Analog Devices Inc./Maxim Integrated MAX823REXK+T

Overview

MAX823REXK+T from Maxim Integrated is a 5-pin SC70-packaged microprocessor supervisory circuit with active-low reset, watchdog timer (1.6s timeout), and manual reset input. It monitors +2.63V power supplies, guarantees RESET validity down to VCC = 1V, and provides 140ms minimum power-on reset delay for embedded controllers and battery-powered equipment.

For engineers reviewing the MAX823REXK+T datasheet, MAX823REXK+T pinout, MAX823REXK+T application, or MAX823REXK+T equivalent, key selection criteria include reset threshold accuracy (2.63V ±30mV), watchdog immunity to software lockup, manual reset pulse handling (≥1.0µs), transient-immune brownout detection, and SC70-5 footprint compatibility with space-constrained PCB layouts.

Technical Context

The MAX823REXK+T integrates a precision voltage comparator with 40ppm/°C temperature coefficient, a monostable watchdog timer cleared by WDI edge transitions or RESET assertion, and an internal 52kΩ MR pullup resistor enabling direct CMOS switch interfacing. Its reset generator ensures monotonic behavior during VCC ramp-up and guarantees valid logic state at 1V supply.

It features dual-stage reset timing: a 200ms nominal reset timeout after VCC rise above threshold, plus 500ns MR-to-RESET propagation delay and 20µs VCC-to-RESET response on falling edge. The WDI input accepts 50ns minimum pulses and disables watchdog when left unconnected or three-stated.

Key Specifications

Pinout & Package

MAX823REXK+T uses the SC70-5 surface-mount package (1.6mm × 1.6mm × 0.9mm), optimized for high-density portable designs. Pin 1 is marked with a dot; pin numbering follows standard SC70 counterclockwise orientation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX823REXK+T, MAX823SEUK+T offers identical functionality in a thermally rugged SOT23 package but requires PCB redesign, while TPS3808G33DBVR reduces cost and complexity by omitting watchdog and MR-making it suitable only for basic reset supervision where those features are unused.

Availability

MAX823REXK+T is available at Aetrix Electronics and suitable for industrial PLC controllers, portable medical devices, automotive body control modules, smart energy meters, and battery-powered instrumentation requiring stable component supply across extended temperature ranges.

Supply support for MAX823REXK+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 industrial, automotive, and computing applications, with expertise in power management and reliability-critical subsystems.

The MAX823 family delivers integrated reset, watchdog, and manual reset functions in ultra-small SC70/SOT23 packages, targeting space-constrained embedded systems where deterministic power-on behavior and firmware fault recovery are mandatory.

FAQ

What is the exact reset threshold voltage for MAX823REXK+T and how tightly is it specified?

The MAX823REXK+T has a nominal reset threshold of 2.63V, with a guaranteed tolerance of ±30mV over the full -40°C to +85°C temperature range. This specification is confirmed in the Reset Threshold Table and Electrical Characteristics section of the official datasheet, where VRST is listed as 2.59V (min), 2.63V (typ), and 2.66V (max) at TA = TMIN to TMAX. The 40ppm/°C temperature coefficient ensures minimal drift across operating conditions.

Does MAX823REXK+T support watchdog functionality, and what is its timeout period?

Yes, MAX823REXK+T includes a watchdog timer with a nominal timeout period of 1.6 seconds, specified as 1.12s (min) to 2.40s (max) over temperature. The watchdog is cleared by any rising or falling edge on the WDI pin and remains disabled if WDI is left unconnected or driven by a three-stated output. This behavior is explicitly documented in the Selector Guide and Electrical Characteristics tables for the MAX823 series.

Can MAX823REXK+T operate reliably when VCC drops below 2.0V, and what happens to the RESET output?

Yes, MAX823REXK+T guarantees RESET output validity down to VCC = 1.0V, meaning the RESET pin remains in a known logic-low state even as supply voltage collapses. This is confirmed in both the General Description ("guaranteed RESET valid to VCC = 1V") and Electrical Characteristics table (VOL test condition: TA = TMIN to TMAX, VCC = 1.2V, VCC falling). At 1V, RESET sinks ≥50µA while holding solid low-critical for orderly shutdown in battery-depleted systems.

What package type and pin count does MAX823REXK+T use, and is it lead-free?

MAX823REXK+T uses the SC70-5 surface-mount package (5-pin, 1.6mm × 1.6mm), as confirmed in the Ordering Information table and Pin Configurations diagram. The "+T" suffix explicitly denotes lead-free packaging per Maxim's ordering convention, replacing the leaded "-T" variant. This is verified in the Selector Guide footnote: "Specify lead-free by replacing '-T' with '+T' when ordering."

How does the manual reset (MR) input behave on MAX823REXK+T, and what external components are needed?

The MR input on MAX823REXK+T is active-low with an internal 52kΩ pullup resistor, so no external components are required. A logic-low pulse ≥1.0µs on MR asserts RESET for 200ms after MR returns high. The datasheet confirms MR can be driven directly from CMOS logic or a momentary switch to GND; capacitive filtering (e.g., 0.1µF to GND) is optional for noise immunity in harsh environments. This eliminates BOM cost and layout area versus discrete reset-button solutions.