Analog Devices Inc./Maxim Integrated DS1231-20N+

Overview

DS1231-20N+ from Maxim Integrated is a precision power monitor IC that detects impending power failure by monitoring both high-voltage input (IN) and +5V supply (VCC), provides dual reset outputs (RST active-high, RST active-low open-drain), generates non-maskable interrupt (NMI), and supports selectable 5% or 10% VCC threshold detection via TOL pin - used in industrial control systems for orderly microprocessor shutdown before brownout.

For engineers reviewing the DS1231-20N+ datasheet, DS1231-20N+ pinout, DS1231-20N+ application, or DS1231-20N+ equivalent, key selection criteria include VCC trip accuracy (±5% or ±10%), IN pin hysteresis (60 mV), dual RST signaling, NMI timing delay (≤200 µs), and compatibility with linear/switching supplies without external capacitors.

Technical Context

The DS1231-20N+ integrates two independent comparators: one monitors VCC against temperature-compensated reference to assert RST/RST at 4.25 V (TOL=VCC) or 4.75 V (TOL=GND); the other monitors IN with mode-selectable input characteristics - high-impedance (MODE=VCC, VTP−=2.3 V) or 30 µA current source (MODE=GND, VTP+=2.5 V).

It delivers automatic power-up reset with ≥150 ms minimum assertion time, supports opto-isolated AC line sensing, provides noise-immune hysteresis on both inputs, and maintains valid RST output down to VCC = 2.0 V - enabling robust interface with 8051-class microprocessors in unregulated environments.

Key Specifications

Pinout & Package

DS1231-20N+ is supplied in an 8-pin DIP package (300 mil width), with pins arranged as follows:

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power monitor applications.

Compared with MAX690CPA+ and TPS3823-50DBVR, DS1231-20N+ uniquely combines VCC supervision, high-voltage input sensing, NMI generation, and dual RST outputs - making it irreplaceable in applications requiring deterministic, multi-stage power-failure response with zero external timing components.

Availability

DS1231-20N+ is available at Aetrix Electronics and suitable for industrial control systems, medical diagnostic equipment, telecom infrastructure, and smart metering applications requiring stable component supply and long-term lifecycle support.

Supply support for DS1231-20N+ 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) is a semiconductor company specializing in analog, mixed-signal, and power management ICs for industrial, communications, and computing markets.

The DS1231-20N+ belongs to Maxim's legacy power supervision product line, designed specifically for microprocessor-based systems needing fail-safe power-loss detection, orderly shutdown, and automatic restart - targeting reliability-critical embedded platforms.

FAQ

What is the function of the MODE pin on the DS1231-20N+?

The MODE pin on the DS1231-20N+ selects the electrical behavior of the IN pin: when tied to VCC, IN becomes a high-impedance input (IIL ≤ 0.1 µA) with 2.3 V trip point (VTP−); when grounded, IN acts as a 30 µA current source with 2.5 V trip point (VTP+). This dual-mode design allows DS1231-20N+ to interface directly with resistor dividers or opto-isolators, supporting both isolated and non-isolated power-loss detection schemes without external components.

How does the TOL pin affect the DS1231-20N+ VCC detection threshold?

The TOL pin on the DS1231-20N+ determines the VCC trip voltage: connecting TOL to GND sets a 5% threshold (4.75 V nominal), while connecting TOL to VCC selects a 10% threshold (4.25 V nominal). These values are specified across temperature (0°C to +70°C) with tight tolerances (e.g., 4.62–4.74 V for 5% mode), enabling DS1231-20N+ to match diverse power supply hold-up times and stability margins in real-world systems.

Does the DS1231-20N+ require external capacitors for reset timing?

No, the DS1231-20N+ does not require external capacitors for reset timing. Its power-up reset duration (≥150 ms) and internal reference are fully self-contained. Unlike many supervisors, DS1231-20N+ integrates temperature-compensated bandgap references and digital samplers - eliminating capacitor dependencies and improving long-term reliability in temperature-varying environments where capacitor drift would degrade timing accuracy.

What is the purpose of having two RST outputs on the DS1231-20N+?

The DS1231-20N+ provides two RST outputs - RST (active-high, push-pull) and RST (active-low, open-drain) - to ensure compatibility with diverse microprocessor reset architectures. RST drives high directly for TTL/CMOS inputs requiring active-high assertion; RST sinks current for processors needing active-low reset with external pull-up. This dual-signaling capability makes DS1231-20N+ interoperable with 8051, Z80, and ARM-based controllers without level-shifting or glue logic.

Can the DS1231-20N+ be used with switching power supplies?

Yes, the DS1231-20N+ is explicitly qualified for use with both linear and switching power supplies. Its VCC comparator features slew-rate immunity (tF = 300 µs for 4.75 V → 4.25 V transition) and its internal reference is temperature-compensated - ensuring stable trip points despite fast-rising or noisy switcher outputs. The DS1231-20N+ datasheet confirms suitability for switching supplies, and its 0.5–2.0 mA operating current avoids loading sensitive feedback paths.