Analog Devices Inc./Maxim Integrated MAX6865UK42D5S+T

Overview

The MAX6865UK42D5S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, combining voltage monitoring (4.200V reset threshold), manual reset input, and watchdog timer with 3.3s typical timeout. It asserts an active-high push-pull RESET output during VCC brownout, MR assertion, or watchdog expiration, and guarantees valid reset down to VCC = +1.1V. It targets ultra-low-power portable medical and consumer devices requiring reliable power-on reset and firmware crash recovery.

For engineers reviewing the MAX6865UK42D5S+T datasheet, MAX6865UK42D5S+T pinout, MAX6865UK42D5S+T application, or MAX6865UK42D5S+T equivalent, key selection criteria include its 4.200V factory-trimmed threshold, 300ms minimum reset timeout, 3.3s watchdog period, active-high push-pull output, and immunity to sub-40µs VCC transients - all critical for battery-powered glucose monitors and wearables.

Technical Context

This device implements a dual-trigger reset architecture: one path responds to VCC falling below 4.200V ±2.5%, the second to MR low assertion, and the third to WDI inactivity exceeding 3.3s (typ). The internal watchdog timer clears on any WDI edge, MR assertion, or RESET assertion, ensuring robust software execution monitoring.

Its 170nA typical supply current at 1.8V enables multi-year operation on coin cells. The push-pull active-high RESET output drives directly into µP reset inputs without external pullups, and the guaranteed validity to VCC = +1.1V ensures deterministic behavior during deep brownout conditions.

Key Specifications

Pinout & Package

MAX6865UK42D5S+T uses a 5-pin SOT23-5 package (2.9mm × 1.6mm × 1.1mm), lead-free, RoHS-compliant, with thermal pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK42D5S+T and TPS3836K33DBVR, the MAX6865UK42D5S+T uniquely delivers active-high reset drive, ultra-low 170nA current, and integrated 3.3s watchdog - making it optimal for next-gen portable medical devices demanding both energy efficiency and autonomous fault recovery.

Availability

MAX6865UK42D5S+T is available at Aetrix Electronics and suitable for glucose monitors, patient vital sign loggers, smart hearing aids, portable diagnostic ultrasound probes, and wearable ECG recorders requiring stable component supply across long-lifecycle medical programs.

Supply support for MAX6865UK42D5S+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 industrial, medical, and communications applications.

The MAX6854–MAX6869 family was engineered specifically for ultra-low-power portable electronics needing guaranteed reset behavior, manual reset capability, and watchdog-based firmware supervision - with emphasis on battery longevity and reliability in medical-grade devices.

FAQ

What is the exact reset threshold voltage of the MAX6865UK42D5S+T?

The MAX6865UK42D5S+T has a factory-trimmed reset threshold of 4.200V with ±2.5% tolerance over temperature (-40°C to +85°C). This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "42" corresponds to 4.200V nominal. The device guarantees valid reset assertion down to VCC = +1.1V, making it suitable for systems with steep battery discharge curves.

Does the MAX6865UK42D5S+T include a watchdog timer, and what is its timeout period?

Yes, the MAX6865UK42D5S+T includes a watchdog timer with a typical timeout period of 3.3 seconds, denoted by the "S" suffix in the part number. The timer clears on any rising or falling edge at the WDI pin and triggers reset if WDI remains static longer than this period. Minimum and maximum values are 1.5s and 7.75s respectively, ensuring robust fault detection across process and temperature variations.

What type of reset output does the MAX6865UK42D5S+T provide, and how is it configured?

The MAX6865UK42D5S+T provides an active-high push-pull RESET output (pin 1), as confirmed in the MAX6865-specific pin description and Selector Guide. It drives high when reset is asserted and low when deasserted, eliminating the need for external pullup resistors. This configuration directly interfaces with µPs requiring active-high reset inputs, such as many ARM Cortex-M and Renesas RL78 devices.

What is the minimum reset timeout period for the MAX6865UK42D5S+T, and how is it selected?

The MAX6865UK42D5S+T has a fixed minimum reset timeout period of 300ms, indicated by the "D5" suffix in the part number per Table 4 (Reset Timeout Periods). Unlike the MAX6861–MAX6863 variants, this device does not feature pin-selectable timeout - the 300ms duration is factory-programmed and cannot be altered externally. It ensures sufficient time for µP core and peripheral initialization after power-up.

How does the MAX6865UK42D5S+T handle short VCC transients, and what is its immunity limit?

The MAX6865UK42D5S+T is immune to VCC transients ≤40µs in duration when the overdrive is 100mV above the 4.200V threshold, as shown in the "Maximum VCC Transient Duration vs. Reset Threshold Overdrive" graph (Figure MAX684 toc05). This immunity prevents false resets caused by switching noise or load-dump events in portable systems, while maintaining fast response to genuine brownout conditions.