Analog Devices Inc./Maxim Integrated MAX6855UK18D6+T

Overview

The MAX6855UK18D6+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 1.8V reset threshold. It asserts reset during VCC brownout, MR assertion, or watchdog timeout (not applicable to MAX6855), with guaranteed reset validity down to VCC = +1.1V and ultra-low 170nA typical supply current. It is used in battery-powered glucose monitors and portable medical devices requiring reliable power-on reset and low-quiescent-current supervision.

For engineers reviewing the MAX6855UK18D6+T datasheet, MAX6855UK18D6+T pinout, MAX6855UK18D6+T application, or MAX6855UK18D6+T equivalent, key selection criteria include its 1.8V reset threshold accuracy (±2.5%), 1200ms minimum reset timeout, active-high push-pull RESET output logic, -40°C to +85°C industrial temperature range, and lead-free SOT23-5 packaging compatibility.

Technical Context

The MAX6855UK18D6+T implements a precision voltage monitor with hysteresis (0.5% of VTH) and an internal reset timeout generator. Its reset assertion is triggered solely by VCC falling below 1.8V or MR being pulled low - it lacks watchdog timer functionality, distinguishing it from MAX6864–MAX6869 variants.

Reset deassertion occurs only after VCC rises above 1.8V *and* remains stable for ≥600ms (typical), with MR simultaneously deasserted. The device guarantees valid reset signaling down to VCC = +1.1V and exhibits immunity to VCC transients ≤40µs at 100mV overdrive.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount, footprint-compatible with industry-standard 5-lead SOT23.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6854UK18D6+T, the MAX6855UK18D6+T provides native active-high reset compatibility without external inverters, while TPS3836K33DBVR trades nanopower efficiency for tighter threshold accuracy and lower unit cost in non-battery-critical applications.

Availability

MAX6855UK18D6+T is available at Aetrix Electronics and suitable for glucose monitors, patient vital sign equipment, and industrial handheld scanners requiring stable component supply across extended production lifecycles.

Supply support for MAX6855UK18D6+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 communications markets.

The MAX685x family was designed specifically for ultra-low-power microprocessor supervision in battery-constrained medical and portable electronics, prioritizing nanoscale current consumption and guaranteed reset behavior under brownout.

FAQ

What is the exact reset threshold voltage of the MAX6855UK18D6+T?

The MAX6855UK18D6+T has a factory-trimmed reset threshold of 1.8V 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 "18" corresponds to 1.755V (min), 1.800V (typ), and 1.845V (max). The device guarantees valid reset assertion down to VCC = +1.1V regardless of threshold drift.

Does the MAX6855UK18D6+T include a watchdog timer function?

No, the MAX6855UK18D6+T does not include a watchdog timer. It belongs to the MAX6854/MAX6855/MAX6856 subgroup, which provides only voltage monitoring and manual reset functions. Watchdog capability is exclusive to MAX6864–MAX6869 variants (e.g., MAX6864UK18D6S+T), identifiable by the "S" or "L" suffix in the ordering code. The MAX6855UK18D6+T pinout omits WDI and contains no watchdog-related circuitry.

What is the function of Pin 4 on the MAX6855UK18D6+T?

Pin 4 on the MAX6855UK18D6+T is unconnected (NC) - it has no internal bond wire or circuit connection. Per the MAX6854/MAX6855/MAX6856 Pin Description table and SOT23 top-view diagram, Pin 4 is designated "-" for these parts. It must be left floating or tied to GND for mechanical stability and noise immunity; connecting it to any active signal will cause undefined behavior.

Can the MAX6855UK18D6+T be used with a 3.3V microcontroller that requires an active-low reset input?

Direct use is not possible because the MAX6855UK18D6+T provides only active-high push-pull RESET output. To interface with an active-low µP reset input, an external inverter (e.g., SN74LVC1G04) or open-drain buffer with pullup is required. Alternatively, select the pin-compatible MAX6854UK18D6+T, which offers identical specifications with active-low push-pull output - eliminating additional components and board space.

What is the minimum VCC voltage at which the MAX6855UK18D6+T guarantees correct reset operation?

The MAX6855UK18D6+T guarantees correct reset assertion and deassertion down to VCC = +1.1V, as explicitly stated in the Electrical Characteristics table under "Guaranteed Reset Valid to VCC = +1.1V". Below this voltage, reset output behavior is not characterized. This specification ensures reliable operation during deep brownout events common in battery-powered medical devices nearing end-of-life.