Measure the temperature with the SPI digital temperature sensor and show it on an LCD display.

 Overview.

The TC77 is a digital temperature sensor with a Serial Peripheral Interface. Temperature data is converted from the internal thermal sensing element and made available at anytime as a 13-bit two’s compliment digital word. Communication with the TC77 is accomplished via a SPI and MICROWIRE compatible interface. It has a 12-bit plus sign temperature resolution of 0.0625°C per Least Significant Bit (LSb). The TC77 offers a temperature accuracy of ±1.0°C (max.) over the temperature range of +25°C to +65°C. When operating, the TC77 consumes only 250 ìA (typ.). The TC77’s Configuration register can be used to activate the low power Shutdown mode, which has a current consumption of only 0.1 uA (typ.).

Features:

  • Digital Temperature Sensing in 5-Pin SOT-23A and 8-Pin SOIC Packages
  • Outputs Temperature as a 13-Bit Digital Word
  • SPI and MICROWIRE™ Compatible Interface
  • Solid State Temperature Sensing
  • ±1°C (max.) accuracy from +25°C to +65°C
  • ±2°C (max.) accuracy from -40°C to +85°C
  • ±3°C (max.) accuracy from -55°C to +125°C
  • 2.7V to 5.5V Operating Range
  • Low Power - 250 uA (typ.) Continuous Conversion Mode - 0.1 uA (typ.) Shutdown Mode

Package

The TCN77 is available in a SOIC package.

TCN77 SOICTCN77 SOIC

Serial Bus Interface

The serial interface consists of the Chip Select (CS),Serial Clock (SCK) and Serial Data (SI/O) signals. The TC77 meets the SPI and MICROWIRE bus specifications,with the serial interface designed to be compatible with the Microchip PICmicro® family of microcontrollers.The CS input is used to select the TC77 when multiple devices are connected to the serial clock and data lines. The CS line is also used to synchronize the data, which is written to, or read from, the device when CS is equal to a logic ‘0’ voltage. The SCK input is disabled when CS is a logic ‘1’. The falling edge of the CS line initiates communication, while the rising edge of CS completes the communication. The SCK input is provided by the external microcontroller and is used to synchronize the data on the SI/O line.The Temperature and Manufacturer ID registers are read only while the Configuration register is a read/write register.

Temperature Data Format

A 13-bit two’s complement digital word is used to represent the temperature. The Least Significant Bit (LSb)is equal to 0.0625°C. Note that the last two LSb bits (Bit 0 and 1) are tri-stated and are represented as a logic ‘1’ in the table. Bit 2 is set to logic ‘1’ after the completion of the first temperature conversion following a powerup or voltage reset event.

TCN77 SOIC

An over-temperature condition can be determined by reading only the first few Most Significant Bits (MSb) of the temperature data. For example, the microprocessor could read only the first four bits of the Temperature register in order to determine that an over-temperature condition exists.

Hardware

TCN77 Application

The circuit is very simple, the device doesn't need any external components.The chip and a connector are placed on a small PCB.The Chip Select (CS),Serial Clock (SCK) and Serial Data (SI/O) signals can be connected to the PORTB of the AVR Microcontroller, and then configured in the software. It can easily be connected to the ATTiny2313 board.

Yuo can buy the ATTiny board at www.bizztronix.net.