Analog Devices Inc./Maxim Integrated MAX6865UK42D4S+T

Overview

The MAX6865UK42D4S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, combining voltage monitoring, manual reset input (MR), and watchdog timer (WDI) functionality. It asserts an active-high push-pull RESET when VCC drops below 4.200V (±2.5%), MR is pulled low, or WDI fails to toggle within 3.3s (typ). Designed for ultra-low-power systems, it draws only 170nA (typ) at 2.5V and guarantees valid reset operation down to VCC = 1.1V.

For engineers reviewing the MAX6865UK42D4S+T datasheet, MAX6865UK42D4S+T pinout, MAX6865UK42D4S+T application, or MAX6865UK42D4S+T equivalent, this device serves as a critical power-on reset and software fault recovery element in battery-constrained embedded systems where supply stability, transient immunity, and deterministic timeout behavior are essential.

Technical Context

The MAX6865UK42D4S+T implements a precision bandgap-based voltage monitor with factory-trimmed 4.200V reset threshold (±2.5%) and 0.5% hysteresis, ensuring reliable brownout detection across -40°C to +85°C. Its integrated watchdog timer monitors WDI transitions and expires after 3.3s (typ) if no edge occurs - cleared on any rising/falling edge, MR assertion, or RESET assertion.

This variant features an active-high push-pull RESET output referenced to VCC, a 10kΩ internal MR pullup, and a fixed 1200ms (min) reset timeout period (D4 option). It requires no external components and operates from 1.2V to 5.5V, maintaining guaranteed reset validity down to VCC = 1.1V.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount. Compact footprint (2.9mm × 1.6mm × 1.1mm) suitable for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6865UK42D4S+T, MAX6864UK42D4S+T offers identical supervision accuracy and ultra-low power but requires redesign of reset signal polarity handling, while TPS3836K33DBVR trades watchdog capability and nanopower operation for lower unit cost in simpler systems.

Availability

MAX6865UK42D4S+T is available at Aetrix Electronics and suitable for portable medical devices, industrial wireless sensors, smart wearables, and battery-powered instrumentation requiring stable component supply with long-term lifecycle support.

Supply support for MAX6865UK42D4S+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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, medical, and communications applications.

The MAX6854–MAX6869 family was designed specifically for nanopower microprocessor supervision in battery-critical systems, integrating voltage monitoring, manual reset, and watchdog functions into minimal-area SOT23 packages.

FAQ

What is the exact reset threshold voltage of the MAX6865UK42D4S+T?

The MAX6865UK42D4S+T has a factory-trimmed reset threshold voltage of 4.200V with ±2.5% tolerance over temperature (-40°C to +85°C) and 0.5% hysteresis. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "42" corresponds to 4.200V nominal. The MAX6865UK42D4S+T uses this precise threshold to reliably detect brownout conditions in 3.3V and 5V systems.

Does the MAX6865UK42D4S+T require external components for basic operation?

No, the MAX6865UK42D4S+T requires no external components for core supervision functionality. Its internal 10kΩ MR pullup, precision voltage reference, and fixed timing elements eliminate the need for resistors, capacitors, or trimming networks. A 0.1µF bypass capacitor on VCC is recommended for noise immunity but not strictly required for functional operation. The MAX6865UK42D4S+T achieves full supervision with zero external parts.

What is the watchdog timeout behavior of the MAX6865UK42D4S+T?

The MAX6865UK42D4S+T features a watchdog timer with a typical timeout period of 3.3s (suffix "S"), as specified in Table 3. The timer resets on any rising or falling edge at WDI, MR assertion, or RESET assertion. It does not count while RESET is asserted. The MAX6865UK42D4S+T guarantees detection of firmware hangs exceeding this interval, triggering a full reset sequence with 1200ms timeout.

How does the MAX6865UK42D4S+T ensure reset validity at low supply voltages?

The MAX6865UK42D4S+T guarantees RESET output validity down to VCC = 1.1V, meaning the active-high push-pull output remains logically defined and capable of driving a µP reset pin even during severe brownout. This specification ensures deterministic system halt before internal logic becomes unreliable. The MAX6865UK42D4S+T meets this requirement across its full operating temperature range without external circuitry.

Is the MAX6865UK42D4S+T pin-compatible with other devices in the MAX68xx family?

The MAX6865UK42D4S+T shares the same 5-pin SOT23-5 pinout as all MAX6854–MAX6869 variants, including identical VCC, GND, MR, WDI, and RESET assignments. However, output polarity differs: MAX6865UK42D4S+T provides active-high push-pull RESET, whereas MAX6864UK42D4S+T provides active-low. Thus, while physically pin-compatible, electrical interface compatibility depends on the target µP's reset input polarity requirement.