Analog Devices Inc./Maxim Integrated MAX6865UK39D4S+T

Overview

The MAX6865UK39D4S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, combining voltage monitoring (3.9V reset threshold), manual reset input (MR), and watchdog timer (3.3s timeout) with ultra-low 170nA typical supply current. It asserts an active-low push-pull RESET output during VCC brownout, MR assertion, or watchdog timeout, and holds reset for 1200ms minimum after recovery - ideal for battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK39D4S+T datasheet, MAX6865UK39D4S+T pinout, MAX6865UK39D4S+T application, or MAX6865UK39D4S+T equivalent, key selection criteria include its 3.9V factory-trimmed reset threshold, 1200ms reset timeout, 3.3s watchdog period, guaranteed reset validity down to VCC = +1.1V, and immunity to sub-40µs VCC transients.

Technical Context

This device implements a dual-trigger reset architecture: one path responds to VCC falling below 3.9V ±2.5%, another to MR low assertion, and a third to WDI inactivity exceeding 3.3s (typ). The internal watchdog timer clears on any WDI edge, MR assertion, or RESET assertion - preventing false timeouts during software initialization or interrupt handling.

The reset timeout generator uses a temperature-stable RC-based timing circuit with ±25% variation over -40°C to +85°C, while the push-pull RESET output delivers VOL ≤0.3V at ISINK = 1.2mA (VCC ≥2.38V) and VOH ≥0.8×VCC at ISOURCE = 500µA - ensuring robust interfacing with 1.8V–5.5V µP reset inputs.

Key Specifications

Pinout & Package

Package: 5-pin SOT23 (2.9mm × 1.6mm × 1.1mm), lead-free, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisory applications.

Compared with MAX6865UK39D4S+T, MAX6864UK39D4S+T offers identical supervision parameters but lacks CT configurability, while TPS3838K33DBVR trades ultra-low power and watchdog capability for lower unit cost and simpler integration in static-rail systems.

Availability

MAX6865UK39D4S+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered instrumentation, and industrial handheld equipment requiring stable component supply across extended product lifecycles.

Supply support for MAX6865UK39D4S+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 MAX68xx family targets ultra-low-power microprocessor supervision in space-constrained, battery-operated systems - emphasizing nanopower operation, high accuracy, and integrated watchdog functionality without external components.

FAQ

What is the exact reset threshold voltage of the MAX6865UK39D4S+T?

The MAX6865UK39D4S+T features a factory-trimmed reset threshold of 3.900V 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 "39" corresponds to 3.900V nominal. The device guarantees valid reset assertion down to VCC = +1.1V, making it suitable for deep brownout detection in lithium-based battery systems.

Does the MAX6865UK39D4S+T include a watchdog timer, and what is its timeout period?

Yes, the MAX6865UK39D4S+T includes a watchdog timer with a typical timeout period of 3.3 seconds, indicated by the "S" suffix in the part number. The timer clears on any rising or falling edge at the WDI pin and expires only if WDI remains static beyond this period. Electrical Characteristics table confirms tWD = 1.5s (min) to 7.75s (max), with 3.3s typ at +25°C.

What is the reset timeout duration for the MAX6865UK39D4S+T, and how is it configured?

The MAX6865UK39D4S+T has a fixed reset timeout of 1200ms minimum, denoted by the "D4" suffix. This value is specified in Table 4 (Reset Timeout Periods) as D4 = 1200ms (min)/1800ms (typ)/2400ms (max). Unlike MAX6861–MAX6863 variants, the MAX6865UK39D4S+T does not feature a CT pin - its timeout is factory-set and non-adjustable.

What package type and pin configuration does the MAX6865UK39D4S+T use?

The MAX6865UK39D4S+T uses a 5-pin SOT23 package (2.9mm × 1.6mm × 1.1mm) with standard pinout: Pin 1 = RESET (active-low push-pull), Pin 2 = GND, Pin 3 = MR (active-low manual reset), Pin 4 = WDI (watchdog input), Pin 5 = VCC. This matches the MAX6864–MAX6866 series pin configuration shown in the datasheet's Pin Description section.

Is the MAX6865UK39D4S+T compatible with 1.8V microcontrollers?

Yes, the MAX6865UK39D4S+T is fully compatible with 1.8V µPs. Its push-pull RESET output delivers VOH ≥0.8×VCC at ISOURCE = 500µA (VCC ≥2.38V) and VOL ≤0.3V at ISINK = 1.2mA (VCC ≥2.38V), meeting standard 1.8V logic thresholds. Additionally, MR input accepts VIH ≥0.7×VCC and VIL ≤0.3×VCC, ensuring robust interfacing across 1.8V–5.5V supply domains.