Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsDS18B20Z+T&R

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.

Summary of content (22 pages)

PAGE 1
LE AVAILAB DS18B20 Programmable Resolution 1-Wire Digital Thermometer DESCRIPTION The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements and has an alarm function with nonvolatile userprogrammable 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.
PAGE 2
DS18B20 ORDERING INFORMATION PART DS18B20 DS18B20+ DS18B20/T&R DS18B20+T&R DS18B20-SL/T&R DS18B20-SL+T&R DS18B20U DS18B20U+ DS18B20U/T&R DS18B20U+T&R DS18B20Z DS18B20Z+ DS18B20Z/T&R DS18B20Z+T&R TEMP RANGE -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C PIN-PACKAGE 3 TO-92 3 TO-92 3 TO-92 (2000 Piece) 3 TO-92 (2000 Piece) 3 TO-92 (
PAGE 3
DS18B20 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 (CPP), which then supplies power to the device when the bus is low.
PAGE 4
DS18B20 Figure 2. Temperature Register Format LS BYTE MS BYTE BIT 7 3 2 BIT 6 22 BIT 5 21 BIT 4 20 BIT 3 2-1 BIT 2 2-2 BIT 1 2-3 BIT 0 2-4 BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8 S S S S 6 S 5 2 24 2 S = SIGN Table 1. Temperature/Data Relationship TEMPERATURE (°C) +125 +85* +25.0625 +10.125 +0.5 0 -0.5 -10.125 -25.
PAGE 5
DS18B20 The master device can check the alarm flag status of all DS18B20s on the bus by issuing an Alarm Search [ECh] command. Any DS18B20s with a set alarm flag will respond to the command, so the master can determine exactly which DS18B20s have experienced an alarm condition. If an alarm condition exists and the TH or TL settings have changed, another temperature conversion should be done to validate the alarm condition.
PAGE 6
DS18B20 Figure 4. Supplying the Parasite-Powered DS18B20 During Temperature Conversions VPU DS18B20 GND DQ VDD VPU µP 4.7k TO OTHER 1-WIRE DEVICES 1-Wire BUS Figure 5. Powering the DS18B20 with an External Supply DS18B20 VPU µP VDD (EXTERNAL SUPPLY) GND DQ VDD 4.7k TO OTHER 1-WIRE DEVICES 1-Wire BUS 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.
PAGE 7
DS18B20 MEMORY The DS18B20’s memory is organized as shown in Figure 7. The memory consists of an SRAM scratchpad with nonvolatile EEPROM storage for the high and low alarm trigger registers (TH and TL) and configuration register. Note that if the DS18B20 alarm function is not used, the TH and TL registers can serve as general-purpose memory. All memory commands are described in detail in the DS18B20 Function Commands section.
PAGE 8
DS18B20 CONFIGURATION REGISTER Byte 4 of the scratchpad memory contains the configuration register, which is organized as illustrated in Figure 8. The user can set the conversion resolution of the DS18B20 using the R0 and R1 bits in this register as shown in Table 2. The power-up default of these bits is R0 = 1 and R1 = 1 (12-bit resolution). Note that there is a direct tradeoff between resolution and conversion time.
PAGE 9
DS18B20 is available in Application Note 27: Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products. Figure 9. CRC Generator INPUT XOR XOR XOR (MSB) (LSB) 1-WIRE BUS SYSTEM The 1-Wire bus system uses a single bus master to control one or more slave devices. The DS18B20 is always a slave. When there is only one slave on the bus, the system is referred to as a “single-drop” system; the system is “multidrop” if there are multiple slaves on the bus.
PAGE 10
DS18B20 TRANSACTION SEQUENCE The transaction sequence for accessing the DS18B20 is as follows: Step 1. Initialization Step 2. ROM Command (followed by any required data exchange) Step 3. DS18B20 Function Command (followed by any required data exchange) It is very important to follow this sequence every time the DS18B20 is accessed, as the DS18B20 will not respond if any steps in the sequence are missing or out of order. Exceptions to this rule are the Search ROM [F0h] and Alarm Search [ECh] commands.
PAGE 11
DS18B20 SKIP ROM [CCh] The master can use this command to address all devices on the bus simultaneously without sending out any ROM code information. For example, the master can make all DS18B20s on the bus perform simultaneous temperature conversions by issuing a Skip ROM command followed by a Convert T [44h] command. Note that the Read Scratchpad [BEh] command can follow the Skip ROM command only if there is a single slave device on the bus.
PAGE 12
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.
PAGE 13
DS18B20 Figure 11.
PAGE 14
DS18B20 Figure 12.
PAGE 15
DS18B20 1-WIRE SIGNALING The DS18B20 uses a strict 1-Wire communication protocol to ensure data integrity. Several signal types are defined by this protocol: reset pulse, presence pulse, write 0, write 1, read 0, and read 1. The bus master initiates all these signals, with the exception of the presence pulse.
PAGE 16
DS18B20 The DS18B20 samples the 1-Wire bus during a window that lasts from 15µs to 60µs after the master initiates the write time slot. If the bus is high during the sampling window, a 1 is written to the DS18B20. If the line is low, a 0 is written to the DS18B20. Figure 14.
PAGE 17
DS18B20 data from the DS18B20 is valid for 15µs after the falling edge that initiated the read time slot. Therefore, the master must release the bus and then sample the bus state within 15µs from the start of the slot. Figure 15 illustrates that the sum of TINIT, TRC, and TSAMPLE must be less than 15µs for a read time slot.
PAGE 18
DS18B20 DS18B20 OPERATION EXAMPLE 1 In this example there are multiple DS18B20s on the bus and they are using parasite power. The bus master initiates a temperature conversion in a specific DS18B20 and then reads its scratchpad and recalculates the CRC to verify the data. MASTER MODE Tx Rx Tx Tx Tx Tx Rx Tx Tx Tx DATA (LSB FIRST) Reset Presence 55h 64-bit ROM code 44h DQ line held high by strong pullup Reset Presence 55h 64-bit ROM code BEh Rx 9 data bytes Tx COMMENTS Master issues reset pulse.
PAGE 19
DS18B20 ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground .................................................................. -0.5V to +6.0V Operating Temperature Range ....................................................................................... -55°C to +125°C Storage Temperature Range ........................................................................................... -55°C to +125°C Solder Temperature .....................................................
PAGE 20
DS18B20 AC ELECTRICAL CHARACTERISTICS—NV MEMORY (-55°C to +100°C; VDD = 3.0V to 5.
PAGE 21
DS18B20 Figure 18.
PAGE 22
DS18B20 REVISION HISTORY REVISION DATE 030107 101207 042208 DESCRIPTION In the Absolute Maximum Ratings section, removed the reflow oven temperature value of +220°C. Reference to JEDEC specification for reflow remains. In the Operation—Alarm Signaling section, added “or equal to” in the desciption for a TH alarm condition In the Memory section, removed incorrect text describing memory. In the Configuration Register section, removed incorrect text describing configuration register.