Analog Devices Inc./Maxim Integrated MAX6865UK28D2L+T

Overview

MAX6865UK28D2L+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 2.800V reset threshold (±2.5%), 40ms minimum reset timeout, and integrated watchdog timer with 209s typical timeout. It monitors VCC, responds to manual reset (MR), and asserts active-high push-pull RESET during brownout or watchdog expiration - used in battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK28D2L+T datasheet, MAX6865UK28D2L+T pinout, MAX6865UK28D2L+T application, or MAX6865UK28D2L+T equivalent, key selection criteria include guaranteed RESET validity down to VCC = +1.1V, immunity to sub-40µs VCC transients, MR glitch rejection of 200ns, and compatibility with 1.2V–5.5V supply rails.

Technical Context

The MAX6865UK28D2L+T implements a precision bandgap-based voltage monitor with 0.5% hysteresis, a digital watchdog timer that clears on any WDI edge (rising or falling) and expires if WDI remains static >209s (typ), and an internal 10kΩ MR pullup. Its reset assertion logic combines VCC undervoltage detection, MR low assertion, and watchdog timeout - all triggering the same active-high push-pull RESET output with 0.8×VCC VOH at 500µA source.

Unlike variants without watchdog (e.g., MAX6854), this device requires WDI toggling to prevent reset; unlike CT-configurable versions (e.g., MAX6861), its 40ms reset timeout is fixed per D2 suffix. The SOT23-5 package places VCC (Pin 5), GND (Pin 2), MR (Pin 3), WDI (Pin 4), and RESET (Pin 1) with no internally connected pins.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, 2.9mm × 1.6mm × 1.1mm body, lead-free (RoHS-compliant) +T variant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK28D2L+T, the MAX6865UK28D2L+T provides identical supervision accuracy and watchdog behavior but simplifies interface design for µPs requiring active-high reset. Against TPS3837K28QDBVR, it delivers 90% lower ICC and adds critical watchdog capability - essential for unattended medical and industrial edge nodes.

Availability

MAX6865UK28D2L+T is available at Aetrix Electronics and suitable for glucose monitors, portable ECG devices, wireless patient alarms, and low-power environmental sensors requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for MAX6865UK28D2L+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, mixed-signal, and power-management ICs for demanding industrial, medical, and communications applications.

The MAX6854–MAX6869 family targets ultra-low-power microprocessor supervision in battery-constrained systems, emphasizing nanoscale ICC, wide VCC range, and integrated watchdog functionality for autonomous recovery.

FAQ

What is the exact reset threshold voltage of the MAX6865UK28D2L+T?

The MAX6865UK28D2L+T has a factory-trimmed reset threshold of 2.800V, with guaranteed tolerance of ±2.5% over -40°C to +85°C. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "28" corresponds to 2.800V nominal. The actual measured threshold falls between 2.730V and 2.870V across temperature and process variation.

Does the MAX6865UK28D2L+T require external components for basic operation?

No, the MAX6865UK28D2L+T operates autonomously with no external components required. Its internal 10kΩ MR pullup, precision voltage reference, and watchdog timer eliminate need for discrete resistors, capacitors, or timing elements. Only a 0.1µF ceramic bypass capacitor on VCC is recommended for noise suppression in electrically noisy environments.

How does the watchdog timer in the MAX6865UK28D2L+T respond to firmware activity?

The MAX6865UK28D2L+T watchdog timer clears on any rising or falling edge at the WDI pin and expires only if WDI remains static for >209s (typ). Unlike windowed watchdogs, it does not require periodic high-low-high toggling - a single edge suffices. This allows flexible firmware integration, such as pulsing WDI at subroutine entry/exit points to detect hangs in specific code sections.

What is the minimum VCC voltage at which the MAX6865UK28D2L+T guarantees valid RESET output?

The MAX6865UK28D2L+T guarantees RESET output validity down to VCC = +1.1V, as specified in the Electrical Characteristics table. Below this voltage, VOL and VOH parameters are not guaranteed, and the internal circuitry may become indeterminate. This feature ensures reliable reset assertion during deep brownout conditions common in battery-depleted medical devices.

Can the MAX6865UK28D2L+T be used with a 1.2V supply rail?

Yes, the MAX6865UK28D2L+T operates across VCC = 1.2V to 5.5V, fully specified at 1.2V. At 1.2V, its supply current is 210nA (max), RESET VOH is guaranteed ≥0.8×VCC (≥0.96V) at 10µA source, and MR VIH is 0.7×VCC (≥0.84V). This makes it suitable for modern ultra-low-voltage MCUs like the Silicon Labs EFM32HG.