DS18B20U+ Datasheet DS18B20U+, DS18B20, DS18B20Z | P1-P3

AVAILABLE

Functional Diagrams

Pin Configurations appear at end of data sheet.

Functional Diagrams continued at end of data sheet.

UCSP is a 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.maxim

integrated.com.

REV: 042208

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.

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 DS1822

 Applications Include Thermostatic Controls,

Industrial Systems, Consumer Products,

Thermometers, or Any Thermally Sensitive

System

PIN CONFIGURATIONS

DS18B20

Programmable Resolution

Wire Digital Thermometer

TO-92

(DS18B20)

(BOTTOM VIEW)

MAXIM

18B20

GND

SO (150 mils)

(DS18B20Z)

N.C.

GND

N.C.

MAXIM

18B20

N.C.

GND

N.C.

18B20

µSOP

(DS18B20U)

1-Wire is a registered trademark of Maxim Integrated Products, Inc.

DS18B20

2 of 22

ORDERING INFORMATION

PART

TEMP RANGE

PIN-PACKAGE

TOP MARK

DS18B20

-55

C to +125

3 TO-92

18B20

DS18B20+

-55°C to +125°C

3 TO-92

18B20

DS18B20/T&R

-55°C to +125°C

3 TO-92 (2000 Piece)

18B20

DS18B20+T&R

-55°C to +125°C

3 TO-92 (2000 Piece)

18B20

DS18B20-SL/T&R

-55

C to +125

3 TO-92 (2000 Piece)*

18B20

DS18B20-SL+T&R

-55°C to +125°C

3 TO-92 (2000 Piece)*

18B20

DS18B20U

-55°C to +125°C

8 µSOP

18B20

DS18B20U+

-55°C to +125°C

8 µSOP

18B20

DS18B20U/T&R

-55

C to +125

SOP (3000 Piece)

18B20

DS18B20U+T&R

-55

C to +125

SOP (3000 Piece)

18B20

DS18B20Z

-55

C to +125

8 SO

DS18B20

DS18B20Z+

-55°C to +125°C

8 SO

DS18B20

DS18B20Z/T&R

-55

C to +125

8 SO (2500 Piece)

DS18B20

DS18B20Z+T&R

-55°C to +125°C

8 SO (2500 Piece)

DS18B20

+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

NAME FUNCTION

SOP

TO-92

1, 2, 6,

7, 8

2, 3, 5,

6, 7

— N.C. No Connection

3 8 3 V

Optional V

. V

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 (T

and T

) 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

, T

, 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

DS18B20

3 of 22

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.

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

), 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

Figure 1. DS18B20 Block Diagram

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.

The DS18B20 output temperature data is calibrated in degrees Celsius; 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 1 gives examples of digital output data and the

corresponding temperature reading for 12-bit resolution conversions.

4.7k

POWER-

SUPPLY

SENSE

64-BIT ROM

AND

1-Wire PORT

INTERNAL V

PARASITE POWER

CIRCUIT

MEMORY CONTROL

LOGIC

SCRATCHPAD

8-BIT CRC GENERATOR

TEMPERATURE SENSOR

ALARM HIGH TRIGGER (T

)

ALARM LOW TRIGGER (T

)

CONFIGURATION REGISTER

(EEPROM)

GND

DS18B20

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P22

DS18B20U+

Mfr. #:

Buy DS18B20U+

Manufacturer:

Maxim Integrated

Description:

Board Mount Temperature Sensors Prgmble Resolution 1-Wire Parasite Pwr

Lifecycle:

New from this manufacturer.

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DS18B20U+

DS18B20U+

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