Analog Devices Inc./Maxim Integrated MAX6865UK38D4S+T

Overview

The MAX6865UK38D4S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, combining voltage monitoring (3.705V ±2.5% reset threshold), manual reset input (MR), and watchdog timer (209s typical timeout) with 170nA typical supply current. It asserts an active-high push-pull RESET output during VCC brownout, MR assertion, or watchdog timeout, ensuring reliable boot-up and fault recovery in ultra-low-power systems.

For engineers reviewing the MAX6865UK38D4S+T datasheet, MAX6865UK38D4S+T pinout, MAX6865UK38D4S+T application, or MAX6865UK38D4S+T equivalent, this device is selected for battery-powered medical monitors, portable instrumentation, and embedded systems requiring guaranteed reset validity down to VCC = +1.1V, immunity to short VCC transients, and minimal quiescent current.

Technical Context

This device implements a precision bandgap-based voltage monitor with 2.5% threshold tolerance and 0.5% hysteresis, coupled with a digitally controlled watchdog timer that clears on any WDI edge and expires if WDI remains static beyond 209s (typ). The internal 10kΩ MR pullup and glitch rejection (200ns) support robust manual reset handling without external components.

The active-high push-pull RESET output delivers VOH ≥ 0.8×VCC at ISOURCE = 500µA (VCC ≥ 2.38V) and VOL ≤ 0.3V at ISINK = 1.2mA (VCC ≥ 2.38V), enabling direct interfacing with 1.8V–5.5V µP reset inputs. Reset timeout is factory-fixed at 1200ms (D4 option), with guaranteed assertion duration independent of temperature drift.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5 (lead-free, +T suffix), footprint-compatible with industry-standard 5-pin SOT23 layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK38D4S+T and TPS3837K33DBVR, the MAX6865UK38D4S+T uniquely delivers active-high RESET, nanopower operation, and integrated watchdog in one 5-pin SOT23 - eliminating design compromises between reset polarity, current budget, and fault coverage.

Availability

MAX6865UK38D4S+T is available at Aetrix Electronics and suitable for glucose monitors, patient vital sign loggers, portable gas detectors, and handheld industrial multimeters requiring stable component supply across automotive-grade temperature range (-40°C to +85°C).

Supply support for MAX6865UK38D4S+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 power, sensing, and interface applications, with emphasis on reliability and low-power innovation.

The MAX6854–MAX6869 family targets ultra-low-power microprocessor supervision in portable medical, industrial, and consumer equipment, prioritizing nanoscale current draw, wide VCC range, and integrated watchdog safety.

FAQ

What is the exact reset threshold voltage of the MAX6865UK38D4S+T?

The MAX6865UK38D4S+T has a factory-trimmed reset threshold of 3.705V with ±2.5% tolerance over -40°C to +85°C. This value is defined by the '38' suffix per Table 2 in the datasheet and is measured at VCC falling. The device guarantees reset assertion down to VCC = +1.1V regardless of threshold drift.

Does the MAX6865UK38D4S+T require external components for basic operation?

No, the MAX6865UK38D4S+T operates autonomously with zero external components. Its internal 10kΩ MR pullup, precision voltage reference, and timing circuitry eliminate the need for external resistors, capacitors, or diodes. Only a 0.1µF VCC bypass capacitor is recommended for noise immunity - not strictly required but strongly advised.

How does the watchdog timer in the MAX6865UK38D4S+T function?

The MAX6865UK38D4S+T watchdog timer expires after 209s (typical) if the WDI pin remains static (no rising or falling edge). Each WDI transition resets the timer. The timer is also cleared during RESET assertion or MR activation. Pulse width detection is guaranteed down to 150ns, supporting high-frequency firmware heartbeat signals.

What is the reset timeout period for the MAX6865UK38D4S+T?

The MAX6865UK38D4S+T has a fixed reset timeout period of 1200ms minimum (D4 option), as indicated by the 'D4' in its part number. This duration begins when VCC rises above the 3.705V threshold or MR is deasserted, and ensures the microprocessor completes power-up initialization before RESET deasserts.

Is the MAX6865UK38D4S+T pin-compatible with other devices in the MAX68xx family?

The MAX6865UK38D4S+T shares the same 5-pin SOT23-5 package and pinout (RESET, GND, MR, WDI, VCC) with MAX6864/MAX6866–MAX6869 variants. However, it is not pin-compatible with MAX6854–MAX6863 or MAX6858/MAX6860 due to differing pin functions (e.g., CT or I.C. pins). Always verify pin mapping against the specific variant's pin description.