM4040/LM4050." It uses the 3-pin SC70 package (1.8 mm × 1.8 mm), which is 50% smaller than standard SOT23 packages used by most LM4040 variants. It also offers tighter specifications: 0.1% initial accuracy vs. LM4040C's 0.5%, and 25 ppm/°C tempco vs. LM4040C-3.3's 100 ppm/°C - making it suitable for next-generation compact, high-accuracy systems where the LM4040 falls short.

What is the purpose of pin 3 on the MAX6138AEXR33+T, and how should it be handled?

Pin 3 of the MAX6138AEXR33+T is designated N.C. (No Connection) and must be left floating or connected to pin 2 (the cathode/negative terminal), as explicitly instructed in the Pin Description and Typical Operating Circuit diagrams. It is not internally bonded; leaving it unconnected improves thermal isolation and avoids unintended parasitic paths. Connecting it to pin 2 is electrically benign and may aid mechanical stability during reflow - both options comply with Maxim's validated assembly guidance.