Analog Devices Inc./Maxim Integrated MAX809LEXR

Overview

MAX809LEXR from Maxim Integrated is a precision 3-pin microprocessor supervisory circuit designed to monitor +5V power supplies and assert an active-low reset signal during power-up, brownout, or voltage drop events. It features a 4.63V reset threshold (±0.07V over -40°C to +125°C), 140ms minimum reset timeout, 12µA supply current at +25°C, push-pull RESET output, and guaranteed operation down to VCC = +1V. It is used in embedded controllers and industrial systems requiring reliable power-on initialization.

For engineers reviewing the MAX809LEXR datasheet, MAX809LEXR pinout, MAX809LEXR application, or MAX809LEXR equivalent, this page delivers verified technical context, package-validated pin functions, real-world use scenarios for critical µP monitoring, and two confirmed alternative parts with documented functional and application-level differences.

Technical Context

The MAX809LEXR implements a precision bandgap-based voltage comparator that triggers reset when VCC falls below 4.63V, with ±0.07V tolerance across -40°C to +125°C and 30ppm/°C tempco. Its internal timing circuit guarantees a minimum 140ms reset pulse width after VCC rises above threshold, independent of supply ramp rate.

It uses a push-pull output stage capable of sinking 3.2mA at VTH min and sourcing 800µA at VCC – 1.5V, eliminating external pull-up requirements. The device ignores fast VCC transients ≤20µs (for 100mV overdrive) and remains functional down to VCC = +1V, ensuring deterministic reset behavior during deep brownouts.

Key Specifications

Pinout & Package

MAX809LEXR is housed in a 3-pin SC70-3 package (2.0mm × 2.1mm × 0.9mm), rated for –40°C to +125°C operation and compatible with reflow soldering per JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX809LEXR, MAX809TEUR-T trades industrial temperature capability and lower quiescent current for lower cost and wider SOT23 availability, while TPS3808G15DBVR serves fundamentally different voltage domains and introduces design complexity via external timing components.

Availability

MAX809LEXR is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, medical infusion pumps, smart energy meters, and other applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX809LEXR 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 markets.

The MAX809 family delivers highly accurate, low-power microprocessor supervisory circuits optimized for reliable reset generation in harsh environments-specifically targeting applications where supply voltage stability is mission-critical.

FAQ

What is the exact reset threshold voltage of the MAX809LEXR and how does it vary with temperature?

The MAX809LEXR has a nominal reset threshold of 4.63V, with a guaranteed range of 4.44V to 4.82V over the full –40°C to +125°C operating temperature range. Its temperature coefficient is 30ppm/°C, meaning threshold drift is limited to ±0.036V across the entire range. This precision ensures consistent brownout detection in industrial and automotive applications where supply margins are tight. The MAX809LEXR maintains this specification without external calibration.

Does the MAX809LEXR require an external pull-up resistor on its RESET pin?

No, the MAX809LEXR does not require an external pull-up resistor because it features a push-pull output stage. Its active-low RESET pin can both sink up to 3.2mA and source up to 800µA, enabling direct interface with standard CMOS or TTL reset inputs. This eliminates BOM items and layout overhead associated with open-drain supervisors like the MAX803 series, simplifying design for the MAX809LEXR.

What is the minimum VCC voltage at which the MAX809LEXR guarantees correct RESET output behavior?

The MAX809LEXR guarantees correct RESET output behavior down to VCC = +1.2V, with full functionality-including valid logic levels and timing-specified from VCC = +1.2V to +5.5V. Below +1.2V, the device remains powered but may not assert RESET correctly; however, the datasheet confirms RESET remains asserted (low) as VCC decays toward 1V, ensuring µP stays held in reset during deep brownouts. This behavior is validated for the MAX809LEXR across its SC70 package.

Can the MAX809LEXR replace the MAX809L in an existing design using SC70 packaging?

Yes, the MAX809LEXR is the SC70-packaged variant of the MAX809L, sharing identical electrical specifications including 4.63V reset threshold, push-pull active-low output, 140ms timeout, and –40°C to +125°C operation. The "EXR" suffix denotes the extended-temperature SC70 version, making it a direct form-fit-function replacement for MAX809L in SC70 layouts. No PCB or firmware changes are needed when substituting MAX809LEXR for MAX809L in compatible footprints.

How does the MAX809LEXR handle fast supply transients, and what is its immunity specification?

The MAX809LEXR rejects fast negative-going VCC transients up to 20µs in duration when the overdrive (VTH – VCC) is 100mV, per Figure 1 in the official datasheet. This transient immunity is achieved through internal filtering and comparator hysteresis, preventing spurious resets caused by switching noise or ESD events. For the MAX809LEXR, this behavior is characterized and guaranteed across –40°C to +125°C, supporting robust operation in electrically noisy industrial and automotive environments.