DS18B20U+T&R is a precision, digital temperature sensor with 1-Wire® interface, designed and manufactured by Analog Devices Inc. (following its acquisition of Maxim Integrated). It belongs to the industry-standard DS18x20 family, renowned for its simplicity, robustness, and ability to operate in parasitic-power mode — eliminating the need for a dedicated VDD supply line. The “U” suffix denotes the 8-pin µSOP package (3.0 mm × 4.4 mm), optimized for compact, surface-mount applications; the “+T&R” indicates tape-and-reel packaging (2,500 units per reel), Pb-free, RoHS-compliant, and qualified for industrial use.
Introduction
The DS18B20U+T&R is a programmable-resolution (9–12-bit), ±0.5°C accuracy (–10°C to +85°C), digital thermometer that communicates over a single-conductor 1-Wire bus, requiring only one data line (plus ground) for bidirectional communication with a host microcontroller. Its standout feature is parasitic power operation: it draws operating power directly from the 1-Wire bus during temperature conversions — enabling ultra-simple two-wire (data + ground) sensor networks ideal for distributed monitoring in HVAC, industrial control, environmental sensing, and consumer electronics.
Each DS18B20 contains a unique 64-bit ROM address, allowing multiple sensors (dozens or more) to coexist on the same bus — enabling multi-point temperature mapping without additional addressing hardware. Conversion time is programmable: 750 ms at 12-bit resolution, scaling down to 94 ms at 9-bit, with typical supply current of just 1.5 µA in standby and 1.5 mA peak during conversion.
The µSOP-8 (U) package features a thermally efficient design with exposed pad (EP) — enhancing thermal response time and enabling direct PCB mounting for accurate ambient or board-temperature measurement. Unlike TO-92 or SOIC variants, the µSOP offers superior manufacturability in high-density layouts while maintaining full functionality and specification compliance.
Key Features
✅ High Accuracy & Programmable Resolution:
• ±0.5°C accuracy over –10°C to +85°C (±1.0°C from –55°C to +125°C);
• User-selectable resolution: 9-bit (0.5°C), 10-bit (0.25°C), 11-bit (0.125°C), or 12-bit (0.0625°C) — configurable via internal configuration register.
✅ Single-Conductor 1-Wire Interface:
• Requires only one data line + ground for communication and power;
• Supports standard and overdrive speeds (up to 16 kbps / 125 kbps);
• Built-in CRC generator ensures data integrity across long cables (>100 m with proper pull-up and termination).
✅ Parasitic Power Mode:
• No external VDD required — powered entirely from the 1-Wire bus during conversion;
• Ideal for battery-powered or space-constrained nodes (e.g., wireless sensor tags, embedded modules);
• Optional external VDD mode available for faster conversions and stronger bus drive.
✅ Unique 64-Bit Addressing & Multi-Drop Capability:
• Each device has a factory-lasered, globally unique 64-bit ROM code — enables plug-and-play identification and eliminates manual addressing;
• Supports up to 100+ sensors on a single bus (with appropriate bus capacitance management and strong pull-up).
✅ Robust Industrial Operation:
• Operating temperature range: –55°C to +125°C;
• Supply voltage: 3.0 V to 5.5 V (VDD mode) or 2.8 V to 5.5 V (parasitic mode);
• ESD rating > 4 kV HBM on data pin;
• Immune to electrical noise — widely deployed in factory floors and outdoor enclosures.
✅ Low-Power & Fast Response:
• Standby current: 1.5 µA (typ.);
• Conversion current: 1.5 mA (peak);
• Thermal response time: ～200 ms in air (faster with thermal coupling to PCB/case).
Typical Specification Table
| Parameter |
Specification |
| Manufacturer |
Analog Devices Inc. (formerly Maxim Integrated) |
| Product Series |
DS18x20 Family (Digital Thermometers) |
| Model |
DS18B20U+T&R |
| Function |
Digital Temperature Sensor with 1-Wire Interface |
| Accuracy |
±0.5°C (–10°C to +85°C); ±1.0°C (–55°C to +125°C) |
| Resolution |
Programmable: 9–12 bits (0.5°C to 0.0625°C steps) |
| Conversion Time |
94 ms (9-bit) to 750 ms (12-bit) |
| Operating Temperature |
–55°C to +125°C |
| Supply Voltage |
3.0 V–5.5 V (VDD mode); 2.8 V–5.5 V (parasitic) |
| Quiescent Current |
1.5 µA (typ., standby) |
| Conversion Current (peak) |
1.5 mA |
| Interface |
1-Wire® (single data line + ground) |
| Unique ID |
Factory-programmed 64-bit ROM address |
| Package |
8-Lead µSOP with Exposed Pad (U) |
| RoHS / Green |
Yes (Pb-free, Halogen-free) |
| Packaging |
Tape-and-Reel (T&R), 2,500 units per reel |
Typical Applications
🔹 Distributed Temperature Monitoring: HVAC ducts, server racks, cold-chain logistics, and smart building systems — where dozens of low-cost, self-identifying sensors share a single microcontroller GPIO.
🔹 Industrial Process Control: Monitoring bearing temperatures, motor windings, hydraulic fluid, or reactor vessels — leveraging ruggedness, wide temperature range, and parasitic power for easy retrofitting.
🔹 Consumer Electronics: Smart thermostats, coffee makers, refrigerators, and wearables — using µSOP’s small footprint and low power for seamless integration.
🔹 Battery-Powered IoT Sensors: Environmental nodes, agricultural soil monitors, and asset trackers — enabled by 1.5 µA sleep current and no external supply requirement.
🔹 Educational & Prototyping Platforms: Arduino, Raspberry Pi, and ESP32-based labs — thanks to abundant open-source libraries, simple wiring (3 wires max), and intuitive command set.
🔹 Medical & Lab Equipment: Incubator temperature logging, sterilization validation, and bioreactor monitoring — where traceability (via unique ID) and calibration stability are critical.
Development & Design Notes
🔧 1-Wire Bus Design & Layout:
- Use a strong 4.7 kΩ pull-up resistor from data line to VDD (or to parasite-supply rail if parasitic mode); for long buses (>20 m), add active pull-ups or repeaters.
- Keep data traces short and avoid routing near switching regulators or clock lines; add a 100 pF capacitor from data to GND near the sensor for EMI filtering (optional but recommended in noisy environments).
- For parasitic mode: ensure host can source ≥ 4 mA during conversion — use a MOSFET-switched auxiliary power supply or a dedicated 1-Wire master IC (e.g., DS2482) if driving >10 sensors.
🔧 Thermal Coupling & Accuracy Optimization:
- Solder the exposed pad (EP) to a ≥ 25 mm² copper area — improves thermal conduction from PCB to die and stabilizes readings under self-heating conditions.
- Avoid placing heat-generating components (e.g., LDOs, power inductors) within 5 mm of the sensor — thermal crosstalk degrades accuracy.
- For ambient air sensing, mount sensor at edge of PCB with EP exposed and airflow unobstructed; for board-temperature sensing, maximize copper contact.
🔧 Firmware & Communication:
- Use standard 1-Wire commands:
Skip ROM (for single-sensor bus), Match ROM (for multi-drop), Convert T, Read Scratchpad.
- Always verify CRC of scratchpad reads (byte 9) — prevents misinterpretation due to bus noise or timing jitter.
- Implement timeout handling: if
Convert T takes > 1 s (12-bit max), abort and retry — avoids firmware lockup on faulty sensors.
🔧 Reliability & Long-Term Stability:
- DS18B20 exhibits < 0.1°C drift over 10 years (per Maxim reliability reports) — suitable for calibration-critical applications without periodic recalibration.
- For IP67 sealing: conformal coat the µSOP (avoiding pads) or use gel-filled encapsulation — the plastic package is moisture-resistant but not fully hermetic.
