Analog Devices Inc./Maxim Integrated MAX824TEXK+T

Overview

MAX824TEXK+T from Maxim Integrated is a 5-pin microprocessor supervisory circuit with active-low watchdog input and complementary active-high reset output, designed for reliable power-on/brownout monitoring of +3.08V supplies in embedded systems. It guarantees RESET validity down to VCC = 1V, features 140ms minimum reset timeout, 1.6s watchdog timeout, and operates at 2µA supply current in SC70-5 package.

For engineers reviewing the MAX824TEXK+T datasheet, MAX824TEXK+T pinout, MAX824TEXK+T application, or MAX824TEXK+T equivalent, key selection criteria include reset threshold accuracy (3.08V ±30mV), transient immunity on VCC, watchdog pulse edge sensitivity (50ns), and compatibility with bidirectional µP reset pins requiring ≤400µA pullup current.

Technical Context

The MAX824TEXK+T integrates a precision voltage comparator with 40ppm/°C temperature coefficient and hysteresis of 5mV to detect VCC drops below 3.08V. Its internal 140–280ms reset timeout timer ensures stable deassertion after power stabilization.

It implements a watchdog function that triggers reset if WDI remains static beyond 1.12–2.40s; the timer clears on any WDI edge or RESET assertion. The complementary RESET output provides active-high logic synchronized to the active-low RESET signal, enabling direct interface to µPs requiring high-true reset inputs.

Key Specifications

Pinout & Package

MAX824TEXK+T is housed in a lead-free SC70-5 package (2.0mm × 1.25mm × 0.9mm), optimized for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX824TEXK+T, MAX824TEUK+T offers identical functionality in a thermally robust SOT23 package but requires PCB redesign, while TPS3808G30DBVR sacrifices watchdog capability for tighter threshold tolerance and longer reset delay-making it viable only for non-watchdog applications where 3.0V vs. 3.08V threshold is acceptable.

Availability

MAX824TEXK+T is available at Aetrix Electronics and suitable for industrial PLC controllers, medical handheld diagnostics, automotive body control modules, and IoT edge sensor nodes requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX824TEXK+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 power, sensing, and interface applications in industrial, automotive, and computing markets.

The MAX823/MAX824/MAX825 family delivers integrated reset, watchdog, and manual reset functions in ultra-small packages for space- and power-constrained microprocessor systems.

FAQ

What is the exact reset threshold voltage of MAX824TEXK+T and how tightly is it specified?

The MAX824TEXK+T has a factory-trimmed reset threshold of 3.08V, with guaranteed limits of 3.04V (min) to 3.11V (max) over full temperature range (-40°C to +85°C). This 3.08V threshold is selected by the "T" suffix per Maxim's Reset Threshold Table and applies specifically to the MAX824TEXK+T variant-not to other members of the MAX824 family. The device achieves ±0.5% accuracy at +25°C and maintains 40ppm/°C temperature coefficient for stable operation across its rated range.

Does MAX824TEXK+T support watchdog functionality, and what are the timing requirements for WDI?

Yes, MAX824TEXK+T includes a watchdog timer with nominal timeout of 1.6s (1.12–2.40s over temperature). The WDI pin must be toggled-either rising or falling edge-within this period to prevent reset assertion. Pulses as short as 50ns are recognized, and the timer clears immediately on any edge or during RESET assertion. Leaving WDI unconnected disables the watchdog, as the internal driver services the timer every ~1.4s.

How does the complementary RESET/RESET output pair operate in MAX824TEXK+T?

In MAX824TEXK+T, pin 4 (RESET) is active-low and pin 5 (RESET) is active-high-logically inverted and synchronized. When VCC drops below 3.08V, both outputs transition simultaneously: pin 4 goes low and pin 5 goes high. After reset timeout, they return to idle states (pin 4 high, pin 5 low). This dual-output architecture eliminates need for external inverters when interfacing to µPs or FPGAs with mixed reset polarity requirements.

What is the supply current of MAX824TEXK+T and under what conditions is it measured?

MAX824TEXK+T draws 2µA typical supply current, measured in SC70-5 package at TA = +25°C with MR and WDI unconnected and VCC = 3.3V. This ultra-low quiescent current is confirmed in the Electrical Characteristics table for MAX824T/S/R/Z/Y variants in SC70. Current increases slightly at temperature extremes but remains below 8µA over full -40°C to +85°C range, making it ideal for battery-critical applications.

Can MAX824TEXK+T operate reliably during fast VCC transients, and what design measures improve immunity?

Yes, MAX824TEXK+T is specifically designed to ignore fast transients on VCC-its comparator includes built-in filtering and hysteresis (5mV) to reject glitches <100ns wide. The Typical Operating Characteristics graph "Maximum VCC Transient Duration vs. Reset Threshold Overdrive" quantifies immunity: e.g., a 100mV dip below 3.08V can last up to ~20µs without triggering reset. Adding a 0.1µF ceramic capacitor close to the VCC pin further enhances immunity to high-frequency noise.