Analog Devices Inc./Maxim Integrated MAX6865UK38D3S+T

Overview

The MAX6865UK38D3S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 3.800V reset threshold (±2.5%), 300ms minimum reset timeout, and integrated watchdog timer with 3.3s typical timeout. It monitors VCC, responds to manual reset (MR), and asserts active-high push-pull RESET during brownout, power-up, or watchdog expiration - used in battery-powered medical and portable electronics.

For engineers reviewing the MAX6865UK38D3S+T datasheet, MAX6865UK38D3S+T pinout, MAX6865UK38D3S+T application, or MAX6865UK38D3S+T equivalent, key selection criteria include its 3.8V threshold accuracy over -40°C to +85°C, guaranteed RESET validity down to VCC = 1.1V, 250ns MR-to-reset delay, and compatibility with noisy low-power systems requiring glitch immunity and no external components.

Technical Context

This device implements a precision bandgap-based voltage monitor with 0.5% hysteresis, a digital timeout counter for reset assertion, and an edge-triggered watchdog timer that clears on any WDI transition. Its internal 10kΩ MR pullup and CMOS-compatible inputs enable direct interfacing with µP GPIOs without external biasing.

The MAX6865UK38D3S+T uses BiCMOS process technology to achieve nanoscale leakage control, supporting operation from 1.2V to 5.5V supply while maintaining reset assertion integrity even as VCC falls below 1.1V - critical for fail-safe behavior in deep-brownout conditions.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount, 2.9mm × 1.6mm footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6865UK38D3S+T, the MAX6864UK38D3S+T offers identical supervision parameters but inverted reset polarity, while TPS3836K33DBVR lacks watchdog functionality and consumes significantly more current - making MAX6865UK38D3S+T the sole choice for low-power, safety-critical firmware monitoring.

Availability

MAX6865UK38D3S+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, smart wearables, and industrial handheld terminals requiring stable component supply across extended product lifecycles.

Supply support for MAX6865UK38D3S+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 in demanding industrial, medical, and portable systems.

The MAX6865UK38D3S+T belongs to the nanopower µP supervisory family, engineered specifically for ultra-low-power battery-operated equipment requiring guaranteed reset behavior, watchdog supervision, and minimal PCB footprint.

FAQ

What is the exact reset threshold voltage of the MAX6865UK38D3S+T?

The MAX6865UK38D3S+T has a factory-trimmed reset threshold of 3.800V with ±2.5% tolerance over -40°C to +85°C, corresponding to the "38" suffix in the part number per Maxim's Threshold Suffix Guide. This value is measured at VCC falling and includes 0.5% hysteresis to prevent chatter near the trip point. The MAX6865UK38D3S+T maintains this accuracy without external calibration.

Does the MAX6865UK38D3S+T require external components for basic operation?

No, the MAX6865UK38D3S+T operates autonomously with no external components required. Its internal 10kΩ MR pullup, precision voltage reference, and digital timeout counter eliminate the need for RC networks, pullup resistors, or trimming elements. A 0.1µF bypass capacitor on VCC is recommended for noise immunity but is not mandatory for functional operation of the MAX6865UK38D3S+T.

How does the watchdog timer in the MAX6865UK38D3S+T function?

The MAX6865UK38D3S+T watchdog timer expires if the WDI input remains static (high or low) for longer than 3.3s (typical). It clears on any rising or falling edge at WDI and resumes counting immediately after RESET deasserts. The timer does not run while RESET is asserted. This behavior ensures the MAX6865UK38D3S+T detects firmware hangs without requiring periodic high-low toggling - a key reliability feature for safety-critical firmware.

What is the minimum VCC voltage at which MAX6865UK38D3S+T guarantees valid RESET output?

The MAX6865UK38D3S+T guarantees valid RESET output down to VCC = 1.1V, as specified in the Electrical Characteristics table. Below this voltage, the internal circuitry may not sustain proper logic levels, but the device continues asserting RESET until VCC falls further. This specification ensures deterministic behavior during deep brownout - a critical requirement for medical devices using the MAX6865UK38D3S+T.

Is the MAX6865UK38D3S+T pin-compatible with other devices in the MAX68xx family?

The MAX6865UK38D3S+T shares the same 5-pin SOT23-5 package and pinout as MAX6864/MAX6866/MAX6867/MAX6869 variants, but differs from MAX6861–MAX6863 (which use CT pin) and MAX6854–MAX6856 (which lack WDI). Pin compatibility is confirmed for all MAX686x devices with active-high push-pull RESET output - enabling drop-in replacement within that subgroup, provided the watchdog and threshold requirements match the MAX6865UK38D3S+T.