UMW DS18B20

Overview

DS18B20 from Maxim Integrated is a programmable-resolution 1-Wire digital thermometer with ±0.5°C accuracy from −10°C to +85°C, −55°C to +125°C operating range, and parasite-power capability requiring only DQ and GND pins. It delivers 9–12-bit temperature data over a single-wire bus and enables distributed thermal monitoring in HVAC control systems.

For engineers reviewing the DS18B20 datasheet, DS18B20 pinout, DS18B20 application, or DS18B20 equivalent, key selection considerations include parasitic vs. VDD-powered operation, 1-Wire multidrop topology support, resolution–conversion time tradeoff (750 ms at 12-bit), alarm trigger register persistence, and TO-92/SO/µSOP package compatibility with legacy thermal sensor footprints.

Technical Context

The DS18B20 implements a fully integrated 1-Wire interface with open-drain DQ pin, internal 64-bit ROM for device addressing, and scratchpad memory containing temperature register, TH/TL alarm thresholds, and configuration byte. Its 1-Wire protocol uses precise timing slots (tSLOT = 60–120 µs) and presence detection (tRSTL/tRSTH ≥ 480 µs) to coordinate master–slave communication without clock lines.

Temperature measurement relies on a calibrated silicon bandgap sensor with user-configurable resolution (9–12 bits), where each bit step corresponds to 0.5°C, 0.25°C, 0.125°C, or 0.0625°C. Alarm functionality compares converted values against nonvolatile EEPROM-stored TH/TL registers, and supports Alarm Search [ECh] to identify out-of-range nodes on shared buses.

Key Specifications

Pinout & Package

DS18B20 is available in three industry-standard packages: 3-pin TO-92 (through-hole), 8-pin SO (150 mil), and 8-pin µSOP (surface-mount). Pin functions are identical across variants; N.C. pins are internally unconnected and must remain floating or grounded per layout guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS18B20, MAX31820 offers higher accuracy at increased power cost, while DS1822 sacrifices EEPROM reliability and parasite power to reduce unit price - neither is pin-compatible without verifying VDD routing and firmware timing margins.

Availability

DS18B20 is available at Aetrix Electronics and suitable for HVAC environmental controls, industrial equipment thermal protection, and consumer appliance temperature regulation requiring stable component supply across multi-year production cycles.

Supply support for DS18B20 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) designs high-performance analog and mixed-signal ICs for industrial, communications, and computing markets, with emphasis on integration, reliability, and low-power operation.

The DS18B20 belongs to Maxim's 1-Wire sensor family, engineered specifically for distributed, low-wiring-count temperature monitoring in harsh or space-constrained environments - not general-purpose microcontrollers or analog front-ends.

FAQ

What is the maximum number of DS18B20 sensors that can operate on a single 1-Wire bus?

The DS18B20 uses a unique 64-bit ROM address, enabling theoretically unlimited devices on one bus. In practice, signal integrity limits reliable operation to ~50–100 units depending on cable length, pullup strength, and noise. For robust deployment beyond 30 nodes, use active repeaters or segment the bus with DS2409 dual-channel couplers. The DS18B20 itself imposes no software or hardware limit on node count.

Does DS18B20 support both parasite power and external VDD modes simultaneously?

No - the DS18B20 operates exclusively in one power mode at a time. When VDD is connected to a valid 3.0–5.5 V supply, parasite power is disabled. When VDD is grounded, the device draws all operating current from the DQ line via the 4.7 kΩ pullup. Mixing modes risks undefined behavior or damage; the DS18B20 does not auto-detect or switch between them.

How does resolution setting affect DS18B20 conversion time and accuracy?

DS18B20 conversion time scales linearly with resolution: 93.75 ms at 9-bit, 187.5 ms at 10-bit, 375 ms at 11-bit, and 750 ms at 12-bit. Accuracy remains ±0.5°C (−10°C to +85°C) regardless of resolution - higher bit depth improves quantization granularity (0.0625°C step at 12-bit) but does not enhance sensor intrinsic error.

Can DS18B20 alarm registers be written and read over the 1-Wire bus?

Yes - TH and TL alarm thresholds are stored in bytes 2 and 3 of the scratchpad and persist in EEPROM after issuing Copy Scratchpad [48h]. They are accessed via standard 1-Wire commands: Write Scratchpad [4Eh] to load values, Read Scratchpad [BEh] to verify, and Recall E2 [B8h] to reload from EEPROM. Alarm Search [ECh] then identifies devices exceeding these thresholds.

Is DS18B20 compatible with modern microcontrollers lacking native 1-Wire peripherals?

Yes - the DS18B20's 1-Wire protocol is bit-banged in firmware using any GPIO with precise timing control (e.g., ARM Cortex-M SysTick, ESP32 RMT, PIC PWM modules). Libraries exist for Arduino, PlatformIO, and Zephyr; critical timing parameters (tSLOT = 60–120 µs, tRSTL ≥ 480 µs) are achievable on MCUs running ≥1 MHz. No dedicated hardware peripheral is required.