Download DS18B20 Digital Thermometer: Features, Description, and Ordering Information and more Study notes Communication in PDF only on Docsity!
FEATURES
Unique 1-Wire®^ Interface Requires Only One Port Pin for Communication Each Device has a Unique 64-Bit Serial Code Stored in an On-Board ROM Multidrop Capability Simplifies Distributed Temperature-Sensing Applications Requires No External Components Can Be Powered from Data Line; Power Supply Range is 3.0V to 5.5V Measures Temperatures from -55°C to +125°C (-67°F to +257°F) ±0.5°C Accuracy from -10°C to +85°C Thermometer Resolution is User Selectable from 9 to 12 Bits Converts Temperature to 12-Bit Digital Word in 750ms (Max) User-Definable Nonvolatile (NV) Alarm Settings Alarm Search Command Identifies and Addresses Devices Whose Temperature is Outside Programmed Limits (Temperature Alarm Condition) Available in 8-Pin SO (150 mils), 8-Pin μSOP, and 3-Pin TO-92 Packages Software Compatible with the DS Applications Include Thermostatic Controls, Industrial Systems, Consumer Products, Thermometers, or Any Thermally Sensitive System
PIN CONFIGURATIONS
DESCRIPTION
The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements and has an alarm function with nonvolatile user-programmable upper and lower trigger points. The DS18B communicates over a 1-Wire bus that by definition requires only one data line (and ground) for communication with a central microprocessor. It has an operating temperature range of -55°C to +125°C and is accurate to ±0.5°C over the range of -10°C to +85°C. In addition, the DS18B20 can derive power directly from the data line (“parasite power”), eliminating the need for an external power supply.
Each DS18B20 has a unique 64-bit serial code, which allows multiple DS18B20s to function on the same 1-Wire bus. Thus, it is simple to use one microprocessor to control many DS18B20s distributed over a large area. Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems inside buildings, equipment, or machinery, and process monitoring and control systems.
Programmable Resolution
1-Wire Digital Thermometer
TO- (DS18B20)
1
(BOTTOM VIEW)
2 3
DALLAS 18B
1
GND
DQVDD
2 3
SO (150 mils) (DS18B20Z)
N.C.
N.C.
N.C.
N.C.
DQ GND
VDD
N.C.
6
8
7
5
3
1
2
4
DALLAS
18B
N.C.
VDD N.C. N.C. GND N.C.
N.C.
DQ
6
8 7
5
3
1 2
4
18B
μ SOP (DS18B20U)
ORDERING INFORMATION
PART TEMP RANGE PIN-PACKAGE TOP MARK
DS18B20 (^) -55°C to +125°C 3 TO-92 18B
DS18B20+ -55°C to +125°C 3 TO-92^ 18B
DS18B20/T&R -55°C to +125°C 3 TO-92 (2000 Piece)^ 18B
DS18B20+T&R -55°C to +125°C 3 TO-92 (2000 Piece)^ 18B
DS18B20-SL/T&R (^) -55°C to +125°C 3 TO-92 (2000 Piece)* 18B
DS18B20-SL+T&R (^) -55°C to +125°C 3 TO-92 (2000 Piece)* 18B
DS18B20U -55°C to +125°C 8 μSOP 18B
DS18B20U+ -55°C to +125°C 8 μSOP 18B
DS18B20U/T&R -55°C to +125°C 8 μSOP (3000 Piece) 18B
DS18B20U+T&R (^) -55°C to +125°C 8 μSOP (3000 Piece) 18B
DS18B20Z (^) -55°C to +125°C 8 SO DS18B
DS18B20Z+ -55°C to +125°C 8 SO^ DS18B
DS18B20Z/T&R -55°C to +125°C 8 SO (2500 Piece)^ DS18B
DS18B20Z+T&R -55°C to +125°C 8 SO (2500 Piece) DS18B
- Denotes a lead-free package. A “+” will appear on the top mark of lead-free packages. T&R = Tape and reel. *TO-92 packages in tape and reel can be ordered with straight or formed leads. Choose “SL” for straight leads. Bulk TO-92 orders are straight leads only.
PIN DESCRIPTION
PIN
SO μ SOP TO-
NAME FUNCTION
— N.C. No Connection
3 8 3 VDD Optional VDD^. VDD^ must be grounded for operation in parasite power mode.
4 1 2 DQ
Data Input/Output. Open-drain 1-Wire interface pin. Also provides power to the device when used in parasite power mode (see the Powering the DS18B20 section.) 5 4 1 GND Ground
OVERVIEW
Figure 1 shows a block diagram of the DS18B20, and pin descriptions are given in the Pin Description table. The 64-bit ROM stores the device’s unique serial code. The scratchpad memory contains the 2-byte temperature register that stores the digital output from the temperature sensor. In addition, the scratchpad provides access to the 1-byte upper and lower alarm trigger registers (TH and TL) and the 1-byte configuration register. The configuration register allows the user to set the resolution of the temperature- to-digital conversion to 9, 10, 11, or 12 bits. The TH, TL, and configuration registers are nonvolatile (EEPROM), so they will retain data when the device is powered down.
The DS18B20 uses Maxim’s exclusive 1-Wire bus protocol that implements bus communication using one control signal. The control line requires a weak pullup resistor since all devices are linked to the bus via a 3-state or open-drain port (the DQ pin in the case of the DS18B20). In this bus system, the microprocessor (the master device) identifies and addresses devices on the bus using each device’s unique 64-bit code. Because each device has a unique code, the number of devices that can be addressed on one
20 of 22
AC ELECTRICAL CHARACTERISTICS—NV MEMORY
(-55°C to +100°C; V DD = 3.0V to 5.5V)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
NV Write Cycle Time t (^) WR 2 10 ms EEPROM Writes NEEWR -55°C to +55°C 50k writes EEPROM Data Retention t (^) EEDR -55°C to +55°C 10 years
AC ELECTRICAL CHARACTERISTICS (-55°C to +125°C; VDD = 3.0V to 5.5V)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS NOTES
9-bit resolution 93. 10-bit resolution 187. 11-bit resolution 375
Temperature Conversion Time
t (^) CONV
12-bit resolution 750
ms 1
Time to Strong Pullup On t (^) SPON
Start Convert T Command Issued
10 μs
Time Slot t (^) SLOT 60 120 μs 1 Recovery Time t (^) REC 1 μs 1 Write 0 Low Time t (^) LOW0 60 120 μs 1 Write 1 Low Time t (^) LOW1 1 15 μs 1 Read Data Valid t (^) RDV 15 μs 1 Reset Time High tRSTH 480 μs 1 Reset Time Low t (^) RSTL 480 μs 1, Presence-Detect High t (^) PDHIGH 15 60 μs 1 Presence-Detect Low t (^) PDLOW 60 240 μs 1 Capacitance CIN/OUT 25 pF
Figure 17. Typical Performance Curve
DS18B20 Typical Error Curve
-0.
-0.
-0.
-0.
-0.
0
0 10 20 30 40 50 60 70
Temperature (°C)
Thermometer Error (°C)Mean Error
+3s Error
-3s Error
