Analog Devices Inc./Maxim Integrated DS1239S-5

Overview

DS1239S-5 from Maxim Integrated (now Analog Devices) is a power supply supervisory and memory backup controller IC for microprocessor systems. It provides power-fail warning (PF), non-maskable interrupt (NMI), reset generation (RST), switched SRAM supply (VCCO), battery-backed write protection, and keyboard-initiated AC power control via PSI/PSO - all in a 16-pin SOIC package with industrial temperature range support (-40°C to +85°C).

For engineers reviewing the DS1239S-5 datasheet, DS1239S-5 pinout, DS1239S-5 application, or DS1239S-5 equivalent, key selection considerations include its dual PF output polarity support, 10% VCC monitoring accuracy, 200 ms minimum PSI-to-VCC turn-on timing, tristate PSO with 10 mA drive capability, and integration of memory backup control without external logic.

Technical Context

The DS1239S-5 implements NMOS-mode-compatible supervision logic derived from the DS1236 architecture, with PSI and PSO replacing RC and RST to enable bidirectional AC power sequencing. Its internal VCC monitoring comparator triggers PF at 10% (or optionally 5%) undervoltage threshold, while the NMI and RST outputs coordinate controlled processor halt and restart during transients.

VBAT-powered operation ensures continuous function during main supply loss; VCCO supplies switched +5 V to SRAM only when VCC is valid, and WC/SC enables low-power stop mode entry. The 0.1 µF debounce-capable PSI input and 500 ms max PSO pulse width support reliable pushbutton-initiated power-up/down sequences in handheld and embedded systems.

Key Specifications

Pinout & Package

DS1239S-5 is housed in a 16-pin SOIC (300-mil width) package with standard DIP pinout compatibility. Pin functions are electrically identical to the DS1236 in NMOS mode, except PSI replaces RC and PSO replaces RST.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power supervision and memory backup applications.

Compared with DS1236S-5 and MAX690TSA+, the DS1239S-5 uniquely integrates AC power sequencing (PSI/PSO), dual-polarity PF, and SRAM supply switching (VCCO) in one 16-pin SOIC - reducing total system components and enabling true keyboard-controlled zero-standby operation.

Availability

DS1239S-5 is available at Aetrix Electronics and suitable for industrial PLC controllers, handheld data collectors, point-of-sale terminals, and medical infusion pumps requiring stable component supply with long-term lifecycle assurance.

Supply support for DS1239S-5 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

Analog Devices (via acquisition of Maxim Integrated) designs precision analog, mixed-signal, and power management ICs for industrial, automotive, and communications applications.

The DS1239S-5 belongs to Maxim's MicroManager family - engineered specifically for microprocessor-based systems needing coordinated power supervision, memory backup, and keyboard-initiated AC power control without external logic.

FAQ

What is the primary function of the DS1239S-5 in a microprocessor system?

The DS1239S-5 serves as an integrated power supervisor and memory backup controller. It manages power-up/down sequencing via PSI/PSO, generates reset (RST) and non-maskable interrupt (NMI) signals, monitors VCC for brown-out conditions, controls switched SRAM supply (VCCO), and provides battery-backed write protection. In every operational mode, the DS1239S-5 ensures deterministic behavior during power transients - making it essential for reliable firmware execution and data integrity in systems using volatile memory.

Does the DS1239S-5 support both active-high and active-low power-fail signaling?

Yes, the DS1239S-5 provides two dedicated PF pins: one active-high and one active-low. This dual-polarity output eliminates the need for external inverters or level shifters when interfacing with microcontrollers or FPGAs that require specific interrupt polarity. Both PF outputs respond identically to the same VCC monitoring event, ensuring consistent timing and simplifying system-level interrupt handling - a feature confirmed in the official DS1239 datasheet and mechanically implemented on the die.

How does the DS1239S-5 enable keyboard-initiated AC power control?

The DS1239S-5 uses the PSI (Power Supply Control Input) and PSO (Power Supply Control Output) pins to implement keyboard-triggered AC power sequencing. When a keypress pulls PSI low, the DS1239S-5 asserts PSO high (up to 10 mA), which can directly drive an opto-SCR to initiate AC-to-DC conversion. Once VCC stabilizes, PSO tracks VCC; a subsequent PSI low pulse tristates PSO to shut down the supply. This functionality is intrinsic to the DS1239S-5 and requires no firmware or external logic.

What is the role of the VCCO pin on the DS1239S-5?

The VCCO pin on the DS1239S-5 delivers switched +5 V power exclusively to CMOS SRAM when VCC is within specification. It remains off during power-up, brown-out, or VCC loss - preventing invalid writes and ensuring data retention in battery-backed memory. This behavior is hardwired in the DS1239S-5's internal logic and is not configurable; it directly enables nonvolatile SRAM operation without external MOSFETs or control circuitry.

Is the DS1239S-5 compatible with the DS1236 in terms of pinout and software interface?

The DS1239S-5 shares identical pinout and electrical behavior with the DS1236 in NMOS mode, except that pins RC and RST are replaced by PSI and PSO. All other pins - including PF, NMI, RST (renamed), CEO/CEI, and WC/SC - retain identical functions and timing. Firmware written for DS1236-based systems requires no modification to use DS1239S-5, though PSI/PSO functionality must be leveraged to exploit its AC power control capability.