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PRELIMINARY
PRELIMINARY
DS1722
Digital Thermometer with
SPI/3-Wire Interface
FEATURES
PIN ASSIGNMENT
Temperature measurements require no
external components
Measures temperatures from -55°C to
+120°C. Fahrenheit equivalent is -67°F to
+248°F
Thermometer accuracy is ±2.0°C
Thermometer resolution is configurable from
V
DDD
CE
SCLK
GND
1
2
3
4
DS1722S
8-Pin SOIC (150-mil)
8
V
7
6
SDI
SDO
5
V
CE
SCLK
GND
DDD
1 8
2 7
3 6
4 5
DS1722U
8-PIN
-SOP
V
DDA
SERMODE
SDI
SDO
8 to 12 bits (1.0°C to 0.0625°C resolution)
Data is read from/written to via a Motorola
Serial Peripheral Interface (SPI) or standard
3-wire serial interface
Wide analog power supply range (2.65V -
5.5V)
Separate digital supply allows for 1.8V logic
Available in an 8-pin SOIC (150 mil), 8-pin
uSOP, and flip chip package
PIN DESCRIPTION
SERMODE - Serial Interface Mode
CE - Chip Enable
SCLK - Serial Clock
GND - Ground
V
DDA
SDO - Serial Data Out
SDI - Serial Data In
V
DDD
- Analog Supply Voltage
- Digital Supply Voltage
DESCRIPTION
The DS1722 Digital Thermometer and Thermostat with SPI/3-Wire Interface provides temperature
readings which indicate the temperature of the device. No additional components are required; the device
is truly a temperature-to-digital converter. Temperature readings are communicated from the DS1722
over a Motorola SPI interface or a stand ard 3-wire serial interface. Th e choice of interface standa rd is
selectable by the user.
For applications that require greater temperature resolution, the user can adjust the readout resolution
from 8 to 12 bits. This is particularly useful in applications where thermal runaway conditions must be
detected quickly.
For application flexibility, the DS1722 features a wide analog supply rail of 2.65V - 5.5V. A separate
digital supply allows a range of 1.8V to 5.5V.
The DS1722 is available in an 8-pin SOIC (150-mil), 8-pin uSOP, and flip chip package.
Applications for the DS1722 include personal computers/servers/workstations, cellular telephones, office
equipment, or any thermally-sensitive system.
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DETAILED PIN DESCRIPTION Table 1
SOIC SYMBOL DESCRIPTION
PIN 1
PIN 2
PIN 3
PIN 4
PIN 5
PIN 6
PIN 7
PIN 8
V
DDD
CE
SCLK
GND
SDO
SDI
SERMODE
V
DDA
Digital Supply Voltage 1.8V-5.5V. Defines the top rails for the digital
inputs and outputs.
Chip Enable Must be asserted high for communication to take place for
either the SPI or 3-wire interface.
Serial Clock Input Used to synchronize data movement on the serial
interface for either the SPI or 3-wire interface.
Ground pin.
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.)
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.)
Serial Interface Mode Input This pin selects which interface standard will
be used: SPI when connected to VCC ; standard 3-wire when connected to
GND.
Analog Supply Voltage 2.65V – 5.5V input power pin.
DS1722
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 powerconserving shutdown state upon power-up. After power-up, the user ma y alter the confi guration 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.
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DS1722
The DS1722 can communicate using either a Motorola Serial Peripheral Interface (SPI) or standard 3wire interface. The user can select ei the r comm unicat ion standa rd t hrou gh the SER MODE pin, tying it to
V
for SPI and to ground for 3-wire.
DDD
The device contains both an analog supply voltage and a digital supply voltage (V
DDA
and V
DDD
respectively). The analog supply powers the device for operation while the digital supply provides the
top rails for the digital inputs and outputs. The DS1722 was designed to be 1.8V Logic-Ready.
DS1722 FUNCTIONAL BLOCK DIAGRAM Figure 1
,
OPERATION-Measuring Temperature
The core of DS1722 functionality is its direct-to-digital temperature sensor. The DS1722 measures
temperature through the use of an on-chip temperature measurem ent technique with an operating range
from -55°=to +120°C. The device powers up in a power-conserving shutdown mode. After power-up, th e
DS1722 may be placed in a continuous conversion mode or in a one-shot conversion mode. In the
continuous conversion mode, the device continuously computes the temperature and stores the most
recent result in the temperature register at addresses 01h (LSB) and 02h (MSB). In the one-shot
conversion mode, the DS1722 performs one temperature conversion and then returns to the shutdown
mode, storing temperature in the temperature register. Details on how to change the setting after powerup are contained in the “OPERATION-Programming” section.
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DS1722
The resolution of the temperature conversion is configurable (8, 9, 10, 11, or 12 bits), with 9-bit readings
the default state. This equates to a temperature resolution of 1.0°C, 0.5°C, 0.25°C, 0.125°C, or 0.0625°C.
Following each conversion, thermal data is stored in the thermometer register in two’s complement
format; the information can be retrieved over the SPI or 3-wire interface with the address set to the
temperature register, 01h (LSB) and then 02h (MSB). Table 2 describes the ex act relationship of output
data to measured temperature. The table assumes the DS1722 is configured for 12-bit resolution; if the
device is configured in a lower resolution mode, those bits will contain 0s. The data is transmitted
serially over the digital interface, MSb first for SPI communication and LSb first for 3-wire
communication. The MSb of the temperature register contains the “sign” (S) bit, denoting whether the
temperature is positive or negative. For Fahrenheit usage, a lookup table or conversion routine must be
used.
Temperature/Data Relationships Table 2
Address
Location
S262
5
MSb (unit = °C) LSb
4
2
3
2
2
2
1
2
0
2
02h
-1
2
TEMPERATURE
-2
2
+120°C
+25.0625°C
+10.125°C
+0.5°C
0°C
-0.5°C
-10.125°C
-25.0625°C
-55°C
-3
2
-4
2
000001h
DIGITAL OUTPUT
(BINARY)
DIGITAL OUTPUT
(HEX)
0111 1000 0000 0000 7800h
0001 1001 0001 0000 1910h
0000 1010 0010 0000 0A20h
0000 0000 1000 0000 0080h
0000 0000 0000 0000 0000h
1111 1111 1000 0000 FF80h
1111 0101 1110 0000 F5E0h
1110 0110 1111 0000 E6F0h
1100 1001 0000 0000 C900h
OPERATION-Programming
The area of interest in programming the DS1722 is the Configuration register. All programming is done
via the SPI or 3-wire communication interface b y selecting the approp riate add ress of the desired register
location. Table 3 illustrates the addresses for the two registers (configuration and temperature) of the
DS1722.
Register Address Structure Table 3
Read Address Write Address Active Register
00h 80h Configuration
01h No access Temperature LSB
02h No access Temperature MSB
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DS1722
CONFIGURATION REGISTER PROGRAMMING
The configuration register is accessed in the DS1722 with the 00h address for reads and the 80h address
for writes. Data is read from or written to the configuration register MSb first for SPI communication and
LSb first for 3-wire communication. The format of the register is illustrated in Figure 2. The effect each
bit has on DS1722 functionality is described below along with the power-up state of the bit. The entire
register is volatile, and thus it will power-up in the default state.
CONFIGURATION/STATUS REGISTER Figure 2
1 1 1 1SHOT R2 R1 R0 SD
MSb LSb
1SHOT = One-shot temperature conversion bit. If the SD bit is "1", (continuous temperature
conversions are not taking place), a "1" written to the 1SHOT bit will cause the DS1722 to perform one
temperature conversion and store the results in the temperature register at addresses 01h (LSB) and 02h
(MSB). The bit will clear itself to "0" upon completion of the temperature conversion. The user has
read/write access to the 1SHOT bit, although writes to this bit will be ignored if the SD bit is a "0",
(continuous conversion mode). The power-up default of the one-shot bit is "0".
R0, R1, R2 = Thermometer resolution bits. Table 4 below defines the resolution of the digital
thermometer, based on the settings of these 3 bits. There is a direct tradeoff between resolution and
conversion time, as depicted in the AC Electrical Characteristics. The user has read/write access to the
R2, R1 and R0 bits and the power-up default state is R2="0", R1="0", and R0="1" (9-bit conversions).
THERMOMETER RESOLUTION CONFIGURATION Table 4
R2 R1 R0 Thermometer Resolution Max Conversion Time
0 0 0 8-bit 0.075s
0 0 1 9-bit 0.15s
0 1 0 10-bit 0.3s
0 1 1 11-bit 0.6s
1 x x 12-bit 1.2s
x=Don’t care.
SD = Shutdown bit. If SD is "0", the DS1722 will continuously perform temperature conversions and
store the last completed result in the temperature register. If SD is changed to a "1", the conversion in
progress will be completed and stored and then the device will revert to a low-power shutdown mode.
The communication port remains active. The user has read/write access to the SD bit and the power-up
default is "1" (shutdown mode).
SERIAL INTERFACE
The DS1722 offers the flexibility to choose between two serial interface modes. The DS1722 can
communicate with the SPI interface or with a standard 3-wire interface. The interface method used is
determined by the SERMODE pin. When this pin is connected to V
When this pin is connected to ground, standard 3-wire communication is selected.
SPI communication is selected.
DDD
SERIAL PERIPHERAL INTERFACE (SPI)
The serial peripheral interface (SPI) is a synchronous bus for address and data transfer. The SP I mode of
serial communication is selected b y tying the SERMODE pin to V
The four pins are the SDO (Serial Data Out), SDI (Serial Data In), CE (Chip Enable), and SCLK (Serial
Clock). The DS1722 is the slave device in an SPI application, with the microcontroller being the master.
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. Four pins are used for the SPI.
DDD
DS1722
The SDI and SDO pins are the serial data input and output pins for the DS1722, respectively. The CE
input is used to initiate and terminate a data transfer. The SCLK pin is used to synchronize data
movement between the master (microcontroller) and the slave (DS1722) devices.
The shift clock (SCLK), which is generated by the microcontroller, is active only when CE is high and
during address and data transfer to any device on the SPI bus. The inactive clock polarity is
programmable in some microcontrollers. The DS1722 offers an important feature in that the level of the
inactive clock is determined by sampling SCLK when CE becomes active. Therefore, either SCLK
polarity can be accommodated. Input data (SDI) is latched on the internal strobe edge and output data
(SDO) is shifted out on the shift edge (See Table 5 and Figure 3). There is one clock for each bit
transferred. Address and data bits are transferred in groups of eight, MSB first.
FUNCTION TABLE Table 5
MODE CE SCLK SDI SDO
Disable Reset L Input Disabled Input Disabled High Z
Write H CPOL=1*
CPOL=0
Read H CPOL=1
CPOL=0
*CPOL is the “Clock Polarity” bit that is set in the control register of the microcontroller.
** SDO remains at High Z until eight bits of data are ready to be shifted out during a read.
Data Bit Latch High Z
X Next data bit
shift**
NOTE:
CPHA bit polarity must be set to “1”.
SERIAL CLOCK AS A FUNCTION OF MICROCONTROLLER CLOCK
POLARITY (CPOL) Figure 3
INTERNAL
STROBE
INTERNAL
STROBE
CPOL=1
CPOL=0
CE
SCLK
CE
SCLK
SHIFT
SHIFT
NOTE:
CPOL is a bit that is set in the microcontroller’s Control Register.
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DS1722
ADDRESS AND DATA BYTES
Address and data bytes are shifted MSB first into the serial data input (SDI) and out of the serial data
output (SDO). Any transfer requires the address of the b yte to specify a write or a read, followed b y one
or more bytes of data. Data is transferred out of the SDO for a read operation and into the SDI for a write
operation.
SPI SINGLE BYTE WRITE Figure 4
SPI SINGLE-BYTE READ Figure 5
The address byte is always the first byte entered after CE is driven high. The most significant bit (A7) of
this byte determines if a read or write will take place. If A7 is "0", one or more read cycles will occur. If
A7 is "1", one or more write cycles will occur.
Data transfers can occur 1 byte at a time in multiple-byte burst mode. After CE is driven high an address
is written to the DS1722. After the address, one or more data bytes can be written or re ad. For a singlebyte transfer, 1 byte is read or written and then CE is driven low (see Figures 4 and 5). For a multiplebyte transfer, however, multiple bytes can be read or written to the DS1722 after the address has been
written (see Figure 6). A single-byte burst read/write will sequentially point through the memory map
and will loop from 02h/82h to 00h/80h.
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DS1722
SPI MULTIPLE BYTE BURST TRANSFER Figure 6
3-WIRE SERIAL DATA BUS
The 3-wire communication mode operates similar to the SPI mode. However, in 3-wire mode, there is
one bi-directional I/O instead of separate data in and data out signals. The 3-wire consists of the I/O (SDI
and SDO pins tied together), CE, and SCLK pins. In 3-wire mode, each byte is shifted in LSB first
unlike SPI mode where each byte is shifted in MSB first. As is the case with the SPI mode, an address
byte is written to the device followed by a single data byte or multiple data bytes. Figure 7 illustrates a
read and write cycle. Figure 8 illustrates a multiple byte burst transfer. In 3-wire mode, data is input on
the rising edge of SCLK and output on the falling edge of SCLK.
3-WIRE SINGLE BYTE TRANSFER Figure 7
3-WIRE MULTIPLE BYTE BURST TRANSFER Figure 8
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DS1722
ABSOLUTE MAXIMUM RATINGS*
Voltage on V DD , Relative to Ground -0.3V to +6.0V
Voltage on any other pin, Relative to Ground -0.3V to +6.0V
Operating Temperature -55°C to +125°C
Storage Temperature -55°C to +125°C
Soldering Temperature 260°C for 10 seconds
* This is a stress rating only and functional operation of the device at these or an y other conditions abov e
those indicated in the operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods of time may affect reliability.
The Dallas Semiconductor DS1722 is built to the highest quality standards and manufactured for long
term reliability. All Dallas Semiconductor devices are made using the same quality materials and
manufacturing methods. However, the DS1722 is not exposed to environmental stresses, such as burn-in,
that some industrial applications require. For specific reliability information on this product, please
contact the factory in Dallas at (972) 371-4448.
RECOMMENDED DC OPERATING CONDITIONS
(-55°C to +120°C, 2.65V ≤≤≤≤ V
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES
Analog Supply Voltage V
Digital Supply Voltage V
DDA
DDD
2.65 5.5 V 1
1.8 5.5 V 1
DDA
≤≤≤≤5.5V)
DC ELECTRICAL CHARACTERISTICS (-55°°°°C to +120°°°°C, 2.65V ≤≤≤≤ V
DDA
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES
Input Logic High V
Input Logic Low V
Logic 0 Output V
Logic 1 Output V
Input Resistance R
Active Current I
Shutdown Current I
OL
OH
CC
CC
IH
IL
I
CE to GND
SDI, SDO,
SCLK to V
2.65V≤ V
3.3V≤V
DDA
DDA
DDD
≤=3.3V
≤5.5V
0.7 x
V
DDD
0.7 x
V
DDD
1
1
V1
0.2 x
V
DDD
0.2 x
V
DDD
V1
V2
V3
MΩ
MΩ
.5 mA 4
0.5
1.0
µA
µA
≤≤≤≤====5.5V)
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ELECTRICAL CHARACTERISTICS: DIGIT AL THERMOME TER
DS1722
(-55°°°°C to +120°°°°C, 2.65V ≤≤≤≤====V
DDA
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES
Thermometer Error T
ERR
-40°C to +85°C ±2.0
°C
-55°C to +120°C ±3.0
Resolution 8 12 bits
Conversion Time t
CONVT
8-bit conversions 67.5 75
ms
9-bit conversions 125 150
10-bit conversions 250 300
11-bit conversions 500 600
12-bit conversions 1000 1200
AC ELECTRICAL CHARACTERISTICS: 3-WIRE INTERFACE
(-55°C to +120°C, 2.65V ≤=V
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES
Data to SCLK Setup t
SCLK to Data Hold t
SCLK to Data Valid t
SCLK Low Ti m e t
SCLK High Time t
SCLK Frequency t
DC
CDH
CDD
CL
CH
CLK
SCLK Rise and Fall tR, t
CE to SCLK Setup t
SCLK to CE Hold t
CE Inactive Time t
CE to Output High Z t
SCLK to Output High Z t
CC
CCH
CWH
CDZ
CCZ
F
35 ns 5, 6
35 ns 5, 6
80 ns 5, 6, 7
100 ns 6
100 ns 6
DC 5.0 MHz 6
200 ns
400 ns 6
100 ns 6
400 ns 6
40 ns 5, 6
40 ns 5, 6
≤≤≤≤====5.5V)
≤=5.5V)
DD
8, 9
TIMING DIAGRAM: 3-WIRE READ DATA TRANSFER Figure 9
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TIMING DIAGRAM: 3-WIRE WRITE DATA TRANSFER Figure 10
*I/O is SDI and SDO tied together.
AC ELECTRICAL CHARACTERISTICS: SPI Interface
DS1722
(-55°°°°C to +120°°°°C, 2.65V ≤≤≤≤====V
PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES
Data to SCLK Setup t
SCLK to Data Hold t
SCLK to Data Valid t
SCLK Low Ti m e t
SCLK High Time t
SCLK Frequency t
DC
CDH
CDD
CL
CH
CLK
SCLK Rise and Fall tR, t
CE to SCLK Setup t
SCLK to CE Hold t
CE Inactive Time t
CE to Output High Z t
CC
CCH
CWH
CDZ
F
35 ns 5, 6
35 ns 5, 6
100 ns 6
100 ns 6
DC 5.0 MHz 6
400 ns 6
100 ns 6
400 ns 6
TIMING DIAGRAM: SPI READ DATA TRANSFER Figure 11
≤≤≤≤====5.5V)
DD
80 ns 5, 6, 7
200 ns
40 ns 5, 6
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TIMING DIAGRAM: SPI WRITE DATA TRANSFER Figure 12
*SCLK can be either polarity, timing shown for CPOL = 1.
NOTES:
1. All voltages are referenced to ground.
2. Logic 0 voltages are specified at a sink current of 4 mA.
DS1722
3. Logic 1 voltages are specified at a source current of 1 mA.
4. ICC specified with SCLK=V
and V
5. Measured at VIH =0.7 V
DDD =
2.65V
.
DDD
and CE=GND. Typical I
DDD
or VIL=0.2 V
and 10 ms maximum rise and fall time.
DDD
is 0.25 µA and ICC is 0.3 mA at 25°C
CC1
6. Measured with 50 pF load
7. Measured at VOH =0.7 V
DDD
or V
=0.2 V
OL
. Measured from the 50% point of SCLK to the V
DDD
OH
minimum of SDO.
8. Figure 13 shows mean thermometer error for a pre-characterization sample. Data covering a larger
sample over the full temperature range is pending.
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TYPICAL DS1722 THERMOMETER ERROR
DS1722
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