Analog Devices Inc./Maxim Integrated MAX6423US44+

Overview

MAX6423US44+ from Maxim Integrated is a low-power microprocessor supervisor IC with open-drain active-low reset output, 4.375V nominal reset threshold (±2.5% over temperature), capacitor-adjustable reset timeout (3.0–5.75ms at CSRT = 1500pF), 1.6µA typical supply current, and guaranteed operation down to VCC = 1V. It monitors power rails in battery-powered embedded controllers and ensures reliable µP reset during brownout conditions.

For engineers reviewing the MAX6423US44+ datasheet, MAX6423US44+ pinout, MAX6423US44+ application, or MAX6423US44+ equivalent, key selection criteria include its 4-pin SOT143 package, open-drain RESET compatibility with multiple logic supplies, immunity to short VCC transients (<50µs at 100mV overdrive), and factory-laser-trimmed voltage threshold stability across –40°C to +125°C.

Technical Context

The MAX6423US44+ implements a precision voltage-detection circuit using laser-trimmed resistors to set its 4.375V reset threshold, with ±2.5% accuracy over –40°C to +125°C and 4mV hysteresis. Its reset timeout is generated by a 240nA internal ramp current charging an external capacitor (CSRT) to a 0.65V internal reference.

It features an open-drain RESET output requiring an external pullup (10kΩ–100kΩ), supports logic-level interfacing up to 5.5V, and maintains valid reset assertion down to VCC = 1V. The SRT pin is sensitive to board leakage and stray capacitance, demanding careful PCB layout to preserve timeout accuracy.

Key Specifications

Pinout & Package

MAX6423US44+ is housed in a 4-pin SOT143 package (outline 21-0052, land pattern 90-0183), lead-free, RoHS-compliant. Pin 1 = VCC, Pin 2 = GND, Pin 3 = RESET (open-drain), Pin 4 = SRT (capacitor-adjustable timeout input).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6423US44+, MAX6423US46+ offers identical functionality at a higher threshold for tighter brownout margins, while NCP302LSN43T1G trades configurability and package compatibility for ultra-low current and integrated timing - neither is pin-compatible, but both serve overlapping supervision roles in cost- or space-constrained designs.

Availability

MAX6423US44+ is available at Aetrix Electronics and suitable for battery-powered medical sensors, automotive body control modules, and industrial handheld terminals requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MAX6423US44+ 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 industrial, automotive, and computing applications.

The MAX6421–MAX6426 family delivers low-power, capacitor-programmable reset supervisors targeting space-constrained, battery-sensitive systems requiring accurate voltage monitoring and flexible timeout control.

FAQ

What is the exact reset threshold voltage of MAX6423US44+ and how stable is it over temperature?

The MAX6423US44+ has a nominal reset threshold of 4.375V, with ±2.5% accuracy guaranteed over the full –40°C to +125°C operating range. This stability is achieved via factory laser trimming of internal resistors, eliminating need for external calibration. At +25°C, tolerance tightens to ±1.5%, and hysteresis is fixed at 4mV - ensuring clean, bounce-free reset assertion and release.

Can MAX6423US44+ drive a 3.3V microcontroller reset pin directly?

Yes, MAX6423US44+ can drive a 3.3V µP reset pin directly using its open-drain RESET output. Connect a 10kΩ–100kΩ pullup resistor from RESET to the µP's 3.3V supply. The output sinks ≥500µA at VCC ≥ 1.8V, ensuring solid logic-low assertion, and tolerates up to 5.5V on the RESET line - enabling safe interfacing without level-shifting circuitry.

How do I calculate the external capacitor value for a 5ms reset timeout with MAX6423US44+?

Use the formula CSRT = (tRP − 275µs) / 2.73×10⁶, where tRP is in seconds. For 5ms (0.005s): CSRT = (0.005 − 0.000275) / 2,730,000 ≈ 1730pF. A standard 1800pF ceramic capacitor yields ~5.2ms timeout - within datasheet's 3.0–5.75ms range at CSRT = 1500pF. Use low-leakage (≤10nA) X7R or C0G dielectric for accuracy.

Does MAX6423US44+ remain functional during deep brownout conditions?

Yes, MAX6423US44+ guarantees valid RESET output down to VCC = 1.0V, per Absolute Maximum Ratings and Electrical Characteristics tables. Below 1V, sink capability degrades, but for most µPs that cease operation above 1V, this ensures reset remains asserted until power fully collapses - critical for preventing corrupted memory writes or undefined state transitions.

Is MAX6423US44+ pin-compatible with other parts in the MAX642x family?

MAX6423US44+ shares the same 4-pin SOT143 pinout with MAX6421USxx+ and MAX6422USxx+ variants, differing only in reset threshold and output polarity. However, it is not pin-compatible with 5-pin SOT23 variants (e.g., MAX6425UKxx+) or SC70-packaged versions (MAX6423XSxx+), which have different pin 1 assignments and thermal characteristics - verify package code (U4+1 vs. X4+1) before substitution.