Analog Devices Inc./Maxim Integrated DS1232LPU+

Overview

DS1232LPU+ from Maxim Integrated (formerly Dallas Semiconductor) is a low-power microprocessor supervisory IC that monitors VCC, implements watchdog timer functionality, and provides pushbutton reset control. It delivers 50 µA quiescent current, 250 ms minimum reset pulse width, and selectable 5% or 10% VCC trip thresholds (4.75 V or 4.5 V), used in embedded systems requiring reliable power-up/power-down sequencing and software fault recovery.

For engineers reviewing the DS1232LPU+ datasheet, DS1232LPU+ pinout, DS1232LPU+ application, or DS1232LPU+ equivalent, key selection considerations include its dual active-high/active-low RST outputs, programmable watchdog timeout (150 ms / 600 ms / 1.2 s), industrial temperature range support, and compatibility with 5 V ±10% supply rails in space-constrained designs.

Technical Context

The DS1232LPU+ integrates three independent monitoring functions: precision voltage detection using a temperature-compensated bandgap reference and comparator, debounced pushbutton reset with guaranteed 250 ms active output, and a non-disableable watchdog timer with TD-pin-selectable timeouts. Its dual RST outputs (one CMOS high-drive, one open-drain) enable flexible interface to diverse microcontroller reset inputs.

Operation is defined by three critical timing behaviors: 250 ms minimum reset assertion on power-up and power-fail, 20 ms debounce delay on PBRST release, and watchdog timeout propagation with 50–175 µs latency from VCC failure detection to RST activation. All functions operate across 0°C to +70°C unless marked 'N' for industrial grade.

Key Specifications

Pinout & Package

DS1232LPU+ is supplied in an 8-pin plastic DIP (300-mil) package, pin-compatible with industry-standard 5 V supervisory IC footprints.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX692AESA+ and TPS3823-50DBVR, the DS1232LPU+ uniquely combines 50 µA operation, dual RST outputs, TD-selectable watchdog, and integrated pushbutton debounce - making it optimal for legacy 5 V embedded systems requiring full-feature supervision without redesign.

Availability

DS1232LPU+ is available at Aetrix Electronics and suitable for industrial automation, medical instrumentation, point-of-sale terminals, and smart metering applications requiring stable component supply and long-term obsolescence management.

Supply support for DS1232LPU+ 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 (acquired by Analog Devices in 2021) designs precision analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.

The DS1232LPU+ belongs to Maxim's MicroMonitor™ family of supervisory circuits, engineered specifically for robust power-up sequencing, software fault recovery, and hardware reset assurance in 5 V microprocessor systems.

FAQ

What is the function of the TD pin on the DS1232LPU+?

The TD pin on the DS1232LPU+ selects the watchdog timer timeout interval: grounded for ~150 ms, left floating for ~600 ms, or tied to VCC for ~1.2 s. This configuration occurs at power-up and remains fixed until reset. The DS1232LPU+ does not support dynamic timeout changes during operation, and the watchdog cannot be disabled - it must be strobed via the ST input to prevent unintended resets.

Does the DS1232LPU+ support both 4.5 V and 4.75 V VCC trip thresholds?

Yes, the DS1232LPU+ supports two precise VCC trip thresholds via the TOL pin: connecting TOL to ground selects a 4.75 V threshold (5% of 5 V), while connecting TOL to VCC selects a 4.5 V threshold (10% of 5 V). These values are specified over temperature and supply variation, with typical trip points of 4.62 V and 4.37 V respectively, ensuring reliable brownout detection in DS1232LPU+ deployments.

How does the DS1232LPU+ handle pushbutton reset input debouncing?

The DS1232LPU+ performs internal hardware debouncing on the PBRST pin: it detects the rising edge after button release and guarantees a minimum 250 ms active reset pulse on both RST and RST̅ outputs. No external RC network or firmware polling is required. The DS1232LPU+ also includes an internal 40 kΩ pull-up on PBRST, simplifying front-panel design and reducing BOM count.

Can the DS1232LPU+ be used in systems with 3.3 V microcontrollers?

The DS1232LPU+ is designed for 5 V operation (4.5–5.5 V) and monitors a 5 V supply rail; it is not rated for direct 3.3 V VCC operation. However, its open-drain RST̅ output can interface to 3.3 V logic domains using an external pull-up to 3.3 V. The DS1232LPU+ itself must be powered from 5 V, and its ST and PBRST inputs accept 3.3 V–compatible logic levels per VIH/VIL specs - but full system integration requires careful voltage domain partitioning.

What is the difference between the RST and RST̅ outputs on the DS1232LPU+?

The DS1232LPU+ provides two complementary reset outputs: RST is a CMOS active-high output capable of sourcing/sinking ±10 mA, while RST̅ is an open-drain active-low output requiring an external pull-up resistor. This dual-output architecture allows the DS1232LPU+ to drive reset inputs on microcontrollers with either active-high or active-low reset polarity - eliminating the need for external inverters or level-shifting circuitry in mixed-signaling environments.