Analog Devices Inc./Maxim Integrated MAX6865UK24D4S+T

Overview

The MAX6865UK24D4S+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) functions. It asserts an active-high push-pull RESET when VCC drops below 2.400V (±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 operation down to VCC = +1.1V.

For engineers reviewing the MAX6865UK24D4S+T datasheet, MAX6865UK24D4S+T pinout, MAX6865UK24D4S+T application, or MAX6865UK24D4S+T equivalent, this device serves as a critical power-on reset and software fault monitor in battery-constrained embedded systems where supply stability, transient immunity, and long-term reliability are essential.

Technical Context

The MAX6865UK24D4S+T implements a precision bandgap-based voltage monitor with factory-trimmed 2.400V reset threshold (±2.5%), hysteresis of 0.5%VTH, and guaranteed operation from VCC = 1.2V to 5.5V. Its internal watchdog timer monitors WDI transitions and triggers reset if no edge occurs within 3.3s (typ), with glitch rejection up to 200ns on MR and 150ns on WDI.

This device integrates a 10kΩ internal MR pullup, supports push-pull active-high RESET output referenced to VCC, and features built-in immunity to short VCC transients - e.g., ≤40µs for a 100mV overdrive - without requiring external components or RC timing networks.

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 MAX6864UK24D4S+T and TPS3836K24DBVR, the MAX6865UK24D4S+T uniquely delivers active-high RESET, nanopower operation, and integrated watchdog in one 5-pin SOT23 - enabling simpler interface design and longer runtime where both reset polarity and firmware supervision are required.

Availability

MAX6865UK24D4S+T is available at Aetrix Electronics and suitable for portable medical devices, wearable health monitors, industrial sensor nodes, and low-power IoT endpoints requiring stable component supply across extended product lifecycles.

Supply support for MAX6865UK24D4S+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 demanding industrial, medical, and communications applications.

The MAX6865UK24D4S+T belongs to Maxim's nanopower µP supervisory family, engineered specifically for battery-critical systems where ultra-low quiescent current, precise voltage monitoring, and robust watchdog supervision must coexist in minimal footprint.

FAQ

What is the exact reset threshold voltage of the MAX6865UK24D4S+T?

The MAX6865UK24D4S+T has a factory-trimmed reset threshold of 2.400V with a tolerance of ±2.5%, meaning the actual threshold falls between 2.340V and 2.460V across temperature and process variation. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "24" corresponds to 2.400V nominal. The MAX6865UK24D4S+T guarantees valid reset assertion down to VCC = +1.1V, independent of threshold accuracy.

Does the MAX6865UK24D4S+T include a watchdog timer, and what is its timeout period?

Yes, the MAX6865UK24D4S+T includes a watchdog timer with a typical timeout period of 3.3 seconds, denoted by the "S" suffix in the part number. The datasheet specifies minimum/typical/maximum values of 1.5s/3.3s/7.75s under varying conditions. The timer resets on any rising or falling edge at the WDI pin and triggers a full reset cycle if no transition occurs within that window. This behavior is explicitly defined for MAX6864–MAX6869 variants including the MAX6865UK24D4S+T.

What type of RESET output does the MAX6865UK24D4S+T provide, and how is it configured?

The MAX6865UK24D4S+T provides an active-high push-pull RESET output, as confirmed by its pin description (Pin 1 = RESET, active-high) and Selector Guide entry. Unlike open-drain variants, it does not require an external pullup resistor and actively drives high during reset assertion. The output is referenced to VCC and can source up to 500µA while maintaining VOH ≥ 0.8 × VCC, making it directly compatible with standard CMOS inputs without level-shifting.

What is the reset timeout period for the MAX6865UK24D4S+T, and how is it selected?

The MAX6865UK24D4S+T has a fixed reset timeout period of 1200ms (minimum), indicated by the "D4" suffix in the part number. This value is one of six factory-programmed options ranging from 10ms to 1200ms, and cannot be adjusted externally. The timeout begins when VCC rises above the 2.400V threshold or MR is deasserted, and ensures the microprocessor remains held in reset long enough for power rails and internal clocks to stabilize before firmware execution resumes.

Is the MAX6865UK24D4S+T compatible with other SOT23-5 supervisory ICs, and what are key layout considerations?

The MAX6865UK24D4S+T uses a standard 5-pin SOT23-5 package with 0.95mm pitch and JEDEC MO-178AC outline, ensuring mechanical compatibility with common SOT23 footprints. Key layout considerations include placing a 0.1µF ceramic capacitor between VCC and GND as close as possible to Pin 5, routing MR and WDI with short traces to minimize noise pickup, and avoiding shared return paths between digital and analog grounds. No PCB changes are required when replacing pin-compatible alternatives like MAX6864UK24D4S+T, though RESET polarity must be verified.