Analog Devices Inc./Maxim Integrated MAX6855UK22D2+T

Overview

The MAX6855UK22D2+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, providing voltage monitoring, manual reset input (MR), and push-pull active-high RESET output. It asserts reset when VCC drops below 2.188V (typ), MR is pulled low, or during power-up/brownout - with guaranteed reset validity down to VCC = +1.1V and ultra-low 170nA typical supply current. It is designed for battery-powered portable electronics requiring reliable, low-power system initialization and fault recovery.

For engineers reviewing the MAX6855UK22D2+T datasheet, MAX6855UK22D2+T pinout, MAX6855UK22D2+T application, or MAX6855UK22D2+T equivalent, key selection criteria include its 2.188V factory-trimmed reset threshold, 40ms minimum reset timeout period, push-pull active-high output configuration, -40°C to +85°C operating range, and immunity to short VCC transients - all critical for low-voltage, long-life embedded systems.

Technical Context

The MAX6855UK22D2+T implements a precision bandgap-based voltage monitor with ±2.5% threshold accuracy over temperature and a dedicated MR input with 10kΩ internal pullup and 250ns MR-to-reset delay. Its reset assertion logic combines VCC undervoltage detection and manual trigger, holding RESET high for ≥40ms after VCC exceeds threshold and MR deasserts.

No watchdog timer or CT pin functionality is present - this variant belongs to the MAX6855 subgroup, which features only push-pull active-high RESET, MR input, and fixed reset timeout (D2 = 40ms min). It lacks WDI, CT, or I.C. pins, distinguishing it from MAX686x or MAX6861–63 variants.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, surface-mount, lead-free (+T suffix), footprint compatible with industry-standard 5-lead SOT23 layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3837K22 and MAX6361K22, the MAX6855UK22D2+T delivers 7× lower supply current and native active-high push-pull drive - making it optimal for space-constrained, battery-critical portable medical and consumer devices where every nanoamp and PCB pad matters.

Availability

The MAX6855UK22D2+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitoring devices, MP3 players, and smart pagers requiring stable component supply across extended production lifecycles.

Supply support for MAX6855UK22D2+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 portable applications.

The MAX6855UK22D2+T belongs to the MAX685x nanopower supervisory family, engineered specifically for ultra-low-power, single-supply microprocessor reset control in battery-operated medical and consumer electronics.

FAQ

What is the exact reset threshold voltage of the MAX6855UK22D2+T?

The MAX6855UK22D2+T has a factory-trimmed reset threshold voltage of 2.188V (typical), with ±2.5% tolerance over the full -40°C to +85°C operating temperature range. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "22" corresponds to 2.188V. The device guarantees valid reset assertion down to VCC = +1.1V, ensuring robust operation during deep brownout conditions.

Does the MAX6855UK22D2+T include a watchdog timer function?

No, the MAX6855UK22D2+T does not include a watchdog timer. It belongs to the MAX6855 subgroup, which provides only voltage monitoring and manual reset (MR) functionality. Watchdog capability is exclusive to MAX6864–MAX6869 variants (e.g., MAX6864UKxxDxxS/T), identifiable by the presence of the WDI pin and "S" or "L" suffix in the ordering code. The MAX6855UK22D2+T pinout contains only VCC, GND×2, MR, and RESET - no WDI terminal.

What is the reset timeout period for the MAX6855UK22D2+T?

The MAX6855UK22D2+T has a minimum reset timeout period of 40ms, indicated by the "D2" suffix in its part number. Per Table 4 (Reset Timeout Periods), D2 specifies 40ms (min), 60ms (typ), and 80ms (max) - with the actual duration varying slightly with temperature and supply voltage. This timeout ensures sufficient hold time for microprocessor power stabilization and firmware initialization after VCC rises above the 2.188V threshold.

Is the RESET output of the MAX6855UK22D2+T push-pull or open-drain?

The MAX6855UK22D2+T features a push-pull active-high RESET output, as confirmed by the Selector Guide and Pin Description sections. Unlike open-drain variants (e.g., MAX6856), this configuration drives the RESET signal high during assertion and low during deassertion - requiring no external pullup resistor and providing direct compatibility with microprocessors that accept active-high reset inputs.

Can the MAX6855UK22D2+T operate from a 1.5V supply?

Yes, the MAX6855UK22D2+T operates from VCC = 1.2V to 5.5V, so it functions reliably at 1.5V. However, its 2.188V reset threshold means it will assert reset continuously at 1.5V - making it unsuitable for monitoring that rail. Instead, it is intended to supervise higher rails (e.g., 2.5V, 3.3V) while being powered from a separate, stable supply. Its guaranteed reset validity down to VCC = +1.1V ensures correct behavior even as the monitored rail collapses.