Analog Devices Inc./Maxim Integrated MAX6855UK18D4+T

Overview

The MAX6855UK18D4+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 1.8V reset threshold (±2.5%), and 1200ms minimum reset timeout period. It provides active-high push-pull RESET output, manual reset input (MR), and operates across -40°C to +85°C for reliable power-up/brownout monitoring in battery-powered medical and portable electronics.

For engineers reviewing the MAX6855UK18D4+T datasheet, MAX6855UK18D4+T pinout, MAX6855UK18D4+T application, or MAX6855UK18D4+T equivalent, this device serves as a low-power voltage monitor with deterministic reset timing, MR-triggered recovery, and guaranteed RESET validity down to VCC = +1.1V - critical for glucose monitors, patient monitors, and energy-constrained embedded systems.

Technical Context

The MAX6855UK18D4+T implements a precision bandgap-based voltage detector with 2.5% threshold tolerance and hysteresis of 0.5%VTH to prevent chatter during slow VCC transitions. Its internal timer ensures reset assertion persists for ≥1200ms after VCC rises above 1.8V and MR deasserts, independent of watchdog functionality (absent in this variant).

This part belongs to the MAX6854–MAX6869 family but excludes WDI and CT pins - it integrates only VCC monitoring, MR input, and active-high push-pull RESET. Its design targets systems requiring deterministic, low-current supervision without software-driven watchdog intervention.

Key Specifications

Pinout & Package

MAX6855UK18D4+T uses a lead-free 5-pin SOT23 package (2.9mm × 1.6mm × 1.1mm height) with gull-wing leads, optimized for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3837K25DBVR and ADM6806-18ARTZ-R7, the MAX6855UK18D4+T delivers 70× lower supply current and guaranteed RESET validity to 1.1V, making it uniquely suitable for multi-year battery operation in medical wearables where deterministic reset timing and minimal quiescent power are non-negotiable.

Availability

MAX6855UK18D4+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, and smart wearables requiring stable component supply with long-term lifecycle support and traceable sourcing.

Supply support for MAX6855UK18D4+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 management, sensing, and connectivity in demanding industrial, medical, and automotive applications.

The MAX6854–MAX6869 product line delivers nanopower supervisory circuits specifically engineered for battery-critical portable medical devices and ultra-low-power embedded systems requiring guaranteed reset behavior under brownout conditions.

FAQ

What is the exact reset threshold voltage of the MAX6855UK18D4+T?

The MAX6855UK18D4+T has a factory-trimmed reset threshold of 1.800V with ±2.5% tolerance (1.755V to 1.845V). This value is specified over the full -40°C to +85°C temperature range and ensures reliable supervision of 1.8V logic rails. The threshold exhibits only 0.01% normalized drift over temperature, as confirmed in the Typical Operating Characteristics graph (Figure toc06).

Does the MAX6855UK18D4+T include a watchdog timer function?

No, the MAX6855UK18D4+T does not include a watchdog timer. It belongs to the MAX6854/MAX6855/MAX6856 subgroup, which supports only VCC monitoring and manual reset (MR) - no WDI pin or watchdog circuitry. Watchdog capability is exclusive to MAX6864–MAX6869 variants, identifiable by "S" or "L" suffixes in the ordering code.

What is the function of Pin 1 on the MAX6855UK18D4+T?

Pin 1 of the MAX6855UK18D4+T is the RESET output terminal, configured as an active-high push-pull driver. When asserted, it drives high (VOH ≥ 0.8×VCC) to signal reset condition to the microprocessor; when deasserted, it drives low (VOL ≤ 0.3V). Unlike open-drain variants, it requires no external pullup resistor and is referenced directly to VCC.

Can the MAX6855UK18D4+T operate with supply voltages below 1.8V?

Yes - the MAX6855UK18D4+T guarantees functional RESET output down to VCC = +1.1V, even though its reset threshold is 1.8V. Below 1.8V, RESET remains asserted (high); as VCC rises above 1.8V, the internal timer enforces a minimum 1200ms hold time before deassertion. Operation below 1.1V is not characterized and may result in undefined output states.

How does the manual reset (MR) input behave on the MAX6855UK18D4+T?

The MR input on the MAX6855UK18D4+T is active-low with internal 10kΩ pullup to VCC. Driving MR low initiates immediate reset assertion; RESET remains high for the full 1200ms timeout after MR returns high. It rejects glitches <200ns and requires ≥1µs pulse width. Leaving MR unconnected defaults to VCC, disabling manual reset.