Dallas Semi digital thermometer integrates dual power supplies
DALLAS--Dallas Semiconductor Inc. here today announced a digital thermometer that supports two separate power supplies and a choice of software-selectable communication interfaces.
By accepting a wide power supply range for analog signals and a very low-power range for digital logic, the DS1722 meets a growing need for multiple-voltage capability in portable, mixed-signal systems. The added choice of standard 3-wire interface or Serial Peripheral Interface (SPI) allows designers to match different networking communication protocols in embedded systems.
Dallas Semiconductor sees applications for the chip in devices with mixed analog and digital signaling, such as cellular telephones, motor controls, personal computers, and office equipment. These devices operate at higher voltages than strictly digital instruments.
"Any heat-sensitive device that handles both analog and digital signals can benefit from using the DS1722," said Chris Beaudoin, product manager at Dallas Semiconductor. "One pin on the DS1772 accepts an analog power supply over the 2.65-to-5.50-volt range, and a separate pin accepts power over the 1.8-to-5.5-V range. The DS1722 can communicate logic signals with low-voltage processors while handling the higher voltage range among analog components."
The choice of software-selectable SPI and 3-wire interfaces provides flexibility in designing system communications. The SPI data protocol employs a serial bus while supporting the high-speed, high-bandwidth network connections most often used in handheld instruments, particularly cellular telephones and other mobile communication platforms. Alternatively, the 3-wire bus is standard and uses a bi-directional I/O instead of separate data in and out signals. Both interfaces use the same number of pins.
The DS1722's direct-to-digital technology provides temperature readings accurate to plus/minus 2.0 oC over a range from -40o C to +85o C without additional components. For applications that require greater temperature resolution, the user can adjust the readout resolution from 8 to 12 bits, a useful feature for applications where thermal runaway conditions must be detected quickly.
The DS1722 Digital Thermometer with SPI/3-Wire Interface is packaged in an 8-pin SOIC and a flip-chip package, which reduces package size to that ofthe chip itself in order to maximize savings in board space and cost. The S1722 is available from stock and costs $1.00 each in quantities of 1,000.