Analog Devices Inc./Maxim Integrated MAX6390XS26D4-T

Overview

MAX6390XS26D4-T from Maxim Integrated is a low-power microprocessor supervisory circuit with open-drain active-low reset output, factory-set 2.63V VCC reset threshold (±2.5% over –40°C to +125°C), 1120ms VCC reset timeout, and 140ms manual reset timeout. It monitors single-supply voltages from +1.8V to +5.0V and guarantees valid reset state down to VCC = 1V - used in battery-powered controllers and portable instrumentation requiring reliable power-on reset and brownout protection.

For engineers reviewing the MAX6390XS26D4-T datasheet, MAX6390XS26D4-T pinout, MAX6390XS26D4-T application, or MAX6390XS26D4-T equivalent, key selection considerations include its 4-pin SC70 package, dual timeout timing (VCC vs. MR), ±2.5% threshold accuracy over temperature, and compatibility with systems needing open-drain reset assertion into shared bus lines.

Technical Context

The MAX6390XS26D4-T implements a precision voltage comparator with internal 2.63V reference and an independent manual reset input (MR) featuring a 1.56kΩ internal pullup resistor. Its reset logic asserts open-drain RESET when VCC falls below 2.63V or MR is pulled low, holding for 1120ms after VCC recovery or 140ms after MR release.

It operates across –40°C to +125°C with supply current as low as 3μA at +1.8V, supports VCC monitoring only (no auxiliary RESET IN), and guarantees RESET output validity down to VCC = 1V - enabling robust operation during deep brownout conditions without external supervision.

Key Specifications

Pinout & Package

MAX6390XS26D4-T is packaged in a RoHS-compliant 4-pin SC70 (package code X4+1, outline 21-0098), footprint-optimized for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor reset applications.

Compared with MAX6390XS26D4-T, MAX6326XR26D4+T omits manual reset and uses push-pull output - reducing BOM count but limiting bus-sharing flexibility; TPS3808G33DBVR offers lower ICC and enable control but shifts threshold upward and increases pin count - making it less suitable for strict 2.63V brownout detection in compact layouts.

Availability

MAX6390XS26D4-T is available at Aetrix Electronics and suitable for portable medical monitors, battery-powered data loggers, industrial PLC I/O modules, and automotive body control units requiring stable component supply with guaranteed long-term availability.

Supply support for MAX6390XS26D4-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 demanding industrial, automotive, and computing applications - emphasizing low power, high reliability, and AEC-Q100 qualification.

The MAX6381–MAX6390 family delivers single/dual-voltage microprocessor supervisory circuits optimized for space-constrained, low-power systems requiring accurate reset timing and robust brownout immunity across extended temperature ranges.

FAQ

What is the exact reset threshold voltage of MAX6390XS26D4-T?

The MAX6390XS26D4-T has a factory-set nominal reset threshold of 2.63V, with guaranteed tolerance of ±2.5% over the full operating temperature range (–40°C to +125°C). This value is fixed by the "26" suffix in the part number and is not adjustable. The device asserts reset when VCC falls below this threshold and holds reset for 1120ms after VCC rises above it.

Does MAX6390XS26D4-T support dual-voltage monitoring like some other MAX638x parts?

No, MAX6390XS26D4-T monitors only the VCC supply - it does not include the auxiliary RESET IN input found in MAX6387/MAX6388/MAX6389. Its function is strictly single-supply supervision with manual reset capability. For dual-rail monitoring, consider MAX6389XS26D4-T instead, which adds the RESET IN comparator referenced to 1.27V.

What is the purpose of the 1.56kΩ internal pullup on the MR pin of MAX6390XS26D4-T?

The 1.56kΩ internal pullup resistor on the MR pin of MAX6390XS26D4-T ensures the input remains logic-high when unconnected, preventing spurious resets. It provides stronger noise immunity than the 63kΩ pullup used in earlier MAX6384–MAX6386 variants - critical for noisy environments or long PCB traces. No external pullup is required unless driving MR from an open-drain source.

Can MAX6390XS26D4-T operate reliably at VCC = 1.2V?

Yes, MAX6390XS26D4-T guarantees correct reset output logic state down to VCC = 1.0V, including full comparator functionality and timeout timing accuracy. At VCC = 1.2V, it continues to monitor and assert RESET if voltage drops below 2.63V (though that condition implies external regulation failure), and maintains valid open-drain output behavior - a key differentiator for fail-safe designs.

Is MAX6390XS26D4-T pin-compatible with MAX809 or MAX6326?

No, MAX6390XS26D4-T is not pin-compatible with MAX809 (3-pin SOT-23) or MAX6326 (3-pin SC70). It uses a 4-pin SC70 package with dedicated MR and RESET pins, whereas those alternatives use 3-pin configurations combining functions. Pin mapping differs fundamentally: MAX6390XS26D4-T assigns Pin 1=VCC, Pin 2=RESET, Pin 3=MR, Pin 4=GND - requiring PCB redesign for substitution.