Analog Devices Inc./Maxim Integrated MAX6865UK21D2S+T

Overview

The MAX6865UK21D2S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 2.100V reset threshold (±2.5%), 40ms 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 MAX6865UK21D2S+T datasheet, MAX6865UK21D2S+T pinout, MAX6865UK21D2S+T application, or MAX6865UK21D2S+T equivalent, key selection criteria include 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

The MAX6865UK21D2S+T integrates voltage monitoring, manual reset assertion, and watchdog timer functionality in a single BiCMOS IC. Its reset logic asserts RESET high when VCC falls below 2.100V, MR is pulled low, or WDI remains static beyond 3.3s - with reset held for ≥40ms after recovery.

It features internal 10kΩ MR pullup, 150ns WDI pulse detection, and operates across -40°C to +85°C. The push-pull active-high RESET output is referenced to VCC and sinks ≤0.3V at 1.2mA, enabling direct interface with µP reset inputs without external components.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount. Compact footprint (2.9mm × 1.6mm × 1.1mm) 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 MAX6865UK21D2S+T, MAX6326UR21+T trades ultra-low power and watchdog capability for simpler architecture and longer timeout, while TPS3836K21DBVR offers lower cost but omits critical safety features and increases system-level current draw by nearly 10×.

Availability

MAX6865UK21D2S+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered IoT sensors, wearable fitness trackers, and industrial handheld terminals requiring stable component supply and long-term lifecycle support.

Supply support for MAX6865UK21D2S+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, mixed-signal, and power-management ICs for demanding industrial, medical, and communications applications.

The MAX6854–MAX6869 family delivers nanopower supervisory functions targeting ultra-low-power portable electronics where battery longevity and autonomous fault recovery are critical design requirements.

FAQ

What is the exact reset threshold voltage of the MAX6865UK21D2S+T?

The MAX6865UK21D2S+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 nominal. The device guarantees reset assertion when VCC falls below this threshold and maintains reset for ≥40ms after VCC exceeds it.

Does the MAX6865UK21D2S+T support active-high or active-low reset output?

The MAX6865UK21D2S+T provides a push-pull active-high RESET output (pin 1), as confirmed in the MAX6864/MAX6865/MAX6866 Pin Description section. When asserted, RESET goes high; when deasserted, it returns low. This matches the MAX6865 variant designation in the Selector Guide and eliminates need for external level-shifting circuitry.

What is the watchdog timeout period for the MAX6865UK21D2S+T?

The MAX6865UK21D2S+T features a watchdog timeout period of 3.3s typical (minimum 1.5s, maximum 7.75s), indicated by the "S" suffix in the part number. This is verified in Table 3 (Watchdog Timeout) and applies to the WDI input: if no edge is detected for >3.3s, the internal timer expires and triggers a reset for the D2 40ms timeout period.

Can the MAX6865UK21D2S+T operate down to 1.2V supply voltage?

Yes, the MAX6865UK21D2S+T is fully specified to operate from VCC = 1.2V to 5.5V, with guaranteed reset functionality down to VCC = +1.1V. Electrical Characteristics table confirms supply voltage range (MIN = 1.2V, MAX = 5.5V) and reset validity to 1.1V, making it suitable for single-cell LiFePO₄ or alkaline battery systems.

Is the MAX6865UK21D2S+T pin-compatible with other devices in the MAX68xx family?

The MAX6865UK21D2S+T uses the standard 5-pin SOT23-5 package with identical pinout to MAX6864/MAX6866 (RESET–GND–MR–WDI–VCC), but differs from MAX6861–MAX6863 (which use CT instead of WDI) and MAX6854–MAX6856 (which lack WDI). Pin compatibility is limited to the MAX6864/MAX6866 variants; substitution with other families requires PCB revision.