Analog Devices Inc./Maxim Integrated DS1238S-10+

Overview

DS1238S-10+ from Maxim Integrated (now part of Analog Devices) is a microprocessor supervisory IC providing power-fail detection, watchdog reset control, non-maskable interrupt generation, battery-backed SRAM support, and 10% VCC trip point (4.5 V nominal). It delivers active-low and active-high reset outputs, chip-enable switching, and PF-driven external power switching in embedded systems requiring reliable power sequencing and orderly shutdown.

For engineers reviewing the DS1238S-10+ datasheet, DS1238S-10+ pinout, DS1238S-10+ application, or DS1238S-10+ equivalent, key selection criteria include its dual-reset outputs, 200 nA battery current, 4.37 V typical VCCTP, 2.7 s internal watchdog timeout, and compatibility with 16-pin SOIC packaging for space-constrained industrial controllers and data loggers.

Technical Context

The DS1238S-10+ integrates a bandgap voltage reference and precision comparator to monitor VCC against a fixed 10% threshold (4.25–4.50 V), triggering RST/RST and RVT simultaneously on undervoltage. Its watchdog timer uses either internal ring oscillator (~30 kHz) or external clock/capacitor timing, with configurable first-cycle and subsequent timeouts.

Early warning is implemented via high-impedance IN pin sensing (VTP = 1.15–1.35 V), requiring three consecutive out-of-tolerance samples (~100 µs) to assert NMI - eliminating noise-induced false interrupts. Memory backup is enabled through VCCO switching between VCC and VBAT, with CEO write-protection delayed until CEI returns high or tCE (5 µs) expires.

Key Specifications

Pinout & Package

DS1238S-10+ is supplied in a 16-pin SOIC (300-mil) package, pin-compatible with industry-standard 16-pin DIP footprints. The device supports both commercial (0°C to +70°C) and optional industrial (−40°C to +85°C) temperature ranges.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691CPD+ and TPS3823-50DBVR, DS1238S-10+ uniquely combines dual-reset outputs, NMI-based early warning, integrated SRAM switching, and <200 nA battery drain - making it irreplaceable in applications demanding deterministic shutdown and long-term nonvolatile data retention.

Availability

DS1238S-10+ is available at Aetrix Electronics and suitable for industrial data loggers, medical patient monitors, point-of-sale terminals, and smart energy meters requiring stable component supply across extended product lifecycles.

Supply support for DS1238S-10+ 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 high-reliability analog and mixed-signal ICs for precision sensing, power management, and system supervision in harsh environments.

The DS1238S-10+ belongs to Maxim's MicroManager family - engineered specifically for microprocessor-based systems needing coordinated power monitoring, reset control, and battery-backed memory protection in industrial and medical applications.

FAQ

What is the exact VCC trip point specification for DS1238S-10+?

The DS1238S-10+ has a guaranteed 10% VCC trip point of 4.25 V (min) to 4.50 V (max), with a typical value of 4.37 V at 25°C. This threshold is set by an internal bandgap reference and comparator, ensuring consistent reset activation across temperature and process variation. The DS1238S-10+ datasheet confirms this range under DC Electrical Characteristics, and it applies specifically to the -10+ variant - distinct from the DS1238-5 (5% option).

Does DS1238S-10+ support both active-low and active-high reset outputs simultaneously?

Yes, DS1238S-10+ provides two independent reset outputs: RST (active-low) and RST (active-high), both asserted simultaneously when VCC falls below the trip point. These outputs are electrically isolated and driven with complementary logic levels, enabling direct connection to microprocessors requiring either polarity without external inverters. The DS1238S-10+ datasheet specifies VOL ≤ 0.4 V and VOH ≥ VCC − 0.1 V for these pins under defined load conditions.

How does the DS1238S-10+ implement noise immunity on the NMI function?

The DS1238S-10+ implements noise immunity on the NMI function by requiring three consecutive out-of-tolerance samples of the IN pin voltage - each taken at ~33 µs intervals by an internal 30 kHz ring oscillator - before asserting NMI. This results in a minimum detection window of ~100 µs, effectively filtering transient spikes shorter than this duration. The DS1238S-10+ datasheet explicitly states this behavior in the Non-Maskable Interrupt section and confirms it applies to the DS1238S-10+ variant.

Can DS1238S-10+ directly power a 128 KB SRAM chip?

No, DS1238S-10+ cannot directly power a 128 KB SRAM chip. Its VCCO pin supplies up to 100 mA at VCC − 0.3 V during normal operation, but typical 128 KB SRAMs draw >150 mA in active mode. The DS1238S-10+ is designed to control external power switching (via PF) or interface with low-power SRAMs (<100 mA). For larger memories, use DS1238S-10+'s PF output to gate an external MOSFET, as documented in Figure 9 of the DS1238S-10+ datasheet.

What is the purpose of the "freshness seal" mode in DS1238S-10+?

The "freshness seal" mode in DS1238S-10+ electrically disconnects the battery (VBAT) from internal circuitry during storage or shipment to prevent capacity loss. It is activated by applying three precise negative pulses to the IN pin while VCC is active, causing VCCO, RST, RST, and CEO to tri-state and WDS to go low. Normal operation resumes automatically upon VCC cycling above VBAT. This feature is confirmed in the DS1238S-10+ datasheet Section 7 and is unique to the DS1238 family.