Analog Devices Inc./Maxim Integrated MAX6423US29

Overview

MAX6423US29 from Maxim Integrated is a low-power microprocessor supervisor IC with open-drain active-low reset output, 2.925V ±2.5% factory-trimmed reset threshold, capacitor-adjustable reset timeout (275µs to 5.75ms), and guaranteed operation down to VCC = 1V. It monitors supply voltage in portable and battery-powered systems to prevent erroneous µP startup during brownout or power-up.

For engineers reviewing the MAX6423US29 datasheet, MAX6423US29 pinout, MAX6423US29 application, or MAX6423US29 equivalent, key selection criteria include its 4-pin SOT143 package, 1.6µA typical quiescent current, open-drain RESET compatibility with mixed-voltage µP interfaces, and immunity to sub-50µs VCC transients below 2.925V.

Technical Context

The MAX6423US29 uses a precision 240nA internal ramp current source charging an external capacitor on the SRT pin to generate a programmable reset timeout period; deassertion occurs when the ramp voltage reaches 0.65V. Its reset threshold is laser-trimmed for ±2.5% accuracy over –40°C to +125°C.

As an open-drain supervisor, it requires an external pullup resistor (10kΩ–100kΩ) to any logic supply up to 5.5V, enabling wired-OR reset capability and flexible voltage-level interfacing. It asserts RESET low when VCC falls below 2.925V and holds it low for the full timeout after VCC recovers.

Key Specifications

Pinout & Package

MAX6423US29 is housed in a 4-pin SOT143 package (package code U4+1), with 1.3mm × 1.3mm footprint and 0.95mm height - optimized for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6423US29, MAX6423XS29+T offers identical supervision functionality in a smaller package but with reduced power dissipation margin, while NCP302LSN29T1G trades programmability and open-drain flexibility for lower cost and simpler integration in non-critical timing applications.

Availability

MAX6423US29 is available at Aetrix Electronics and suitable for portable medical sensors, battery-powered telematics units, and industrial edge controllers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6423US29 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 power, sensing, and interface applications in demanding environments.

The MAX6421–MAX6426 family delivers ultra-low-power, capacitor-programmable reset supervision for battery-critical and automotive-grade systems where reliability under voltage stress is mandatory.

FAQ

What is the exact reset threshold voltage of MAX6423US29 and how is it trimmed?

The MAX6423US29 has a nominal reset threshold of 2.925V, with ±2.5% accuracy over –40°C to +125°C. This value is achieved via factory laser trimming of internal resistors during wafer test, ensuring high initial accuracy without requiring external calibration. The '29' suffix in MAX6423US29 directly references the 2.925V threshold per Table 1 in the datasheet.

Can MAX6423US29 operate reliably when VCC drops below 2.0V?

Yes - the MAX6423US29 guarantees valid RESET assertion down to VCC = 1.0V, with supply current dropping to 1.6µA typical at VCC ≤ 2.0V. Its internal comparators and ramp circuit remain functional throughout this range, making it suitable for brownout detection in deeply discharged battery scenarios where other supervisors fail.

How do I calculate the capacitor value needed for a 3.5ms reset timeout with MAX6423US29?

Use the formula CSRT = (tRP – 275µs) / 2.73×10⁶, where tRP is in seconds. For 3.5ms: CSRT = (0.0035 – 0.000275) / 2,730,000 ≈ 1182pF. A standard 1200pF ceramic capacitor (low-leakage, X7R or C0G) yields ~3.53ms timeout, well within the specified 3.00–4.375ms range at 1500pF.

Is MAX6423US29 pin-compatible with any industry-standard supervisors?

No - MAX6423US29 uses a 4-pin SOT143 package with unique pinout (VCC, GND, RESET, SRT). While MAX6340UK29+T shares the same 2.925V threshold and open-drain output, it uses a 5-pin SOT23-5 package and is not pin-compatible. Direct replacement requires PCB layout revision.

Does MAX6423US29 require special layout considerations for the SRT pin?

Yes - the SRT pin connects to a precision 240nA current source. Layout must minimize stray capacitance and leakage: keep SRT traces short (<2mm), avoid routing near digital signals or high-voltage nodes, and exclude conformal coating or flux residue near the pad. Probe contact during validation will distort timeout accuracy.