DS1721U+T&R Maxim Integrated Products, DS1721U+T&R Datasheet - Page 4
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DS1721U+T&R
Manufacturer Part Number
DS1721U+T&R
Description
IC THERMOMETER/STAT DIG HP 8USOP
Manufacturer
Maxim Integrated Products
Datasheet
1.DS1721STR.pdf
(17 pages)
Specifications of DS1721U+T&R
Function
Thermometer, Thermostat
Topology
ADC, Comparator, Register Bank
Sensor Type
Internal
Sensing Temperature
-55°C ~ 125°C
Output Type
I²C™/SMBus™
Output Alarm
Yes
Output Fan
Yes
Voltage - Supply
2.7 V ~ 5.5 V
Operating Temperature
-55°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
Full Temp Accuracy
+/- 2 C
Digital Output - Bus Interface
Serial (2-Wire)
Digital Output - Number Of Bits
12 bit
Maximum Operating Temperature
+ 125 C
Minimum Operating Temperature
- 55 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
OPERATION-Measuring Temperature
The core of DS1721 functionality is its direct-to-digital temperature sensor. The DS1721 measures
temperature through the use of an on-chip temperature measurement technique with an operation range
from -55°C to +125°C. The device can be configured to perform continuous conversions with the most
recent result being stored in the thermometer register. The device can also be configured to perform a
single conversion, store the result, and return to a standby mode. Regardless of the mode used, the digital
temperature is retrieved from the temperature register using the Read Temperature (AAh) command, as
described in detail in the “Command Set” section. The DS1721 power-up default has the sensor set to
automatically perform 12-bit conversions continuously once the Start Convert T (51h) command is
issued. Details on how to change the settings after power-up are contained in the “OPERATION-
Programming” section.
The resolution of the temperature conversion can be configured as 9, 10, 11, or 12 bits, with 12-bit
readings as the default state. This equates to a temperature resolution of 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 2-wire interface by issuing a Read
Temperature (AAh) command. Table 2 describes the exact relationship of output data to measured
temperature. The table assumes the DS1721 is configured for 12-bit resolution; if the device is configured
in a lower resolution mode, insignificant bits will contain zeros. The data is transmitted serially over the
2-wire serial interface, MSb first. 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
OPERATION-Thermostat Control
In its operating mode, the DS1721 functions as a thermostat with programmable hysteresis, as shown in
Figure 2. The thermostat output updates as soon as a temperature conversion is complete. When the
DS1721’s temperature meets or exceeds the value stored in the high temperature trip register (TH), the
output becomes active, and will stay active until the temperature is equal to or below the temperature
stored in the low temperature trigger register (TL). In this way, any amount of hysteresis may be
obtained.
MSb
2
S
-1
+25.0625°C
-25.0625°C
+10.125°C
-10.125°C
+125°C
TEMP
+0.5°C
-0.5°C
-55°C
+0°C
2
2
-2
6
2
2
-3
5
2
2
(UNIT = °C)
-4
4
DIGITAL OUTPUT
0111 1101 0000 0000
0001 1001 0001 0000
0000 1010 0010 0000
0000 0000 1000 0000
0000 0000 0000 0000
1111 1111 1000 0000
1111 0101 1110 0000
1110 0110 1111 0000
1100 1001 0000 0000
4 of 17
(Binary)
2
0
3
2
0
2
2
0
1
DIGITAL OUTPUT
7D00h
0A20h
FF80h
F5E0h
E6F0h
C900h
1910h
0080h
0000h
(Hex)
LSb
2
0
0
MSB
LSB