DS1821 Maxim Integrated Products, DS1821 Datasheet - Page 3
![IC THERMOMETER/STAT PROG 3-PR35](/photos/7/26/72615/406-3-pr35_sml.jpg)
DS1821
Manufacturer Part Number
DS1821
Description
IC THERMOMETER/STAT PROG 3-PR35
Manufacturer
Maxim Integrated Products
Datasheet
1.DS1821.pdf
(18 pages)
Specifications of DS1821
Function
Thermometer, Thermostat
Topology
Comparator, Register Bank
Sensor Type
Internal
Sensing Temperature
-55°C ~ 125°C
Output Type
Digital
Output Alarm
No
Output Fan
No
Voltage - Supply
2.7 V ~ 5.5 V
Operating Temperature
-55°C ~ 125°C
Mounting Type
Through Hole
Package / Case
TO-92-3 (Long Body), TO-226
Full Temp Accuracy
+/- 1 C
Digital Output - Bus Interface
Serial (1-Wire)
Digital Output - Number Of Bits
8 bit
Maximum Operating Temperature
+ 125 C
Minimum Operating Temperature
- 55 C
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
DS1821C+
Manufacturer:
EPCOS
Quantity:
1 000
Company:
Part Number:
DS1821S
Manufacturer:
DALLAS
Quantity:
8 680
Part Number:
DS1821S
Manufacturer:
DALLAS
Quantity:
20 000
Company:
Part Number:
DS1821S+
Manufacturer:
MAXIM
Quantity:
202
Part Number:
DS1821S+TR
Manufacturer:
MAXIM/美信
Quantity:
20 000
DS1821 BLOCK DIAGRAM Figure 1
TEMPERATURE SENSOR FUNCTIONALITY
The core functionality of the DS1821 is its proprietary direct-to-digital temperature sensor, which
provides 8-bit (1°C increment) centigrade temperature readings over the range of -55°C to +125°C.
A block diagram of the temperature measurement circuitry is shown in Figure 2. This circuit measures
the temperature by counting the number of clock cycles generated by an oscillator with a low temperature
coefficient (temp-co) during a gate period determined by a high temp-co oscillator. The low temp-co
counter is preset with a base count that corresponds to –55°C. If the counter reaches 0 before the gate
period is over, the temperature register, which is preset to –55°C, is incremented by one degree, and the
counter is again preset with a starting value determined by the slope accumulator circuitry. The preset
counter value is unique for every temperature increment and compensates for the parabolic behavior of
the oscillators over temperature.
At this time, the counter is clocked again until it reaches 0. If the gate period is not over when the counter
reaches 0, the temperature register is incremented again. This process of presetting the counter, counting
down to zero, and incrementing the temperature register is repeated until the counter takes less time to
reach zero than the duration of the gate period of the high temp-co oscillator. When this iterative process
is complete, the value in the temperature register will indicate the centigrade temperature of the device.
4.7K
V
GND
V
DD
DQ
DD
DS1821
SUPPLY
POWER
SENSE
I/O CONTROL
INTERFACE
1-WIRE
AND
3 of 18
CONFIGURATION REGISTER
TEMPERATURE SENSOR
TH REGISTER
TL REGISTER
AND CONTROL LOGIC
COMPARATOR/
DIGITAL
LOGIC