Rainbow Electronics DS1722 - Manual (Page 2)

DS1722
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DETAILED PIN DESCRIPTION Table 1
SOIC SYMBOL DESCRIPTION
PIN 1 V
DDD
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
be used: SPI when connected to V
CC
; standard 3-wire when connected to
GND.
PIN 8 V
DDA
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.