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, supports 5% or 10% VCC threshold detection (4.5 V or 4.75 V trip points), and guarantees ≥250 ms active reset pulse width. 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 RST/RST outputs (active-high and open-drain active-low), selectable watchdog timeout (150 ms/600 ms/1.2 s), TOL-configurable supply tolerance, industrial temperature range support, and compatibility with 5 V ±10% operation.

Technical Context

The DS1232LPU integrates three independent monitoring functions: precision VCC comparator with temperature-compensated reference, debounced pushbutton reset input (PBRST), and programmable watchdog timer triggered by ST strobe. Its dual-reset architecture enables direct interface to both CMOS and TTL processors without external level-shifting.

Watchdog timeout is set via TD pin state (GND/float/VCC), while VCC detection threshold is selected by TOL pin connection (GND = 4.75 V, VCC = 4.5 V). Reset assertion persists ≥250 ms after VCC recovery or PBRST release, ensuring stable processor initialization before execution resumes.

Key Specifications

Pinout & Package

DS1232LPU is supplied in an 8-pin plastic DIP (300-mil) package. Pin assignments are identical to the DS1232LP variant and validated per Dallas Semiconductor mechanical drawings.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX692CPA+ and TPS3823-50DBVR, DS1232LPU uniquely combines ultra-low 50 µA supply current, user-selectable VCC threshold (5%/10%), integrated watchdog with three timeout options, and dual RST outputs - enabling compact, self-contained supervision without external components or firmware overhead.

Availability

DS1232LPU is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, telecom infrastructure, and automotive body electronics requiring stable component supply and long-term lifecycle assurance.

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™ supervisory IC family, engineered specifically for robust microprocessor reset and watchdog control in harsh, resource-constrained embedded systems.

FAQ

What is the function of the TOL pin on the DS1232LPU?

The TOL pin on the DS1232LPU selects the VCC undervoltage detection threshold: connecting TOL to GND configures a 4.75 V trip point (5% tolerance for 5 V supply), while connecting TOL to VCC sets a 4.5 V threshold (10% tolerance). This allows system designers to match the DS1232LPU's reset activation point to their power supply regulation margin and noise environment without changing the bill of materials.

Does the DS1232LPU provide both active-high and active-low reset outputs?

Yes, the DS1232LPU provides two independent reset outputs: RST is a push-pull active-high output compatible with CMOS inputs, and RST is an open-drain active-low output requiring an external pull-up resistor. This dual-output architecture enables seamless integration into systems using mixed logic families or shared reset buses, and eliminates the need for external inverters or level translators when interfacing with legacy 5 V TTL peripherals.

How is the watchdog timeout configured on the DS1232LPU?

The watchdog timeout on the DS1232LPU is configured solely by the voltage state of the TD pin: grounding TD selects ~150 ms, leaving TD floating selects ~600 ms, and connecting TD to VCC selects ~1.2 s. The watchdog cannot be disabled - it must be periodically strobed via the ST input to prevent unintended reset assertion. This design ensures fail-safe behavior even if firmware fails to initialize or maintain the watchdog.

What is the guaranteed minimum reset pulse width generated by the DS1232LPU?

The DS1232LPU guarantees a minimum reset pulse width of 250 ms for all reset sources - including power-up, power-down, pushbutton release, and watchdog timeout. This duration is fixed and not dependent on external capacitors or resistors. It ensures sufficient time for the microprocessor's internal power rails, clocks, and memory subsystems to stabilize before instruction execution resumes, preventing erratic startup behavior in real-world PCB layouts with parasitic capacitance and inductance.

Is the DS1232LPU suitable for industrial temperature applications?

Yes, the DS1232LPU is rated for operation from −40°C to +85°C, meeting industrial temperature grade specifications. Electrical parameters including VCC trip points, reset timing, and quiescent current are fully characterized and guaranteed across this range. No derating or additional thermal design margin is required, making the DS1232LPU appropriate for deployment in uncontrolled environments such as factory floors, outdoor telecom cabinets, and vehicle under-hood locations.