Analog Devices Inc./Maxim Integrated MAX6865UK39D5L+T

Overview

The MAX6865UK39D5L+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 3.9V reset threshold (±2.5%), 300ms minimum reset timeout, and integrated watchdog timer with 209s typical timeout. It monitors VCC, responds to manual reset (MR), and asserts active-high push-pull RESET during brownout, power-up, or watchdog expiration - used in battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK39D5L+T datasheet, MAX6865UK39D5L+T pinout, MAX6865UK39D5L+T application, or MAX6865UK39D5L+T equivalent, key selection criteria include guaranteed RESET validity down to VCC = +1.1V, immunity to sub-40µs VCC transients, pin-selectable reset delay absence (fixed D5 timeout), and compatibility with 1.2V–5.5V supply rails in space-constrained embedded systems.

Technical Context

This device belongs to the MAX6864–MAX6869 family with integrated watchdog timer and manual reset input. Its watchdog circuit clears on any WDI edge (rising/falling) or MR assertion, and expires only if WDI remains static >209s (typ), ensuring robust detection of firmware hangs. The reset logic guarantees monotonic assertion/deassertion with hysteresis (0.5% VTH) and fixed 300ms timeout after VCC recovery or MR release.

It uses BiCMOS process (2848 transistors) for low leakage and stable threshold performance across -40°C to +85°C. Unlike MAX6861–MAX6863, it lacks CT pin; unlike MAX6854–MAX6856, it includes WDI and supports L-suffix (209s) watchdog timeout - distinguishing it as a watchdog-enabled, active-high push-pull RESET variant with 3.9V threshold.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free (RoHS-compliant), 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 MAX6865UK39D5L+T, the S-suffix variant offers faster watchdog response but sacrifices long-duration hang detection, while TPS3838K33DBVR trades watchdog capability and nanopower operation for cost and simplicity in non-critical applications.

Availability

MAX6865UK39D5L+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered industrial scanners, and smart wearable sensors requiring stable component supply with guaranteed long-term availability and RoHS-compliant packaging.

Supply support for MAX6865UK39D5L+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 industrial, medical, and communications markets.

The MAX6864–MAX6869 product line delivers nanopower supervisory functions with integrated watchdog timers for battery-critical embedded systems where reliability, longevity, and space constraints dominate design requirements.

FAQ

What is the exact reset threshold voltage of the MAX6865UK39D5L+T?

The MAX6865UK39D5L+T has a factory-trimmed reset threshold voltage of 3.900V with ±2.5% tolerance over temperature (-40°C to +85°C), corresponding to the '39' suffix in the part number per Maxim's Threshold Suffix Guide. This value is specified at VCC falling and includes 0.5% hysteresis to prevent chatter near the trip point. The MAX6865UK39D5L+T guarantees valid reset assertion down to VCC = +1.1V, making it suitable for deep brownout detection in battery-powered systems.

Does the MAX6865UK39D5L+T support active-low reset output?

No, the MAX6865UK39D5L+T provides an active-high push-pull RESET output only, as confirmed by its position in the Selector Guide (row MAX6865, column "Push-Pull ACTIVE HIGH") and Pin Description section. It does not offer open-drain or active-low variants. If active-low logic is required, external inversion or selection of a different variant (e.g., MAX6864UK39D5L+T) is necessary. The MAX6865UK39D5L+T drive strength supports ISOURCE = 500µA at VOH ≥ 0.8 × VCC, ensuring compatibility with standard CMOS reset inputs.

What is the watchdog timeout behavior of the MAX6865UK39D5L+T?

The MAX6865UK39D5L+T features a watchdog timer with 209s typical timeout (L suffix), with min/max values of 95s and 487s respectively. The timer clears on any rising or falling edge at WDI, MR assertion, or RESET assertion - meaning it only expires if WDI remains static (high or low) beyond the timeout window. During RESET assertion, the watchdog is disabled; it resumes counting immediately upon RESET deassertion. This behavior is explicitly defined in the Electrical Characteristics table and Functional Diagram for MAX6865UK39D5L+T.

Can the MAX6865UK39D5L+T operate from a 1.8V supply?

Yes, the MAX6865UK39D5L+T operates across 1.2V to 5.5V supply range, and its 170nA typical supply current is specified at VCC = 1.8V. At this voltage, RESET output maintains VOH ≥ 0.8 × VCC (≥1.44V) with ISOURCE = 200µA, and VOL ≤ 0.3V with ISINK = 500µA - fully compatible with 1.8V logic families. The device also guarantees RESET validity down to VCC = +1.1V, enabling robust operation during battery discharge in 1.8V systems.

Is the MAX6865UK39D5L+T pin-compatible with other MAX68xx supervisory ICs?

The MAX6865UK39D5L+T uses the standard 5-pin SOT23-5 package and shares identical pinout with MAX6864/MAX6866/MAX6867/MAX6868/MAX6869 (Pin 1 = RESET, Pin 2 = GND, Pin 3 = MR, Pin 4 = WDI, Pin 5 = VCC). However, it is not pin-compatible with MAX6861–MAX6863 (which use CT instead of WDI on Pin 4) or MAX6854–MAX6856 (which lack WDI entirely). Board-level substitution requires verification of WDI connectivity and RESET polarity alignment.