The DS1821 is a programmable digital thermostat and thermometer from Texas Instruments that uses a unique 1-Wire interface that requires only one port pin for communication. It operates over a temperature range of -55°C to +125°C and has user-definable trip points. It provides 8-bit (1°C resolution) centigrade temperature measurements with an accuracy of ±1°C over a range of 0°C to +85°C. It can convert temperature to a digital word in 1 second (max) and is available in 3-pin PR35 and 8-pin SO packages. Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermally sensitive system.
The DS1821 is a programmable digital thermostat and thermometer that can operate either as a standalone thermostat with user‑definable trip‑points or as an 8‑bit temperature sensor accessed via Dallas' 1‑Wire bus. It provides a temperature range of –55 °C to +125 °C, 1 °C resolution, and ±1 °C accuracy from 0 °C to +85 °C. The device includes non‑volatile EEPROM for storing configuration and thermostat settings.
The datasheet describes two operating modes (1‑Wire and thermostat), pin assignments for the 3‑pin PR35 and 8‑pin SO packages, and the configuration register bits that control power‑up mode, output polarity, and conversion mode. Timing diagrams, performance curves, and high‑resolution temperature calculation methods are also provided.
| Accuracy | ±1 °C over 0 °C to +85 °C |
|---|---|
| Resolution | 8‑bit (1 °C increment) |
| Package options | 3‑pin PR35 and 8‑pin 208‑mil SO |
| Power supply pin | Vpp (Power Supply Voltage) |
It provides an 8‑bit resolution, which corresponds to 1 °C increments.