Analog Devices Inc./Maxim Integrated MAX6865UK40D1S+T

Overview

The MAX6865UK40D1S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, integrating voltage monitoring, manual reset input (MR), and watchdog timer (WDI) functions. It asserts an active-low push-pull RESET output when VCC drops below 4.000V (±2.5%), MR is pulled low, or the watchdog expires after 3.3s (typ). Designed for ultra-low-power systems, it draws only 170nA (typ) at 2.5V and guarantees valid reset down to VCC = 1.1V.

For engineers reviewing the MAX6865UK40D1S+T datasheet, MAX6865UK40D1S+T pinout, MAX6865UK40D1S+T application, or MAX6865UK40D1S+T equivalent, this device supports critical power sequencing, brownout protection, and software fault recovery in battery-constrained medical and portable electronics where supply current, reset accuracy, and watchdog timeout stability are design-critical.

Technical Context

The MAX6865UK40D1S+T implements a precision bandgap-based voltage monitor with factory-trimmed 4.000V reset threshold (±2.5%) and 0.5% hysteresis, ensuring reliable detection of VCC brownouts across -40°C to +85°C. Its watchdog timer monitors WDI transitions and triggers reset if no edge occurs within 3.3s (typ), with guaranteed immunity to pulses shorter than 150ns.

This device uses a BiCMOS process (2848 transistors) and features internal 10kΩ MR pullup, glitch rejection on MR (200ns), and MR-to-reset delay of 250ns. The push-pull active-high RESET output drives high to VCC (≥0.8×VCC at 500µA source) and remains asserted for 10ms (min) after VCC recovery and MR deassertion.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount, 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 MAX6864UK40D1S+T, the MAX6865UK40D1S+T provides active-high RESET compatibility without external inverters; versus TPS3836K33DBVR, it delivers 20× lower supply current and integrated watchdog-critical for battery longevity and firmware reliability in medical wearables.

Availability

MAX6865UK40D1S+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, smart wearables, and industrial handheld terminals requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.

Supply support for MAX6865UK40D1S+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 ultra-low-power microprocessor supervision in battery-operated medical and portable electronics, emphasizing nanoscale ICC, precision reset thresholds, and integrated watchdog functionality.

FAQ

What is the exact reset threshold voltage of the MAX6865UK40D1S+T?

The MAX6865UK40D1S+T has a factory-trimmed reset threshold of 4.000V with ±2.5% tolerance over -40°C to +85°C, as defined by the "40" suffix in its 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 MAX6865UK40D1S+T guarantees valid reset assertion down to VCC = 1.1V, making it suitable for deep-brownout scenarios in battery-powered systems.

Does the MAX6865UK40D1S+T include a watchdog timer, and what is its timeout period?

Yes, the MAX6865UK40D1S+T includes a watchdog timer with a typical timeout period of 3.3s, indicated by the "S" suffix in its part number. The timer resets on any rising or falling edge at the WDI pin and triggers a reset if no transition occurs within that window. It is guaranteed to detect pulses as short as 150ns and remains disabled if WDI is left floating. The MAX6865UK40D1S+T uses this feature to recover from firmware hangs without requiring host µP intervention.

What is the reset timeout duration for the MAX6865UK40D1S+T, and how is it configured?

The MAX6865UK40D1S+T has a fixed minimum reset timeout of 10ms, specified by the "D1" suffix. This duration begins after VCC rises above the 4.000V threshold and MR is deasserted, ensuring the µP receives a sufficiently long reset pulse for complete initialization. Unlike variants with CT pins (e.g., MAX6861–MAX6863), the MAX6865UK40D1S+T does not support pin-selectable timeout; the 10ms value is factory-programmed and unchangeable in-circuit.

What type of reset output does the MAX6865UK40D1S+T provide, and how is it connected?

The MAX6865UK40D1S+T provides an active-high push-pull RESET output on Pin 1. It drives high to VCC (≥0.8×VCC at 500µA source) when asserted and actively pulls low when deasserted-no external pullup resistor is required. This output is referenced to VCC and interfaces directly with µPs having active-high reset inputs. The MAX6865UK40D1S+T's push-pull architecture eliminates leakage concerns associated with open-drain alternatives and ensures fast, rail-to-rail switching.

How does the manual reset (MR) input function on the MAX6865UK40D1S+T?

The MR input on the MAX6865UK40D1S+T is an active-low signal with internal 10kΩ pullup to VCC. Driving MR ≤0.3×VCC initiates a reset that persists for the full 10ms timeout after MR returns high. It rejects glitches <200ns and exhibits 250ns propagation delay from MR low-to-RESET high. If unused, MR may be left floating or tied to VCC; no external components are needed. The MAX6865UK40D1S+T thus simplifies hardware reset implementation in space-constrained portable designs.