Analog Devices Inc./Maxim Integrated MAX809MEUR

Overview

MAX809MEUR from Maxim Integrated is a 3-pin SOT23-3 microprocessor supervisory circuit with push-pull active-low RESET output, 4.38V reset threshold (±1.5% over -40°C to +85°C), 140ms minimum reset timeout, and 12µA supply current at +25°C. It monitors +5V or +3.3V power rails in embedded controllers and portable systems to prevent erroneous code execution during power-up, brownout, or power-down.

For engineers reviewing the MAX809MEUR datasheet, MAX809MEUR pinout, MAX809MEUR application, or MAX809MEUR equivalent, key selection criteria include its guaranteed reset validity down to VCC = +1V, immunity to fast VCC transients (<20µs at 100mV overdrive), push-pull drive capability (3.2mA sink), and SOT23-3 footprint compatibility with space-constrained PCB layouts.

Technical Context

The MAX809MEUR implements a precision bandgap-based voltage comparator with 30ppm/°C tempco to detect VCC falling below 4.38V, asserting active-low RESET until VCC rises above threshold and remains stable for ≥140ms. Its internal logic ensures no false resets from sub-20µs negative VCC glitches.

Designed for direct interface with µP reset inputs, it delivers rail-to-rail push-pull output swing (VOL ≤ 0.4V at 3.2mA sink; VOH ≥ VCC–1.5V at 800µA source) without external pull-ups, and operates reliably across VCC = 1.2V to 5.5V while maintaining reset assertion down to VCC = 1V.

Key Specifications

Pinout & Package

MAX809MEUR is housed in a RoHS-compliant 3-pin SOT23-3 package (drawing 21-0051G, pkgcode U3-1), with 1.3mm × 2.9mm footprint and 1.1mm height, optimized for automated assembly and high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX809SEUR, MAX809MEUR provides higher reset threshold for +5V systems and eliminates need for threshold recalibration; versus TPS3808G12DBVR, it offers lower ICC and zero-component simplicity at the cost of fixed threshold and shorter timeout.

Availability

MAX809MEUR is available at Aetrix Electronics and suitable for industrial controllers, portable medical devices, automotive body electronics, networked smart sensors, and battery-powered instrumentation requiring stable component supply across extended temperature ranges.

Supply support for MAX809MEUR 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 and mixed-signal ICs for power, sensing, and interface applications, with emphasis on reliability and integration.

The MAX809 series belongs to Maxim's microprocessor supervisory product line, engineered specifically for deterministic power-on reset generation in resource-constrained embedded systems with strict BOM and footprint constraints.

FAQ

What is the exact reset threshold voltage of MAX809MEUR and how tightly is it specified?

The MAX809MEUR has a nominal reset threshold of 4.38V, specified with ±1.5% tolerance over the full operating temperature range of -40°C to +85°C. This means the actual threshold falls between 4.31V and 4.45V under all conditions, ensuring consistent brownout detection for +5V systems without requiring calibration. The MAX809MEUR uses laser-trimmed bandgap circuitry to achieve this precision, eliminating the need for external resistive dividers.

Does MAX809MEUR require an external pull-up resistor on its RESET pin?

No, MAX809MEUR does not require an external pull-up resistor because it features a push-pull active-low RESET output. Unlike open-drain supervisors such as the MAX803, the MAX809MEUR internally drives the RESET line high or low, enabling direct connection to microcontroller reset inputs without additional components. This simplifies design, reduces BOM count, and improves noise immunity in compact layouts.

Can MAX809MEUR operate reliably when the supply voltage drops below 2.0V?

Yes, MAX809MEUR guarantees correct RESET logic state down to VCC = +1V, meaning it continues asserting active-low RESET even as the supply decays from 4.38V to 1.0V. However, below 1.2V the device exits specification - the datasheet specifies minimum VCC as 1.2V for functional operation, and RESET behavior is not guaranteed below that point. For applications requiring reset assertion all the way to 0V, a pull-down resistor on RESET is recommended.

What is the maximum transient duration MAX809MEUR can ignore on the VCC line without issuing a false reset?

At a reset comparator overdrive of 100mV (i.e., VCC dropping 100mV below the 4.38V threshold), MAX809MEUR ignores transients up to 20µs in duration at +25°C. This immunity extends across temperature: at -40°C to +85°C, the device rejects sub-20µs glitches, preventing spurious resets in electrically noisy environments like motor drives or switching power supplies. A 0.1µF ceramic capacitor placed near the VCC pin further enhances this immunity.

How does the reset timeout of MAX809MEUR behave across temperature and supply voltage?

MAX809MEUR guarantees a minimum reset timeout of 140ms after VCC rises above threshold, with typical values ranging from 240ms to 560ms depending on temperature and package. In the SOT23-3 package (used by MAX809MEUR), timeout is 140–240ms at -40°C to +85°C and extends to 100–840ms at +85°C to +105°C. The timeout is internally generated and independent of external RC networks, ensuring consistent boot sequencing regardless of VCC ramp rate or board parasitics.