Analog Devices Inc./Maxim Integrated MAX6855UK18D1+T

Overview

The MAX6855UK18D1+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 1.800V (factory-trimmed threshold), MR is pulled low, or watchdog timer expires (not applicable to MAX6855). Designed for ultra-low-power systems, it draws only 170nA typical supply current and guarantees valid reset down to VCC = +1.1V - ideal for glucose monitors and portable medical devices.

For engineers reviewing the MAX6855UK18D1+T datasheet, MAX6855UK18D1+T pinout, MAX6855UK18D1+T application, or MAX6855UK18D1+T equivalent, key selection criteria include its 1.800V reset threshold, 10ms minimum reset timeout, active-high push-pull output configuration, and immunity to short VCC transients - all critical for reliable power-up sequencing in battery-powered embedded systems.

Technical Context

This device implements a precision bandgap-based voltage monitor with ±2.5% threshold accuracy over -40°C to +85°C, coupled with a digital reset timeout generator that holds RESET high for ≥10ms after VCC rises above VTH and MR deasserts. The internal 10kΩ MR pullup enables direct interface with momentary switches or CMOS logic without external components.

No watchdog timer or CT pin functionality is present in the MAX6855 variant - it belongs to the MR-only, fixed-reset-timeout subgroup (D1 option) and uses a dedicated active-high push-pull output stage referenced to VCC, distinct from open-drain or active-low variants in the same family.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, surface-mount, lead-free (RoHS-compliant).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6855UK18D1+T, the TPS3837K25DBVR offers longer timeout and TI ecosystem alignment but consumes ~7x more current, while the MAX6315US29D3+ provides superior accuracy and voltage range at the cost of incompatible reset polarity and higher threshold - making MAX6855UK18D1+T optimal for 1.8V, ultra-low-power, active-high reset architectures.

Availability

MAX6855UK18D1+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, MP3 players, and feature cell phones requiring stable component supply across extended production lifecycles.

Supply support for MAX6855UK18D1+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 and medical applications.

The MAX6855UK18D1+T belongs to the nanopower µP supervisory family engineered specifically for battery-critical portable healthcare and consumer electronics where sub-µA quiescent current and guaranteed low-VCC reset validity are mandatory.

FAQ

What is the exact reset threshold voltage of the MAX6855UK18D1+T?

The MAX6855UK18D1+T has a factory-trimmed reset threshold of 1.800V with ±2.5% accuracy over the full -40°C to +85°C temperature range. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix '18' corresponds to 1.800V nominal. The device guarantees reset assertion when VCC falls below this threshold and maintains reset until VCC exceeds it plus hysteresis (0.5% of VTH).

Does the MAX6855UK18D1+T include a watchdog timer function?

No, the MAX6855UK18D1+T does not include a watchdog timer. It belongs to the MAX6854/MAX6855/MAX6856 subgroup, which provides only voltage monitoring and manual reset (MR) functionality. Watchdog capability is exclusive to MAX6864–MAX6869 variants, as clearly indicated in the Selector Guide and Pin Description sections of the datasheet.

What is the reset output configuration of the MAX6855UK18D1+T?

The MAX6855UK18D1+T features a push-pull active-high RESET output (Pin 1), meaning it drives the output high during reset and low otherwise. This differs from MAX6854 (active-low push-pull) and MAX6856 (active-low open-drain). The active-high configuration eliminates the need for an external pullup resistor and directly interfaces with µPs requiring high-level reset assertion.

What is the minimum reset timeout period for the MAX6855UK18D1+T?

The MAX6855UK18D1+T has a minimum reset timeout period of 10ms, corresponding to the 'D1' suffix in its part number. This is verified in Table 4 (Reset Timeout Periods), where D1 specifies 10ms (min), 15ms (typ), and 25ms (max). The timeout begins after VCC rises above the reset threshold and MR is deasserted, ensuring sufficient hold time for microprocessor initialization.

Is the MAX6855UK18D1+T compatible with 1.2V supply rails?

Yes, the MAX6855UK18D1+T operates down to VCC = 1.2V per Absolute Maximum Ratings and Electrical Characteristics tables, and guarantees valid reset signaling down to VCC = +1.1V. However, its 1.800V reset threshold means it will assert reset when a 1.2V rail drops below 1.2V - i.e., it cannot supervise a 1.2V rail *at* its nominal level, but functions correctly as a supervisor for higher rails (e.g., 1.8V, 2.5V, 3.3V) that may brown out toward 1.2V.