Analog Devices Inc./Maxim Integrated MAX809REUR.

Overview

MAX809REUR from Maxim Integrated is a 3-pin SOT23-3 microprocessor supervisory circuit with push-pull active-low RESET output, designed to monitor +2.5V to +5V power supplies in embedded systems. It asserts reset when VCC falls below 2.63V (±1.5% threshold accuracy), holds reset for ≥140ms after VCC recovers, operates down to VCC = 1V, draws only 17–100µA supply current, and provides transient immunity up to 100mV overdrive.

For engineers reviewing the MAX809REUR datasheet, MAX809REUR pinout, MAX809REUR application, or MAX809REUR equivalent, this device serves as a precision voltage-monitoring reset supervisor for portable, automotive, and industrial µP systems where reliable power-on initialization and brownout protection are critical - especially where low quiescent current, guaranteed reset timing, and SOT23-3 footprint compatibility are required.

Technical Context

The MAX809REUR implements a precision bandgap-based voltage comparator that triggers reset when VCC drops below its factory-trimmed 2.63V threshold. Its internal timing circuit ensures a minimum 140ms reset pulse width after VCC rises above threshold, with timeout extended up to 840ms at high temperature.

It features push-pull output logic compatible with standard CMOS inputs, guarantees valid RESET state down to VCC = 1V, and rejects fast transients via built-in comparator hysteresis and filtering - no external components required for basic operation.

Key Specifications

Pinout & Package

MAX809REUR is housed in a 3-pin SOT23-3 package (JEDEC MO-178AA), with 1.3mm × 2.9mm footprint, 0.95mm height, and gull-wing leads. Pin 1 = RESET (active-low push-pull output), Pin 2 = GND, Pin 3 = VCC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX809REUR, MAX809SEUR offers higher threshold for 3.3V systems but lacks compatibility with 3.0V rails, while TPS3808G12DBVR provides broader VCC range and longer timeout but demands layout revision - MAX809REUR remains optimal for cost-sensitive, space-constrained +3.0V embedded designs requiring exact 2.63V trip point and SOT23-3 fit.

Availability

MAX809REUR is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, and portable medical sensors requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for MAX809REUR 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) is a semiconductor company specializing in analog, mixed-signal, and power management ICs for industrial, automotive, communications, and computing markets.

The MAX809 series belongs to Maxim's microprocessor supervisory product line, engineered specifically to deliver precision voltage monitoring and robust reset generation for embedded systems where reliability, low power, and small footprint are essential.

FAQ

What is the exact reset threshold voltage of the MAX809REUR and how tightly is it specified?

The MAX809REUR has a factory-trimmed reset threshold of 2.63V with a tolerance of ±1.5% over the full operating temperature range (-40°C to +105°C). This specification is guaranteed by design and production-tested per Maxim's datasheet, ensuring consistent trip-point behavior across voltage and temperature - critical for reliable operation in +3.0V systems where margin between nominal supply and reset assertion must be precisely controlled.

Does the MAX809REUR require an external pull-up resistor on its RESET pin?

No, the MAX809REUR does not require an external pull-up resistor because it features a push-pull active-low RESET output. The internal output stage actively drives the RESET pin low during reset assertion and high (to VCC) when deasserted - eliminating dependency on external biasing and simplifying interface to standard CMOS microcontroller reset inputs. This differs from the open-drain MAX803 family, which does require a pull-up.

What is the minimum VCC voltage at which the MAX809REUR guarantees correct RESET output logic state?

The MAX809REUR guarantees correct RESET output logic state down to VCC = 1.0V. Below this voltage, the output may become indeterminate; however, the device continues asserting RESET as long as VCC remains below the 2.63V threshold and sustains the ≥140ms timeout after recovery. This behavior ensures deterministic reset during deep brownout events common in battery-powered or automotive applications.

Can the MAX809REUR be used in automotive applications, and what temperature range does it support?

Yes, the MAX809REUR is qualified for automotive use with an operating temperature range of -40°C to +105°C - matching AEC-Q100 Grade 3 requirements. Its SOT23-3 package, precision 2.63V threshold, transient immunity, and guaranteed reset timing make it suitable for body control modules, infotainment power supervisors, and other under-hood or cabin-mounted electronics where reliability under thermal stress is mandatory.

How does the MAX809REUR handle fast power-supply transients, and what is its immunity specification?

The MAX809REUR rejects fast negative-going VCC transients via internal comparator hysteresis and filtering. Per datasheet characterization, it ignores transients ≤20µs wide when the overdrive (VTH – VCC) is ≤100mV - preventing false resets caused by switching noise or load-dump coupling. This immunity is verified across temperature and does not require external RC networks, supporting robust operation in electrically noisy environments like motor drives or power converters.