Analog Devices Inc./Maxim Integrated MAX6861UK225+

Overview

The MAX6861UK225+ from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 2.235V reset threshold (suffix "225"), and pin-selectable 10ms/150ms minimum reset timeout via CT input. It provides active-low push-pull RESET output, manual reset (MR) input, and operates down to VCC = +1.1V - ideal for battery-powered glucose monitors and portable medical devices requiring reliable power-on reset and brownout protection.

For engineers reviewing the MAX6861UK225+ datasheet, MAX6861UK225+ pinout, MAX6861UK225+ application, or MAX6861UK225+ equivalent, key selection criteria include its 2.235V threshold accuracy (±2.5%), immunity to short VCC transients (<40µs at 100mV overdrive), guaranteed reset validity at low VCC, and compatibility with CMOS-level MR signaling in space-constrained portable systems.

Technical Context

The MAX6861UK225+ integrates a precision voltage monitor, manual reset controller, and reset timeout generator - but no watchdog timer (unlike MAX6864–MAX6869). Its CT pin selects between two fixed timeout options (D1: 10ms min or D3: 150ms min), and the internal 10kΩ MR pullup eliminates external components. Reset assertion is guaranteed valid down to VCC = +1.1V, with hysteresis of 0.5% VTH.

It uses BiCMOS process technology (2848 transistors) and features glitch rejection on MR (200ns), 250ns MR-to-reset delay, and open-drain leakage <25nA when RESET is deasserted. The device asserts RESET low when VCC falls below 2.235V, MR is pulled low, or after power-up until timeout expires - with no external capacitor required.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3836K33DBVR and STM6315RWX6F, the MAX6861UK225+ delivers superior energy efficiency (170nA vs. 350nA–1.5µA), precise 2.235V threshold matching common low-voltage rails, and integrated CT-selectable timing - making it optimal for long-life, multi-rail portable medical devices where BOM count and battery runtime are primary constraints.

Availability

The MAX6861UK225+ is available at Aetrix Electronics and suitable for glucose monitors, patient vital sign loggers, and portable pulse oximeters requiring stable component supply across extended production lifecycles and global regulatory compliance.

Supply support for MAX6861UK225+ 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 demanding industrial, medical, and communications applications - emphasizing low power, high reliability, and small form factor.

The MAX6861UK225+ belongs to the MAX6854–MAX6869 nanopower µP supervisory family, engineered specifically for battery-critical portable medical and handheld electronics where sub-µA quiescent current and guaranteed low-VCC reset behavior are essential.

FAQ

What is the exact reset threshold voltage of the MAX6861UK225+?

The MAX6861UK225+ has a factory-trimmed reset threshold of 2.235V, with ±2.5% tolerance over -40°C to +85°C. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "225" corresponds to nominal 2.235V. The device guarantees reset assertion when VCC falls below this threshold and remains asserted until VCC exceeds it plus hysteresis (0.5% of VTH).

Does the MAX6861UK225+ include a watchdog timer?

No, the MAX6861UK225+ does not include a watchdog timer. It is part of the MAX6861/MAX6862/MAX6863 subgroup, which provides manual reset (MR) and pin-selectable reset timeout via CT - but omits WDI and watchdog circuitry. Watchdog functionality is exclusive to MAX6864–MAX6869 variants, as confirmed in the Selector Guide and Pin Description sections.

How do I configure the reset timeout period on the MAX6861UK225+?

Configure the reset timeout period on the MAX6861UK225+ using the CT pin (Pin 1): connect CT to GND for 10ms minimum timeout (D1), or to VCC for 150ms minimum timeout (D3). This selection is latched at power-up and remains active until the next power cycle. Table 1 in the datasheet confirms these values as 10/15/25ms (min/typ/max) and 150/225/300ms respectively.

Is the MAX6861UK225+ pin-compatible with other supervisory ICs?

Yes, the MAX6861UK225+ is pin-compatible with the TPS3836/TPS3837/TPS3838 series per the datasheet's Features section. All share identical 5-pin SOT23-5 pinout (CT/MR/GND/RESET/VCC), enabling drop-in replacement in existing layouts - though electrical differences (e.g., threshold voltage, ICC, timeout) require validation in the target application.

What is the minimum operating voltage for guaranteed reset functionality of the MAX6861UK225+?

The MAX6861UK225+ guarantees valid reset output down to VCC = +1.1V, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. Below this voltage, RESET may become indeterminate. This feature ensures reliable operation during deep battery discharge in medical devices powered by single-cell Li-ion or alkaline sources.