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DS18B20 Schematic ( PDF Datasheet ) - Maxim Integrated Products

Teilenummer DS18B20
Beschreibung Programmable Resolution 1-Wire Digital Thermometer
Hersteller Maxim Integrated Products
Logo Maxim Integrated Products Logo 




Gesamt 22 Seiten
DS18B20 Datasheet, Funktion
AVAILABLE
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 DS18B20 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.
Functional Diagrams
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
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750ms (Max)
DS18B20
Programmable Resolution
1-Wire Digital Thermometer
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 DS1822
Applications Include Thermostatic Controls,
Industrial Systems, Consumer Products,
Thermometers, or Any Thermally Sensitive
System
PIN CONFIGURATIONS
MAXIM
18B20
123
N.C. 1
8
N.C. 2
7
VDD
3
6
DQ 4
5
SO (150 mils)
(DS18B20Z)
N.C.
N.C.
N.C.
GND
12 3
(BOTTOM VIEW)
TO-92
(DS18B20)
DQ
N.C.
N.C.
GND
18
27
36
45
µSOP
(DS18B20U)
VDD
N.C.
N.C.
N.C.
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
REV: 042208






DS18B20 Datasheet, Funktion
DS18B20
Figure 4. Supplying the Parasite-Powered DS18B20 During Temperature Conversions
VPU
VPU
µP
4.7k
DS18B20
GND DQ VDD
1-Wire BUS
TO OTHER
1-WIRE DEVICES
Figure 5. Powering the DS18B20 with an External Supply
VPU
µP
DS18B20
GND DQ VDD
VDD (EXTERNAL SUPPLY)
4.7k
1-Wire BUS
TO OTHER
1-WIRE DEVICES
64-BIT LASERED ROM CODE
Each DS18B20 contains a unique 64–bit code (see Figure 6) stored in ROM. The least significant 8 bits
of the ROM code contain the DS18B20’s 1-Wire family code: 28h. The next 48 bits contain a unique
serial number. The most significant 8 bits contain a cyclic redundancy check (CRC) byte that is
calculated from the first 56 bits of the ROM code. A detailed explanation of the CRC bits is provided in
the CRC Generation section. The 64-bit ROM code and associated ROM function control logic allow the
DS18B20 to operate as a 1-Wire device using the protocol detailed in the 1-Wire Bus System section.
Figure 6. 64-Bit Lasered ROM Code
MSB
8-BIT CRC
48-BIT SERIAL NUMBER
8-BIT FAMILY CODE (28h)
LSB MSB
LSB MSB
LSB
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DS18B20 pdf, datenblatt
DS18B20
COPY SCRATCHPAD [48h]
This command copies the contents of the scratchpad TH, TL and configuration registers (bytes 2, 3 and 4)
to EEPROM. If the device is being used in parasite power mode, within 10µs (max) after this command is
issued the master must enable a strong pullup on the 1-Wire bus for at least 10ms as described in the
Powering the DS18B20 section.
RECALL E2 [B8h]
This command recalls the alarm trigger values (TH and TL) and configuration data from EEPROM and
places the data in bytes 2, 3, and 4, respectively, in the scratchpad memory. The master device can issue
read time slots following the Recall E2 command and the DS18B20 will indicate the status of the recall by
transmitting 0 while the recall is in progress and 1 when the recall is done. The recall operation happens
automatically at power-up, so valid data is available in the scratchpad as soon as power is applied to the
device.
READ POWER SUPPLY [B4h]
The master device issues this command followed by a read time slot to determine if any DS18B20s on the
bus are using parasite power. During the read time slot, parasite powered DS18B20s will pull the bus
low, and externally powered DS18B20s will let the bus remain high. See the Powering the DS18B20
section for usage information for this command.
Table 3. DS18B20 Function Command Set
COMMAND
Convert T
Read
Scratchpad
Write
Scratchpad
Copy
Scratchpad
Recall E2
Read Power
Supply
1-Wire BUS
DESCRIPTION
PROTOCOL
ACTIVITYAFTER
COMMAND IS ISSUED
TEMPERATURE CONVERSION COMMANDS
Initiates temperature
DS18B20 transmits
conversion.
44h
conversion status to master
(not applicable for parasite-
powered DS18B20s).
MEMORY COMMANDS
Reads the entire scratchpad
including the CRC byte.
BEh
DS18B20 transmits up to 9
data bytes to master.
Writes data into scratchpad
Master transmits 3 data bytes
bytes 2, 3, and 4 (TH, TL,
and configuration
4Eh to DS18B20.
registers).
Copies TH, TL, and
configuration register data
from the scratchpad to
None
48h
EEPROM.
Recalls TH, TL, and
DS18B20 transmits recall
configuration register data
from EEPROM to the
B8h status to master.
scratchpad.
Signals DS18B20 power
supply mode to the master.
B4h
DS18B20 transmits supply
status to master.
NOTES
1
2
3
1
Note 1:
Note 2:
Note 3:
For parasite-powered DS18B20s, the master must enable a strong pullup on the 1-Wire bus during temperature
conversions and copies from the scratchpad to EEPROM. No other bus activity may take place during this time.
The master can interrupt the transmission of data at any time by issuing a reset.
All three bytes must be written before a reset is issued.
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