DS18S20Z Datasheet DS18S20Z, DS1820, DS18S20+ | 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.maximintegrated.com.

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

 9-Bit Thermometer Resolution

 Converts Temperature 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)

 Applications Include Thermostatic Controls,

Industrial Systems, Consumer Products,

Thermometers, or Any Thermally Sensitive

System

PIN CONFIGURATIONS

DESCRIPTION

The DS18S20 digital thermometer provides 9-bit Celsius temperature measurements and has an alarm

function with nonvolatile user-programmable upper and lower trigger points. The DS18S20

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 DS18S20 can derive power

directly from the data line (“parasite power”), eliminating the need for an external power supply.

Each DS18S20 has a unique 64-bit serial code, which allows multiple DS18S20s to function on the same

1-Wire bus. Thus, it is simple to use one microprocessor to control many DS18S20s 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.

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

TO-92

(DS18S20)

(BOTTOM VIEW)

MAXIM

DS1820

GND

SO (150 mils)

(DS18S20Z)

N.C.

GND

N.C.

DS1820

19-5474; Rev 8/10

DS18S20

High-Precision 1-

Wire Digital Thermometer

DS18S20

2 of 23

ORDERING INFORMATION

PART

TEMP RANGE

PIN-PACKAGE

DS18S20

–55°C to +125°C

3 TO-92

DS18S20+

–55°C to +125°C

3 TO-92

DS18S20/T&R

–55°C to +125°C

3 TO-92 (2000 Piece)

DS18S20+T&R

–55°C to +125°C

3 TO-92 (2000 Piece)

DS18S20-SL/T&R

–55°C to +125°C

3 TO-92 (2000 Piece)*

DS18S20-SL+T&R

–55°C to +125°C

3 TO-92 (2000 Piece)*

DS18S20Z

–55°C to +125°C

8 SO

DS18S20Z+

–55°C to +125°C

8 SO

DS18S20Z/T&R

–55°C to +125°C

8 SO (2500 Piece)

DS18S20Z+T&R

–55°C to +125°C

8 SO (2500 Piece)

+Denotes a lead(Pb)-free/RoHS-compliant package. A “+” appears on the top mark of lead(Pb)-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

TO-92 SO

1 5 GND Ground

2 4 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 DS18S20 section.)

3 3 V

Optional V

. V

must be grounded for operation in parasite

power mode.

—

1, 2, 6, 7,

N.C. No Connection

OVERVIEW

Figure 1 shows a block diagram of the DS18S20, 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

). The T

and T

registers

are nonvolatile (EEPROM), so they will retain data when the device is powered down.

The DS18S20 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 DS18S20). 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.

Another feature of the DS18S20 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 DS18S20 may also be powered by an external supply on V

DS18S20

3 of 23

Figure 1. DS18S20 Block Diagram

OPERATION—MEASURING TEMPERATURE

The core functionality of the DS18S20 is its direct-to-digital temperature sensor. The temperature sensor

output has 9-bit resolution, which corresponds to 0.5°C steps. The DS18S20 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 DS18S20 returns to its idle state. If the DS18S20

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 DS18S20 will respond by transmitting 0 while the

temperature conversion is in progress and 1 when the conversion is done. If the DS18S20 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 DS18S20 section.

The DS18S20 output 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. Table 1

gives examples of digital output data and the corresponding temperature reading.

Resolutions greater than 9 bits can be calculated using the data from the temperature, COUNT REMAIN

and COUNT PER °C registers in the scratchpad. Note that the COUNT PER °C register is hard-wired to

16 (10h). After reading the scratchpad, the TEMP_READ value is obtained by truncating the 0.5°C bit

(bit 0) from the temperature data (see Figure 2). The extended resolution temperature can then be

calculated using the following equation:

CPERCOUNT

REMAINCOUNTCPERCOUNT

READTEMPETEMPERATUR

___

25.0_

−

+−=

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

)

GND

DS18S20

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P23

DS18S20Z

Mfr. #:

Buy DS18S20Z

Manufacturer:

Maxim Integrated

Description:

Board Mount Temperature Sensors 1-Wire Parasite-Power Digital Thermometer

Lifecycle:

New from this manufacturer.

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DS18S20Z

DS18S20Z

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