Analog Devices Inc./Maxim Integrated MAX6805US31D3+T

Overview

MAX6805US31D3+T from Maxim Integrated is an open-drain, active-low microprocessor supervisory circuit in a 4-pin SOT143 package, designed for precise power supply monitoring at 3.08V reset threshold with 100ms minimum reset timeout. It operates from 1.0V to 5.5V, draws only 4–12µA supply current, and features debounced manual reset input-ideal for battery-powered controllers and embedded systems requiring reliable brownout detection.

For engineers reviewing the MAX6805US31D3+T datasheet, MAX6805US31D3+T pinout, MAX6805US31D3+T application, or MAX6805US31D3+T equivalent, key selection criteria include its open-drain RESET output compatibility with bidirectional µP reset pins (e.g., Motorola 68HC11), guaranteed operation down to VCC = 1.0V, factory-trimmed ±3% threshold accuracy over –40°C to +125°C, and immunity to fast VCC transients up to 30µs at 10V/ms slew rate.

Technical Context

The MAX6805US31D3+T implements a precision voltage comparator with factory-trimmed 3.08V threshold (±1.8% at +25°C, ±3% over full temperature range) and internal hysteresis to reject noise. Its reset assertion logic combines VCC monitoring and MR input, with reset remaining active for ≥100ms after VCC rises above threshold or MR deasserts.

Unlike push/pull variants (MAX6803/MAX6804), the open-drain RESET output requires an external pullup resistor and supports wired-OR configurations-enabling direct interface with µPs having bidirectional reset pins without level-shifting or additional logic.

Key Specifications

Pinout & Package

Package: 4-pin SOT143 (U4-1 outline, 21-0052 footprint), surface-mount, lead-free (RoHS-compliant).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6804US31D3+T and TPS3808G33DBVR, the MAX6805US31D3+T uniquely supports shared reset buses and bidirectional µP interfaces via its open-drain output-making it essential for designs requiring reset arbitration or legacy µP compatibility, despite higher minimum operating voltage.

Availability

MAX6805US31D3+T is available at Aetrix Electronics and suitable for industrial controllers, battery-powered instruments, embedded communication modules, and medical diagnostic sensors requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6805US31D3+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 high-reliability industrial, automotive, and communications applications.

The MAX680x family delivers ultra-low-power, pin-compatible µP supervisory circuits with factory-trimmed thresholds and configurable reset timeouts-targeting space-constrained embedded systems needing robust power-fail detection without external components.

FAQ

What is the exact reset threshold voltage of the MAX6805US31D3+T and how accurate is it over temperature?

The MAX6805US31D3+T has a factory-trimmed nominal reset threshold of 3.08V. At +25°C, accuracy is ±1.8%; over the full –40°C to +125°C operating range, it is guaranteed within ±3%. This ensures reliable brownout detection in 3.3V systems across industrial temperature extremes without calibration.

Why does the MAX6805US31D3+T use an open-drain RESET output instead of push/pull?

The MAX6805US31D3+T uses an open-drain RESET output to enable wired-OR configurations and direct interfacing with microprocessors that have bidirectional reset pins (e.g., Motorola 68HC11). This architecture allows multiple devices-including the MAX6805US31D3+T-to share a common reset line using a single external pullup resistor.

What is the minimum supply voltage required for the MAX6805US31D3+T to guarantee correct reset behavior?

The MAX6805US31D3+T is guaranteed to maintain correct reset state down to VCC = 1.0V at –40°C to +125°C, and down to 1.2V across the full temperature range. Below this, reset assertion may become unreliable-unlike the MAX6803/MAX6804, which operate down to 0.7V.

Does the MAX6805US31D3+T require external components for manual reset functionality?

No. The MAX6805US31D3+T includes an internal 20kΩ pullup resistor on the MR pin, so a simple normally-open momentary switch from MR to GND provides fully debounced manual reset-no external capacitors, resistors, or logic gates are needed.

How does the MAX6805US31D3+T handle fast transients on the VCC supply line?

The MAX6805US31D3+T's reset comparator rejects fast negative-going VCC transients up to 30µs duration when the slew rate is 10V/ms. This immunity prevents spurious resets caused by switching noise or load dumps, as confirmed by the "Maximum Transient Duration vs. Reset Comparator Overdrive" graph in the datasheet.