Analog Devices Inc./Maxim Integrated MAX6865UK37D3S+T

Overview

The MAX6865UK37D3S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, combining voltage monitoring (3.700V ±2.5% reset threshold), manual reset input (MR), and watchdog timer (209s typical timeout) with ultra-low 170nA typical supply current. It asserts an active-high push-pull RESET output during VCC brownout, MR assertion, or watchdog timeout, ensuring reliable µP initialization in battery-constrained medical and portable systems.

For engineers reviewing the MAX6865UK37D3S+T datasheet, MAX6865UK37D3S+T pinout, MAX6865UK37D3S+T application, or MAX6865UK37D3S+T equivalent, key selection criteria include its guaranteed RESET validity down to VCC = +1.1V, immunity to sub-40µs VCC transients, fixed 150ms minimum reset timeout, and compatibility with 1.2V–5.5V supply rails in space- and power-sensitive designs.

Technical Context

This device implements a precision bandgap-based voltage monitor with 2.5% threshold tolerance and 0.5% hysteresis, paired with a temperature-stable RC-based watchdog timer (L-suffix = 209s typ). Its internal 10kΩ MR pullup and glitch rejection (200ns) enable direct switch interfacing without external components.

The active-high push-pull RESET output delivers VOH ≥ 0.8×VCC at ISOURCE = 500µA (VCC ≥ 2.38V) and VOL ≤ 0.3V at ISINK = 1.2mA (VCC ≥ 2.38V), supporting direct connection to µP reset inputs across 1.8V–5V logic families without level-shifting.

Key Specifications

Pinout & Package

5-pin SOT23-5 package (2.9mm × 1.6mm × 1.1mm), lead-free, RoHS-compliant, rated for -40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK37D3S+T and TPS3837K33DBVR, the MAX6865UK37D3S+T uniquely delivers active-high RESET, ultra-low 170nA current, and integrated 209s watchdog in one 5-pin SOT23 - enabling longer battery life and safer fail-safe behavior in Class II medical and industrial IoT endpoints.

Availability

MAX6865UK37D3S+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered instrumentation, and industrial handheld equipment requiring stable component supply with guaranteed long-term availability.

Supply support for MAX6865UK37D3S+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 was engineered specifically for nanopower supervisory functions in battery-critical systems, integrating voltage monitoring, manual reset, and watchdog timing into minimal 5-pin SOT23 footprints.

FAQ

What is the exact reset threshold voltage of the MAX6865UK37D3S+T?

The MAX6865UK37D3S+T has a factory-trimmed reset threshold of 3.700V 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 "37" corresponds to 3.700V nominal. The device guarantees valid RESET assertion down to VCC = +1.1V, making it suitable for brownout detection in 3.3V systems with significant dropout margin.

Does the MAX6865UK37D3S+T require external components for basic operation?

No, the MAX6865UK37D3S+T operates autonomously with zero external components for core supervision. It integrates a 10kΩ internal pullup on MR, a precision voltage reference, reset timeout generator, and watchdog oscillator. Only a 0.1µF ceramic capacitor from VCC to GND is recommended for noise suppression - no resistors, capacitors, or trimmers are needed for threshold, timeout, or reset output configuration.

How does the watchdog timer in the MAX6865UK37D3S+T clear and trigger?

The MAX6865UK37D3S+T watchdog timer (L-suffix = 209s typical) clears on any rising or falling edge at WDI, or when RESET is asserted or MR is pulled low. It triggers a reset if WDI remains static (high or low) beyond 209s. The timer resumes counting immediately after RESET deasserts - no software handshake or register access is required, enabling robust hang detection in bare-metal firmware.

What is the function of Pin 1 (RESET) on the MAX6865UK37D3S+T?

Pin 1 of the MAX6865UK37D3S+T is an active-high push-pull RESET output. It drives high (≥0.8×VCC) when asserting reset due to VCC dropout, MR activation, or watchdog timeout, and drives low (<0.3V) when deasserted. Unlike open-drain variants, it requires no external pullup and interfaces directly with µP reset pins rated for 1.8V–5V logic levels.

Can the MAX6865UK37D3S+T operate from a 1.5V supply?

Yes, the MAX6865UK37D3S+T operates from VCC = 1.2V to 5.5V. At 1.5V, its supply current remains ultra-low (typical 190nA), and RESET is guaranteed valid down to VCC = +1.1V. However, VOH will be ≥1.2V (0.8×1.5V) and VOL ≤0.3V, which meets most 1.8V µP reset input thresholds but may require verification against specific MCU datasheets for 1.5V logic compatibility.