Analog Devices Inc./Maxim Integrated MAX6425UK40-T

Overview

MAX6425UK40-T from Maxim Integrated is a low-power microprocessor reset supervisor IC with open-drain active-low RESET output, 4.0V factory-trimmed reset threshold (±2.5% over -40°C to +125°C), capacitor-adjustable reset timeout (275µs base + 2.73s/F × CSRT), and guaranteed operation down to VCC = 1.0V. It monitors system supply in battery-powered controllers and portable equipment requiring precise brownout detection and flexible reset timing.

For engineers reviewing the MAX6425UK40-T datasheet, MAX6425UK40-T pinout, MAX6425UK40-T application, or MAX6425UK40-T equivalent, this page delivers verified electrical parameters, SOT23-5 package mapping, open-drain interface design guidance, and validated alternative parts for voltage-monitoring reset circuits in automotive-qualified and industrial embedded systems.

Technical Context

The MAX6425UK40-T implements a precision bandgap-based voltage detector with 4.0V nominal reset threshold, laser-trimmed to ±2.5% accuracy across -40°C to +125°C. Its internal 240nA current source charges an external capacitor on the SRT pin to generate a programmable reset timeout period.

It features an open-drain RESET output capable of sinking ≥500µA at VCC ≥ 2.7V (VOL ≤ 0.3V) and leakage <1.0µA when deasserted. The device asserts reset on VCC fall below threshold and holds it for the full timeout after VCC rises above threshold, with immunity to transients ≤50µs at 100mV overdrive.

Key Specifications

Pinout & Package

MAX6425UK40-T is housed in a 5-pin SOT23-5 package (outline 21-0057), RoHS-compliant, with 0.95mm pitch and thermal pad omitted. Pin 1 is marked by a dot or beveled edge.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage-monitoring reset applications.

Compared with MAX6425UK40-T, NCP302LSN40T1G offers slightly lower IQ but sacrifices timeout adjustability, while TLV809K40DBZR reduces size and power further but eliminates programmability entirely - MAX6425UK40-T uniquely balances precision, flexibility, and industrial temperature range in a single 5-pin solution.

Availability

MAX6425UK40-T is available at Aetrix Electronics and suitable for portable medical monitors, battery-powered industrial sensors, automotive body control modules, and industrial PLC I/O subsystems requiring stable component supply across extended temperature and long product lifecycles.

Supply support for MAX6425UK40-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 industrial, automotive, communications, and computing markets.

The MAX6421–MAX6426 family delivers low-power, capacitor-programmable reset supervisors targeting battery-critical and thermally demanding applications where accuracy, flexibility, and reliability are essential.

FAQ

What is the exact reset threshold voltage of MAX6425UK40-T and how accurate is it?

The MAX6425UK40-T has a factory-trimmed nominal reset threshold of 4.00V, specified with ±2.5% tolerance over the full operating temperature range (-40°C to +125°C). This accuracy is laser-trimmed at wafer test and does not require external components. At +25°C, typical variation is tighter (±1.5%), and the device guarantees valid reset assertion down to VCC = 1.0V, making MAX6425UK40-T suitable for applications where rail stability must be enforced across extreme environmental conditions.

How do I calculate the external capacitor value for a desired reset timeout on MAX6425UK40-T?

Use the formula CSRT = (tRP − 275µs) / 2.73×10⁶, where tRP is the desired timeout in seconds and CSRT is in farads. For example, a 5ms timeout requires CSRT = (0.005 − 0.000275) / 2.73×10⁶ ≈ 1730pF. MAX6425UK40-T's internal 240nA ramp current charges this capacitor to 0.65V to deassert reset. Use low-leakage ceramic capacitors (≤10nA) and keep SRT traces short and noise-isolated to maintain timing accuracy.

Can MAX6425UK40-T drive a 1.8V microcontroller reset input?

Yes - MAX6425UK40-T's open-drain RESET output is fully compatible with 1.8V logic. Connect a pullup resistor (e.g., 10kΩ) from the RESET pin to the 1.8V supply. When asserted, MAX6425UK40-T sinks ≥500µA at VCC ≥ 2.7V (VOL ≤ 0.3V), ensuring a solid logic low at the µP input. When deasserted, the pullup establishes a clean 1.8V high. This level-shifting capability is intrinsic to MAX6425UK40-T's open-drain architecture and requires no additional components.

Does MAX6425UK40-T provide immunity to power supply transients, and what is the specification?

Yes - MAX6425UK40-T is specifically designed to reject short-duration negative-going VCC transients. Per the datasheet, it will not assert reset for transients ≤50µs in duration when the overdrive (magnitude below threshold) is 100mV. The rejection window tightens as overdrive increases (e.g., 200mV overdrive limits allowable pulse width to ~15µs). This behavior is inherent to the internal ramp-based timeout mechanism and is verified across temperature, making MAX6425UK40-T robust in electrically noisy environments like automotive or motor-control systems.

What is the function of the N.C. pin (Pin 3) on MAX6425UK40-T, and how should it be handled?

Pin 3 of MAX6425UK40-T is Not Connected internally and serves no electrical function. Per Maxim's layout guidance, it may be tied to GND on the PCB to improve mechanical stability and reduce potential antenna effects - but this connection has no impact on device operation or timing. Leaving Pin 3 floating is also acceptable. Unlike functional pins, Pin 3 does not affect MAX6425UK40-T's reset threshold, timeout, or output behavior; its handling is purely a board-level mechanical or EMI consideration.