Analog Devices Inc./Maxim Integrated MAX823MEUK-T

Overview

MAX823MEUK-T from Maxim Integrated is a 5-pin SOT23 microprocessor supervisory circuit with active-low reset, watchdog timer (1.6s timeout), and manual reset input. It monitors +4.38V power supplies, guarantees RESET validity down to VCC = 1V, and provides 140ms minimum power-on reset delay for embedded controllers and automotive systems.

For engineers reviewing the MAX823MEUK-T datasheet, MAX823MEUK-T pinout, MAX823MEUK-T application, or MAX823MEUK-T equivalent, key selection criteria include reset threshold accuracy (4.38V ±7mV), watchdog immunity to WDI leakage (<10µA), MR internal pullup (52kΩ), transient immunity up to 100ns glitches, and operation across –40°C to +125°C.

Technical Context

The MAX823MEUK-T integrates a precision voltage comparator with 40ppm/°C temperature coefficient, a monostable watchdog timer cleared by WDI edges or RESET assertion, and a manual reset input with 500ns MR-to-RESET delay. Its BiCMOS process enables 6µA supply current at +25°C while maintaining guaranteed reset assertion below 1V VCC.

It features hysteresis of 10mV (for L/M variants), 20µs VCC-to-RESET propagation delay under overdrive, and internal RESET output capable of sourcing 800µA (L/M) or sinking 3.2mA - enabling direct interface with bidirectional µP reset pins like the 68HC11 without external components.

Key Specifications

Pinout & Package

Package: SOT23-5 (5-pin, surface-mount, 2.9mm × 1.6mm × 1.1mm).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX823MEUK-T, MAX823SEUK-T offers identical supervision architecture but targets lower-voltage systems, while TPS3808G33DBVR reduces cost and complexity at the expense of functional completeness - omitting both watchdog and manual reset capabilities essential for robust embedded recovery.

Availability

MAX823MEUK-T is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLCs, and medical infusion pumps requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX823MEUK-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 and mixed-signal ICs for demanding industrial, automotive, and computing applications.

The MAX823 family delivers integrated power-supply monitoring, watchdog, and manual reset in ultra-small packages - engineered specifically for space-constrained, high-reliability embedded systems where deterministic reset behavior is non-negotiable.

FAQ

What is the reset threshold voltage of the MAX823MEUK-T and how tightly is it specified?

The MAX823MEUK-T has a factory-trimmed reset threshold of 4.38V, with ±7mV tolerance at +25°C and ±12mV over the full –40°C to +125°C temperature range. This precision is achieved via laser trimming during wafer sort and is documented in the Reset Threshold Table of the datasheet. The 40ppm/°C temperature coefficient ensures minimal drift across operating conditions, making MAX823MEUK-T suitable for applications where supply rail stability must be verified within tight margins.

Does the MAX823MEUK-T require external components to operate?

No, the MAX823MEUK-T operates autonomously with no external components required. It integrates an internal 52kΩ pullup resistor on the MR pin, a precision voltage reference, hysteresis circuitry, a 1.6s watchdog timer, and a reset delay monostable - all within the SOT23-5 package. Unlike discrete solutions, MAX823MEUK-T eliminates the need for external RC networks, pullup resistors, or Schmitt triggers, reducing BOM count and PCB area while improving reliability.

How does the watchdog function behave if the WDI pin is left unconnected on the MAX823MEUK-T?

When the WDI pin is left unconnected on the MAX823MEUK-T, the internal watchdog circuit is automatically disabled. This occurs because the WDI input is internally driven low for 7/8 of the timeout period and high for 1/8 - generating a periodic low-high-low pulse every ~1.4s that continuously resets the 1.6s timer. As a result, no watchdog timeout occurs. To enable watchdog supervision, WDI must be actively toggled by the host µP at intervals shorter than 1.6s; otherwise, MAX823MEUK-T operates as a reset-only supervisor.

Can the MAX823MEUK-T drive a microcontroller with a bidirectional reset pin?

Yes, the MAX823MEUK-T RESET output can interface directly with bidirectional µP reset pins such as those found on the Motorola 68HC11. Its RESET pin sources up to 800µA (for L/M variants) and sinks up to 3.2mA, allowing the µP to override the supervisory signal when needed. This push-pull capability eliminates the need for external open-drain buffers or level shifters, and is explicitly validated in the "Interfacing to µPs with Bidirectional Reset Pins" section of the MAX823MEUK-T datasheet.

What is the minimum VCC level at which the MAX823MEUK-T guarantees correct RESET output state?

The MAX823MEUK-T guarantees correct RESET output state - specifically, that RESET remains asserted (low) - for VCC down to 1V. This specification is tested and guaranteed across the full –40°C to +125°C temperature range. It ensures fail-safe behavior during severe brownout or battery-depletion scenarios, a critical requirement for automotive and portable medical devices where supply collapse must trigger controlled shutdown before data corruption occurs. This 1V guarantee is a key differentiator versus many competing supervisors rated only to 2.0V or higher.