Analog Devices Inc./Maxim Integrated DS1238A-5+

Overview

DS1238A-5+ from Maxim Integrated (now part of Analog Devices) is a microprocessor supervisory IC providing power-fail detection, watchdog timer, non-maskable interrupt, and SRAM backup control in 5V systems. It features 4.75V ±0.13V power supply trip point, 2.7s typical watchdog timeout with internal oscillator, <200nA battery current, and dual active-low/high reset outputs. Used in industrial controllers for orderly shutdown during brownouts.

For engineers reviewing the DS1238A-5+ datasheet, DS1238A-5+ pinout, DS1238A-5+ application, or DS1238A-5+ equivalent, key selection criteria include precise 5% VCC threshold monitoring, NMI-driven early warning capability, VCCO-controlled SRAM write protection timing, and compatibility with battery-backed memory retention architectures.

Technical Context

The DS1238A-5+ integrates a bandgap voltage reference and precision comparator to monitor VCC against a factory-trimmed 4.75V threshold (±0.13V typ), triggering RST/RST and CEO within 175µs. Its watchdog timer uses an internal ring oscillator (~30kHz) or external clock/capacitor to generate 2.7s/170ms timeout periods, resettable via ST strobe.

Early warning is implemented through a high-impedance IN pin referenced to 1.27V internal bandgap; NMI asserts after three consecutive 33µs samplings below VTP. The device supports SRAM nonvolatility via VCCO switching between VCC and VBAT, with CEO held high during power failure to enforce write protection only after CEI returns high or tCE (5µs) expires.

Key Specifications

Pinout & Package

DS1238A-5+ is available in 16-pin SOIC (300-mil) and 16-pin DIP packages, both RoHS-compliant and rated for commercial (0°C to +70°C) operation. Pin functions are identical across packages.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691CPD+ and TPS3823-50DBVR, DS1238A-5+ uniquely integrates 5% VCC monitoring, NMI-based early warning, SRAM CEO control with tCE timing, and configurable watchdog - eliminating four discrete functions in one 16-pin package.

Availability

DS1238A-5+ is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, point-of-sale terminals, and smart metering applications requiring stable component supply and long-term obsolescence management.

Supply support for DS1238A-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 high-reliability industrial, automotive, and medical systems.

The DS1238A-5+ belongs to Maxim's MicroManager family - engineered specifically for microprocessor-based systems needing coordinated power supervision, memory backup, and fail-safe shutdown capabilities.

FAQ

What is the exact VCC trip voltage for DS1238A-5+ and how is it verified?

The DS1238A-5+ has a factory-trimmed VCC trip point of 4.75V (5% of 5V), with typical tolerance ±0.13V (4.62V to 4.75V). This value is confirmed in the "RECOMMENDED DC OPERATING CONDITIONS" table and "DC ELECTRICAL CHARACTERISTICS" section of the official datasheet, explicitly designated for the DS1238A-5 variant. DS1238A-5+ maintains this specification across its commercial temperature range (0°C to +70°C).

Does DS1238A-5+ support both active-low and active-high reset outputs simultaneously?

Yes, DS1238A-5+ provides two independent reset outputs: RST (active low) and RST (active high), both asserted synchronously when VCC falls below 4.75V. These outputs drive complementary logic levels to interface directly with diverse microprocessor families - for example, RST connects to ARM reset pins while RST drives FPGA configuration logic requiring high-active assertion.

How does the DS1238A-5+ prevent SRAM data corruption during power loss?

DS1238A-5+ prevents SRAM data corruption by delaying CEO assertion until either CEI returns high or tCE (5µs maximum) expires - ensuring the current memory cycle completes before write protection engages. Simultaneously, VCCO switches from VCC to VBAT with ≤0.8V drop, maintaining SRAM supply during the transition. This dual-timing mechanism is documented in the MEMORY BACKUP section and AC Electrical Characteristics table.

Can DS1238A-5+ generate an early warning interrupt before the main reset triggers?

Yes, DS1238A-5+ generates a non-maskable interrupt (NMI) via the IN pin when a user-defined voltage threshold is crossed - typically configured to trigger 100–200ms before the 4.75V VCC trip point. The IN pin references an internal 1.27V bandgap; applying a resistor divider sets the sense point (e.g., 4.8V on a 5V rail). NMI activates after three 33µs samplings below threshold, rejecting noise while delivering deterministic early warning.

What is the maximum load current DS1238A-5+ can deliver through the VCCO pin?

DS1238A-5+ delivers up to 100mA through VCCO when powered from VCC (VCCO = VCC − 0.3V), as specified in the DC Electrical Characteristics table. During battery backup (VCC < VBAT), it supplies 1mA with ≤0.8V drop. These values are measured under recommended operating conditions and define the practical SRAM capacity supported - e.g., up to 128KB of standard 5V CMOS SRAM.