Analog Devices Inc./Maxim Integrated DS18S20+

Overview

DS18S20+ from Maxim Integrated is a high-precision 1-Wire digital thermometer IC providing 9-bit Celsius temperature measurements with ±0.5°C accuracy from −10°C to +85°C, nonvolatile user-programmable alarm thresholds (TH/TL), and parasite power capability via the DQ pin. It operates across −55°C to +125°C and is used in distributed thermal monitoring systems such as HVAC controls, industrial equipment sensors, and embedded thermometers.

For engineers reviewing the DS18S20+ datasheet, DS18S20+ pinout, DS18S20+ application, or DS18S20+ equivalent, key selection considerations include 1-Wire bus compatibility, parasitic vs. VDD-powered operation, alarm search functionality, 64-bit ROM uniqueness for multidrop addressing, and TO-92/SO package options.

Technical Context

The DS18S20+ implements a dedicated 1-Wire interface using open-drain DQ communication with strict timing-defined time slots (60–120 µs), reset pulses (>480 µs low), and presence detection. Its internal architecture integrates a 9-bit temperature sensor, scratchpad SRAM (9 bytes), EEPROM-stored TH/TL registers, and CRC-8 generator for data integrity.

It supports two power modes: local VDD supply (3.0–5.5 V) or parasite power via DQ with mandatory strong pullup during temperature conversion (tCONV = 750 ms) and EEPROM writes (tWR = 2–10 ms). Alarm flag status is updated after each conversion and discoverable via ECh command.

Key Specifications

Pinout & Package

DS18S20+ is available in two packages: 3-pin TO-92 (DS18S20) and 8-pin SO (150 mils, DS18S20Z). The TO-92 variant is most common for through-hole prototyping and cost-sensitive deployments; the SO package supports automated assembly and higher-density layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital thermometer applications.

Compared with DS18B20+ and MAX31820M+, the DS18S20+ delivers the lowest system cost and simplest firmware integration for 0.5°C-step applications, while maintaining full 1-Wire interoperability and industrial-grade temperature range-making it ideal for high-volume thermostats and embedded monitors where resolution beyond 9 bits is unnecessary.

Availability

DS18S20+ is available at Aetrix Electronics and suitable for HVAC environmental controls, industrial equipment monitoring, and consumer thermometer designs requiring stable component supply, long-term lifecycle assurance, and consistent parametric performance across production batches.

Supply support for DS18S20+ 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 (now part of Analog Devices) is a semiconductor company specializing in precision analog, mixed-signal, and digital ICs for industrial, communications, and computing applications.

The DS18S20+ belongs to Maxim's 1-Wire temperature sensor family, designed specifically for low-wiring-count, multidrop thermal sensing in space-constrained or remotely powered systems-emphasizing simplicity, uniqueness, and robustness over high-speed or ultra-high-resolution requirements.

FAQ

What is the maximum number of DS18S20+ sensors that can operate on a single 1-Wire bus?

The DS18S20+ features a factory-programmed 64-bit unique ROM address, enabling theoretically unlimited devices on one bus. In practice, signal integrity limits depend on bus capacitance and pullup strength; tested deployments reliably support 50–100 DS18S20+ units with proper 4.7 kΩ pullup and twisted-pair cabling. Each DS18S20+ responds only to its own ROM match or global commands like Skip ROM, ensuring deterministic arbitration.

Does the DS18S20+ require an external power supply, or can it run solely on parasite power?

The DS18S20+ supports both configurations: it can be powered externally via the VDD pin (3.0–5.5 V), or operate in parasite power mode using only DQ and GND. In parasite mode, a strong pullup (e.g., MOSFET-switched rail) is mandatory during temperature conversion (750 ms) and EEPROM writes (up to 10 ms) to supply peak current (~1.5 mA). Parasite power is validated for operation up to +100°C; above this, external VDD is recommended.

How does the DS18S20+ alarm function work, and how is it configured?

The DS18S20+ includes nonvolatile TH and TL registers (EEPROM) storing user-defined Celsius thresholds. After each temperature conversion, the measured value is compared against these limits; if exceeded, an internal alarm flag is set. Configuration is done via Write Scratchpad (4Eh) and Copy Scratchpad (48h) commands. Alarm status is queried globally using the Alarm Search (ECh) command, which returns only devices currently in alarm-enabling rapid fault identification in large networks.

What is the temperature resolution and accuracy of the DS18S20+?

The DS18S20+ provides fixed 9-bit resolution (0.5°C per LSB) with ±0.5°C accuracy over the −10°C to +85°C range, and ±2.0°C accuracy across its full −55°C to +125°C operating range. Accuracy is specified under local VDD supply conditions; parasite power operation maintains the same tolerance. The device outputs signed 16-bit two's complement data, with bit 0 representing 0.5°C-no interpolation or oversampling is performed internally.

Can the DS18S20+ be used interchangeably with the DS18B20+ in existing designs?

No-the DS18S20+ and DS18B20+ are not pin- or firmware-compatible drop-in replacements. While both share the same 1-Wire protocol, TO-92/SO packages, and basic command set, they differ in resolution (9-bit vs. 12-bit), conversion time (750 ms vs. 750–937.5 ms), and scratchpad memory layout (e.g., DS18B20+ includes configuration register). Firmware must be updated to handle different data formats and timing margins; hardware layout may remain identical, but functional validation is required.