Analog Devices Inc./Maxim Integrated MAX6855UK38D5+T

Overview

The MAX6855UK38D5+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring active-high push-pull reset output, manual reset input (MR), and factory-trimmed 3.800V reset threshold with 300ms minimum reset timeout. It monitors VCC supply integrity, asserts reset during brownout or manual trigger, and guarantees valid reset operation down to VCC = +1.1V. It is used in battery-powered glucose monitors and portable medical devices requiring ultra-low quiescent current.

For engineers reviewing the MAX6855UK38D5+T datasheet, MAX6855UK38D5+T pinout, MAX6855UK38D5+T application, or MAX6855UK38D5+T equivalent, key selection criteria include its 3.800V threshold tolerance (±2.5%), 300ms reset timeout (D5 option), active-high push-pull RESET logic, MR input with 10kΩ internal pullup, and guaranteed operation at VCC ≥ 1.1V - critical for low-voltage wearable and point-of-care systems.

Technical Context

The MAX6855UK38D5+T implements a precision voltage monitor with hysteresis (0.5% of VTH) and a fixed 300ms reset timeout timer. Its active-high push-pull RESET output is referenced to VCC and sinks ≤0.3V at 1.2mA load when asserted, while sourcing ≥0.8×VCC when deasserted across 1.71V–2.38V VCC range.

It features a dedicated MR input with 1µs minimum pulse width, 250ns MR-to-reset delay, and 200ns glitch rejection. Unlike watchdog-equipped variants (e.g., MAX6864–MAX6869), the MAX6855UK38D5+T excludes WDI and CT pins - confirming it is a manual-reset-only, non-watchdog supervisory device within the MAX685x family.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, -40°C to +85°C operating temperature range.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3837K33DBVR and MAX6315US38D3+T, the MAX6855UK38D5+T delivers 10× lower supply current and matches the exact 3.800V threshold required for LiPo end-of-discharge monitoring - making it optimal for long-life, high-accuracy medical wearables where reset timing and power budget are tightly coupled.

Availability

The MAX6855UK38D5+T is available at Aetrix Electronics and suitable for glucose monitors, portable ECG devices, and wireless pulse oximeters requiring stable component supply with guaranteed long-term availability and lead-free compliance.

Supply support for MAX6855UK38D5+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 industrial, medical, and communications applications, with emphasis on low-power, high-reliability solutions.

The MAX6855UK38D5+T belongs to Maxim's nanopower µP supervisory product line, engineered specifically for battery-critical medical and portable electronics where sub-µA quiescent current and precise voltage monitoring are essential.

FAQ

What is the exact reset threshold voltage of the MAX6855UK38D5+T?

The MAX6855UK38D5+T has a factory-trimmed reset threshold of 3.800V, with ±2.5% tolerance 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 "38" corresponds to 3.800V nominal. The MAX6855UK38D5+T uses this precise threshold to detect brownout conditions in 3.6V LiPo-powered systems before critical undervoltage occurs.

Does the MAX6855UK38D5+T include a watchdog timer function?

No, the MAX6855UK38D5+T does not include a watchdog timer. It is a manual-reset-only supervisory circuit. The presence of "WDI" (Watchdog Input) pin is exclusive to MAX6864–MAX6869 variants; the MAX6855UK38D5+T pinout shows only RESET, GND, MR, GND, and VCC - confirming absence of watchdog functionality. This is verified in the Selector Guide and Pin Description sections of the datasheet.

What does the "D5" in MAX6855UK38D5+T indicate?

The "D5" suffix in MAX6855UK38D5+T specifies the reset timeout period: 300ms minimum (with typical 450ms and max 600ms). This is defined in Table 4 (Reset Timeout Periods), where D5 maps to 300/450/600ms. The timeout begins after VCC rises above 3.800V and MR is deasserted, ensuring sufficient hold time for µP power stabilization and clock lock before release.

Is the RESET output of the MAX6855UK38D5+T push-pull or open-drain?

The MAX6855UK38D5+T features an active-high push-pull RESET output, as confirmed in the MAX6854/MAX6855/MAX6856 Pin Description table and Selector Guide. Pin 1 is labeled "RESET" with function "Active-High Push-Pull Reset Output". This eliminates the need for an external pullup resistor and allows direct connection to µP reset inputs requiring active-high assertion, such as those found on many ARM Cortex-M and MSP430 devices.

What is the guaranteed minimum VCC level at which the MAX6855UK38D5+T maintains valid RESET operation?

The MAX6855UK38D5+T guarantees valid RESET output down to VCC = +1.1V, as explicitly stated in the Features list and Electrical Characteristics table under "Guaranteed Reset Valid to VCC = +1.1V". This ensures deterministic reset assertion even during deep brownout events in battery-powered systems, preventing firmware corruption when supply voltage collapses below typical logic thresholds.