Analog Devices Inc./Maxim Integrated MAX809REUR+T

Overview

MAX809REUR+T from Maxim Integrated is a 3-pin SOT23 microprocessor supervisory circuit with push-pull active-low RESET output, designed to monitor +2.5V power supplies. It asserts reset when VCC falls below 2.63V (±1.5% over temperature), maintains reset for ≥140ms after VCC recovery, draws only 17µA typical supply current at +25°C, and guarantees valid reset operation down to VCC = +1V. It is used in battery-powered microcontroller systems requiring reliable brownout detection.

For engineers reviewing the MAX809REUR+T datasheet, MAX809REUR+T pinout, MAX809REUR+T application, or MAX809REUR+T equivalent, this page delivers verified electrical parameters, thermal performance across –40°C to +105°C, SOT23 package compatibility, and real-world reset timing behavior under transient conditions - all critical for embedded system power integrity validation.

Technical Context

The MAX809REUR+T implements a precision voltage comparator with 30ppm/°C tempco to detect VCC drops below its 2.63V threshold, coupled with an internal timer that enforces a minimum 140ms reset pulse width after VCC rises above threshold. Its push-pull output drives low with ≤0.3V VOL at 1.2mA sink, eliminating external pull-up components required by open-drain variants like the MAX803R.

It operates across full VCC range of 1.2V to 5.5V and remains functional down to VCC = 1V, where RESET output is guaranteed to stay in correct logic state. The device ignores fast transients - e.g., a 100mV VCC dip lasting ≤20µs does not trigger spurious reset - due to built-in noise immunity in the reset comparator.

Key Specifications

Pinout & Package

MAX809REUR+T is housed in a RoHS-compliant 3-pin SOT23 package (package code U3+1), with 1.3mm × 2.9mm footprint and 0.95mm height, optimized for high-density PCB layouts in portable electronics.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV809RDBZR and TPS3808G33DBVR, the MAX809REUR+T offers superior temperature stability (30ppm/°C), guaranteed reset validity down to 1V, and documented immunity to 20µs/100mV transients - making it the preferred choice for robust +2.5V microcontroller supervision in harsh environments.

Availability

MAX809REUR+T is available at Aetrix Electronics and suitable for battery-powered IoT sensors, industrial PLC controllers, automotive body modules, and medical portable diagnostics requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX809REUR+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 industrial, automotive, communications, and computing applications.

The MAX809 series belongs to Maxim's microprocessor supervisory product line, engineered specifically to provide highly accurate, low-power, and transient-immune reset functionality for microcontrollers operating from +2.5V, +3.0V, +3.3V, and +5V rails.

FAQ

What is the exact reset threshold voltage of the MAX809REUR+T and how stable is it over temperature?

The MAX809REUR+T has a nominal reset threshold of 2.63V, with ±1.5% tolerance over the full operating temperature range of –40°C to +105°C. Its reset comparator exhibits a tight 30ppm/°C temperature coefficient, meaning threshold drift is limited to approximately ±10mV across the entire range - critical for consistent brownout detection in automotive and industrial applications where ambient temperature varies widely.

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

No, the MAX809REUR+T does not require an external pull-up resistor because it features a push-pull active-low RESET output. Unlike open-drain variants such as the MAX803R, the MAX809REUR+T actively drives both low (≤0.3V at 1.2mA) and high (≥0.8×VCC) states, enabling direct connection to standard CMOS reset inputs without additional components - reducing BOM count and PCB area.

Can the MAX809REUR+T operate reliably when the supply voltage drops below 2.0V?

Yes, the MAX809REUR+T guarantees correct RESET logic state down to VCC = +1V. While its specified operating range starts at 1.2V, the device continues to assert or deassert RESET predictably even as VCC decays to 1V - a key feature that prevents floating reset lines and undefined MCU behavior during deep brownout conditions common in battery-depleted systems.

What is the minimum reset pulse width guaranteed by the MAX809REUR+T, and is it affected by temperature?

The MAX809REUR+T guarantees a minimum reset pulse width of 140ms after VCC rises above the 2.63V threshold, with typical values ranging from 240ms to 560ms depending on temperature and package. At –40°C to +85°C, the timeout is 140ms to 560ms; at +85°C to +105°C, it narrows to 100ms to 840ms. This wide margin ensures robust power-on sequencing across all rated conditions without external timing components.

How does the MAX809REUR+T handle fast supply transients, and what level of immunity is specified?

The MAX809REUR+T is designed to ignore fast negative-going VCC transients: a 100mV dip below the 2.63V threshold lasting ≤20µs will not trigger a false reset pulse. This immunity is achieved through internal comparator hysteresis and filtering, eliminating the need for large bypass capacitors solely for glitch rejection - simplifying layout while maintaining reliability in electrically noisy environments like motor drives or automotive ECUs.