Analog Devices Inc./Maxim Integrated MAX6867UK225D3S

Overview

The MAX6867UK225D3S from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, a factory-trimmed 2.235V reset threshold (suffix "225"), 225ms minimum reset timeout (suffix "D3"), and watchdog timer with 3.3s typical timeout (suffix "S"). It monitors VCC, responds to manual reset (MR), and triggers reset on watchdog timeout - used in battery-powered medical and portable electronics for reliable power-on initialization and fault recovery.

For engineers reviewing the MAX6867UK225D3S datasheet, MAX6867UK225D3S pinout, MAX6867UK225D3S application, or MAX6867UK225D3S equivalent, key selection criteria include its 2.235V reset threshold accuracy, 225ms reset timeout, 3.3s watchdog period, guaranteed reset validity down to VCC = +1.1V, and immunity to short VCC transients - all critical for low-power, safety-critical embedded systems.

Technical Context

The MAX6867UK225D3S integrates a precision voltage monitor, manual reset input (MR), and watchdog timer with WDI input. Its reset assertion logic combines three independent conditions: VCC falling below 2.235V ±2.5%, MR pulled low, or WDI remaining static beyond 3.3s (typ). The internal reset timeout timer ensures 225ms (min) reset pulse width after any trigger condition clears.

It uses BiCMOS process technology (2848 transistors) and features push-pull active-low RESET output referenced to VCC, 10kΩ internal MR pullup, and 20nA max WDI input current. Reset remains valid down to VCC = +1.1V, and it rejects VCC transients ≤40µs at 100mV overdrive - enabling robust operation in noisy, battery-constrained environments.

Key Specifications

Pinout & Package

Package: 5-pin SOT23 (lead-free, RoHS-compliant), 2.9mm × 1.6mm footprint, 1.1mm height - suitable for space-constrained portable PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK225D3S and TPS3836K22, the MAX6867UK225D3S uniquely delivers integrated watchdog protection at nanopower levels - essential for autonomous, unattended medical devices where firmware hang detection cannot rely on external logic.

Availability

MAX6867UK225D3S is available at Aetrix Electronics and suitable for glucose monitors, patient vital sign recorders, industrial handheld scanners, and smart wearable sensors requiring stable component supply, long-term lifecycle support, and guaranteed lead-free packaging.

Supply support for MAX6867UK225D3S 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, mixed-signal, and power management ICs for demanding industrial, medical, and communications applications.

The MAX6854–MAX6869 family was engineered specifically for ultra-low-power microprocessor supervision in battery-critical systems - delivering sub-200nA ICC, factory-trimmed thresholds, and integrated watchdogs without external components.

FAQ

What is the exact reset threshold voltage of the MAX6867UK225D3S?

The MAX6867UK225D3S 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" explicitly denotes 2.235V (min 2.180V, typ 2.235V, max 2.290V). The MAX6867UK225D3S uses this precise threshold to reliably detect brownout on 2.2V–2.3V supply rails.

Does the MAX6867UK225D3S require external components for basic operation?

No, the MAX6867UK225D3S operates autonomously with no external components required. It integrates a 10kΩ internal pullup on MR, precision voltage reference, watchdog oscillator, and push-pull RESET driver. Only a 0.1µF ceramic bypass capacitor from VCC to GND is recommended for noise suppression - a standard practice, not a functional requirement. The MAX6867UK225D3S achieves full supervision capability in a minimal 5-pin SOT23 footprint.

What is the watchdog timeout behavior of the MAX6867UK225D3S?

The MAX6867UK225D3S provides a 3.3s typical watchdog timeout period (S-suffix), with min 1.5s and max 7.75s over temperature. The watchdog timer resets on any WDI edge (rising or falling) and triggers reset if WDI remains static beyond timeout. While reset is asserted, the watchdog timer halts - preventing race conditions. This behavior is documented in the "WATCHDOG TIMER" section and Figure 3 of the MAX6867UK225D3S datasheet.

Can the MAX6867UK225D3S operate with supply voltages below 1.8V?

Yes, the MAX6867UK225D3S is fully specified from VCC = 1.2V to 5.5V and guarantees valid RESET output down to VCC = +1.1V. At 1.2V, supply current is 190nA (typ), and reset threshold remains accurate within ±2.5%. This extended low-voltage operation enables use with single-cell LiFePO₄ or deeply discharged alkaline batteries - a key capability confirmed in the "ELECTRICAL CHARACTERISTICS" table of the MAX6867UK225D3S datasheet.

How does the MAX6867UK225D3S handle VCC supply transients?

The MAX6867UK225D3S rejects short VCC transients using built-in hysteresis and timing discrimination. As shown in the "MAXIMUM VCC TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE" graph, it ignores glitches ≤40µs wide when overdrive is 100mV - preventing false resets from switching noise or load dumps. This transient immunity is intrinsic to the MAX6867UK225D3S architecture and requires no external RC filtering.