Analog Devices Inc./Maxim Integrated MAX6865UK21D5L+T

Overview

The MAX6865UK21D5L+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 output when VCC drops below 2.100V (±2.5%), MR is pulled low, or the watchdog expires after 209s (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 MAX6865UK21D5L+T datasheet, MAX6865UK21D5L+T pinout, MAX6865UK21D5L+T application, or MAX6865UK21D5L+T equivalent, key selection criteria include its factory-trimmed 2.100V reset threshold, 450ms minimum reset timeout (D5), 209s watchdog period (L suffix), active-high push-pull RESET output, and compatibility with battery-powered medical and portable electronics requiring guaranteed reset assertion below 1.1V.

Technical Context

The MAX6865UK21D5L+T implements a dual-trigger reset architecture: one path monitors VCC against a precision bandgap-derived 2.100V threshold with 0.5% hysteresis, while a second path responds to MR assertion or WDI inactivity exceeding 209s (typ). Its internal watchdog timer clears on any WDI edge (rising or falling) and remains disabled during reset assertion.

This device uses BiCMOS process technology to achieve 170nA typical supply current and operates across –40°C to +85°C. The active-high push-pull RESET output delivers VOH ≥ 0.8×VCC (ISOURCE = 500µA) and VOL ≤ 0.3V (ISINK = 1.2mA), with guaranteed validity down to VCC = 1.1V - critical for brownout recovery in low-voltage microcontroller systems.

Key Specifications

Pinout & Package

MAX6865UK21D5L+T is housed in a RoHS-compliant, lead-free 5-pin SOT23-5 package (2.9mm × 1.6mm × 1.1mm), optimized 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 MAX6864UK21D5S+T and TPS3836K21DBVR, the MAX6865UK21D5L+T uniquely balances ultra-low 170nA current, integrated 209s watchdog, and active-high push-pull RESET - making it optimal for battery-critical medical and portable devices where long watchdog intervals and zero external components are mandatory.

Availability

MAX6865UK21D5L+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 production lifecycles.

Supply support for MAX6865UK21D5L+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 MAX68xx family was designed specifically for nanopower microprocessor supervision in battery-operated medical and portable electronics, emphasizing ultra-low ICC, guaranteed low-VCC reset validity, and integrated watchdog functionality without external components.

FAQ

What is the exact reset threshold voltage of the MAX6865UK21D5L+T?

The MAX6865UK21D5L+T has a factory-trimmed reset threshold of 2.100V with ±2.5% tolerance over –40°C to +85°C. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "21" corresponds to 2.100V. The device guarantees reset assertion when VCC falls below this threshold and maintains RESET assertion for 450ms (min) after VCC rises above it.

Does the MAX6865UK21D5L+T include a watchdog timer, and what is its timeout period?

Yes, the MAX6865UK21D5L+T includes a watchdog timer with a typical timeout period of 209s, indicated by the "L" suffix in the part number. This long interval is intended for applications where firmware performs infrequent critical operations - such as periodic sensor calibration - and requires supervision without frequent refresh overhead. The timer resets on any rising or falling edge at the WDI pin.

What type of RESET output does the MAX6865UK21D5L+T provide, and how is it interfaced?

The MAX6865UK21D5L+T provides an active-high push-pull RESET output (Pin 1), eliminating the need for an external pullup resistor. It sources ≥0.8×VCC at 500µA and sinks ≤0.3V at 1.2mA, enabling direct connection to standard µP reset inputs across 1.8V–5.5V logic families. This configuration is confirmed in the MAX6865 pin description and functional diagram.

What is the minimum supply voltage at which the MAX6865UK21D5L+T guarantees valid RESET operation?

The MAX6865UK21D5L+T guarantees valid RESET assertion down to VCC = +1.1V, as explicitly stated in the Electrical Characteristics table and Applications Information section. This ensures reliable brownout detection and reset hold-down even as battery voltage decays below typical logic thresholds - a critical feature for medical and portable equipment operating near end-of-life battery voltage.

How does the manual reset (MR) input function on the MAX6865UK21D5L+T?

The MR input (Pin 3) is active-low with an internal 10kΩ pullup to VCC. Driving MR low initiates a reset that remains asserted for the full 450ms timeout period after MR returns high. It accepts CMOS logic levels or direct connection to a momentary switch tied to GND. No external debounce components are needed, and MR remains functional across the full –40°C to +85°C temperature range.