Analog Devices Inc./Maxim Integrated MAX6865UK26D4S+T

Overview

The MAX6865UK26D4S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 2.625V reset threshold (suffix '26'), 1200ms minimum reset timeout (suffix 'D4'), and watchdog timer with 3.3s typical timeout (suffix 'S'). It monitors VCC, responds to manual reset (MR), and triggers reset on watchdog expiration - designed for battery-critical portable medical and handheld devices.

For engineers reviewing the MAX6865UK26D4S+T datasheet, MAX6865UK26D4S+T pinout, MAX6865UK26D4S+T application, or MAX6865UK26D4S+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 1.2V–5.5V supply rails in space-constrained designs.

Technical Context

This device implements a precision voltage monitor with ±2.5% threshold accuracy over –40°C to +85°C, integrated watchdog timer with 3.3s typical timeout (S-suffix), and MR input with 10kΩ internal pullup and 250ns MR-to-reset delay. The reset assertion logic combines VCC undervoltage detection, MR low assertion, and WDI timeout - all triggering a single push-pull active-high RESET output.

It uses BiCMOS process (2848 transistors) and requires no external components. The watchdog clears on any WDI edge (rising/falling), MR assertion, or RESET assertion, and tolerates WDI pulses as short as 150ns. Reset deassertion occurs only after VCC exceeds threshold *and* the full 1200ms timeout elapses post-recovery.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5 (lead-free, +T suffix), 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 MAX6865UK26D4S+T, MAX6864UK26D4S+T offers identical supervision parameters but inverted RESET polarity, requiring logic-level adaptation; TPS3836K26DBVR provides basic reset only, with 7× higher supply current and no watchdog - limiting use to non-critical, non-battery-powered applications.

Availability

MAX6865UK26D4S+T is available at Aetrix Electronics and suitable for portable medical devices, industrial handhelds, and smart energy metering systems requiring stable component supply, long-term lifecycle support, and lead-free compliance.

Supply support for MAX6865UK26D4S+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 communications systems.

The MAX6865UK26D4S+T belongs to the MAX68xx nanopower supervisory family, engineered specifically for ultra-low-power, space-constrained battery-operated devices requiring simultaneous voltage monitoring, manual reset, and watchdog timer functionality.

FAQ

What is the exact reset threshold voltage of the MAX6865UK26D4S+T?

The MAX6865UK26D4S+T has a factory-trimmed reset threshold voltage of 2.625V, with ±2.5% tolerance over the full –40°C to +85°C operating temperature range. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix '26' corresponds to VTH = 2.625V (min 2.559V, typ 2.625V, max 2.691V). The MAX6865UK26D4S+T guarantees this threshold without external calibration.

Does the MAX6865UK26D4S+T support active-high or active-low reset output?

The MAX6865UK26D4S+T features a push-pull active-high RESET output, as confirmed in the Pin Description section for MAX6865 (page 8) and Selector Guide (page 16). When asserted, RESET goes high; when deasserted, it returns low. This matches MCUs with active-high reset inputs and eliminates the need for an external pullup resistor - a key differentiator from open-drain or active-low variants like MAX6864UK26D4S+T.

What is the watchdog timeout period for the MAX6865UK26D4S+T?

The MAX6865UK26D4S+T has a watchdog timeout period of 3.3s (typical), corresponding to suffix 'S' per Table 3 (Watchdog Timeout). The datasheet specifies min/typ/max as 1.5s/3.3s/7.75s. This timeout is independent of the 1200ms reset timeout (D4) and is cleared on any WDI edge, MR assertion, or RESET assertion - ensuring robust firmware hang detection without requiring precise timing margins.

Can the MAX6865UK26D4S+T operate with supply voltages below 1.8V?

Yes, the MAX6865UK26D4S+T operates from 1.2V to 5.5V, and its reset function remains guaranteed down to VCC = +1.1V, as stated in the Electrical Characteristics table (page 2) and Detailed Description (page 11). At 1.2V, supply current is 190nA (typ), and RESET output retains valid logic levels - making it suitable for single-cell alkaline or lithium primary battery systems where voltage sags below 1.8V during discharge.

Is the MAX6865UK26D4S+T pin-compatible with other MAX68xx devices?

The MAX6865UK26D4S+T uses the standard 5-pin SOT23-5 package and shares identical pinout with MAX6864/MAX6866 (pin 1 = RESET, pin 2 = GND, pin 3 = MR, pin 4 = WDI, pin 5 = VCC), as shown in the Pin Configurations diagram (page 15). However, it is not pin-compatible with MAX6861–MAX6863 (which use CT instead of WDI) or MAX6854–MAX6856 (which lack WDI). Board reuse is possible only within the MAX6864/MAX6865/MAX6866 group.