Analog Devices Inc./Maxim Integrated MAX6865UK40D4S+T

Overview

The MAX6865UK40D4S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 4.000V reset threshold (±2.5%), 1200ms minimum reset timeout, manual reset input (MR), and watchdog timer with 3.3s typical timeout. It monitors VCC in battery-powered portable electronics to ensure reliable µP initialization during power-up, brownout, or software lockup.

For engineers reviewing the MAX6865UK40D4S+T datasheet, MAX6865UK40D4S+T pinout, MAX6865UK40D4S+T application, or MAX6865UK40D4S+T equivalent, key selection criteria include its guaranteed reset validity down to VCC = +1.1V, immunity to short VCC transients (<40µs at 100mV overdrive), push-pull active-high RESET output, and compatibility with noisy low-power systems requiring minimal quiescent current.

Technical Context

This device integrates three core functions: precision voltage monitoring with hysteresis (0.5% of VTH), a glitch-immune manual reset input with 1µs minimum pulse width and 200ns noise rejection, and a watchdog timer that clears on any WDI edge and expires if WDI remains static beyond 3.3s (typ). The internal 10kΩ MR pullup eliminates external components.

The reset assertion logic combines VCC undervoltage detection, MR assertion, and watchdog timeout - all triggering the same RESET output. After any trigger, RESET remains asserted for the full 1200ms timeout period, independent of subsequent VCC recovery or MR deassertion timing, ensuring µP reset hold time compliance.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount. Compact footprint (2.9mm × 1.6mm) 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 MAX6864UK40D4S+T and TPS3837K33DBVR, the MAX6865UK40D4S+T uniquely delivers active-high RESET, nanopower operation, and integrated watchdog in one SOT23-5 package - essential for space- and energy-constrained portable medical and wearable designs.

Availability

MAX6865UK40D4S+T is available at Aetrix Electronics and suitable for portable medical devices, industrial handheld terminals, wearable fitness trackers, and smart remote controls requiring stable component supply across extended production lifecycles.

Supply support for MAX6865UK40D4S+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 management, sensing, and interface applications in demanding industrial and portable environments.

The MAX6854–MAX6869 family was engineered specifically for ultra-low-power microprocessor supervision in battery-operated equipment, emphasizing nanoscale current consumption, factory-trimmed accuracy, and integrated watchdog reliability.

FAQ

What is the reset threshold voltage of the MAX6865UK40D4S+T?

The MAX6865UK40D4S+T has a factory-trimmed reset threshold of 4.000V with ±2.5% tolerance over temperature. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "40" corresponds to 4.000V nominal. The device guarantees reset assertion when VCC falls below this threshold and maintains reset until VCC exceeds it plus hysteresis (0.5% of VTH).

Does the MAX6865UK40D4S+T require external components for basic operation?

No, the MAX6865UK40D4S+T operates autonomously with no external components required. Its internal 10kΩ MR pullup, factory-trimmed 4.000V threshold, fixed 1200ms reset timeout, and edge-triggered watchdog eliminate need for resistors, capacitors, or trimming networks - simplifying design and reducing BOM count.

How does the watchdog timer in the MAX6865UK40D4S+T function?

The MAX6865UK40D4S+T watchdog timer expires if the WDI pin remains static (high or low) for longer than 3.3s (typical). It clears on any rising or falling edge at WDI and also resets when MR is asserted or RESET is active. The timer does not run while RESET is asserted, ensuring deterministic behavior during fault recovery.

What is the supply current specification of the MAX6865UK40D4S+T under typical conditions?

The MAX6865UK40D4S+T draws 170nA typical supply current at VCC = 1.8V and TA = +25°C, as specified in the Electrical Characteristics table. This ultra-low ICC enables multi-year operation from primary batteries in applications like glucose monitors and wearables, with current increasing only marginally up to 5.5V.

Is the MAX6865UK40D4S+T pin-compatible with other devices in the MAX68xx family?

The MAX6865UK40D4S+T shares the same 5-pin SOT23-5 package and pinout (RESET, GND, MR, WDI, VCC) with MAX6864/MAX6866 variants. However, it is not pin-compatible with MAX6861–MAX6863 (which use CT instead of WDI) or MAX6854–MAX6856 (which lack WDI). Always verify pin function alignment per the specific variant's Pin Description section.