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DS18B20英文手册
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DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传感器手册DS18B20温度传
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1 of 21 050102
FEATURES
§ Unique 1-Wire
®
interface requires only one
port pin for communication
§ Each device has a unique 64-bit serial code
stored in an onboard 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 of programmed limits (temperature
alarm condition)
§ Available in 8-pin SO (150mil), 8-pin mSOP,
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 ASSIGNMENT
PIN DESCRIPTION
GND - Ground
DQ - Data In/Out
V
DD
- Power Supply Voltage
NC - No Connect
DESCRIPTION
The DS18B20 Digital Thermometer provides 9 to 12–bit centigrade 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.
DS18B20
Programmable Resolution
1-Wire Digital Thermomete
r
www.maxim
-
ic.c
om
8-Pin 150mil SO
(DS18B20Z)
TO-92
(
DS18B20
)
1
(
BOTTOM VIEW
)
2 3
DALLAS
18B20
1
GND
DQ
V
DD
2 3
N
C
NC
NC
NC
GND
DQ
V
DD
N
C
6
8
7
5
3
1
2
4
DALLAS
18B20
N
C
V
DD
NC
NC
NC
GND
NC
D
Q
6
8
7
5
3
1
2
4
18B20
8-Pin
m
SOP
(
DS18B20U
)
1-Wire is a registered trademark of Dallas Semiconductor.
DS18B20
2 of 21
ORDER INFORMATION
ORDERING
NUMBER
PACKAGE
MARKING
DESCRIPTION
DS18B20 18B20 DS18B20 in 3-pin TO92
DS18B20/T&R 18B20 DS18B20 in 3-pin TO92, 2000 Piece Tape-and-Reel
DS18B20+ 18B20 (See Note) DS18B20 in Lead-Free 3-pin TO92
DS18B20+T&R 18B20 (See Note) DS18B20 in Lead-Free 3-pin TO92, 2000 Piece Tape-
and-Reel
DS18B20U 18B20 DS18B20 in 8-pin uSOP
DS18B20U/T&R 18B20 DS18B20 in 8-pin uSOP, 3000 Piece Tape-and-Reel
DS18B20U+ 18B20 (See Note) DS18B20 in Lead-Free 8-pin uSOP
DS18B20U+T&R 18B20 (See Note) DS18B20 in Lead-Free 8-pin uSOP, 3000 Piece Tape-
and-Reel
DS18B20Z DS18B20 DS18B20 in 150 mil 8-pin SO
DS18B20Z/T&R DS18B20 DS18B20 in 150 mil 8-pin SO, 2500 Piece Tape-and-
Reel
DS18B20Z+ DS18B20 (See Note) DS18B20 in Lead-Free 150 mil 8-pin SO
DS18B20Z+T&R DS18B20 (See Note) DS18B20 in Lead-Free 150 mil 8-pin SO, 2500 Piece
Tape-and-Reel
DS18B20X 28 DS18B20 in Flip Chip, 10000 Piece Tape-and-Reel
Note: A “+” symbol will also be marked on the package.
DETAILED PIN DESCRIPTIONS Table 1
SO*
mSOP*
TO-92 SYMBOL DESCRIPTION
5 4 1 GND
Ground.
4 1 2 DQ Data Input/Output pin. Open-drain 1-Wire interface pin.
Also provides power to the device when used in parasite
power mode (see “Parasite Power” section.)
3 8 3 V
DD
Optional V
DD
pin. V
DD
must be grounded for operation in
parasite power mode.
*All pins not specified in this table are “No Connect” pins.
OVERVIEW
Figure 1 shows a block diagram of the DS18B20, and pin descriptions are given in Table 1. 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 (T
H
and T
L
), 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 T
H
, T
L
and configuration
registers are nonvolatile (EEPROM), so
they will retain data when the device is powered down.
The DS18B20 uses Dallas’ 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
bus is virtually unlimited. The 1-Wire bus protocol, including detailed explanations of the commands and
“time slots,” is covered in the 1-WIRE BUS SYSTEM section of this datasheet.
DS18B20
3 of 21
Another feature of the DS18B20 is the ability to operate without an external power supply. Power is
instead supplied through the 1-Wire pullup resistor via the DQ pin when the bus is high. The high bus
signal also charges an internal capacitor (C
PP
), which then supplies power to the device when the bus is
low. This method of deriving power from the 1-Wire bus is referred to as “parasite power.” As an
alternative, the DS18B20 may also be powered by an external supply on V
DD
.
DS18B20 BLOCK DIAGRAM Figure 1
V
PU
4.7k
POWER
SUPPLY
SENSE
64-BIT ROM
AND
1-wire PORT
D
Q
V
DD
INTERNAL V
DD
C
PP
PARASITE POWER
CIRCUIT
MEMORY CONTROL
LOGIC
SCRATCHPAD
8-BIT CRC GENERATOR
TEMPERATURE SENSOR
ALARM HIGH TRIGGER (T
H
)
REGISTER (EEPROM)
ALARM LOW TRIGGER (T
L
)
REGISTER (EEPROM)
CONFIGURATION REGISTER
(EEPROM)
GND
DS18B20
DS18B20
4 of 21
OPERATION — MEASURING TEMPERATURE
The core functionality of the DS18B20 is its direct-to-digital temperature sensor. The resolution of the
temperature sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C,
0.25°C, 0.125°C, and 0.0625°C, respectively. The default resolution at power-up is 12-bit. The DS18B20
powers-up in a low-power idle state; to initiate a temperature measurement and A-to-D conversion, the
master must issue a Convert T [44h] command. Following the conversion, the resulting thermal data is
stored in the 2-byte temperature register in the scratchpad memory and the DS18B20 returns to its idle
state. If the DS18B20 is powered by an external supply, the master can issue “read time slots” (see the 1-
WIRE BUS SYSTEM section) after the Convert T command and the DS18B20 will respond by
transmitting 0 while the temperature conversion is in progress and 1 when the conversion is done. If the
DS18B20 is powered with parasite power, this notification technique cannot be used since the bus must
be pulled high by a strong pullup during the entire temperature conversion. The bus requirements for
parasite power are explained in detail in the POWERING THE DS18B20 section of this datasheet.
The DS18B20 output temperature data is calibrated in degrees centigrade; for Fahrenheit applications, a
lookup table or conversion routine must be used. The temperature data is stored as a 16-bit sign-extended
two’s complement number in the temperature register (see Figure 2). The sign bits (S) indicate if the
temperature is positive or negative: for positive numbers S = 0 and for negative numbers S = 1. If the
DS18B20 is configured for 12-bit resolution, all bits in the temperature register will contain valid data.
For 11-bit resolution, bit 0 is undefined. For 10-bit resolution, bits 1 and 0 are undefined, and for 9-bit
resolution bits 2, 1 and 0 are undefined. Table 2 gives examples of digital output data and the
corresponding temperature reading for 12-bit resolution conversions.
TEMPERATURE REGISTER FORMAT Figure 2
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
LS Byte
2
3
2
2
2
1
2
0
2
-1
2
-2
2
-3
2
-4
bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8
MS Byte
S S S S S 2
6
2
5
2
4
TEMPERATURE/DATA RELATIONSHIP Table 2
TEMPERATURE DIGITAL OUTPUT
(Binary)
DIGITAL OUTPUT
(Hex)
+125°C 0000 0111 1101 0000 07D0h
+85°C* 0000 0101 0101 0000 0550h
+25.0625°C 0000 0001 1001 0001 0191h
+10.125°C 0000 0000 1010 0010 00A2h
+0.5°C 0000 0000 0000 1000 0008h
0°C 0000 0000 0000 0000 0000h
-0.5°C 1111 1111 1111 1000 FFF8h
-10.125°C 1111 1111 0101 1110 FF5Eh
-25.0625°C 1111 1110 0110 1111 FE6Fh
-55°C 1111 1100 1001 0000 FC90h
*The power-on reset value of the temperature register is +85°C
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