Analog Devices Inc./Maxim Integrated MAX6855UK39D2+T

Overview

The MAX6855UK39D2+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, combining voltage monitoring, manual reset input (MR), and reset timeout functionality. It asserts an active-high push-pull RESET output when VCC drops below its factory-trimmed 3.9V threshold (±2.5%), upon MR assertion, or after power-up/brownout - with guaranteed reset validity down to VCC = +1.1V. Designed for ultra-low-power portable systems, it delivers 170nA typical supply current and supports 40ms minimum reset timeout.

For engineers reviewing the MAX6855UK39D2+T datasheet, MAX6855UK39D2+T pinout, MAX6855UK39D2+T application, or MAX6855UK39D2+T equivalent, key selection criteria include its 3.9V reset threshold accuracy, 40ms reset timeout, active-high push-pull output drive capability (VOH ≥ 0.8×VCC at ISOURCE = 500µA), and immunity to short VCC transients - critical for battery-powered medical and handheld devices requiring reliable cold-start behavior and minimal quiescent power.

Technical Context

This device implements a precision bandgap-based voltage monitor with 2.5% threshold tolerance over –40°C to +85°C, coupled to a digital reset timeout timer that holds RESET asserted for ≥40ms after VCC rises above VTH and MR deasserts. Its internal 10kΩ MR pullup enables direct connection of a momentary switch to GND without external components.

The active-high push-pull RESET output is referenced to VCC and guarantees VOH ≥ 0.8×VCC across 1.71V–5.5V supply range while sourcing up to 500µA, eliminating need for external level-shifting or pullups. Unlike watchdog-equipped variants (e.g., MAX6864–MAX6869), the MAX6855UK39D2+T excludes WDI functionality - confirming its role as a dedicated voltage-monitoring + manual-reset supervisor.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, surface-mount, 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 TPS3837K33DBVR and MAX6315US39D2+T, the MAX6855UK39D2+T uniquely combines 3.9V precision threshold, 40ms timeout, active-high push-pull output, and SOT23-5 packaging - delivering optimal balance of timing control, interface simplicity, and manufacturability for next-gen portable electronics.

Availability

MAX6855UK39D2+T is available at Aetrix Electronics and suitable for portable medical devices, wearable health monitors, industrial handheld terminals, and smart remote controls requiring stable component supply and long-term lifecycle support.

Supply support for MAX6855UK39D2+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 - emphasizing ultra-low-power operation and high reliability.

The MAX6855UK39D2+T belongs to the MAX6854–MAX6869 nanopower µP supervisory family, engineered specifically for battery-critical applications where sub-µA quiescent current, guaranteed low-VCC reset validity, and minimal external components are mandatory.

FAQ

What is the exact reset threshold voltage of the MAX6855UK39D2+T?

The MAX6855UK39D2+T has a factory-trimmed reset threshold voltage of 3.900V with ±2.5% tolerance over –40°C to +85°C, corresponding to suffix "39" per Maxim's Threshold Suffix Guide. This value is specified at VCC falling and guarantees reliable detection of brownout conditions on 3.3V or 3.9V rails. The MAX6855UK39D2+T maintains this accuracy without calibration or external components.

Does the MAX6855UK39D2+T include a watchdog timer function?

No, the MAX6855UK39D2+T does not include a watchdog timer. It is a voltage-monitoring + manual-reset supervisory circuit only. Watchdog functionality is present only in MAX6864–MAX6869 variants (e.g., MAX6864UK39D2S+T), which add WDI input and selectable watchdog timeout. The MAX6855UK39D2+T pinout lacks WDI, and its functional diagram confirms absence of watchdog circuitry.

What is the reset timeout period for the MAX6855UK39D2+T?

The MAX6855UK39D2+T provides a 40ms minimum reset timeout period, indicated by suffix "D2" per Maxim's Reset Timeout Period table. Typical and maximum values are 60ms and 80ms respectively. This timeout ensures sufficient duration for microprocessor initialization and clock stabilization before release from reset - meeting requirements of most ARM Cortex-M and PIC microcontrollers.

How does the MAX6855UK39D2+T handle low-supply conditions during battery discharge?

The MAX6855UK39D2+T guarantees valid RESET assertion down to VCC = +1.1V, enabling fail-safe operation even during deep battery discharge. Its internal voltage reference remains stable below 1.8V, and the active-high push-pull output maintains VOH ≥ 0.8×VCC down to 1.71V. This ensures deterministic reset behavior in glucose monitors and wearables where battery voltage may fall to 1.2V before cutoff.

Is the MAX6855UK39D2+T pin-compatible with other supervisory ICs?

The MAX6855UK39D2+T uses a standard 5-pin SOT23-5 package and is pin-compatible with the TPS3836/TPS3837/TPS3838 family per Maxim's datasheet. Pin 1 is RESET (active-high push-pull), Pins 2 & 4 are GND, Pin 3 is MR, and Pin 5 is VCC - matching TPS3837K33DBVR's pinout except for RESET polarity and threshold. Direct replacement requires verification of reset polarity and timeout requirements.