Analog Devices Inc./Maxim Integrated MAX6865UK31D3L+T

Overview

The MAX6865UK31D3L+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, a factory-trimmed 3.075V reset threshold (suffix "31"), 150ms minimum reset timeout (suffix "D3"), and a 209s typical watchdog timeout (suffix "L"). It monitors VCC, responds to manual reset (MR), and triggers reset on watchdog timeout - designed for battery-critical systems like glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK31D3L+T datasheet, MAX6865UK31D3L+T pinout, MAX6865UK31D3L+T application, or MAX6865UK31D3L+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 1.2V–5.5V supply rails.

Technical Context

This device integrates three core functions: precision voltage monitoring with ±2.5% threshold accuracy, a manual reset input with 250ns MR-to-reset delay and internal 10kΩ pullup, and a watchdog timer that clears on any WDI edge and expires after 209s (typ) if inactive - all operating from a single supply without external components.

The reset logic asserts RESET high when VCC falls below 3.075V, MR is pulled low, or the watchdog times out; RESET remains asserted for ≥150ms after recovery, with output valid down to VCC = 1.1V and VOL ≤ 0.3V at ISINK = 1.2mA (VCC ≥ 2.38V).

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, -40°C to +85°C operating range.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6865UK31D3L+T, MAX6864UK31D3L+T offers identical supervision timing but inverted RESET polarity, while TPS3837K33DBVR trades 10× higher supply current and no watchdog for TI's long-term availability and broader distribution - making it viable only for non-battery-critical or watchdog-free designs.

Availability

MAX6865UK31D3L+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitoring devices, and industrial handheld terminals requiring stable component supply across extended production lifecycles.

Supply support for MAX6865UK31D3L+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 industrial, medical, and communications markets.

The MAX6854–MAX6869 family delivers nanopower supervision with integrated watchdog and manual reset - engineered specifically for battery-constrained portable medical and instrumentation systems demanding sub-µA quiescent current and guaranteed low-VCC reset validity.

FAQ

What is the exact reset threshold voltage of the MAX6865UK31D3L+T?

The MAX6865UK31D3L+T has a factory-trimmed reset threshold voltage of 3.075V, with ±2.5% tolerance over temperature (-40°C to +85°C). This value is defined by the "31" suffix in the part number and is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet. The device asserts RESET high when VCC falls below this threshold and holds it for ≥150ms after recovery.

Does the MAX6865UK31D3L+T require external components for basic operation?

No, the MAX6865UK31D3L+T operates autonomously with no external components required for core supervision. A 0.1µF bypass capacitor on VCC is recommended per the datasheet for noise immunity, but no resistors, capacitors, or timing elements are needed for reset timeout, watchdog, or MR functionality - all are fully integrated and factory-configured.

How does the watchdog timer in the MAX6865UK31D3L+T respond to software activity?

The MAX6865UK31D3L+T watchdog timer clears on every rising or falling edge at the WDI pin and expires only if WDI remains static (high or low) for ≥209s (typ). It does not require periodic toggling - a single edge suffices to reset the timer. During RESET assertion, the watchdog is paused; it resumes counting immediately upon RESET deassertion.

What is the RESET output configuration of the MAX6865UK31D3L+T?

The MAX6865UK31D3L+T features a push-pull active-high RESET output (confirmed by "65" in the part number and Pin Description section). When asserted, RESET drives high (VOH ≥ 0.8×VCC); when deasserted, it drives low (VOL ≤ 0.3V). This eliminates the need for an external pullup resistor and interfaces directly with µPs having active-high reset inputs.

Can the MAX6865UK31D3L+T operate reliably at very low supply voltages?

Yes, the MAX6865UK31D3L+T guarantees valid RESET assertion down to VCC = +1.1V, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. Below this voltage, reset behavior is not characterized, but the device maintains functional integrity through brownout - critical for preserving data integrity in battery-powered medical devices during end-of-life discharge.