DS1722

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DETAILED PIN DESCRIPTION Table 1

SOIC

SYMBOL

DESCRIPTION

PIN 1

Digital Supply Voltage 1.8V-5.5V. Defines the top rails for the digital

inputs and outputs.

PIN 2

CE

Chip Enable Must be asserted high for communication to take place for

either the SPI or 3-wire interface.

PIN 3

SCLK

Serial Clock Input Used to synchronize data movement on the serial

interface for either the SPI or 3-wire interface.

PIN 4

GND

Ground pin.

PIN 5

SDO

Serial Data Output When SPI communication is selected, the SDO pin is

the serial data output for the SPI bus.

When 3-wire communication is

selected, this pin must be tied to the SDI pin (the SDI and SDO pins function

as a single I/O pin when tied together.)

PIN 6

SDI

Serial Data Input When SPI communication is selected, the SDI pin is the

serial data input for the SPI bus. When 3-wire communication is selected,

this pin must be tied to the SDO pin (the SDI and SDO pins function as a

single I/O pin when tied together.)

PIN 7

SERMODE

Serial Interface Mode Input This pin selects which interface standard will

GND.

PIN 8

Analog Supply Voltage 2.65V – 5.5V input power pin.

OVERVIEW

A block diagram of the DS1722 is shown in Figure 1. The DS1722 consists of four major components:

1. Precision temperature sensor

2. Analog-to-digital converter

3. SPI/3-wire interface electronics

4. Data registers

The factory-calibrated temperature sensor requires no external components. The DS1722 is in a power-

conserving shutdown state upon power-up. After power-up, the user may alter the configuration register

to place the device in a continuous temperature conversion mode or in a one-shot conversion mode. In

the continuous conversion mode, the DS1722 continuously converts the temperature and stores the result

in the temperature register. As conversions are performed in the background, reading the temperature

register does not affect the conversion in progress. In the one-shot temperature conversion mode, the

DS1722 will perform one temperature conversion, store the result in the temperature register, and then

return to the shutdown state. This conversion mode is ideal for power sensitive applications. More

information on the configuration register is contained in the “OPERATION-Programming” section.

The temperature conversion results will have a default resolution of 9 bits. In applications where small

incremental temperature changes are critical, the user can change the conversion resolution from 9 bits to

8, 10, 11, or 12. This is accomplished by programming the configuration register. Each additional bit of

resolution approximately doubles the conversion time.