Datasheet

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General 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. 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.

Applications

● Thermostatic Controls

● Industrial Systems

● Consumer Products

● Thermometers

● Thermally Sensitive Systems

Benets and Features

● Unique 1-Wire

Interface Requires Only One Port

Pin for Communication

● Reduce Component Count with Integrated

Temperature Sensor and EEPROM

• Measures Temperatures from -55°C to +125°C

(-67°F to +257°F)

• ±0.5°C Accuracy from -10°C to +85°C

• Programmable Resolution from 9 Bits to 12 Bits

• No External Components Required

● Parasitic Power Mode Requires Only 2 Pins for

Operation (DQ and GND)

● Simplifies Distributed Temperature-Sensing

Applications with Multidrop Capability

• Each Device Has a Unique 64-Bit Serial Code

Stored in On-Board ROM

● Flexible User-Definable Nonvolatile (NV) Alarm Settings

with Alarm Search Command Identifies Devices with

Temperatures Outside Programmed Limits

● Available in 8-Pin SO (150 mils), 8-Pin µSOP, and

3-Pin TO-92 Packages

19-7487; Rev 6; 7/19

Ordering Information appears at end of data sheet.

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

Pin Congurations

BOTTOM VIEW

N.C.

GND

DS18B20

SO (150 mils)

(DS18B20Z)

N.C.

GND

N.C.

DS18B20

µSOP

(DS18B20U)

DS18B20

1 2 3

GND DQ V

1 2 3

TOP VIEW

TO-92

(DS18B20)

DS18B20 Programmable Resolution

1-Wire Digital Thermometer

Click here for production status of specific part numbers.

Summary of content (20 pages)

PAGE 1
Click here for production status of specific part numbers. DS18B20 General 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.
PAGE 2
DS18B20 Programmable Resolution 1-Wire Digital Thermometer 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................................Refer to the IPC/JEDEC J-STD-020 Specification.
PAGE 3
DS18B20 Programmable Resolution 1-Wire Digital Thermometer AC Electrical Characteristics–NV Memory (-55°C to +125°C; VDD = 3.0V to 5.5V) PARAMETER SYMBOL NV Write Cycle Time CONDITIONS MIN tWR EEPROM Writes TYP MAX UNITS 2 10 ms NEEWR -55°C to +55°C 50k writes tEEDR -55°C to +55°C 10 years EEPROM Data Retention AC Electrical Characteristics (-55°C to +125°C; VDD = 3.0V to 5.5V) PARAMETER SYMBOL CONDITIONS MIN TYP 9-bit resolution Temperature Conversion Time tCONV UNITS 93.
PAGE 4
DS18B20 Programmable Resolution 1-Wire Digital Thermometer 1-WIRE WRITE ZERO TIME SLOT tSLOT tREC START OF NEXT CYCLE tLOW0 1-WIRE READ ZERO TIME SLOT tSLOT START OF NEXT CYCLE tREC tRDV 1-WIRE RESET PULSE RESET PULSE FROM HOST tRSTL tRSTH PRESENCE DETECT 1-WIRE PRESENCE DETECT tPDIH tPDLOW Figure 2. Timing Diagrams Pin Description PIN NAME FUNCTION SO µSOP TO-92 1, 2, 6, 7, 8 2, 3, 5, 6, 7 — N.C. No Connection 3 8 3 VDD Optional VDD.
PAGE 5
DS18B20 Programmable Resolution 1-Wire Digital Thermometer Overview Figure 3 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 (TH and TL) and the 1-byte configuration register.
PAGE 6
DS18B20 Programmable Resolution 1-Wire Digital Thermometer Operation—Alarm Signaling 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 4). The sign bits (S) indicate if the temperature is positive or negative: for positive numbers S = 0 and for negative numbers S = 1.
PAGE 7
DS18B20 Programmable Resolution 1-Wire Digital Thermometer or equal to TL or higher than or equal to TH, an alarm condition exists and an alarm flag is set inside the DS18B20. This flag is updated after every temperature measurement; therefore, if the alarm condition goes away, the flag will be turned off after the next temperature conversion. The master device can check the alarm flag status of all DS18B20s on the bus by issuing an Alarm Search [ECh] command.
PAGE 8
DS18B20 Programmable Resolution 1-Wire Digital Thermometer 64-BIT Lasered ROM code Each DS18B20 contains a unique 64–bit code (see Figure 8) 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.
PAGE 9
DS18B20 Programmable Resolution 1-Wire Digital Thermometer Configuration Register received error free. The comparison of CRC values and the decision to continue with an operation are determined entirely by the bus master. There is no circuitry inside the DS18B20 that prevents a command sequence from proceeding if the DS18B20 CRC (ROM or scratchpad) does not match the value generated by the bus master.
PAGE 10
DS18B20 Programmable Resolution 1-Wire Digital Thermometer 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. All data and commands are transmitted least significant bit first over the 1-Wire bus.
PAGE 11
DS18B20 If there is only one slave on the bus, the simpler Read ROM [33h] command can be used in place of the Search ROM process. For a detailed explanation of the Search ROM procedure, refer to Application Note 937: Book of iButton® Standards. After every Search ROM cycle, the bus master must return to Step 1 (Initialization) in the transaction sequence. Read Rom [33h] This command can only be used when there is one slave on the bus.
PAGE 12
DS18B20 Programmable Resolution 1-Wire Digital Thermometer 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 Programmable Resolution 1-Wire Digital Thermometer MASTER Tx RESET PULSE INITIALIZATION SEQUENCE DS18B20 Tx PRESENCE PULSE MASTER Tx ROM COMMAND 33h READ ROM COMMAND N Y 55h MATCH ROM COMMAND F0h SEARCH ROM COMMAND N Y Y MASTER Tx BIT 0 BIT 0 MATCH ? DS18B20 TX FAMILY CODE 1 BYTE DS18B20 Tx SERIAL NUMBER 6 BYTES DS18B20 Tx CRC BYTE N N N Y ECh ALARM SEARCH COMMAND Y DS18B20 Tx BIT 0 DS18B20 Tx BIT 0 DS18B20 Tx BIT 0 DS18B20 Tx BIT 0 MASTER Tx BIT 0 MASTER TX BIT 0 BIT 0 MA
PAGE 14
DS18B20 Programmable Resolution 1-Wire Digital Thermometer N 44h CONVERT TEMPERATURE ? MASTER Tx FUNCTION COMMAND Y Y N N 48h COPY SCRATCHPAD ? N Y PARASITE POWER ? Y PARASITE POWER ? DS18B20 BEGINS CONVERSION MASTER ENABLES STRONG PULL-UP ON DQ MASTER ENABLES STRONG PULL-UP ON DQ DEVICE CONVERTING TEMPERATURE ? DS18B20 CONVERTS TEMPERATURE N Y N N B4h READ POWER SUPPLY ? PARASITE POWER ? MASTER Rx “1s” N B8h RECALL E2 ? Y MASTER Rx “0s” DEVICE BUSY RECALLING DATA ? MASTER Tx
PAGE 15
DS18B20 Programmable Resolution 1-Wire Digital Thermometer 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 Programmable Resolution 1-Wire Digital Thermometer START OF SLOT START OF SLOT MASTER WRITE “0” SLOT 1µs < TREC < ∞ 60µs < Tx “0” < 120µs MASTER WRITE “1” SLOT 1µs VPU 1-Wire BUS GND DS18B20 SAMPLES DS18B20 SAMPLES MIN 15µs TYP 15µs MIN MAX 15µs 30µs MASTER READ “0” SLOT TYP MAX 15µs 30µs MASTER READ “1” SLOT 1µs < TREC < ∞ VPU 1-Wire BUS GND MASTER SAMPLES > 1µs MASTER SAMPLES > 1µs 45µs 15µs 15µs LINE TYPE LEGEND BUS MASTER PULLING LOW DS18B20 PULLING LOW RESISTOR PULLU
PAGE 17
DS18B20 Programmable Resolution 1-Wire Digital Thermometer VPU VIH OF MASTER 1-Wire BUS GND TINT > 1µs TRC MASTER SAMPLES 15µs Figure 17. Detailed Master Read 1 Timing VPU VIH OF MASTER 1-Wire BUS GND TINT = SMALL TRC = SMALL MASTER SAMPLES 15µs LINE TYPE LEGEND BUS MASTER PULLING LOW RESISTOR PULLUP Figure 18. Recommended Master Read 1 Timing Related Application Notes The following application notes can be applied to the DS18B20 and are available at www.maximintegrated.com.
PAGE 18
DS18B20 Programmable Resolution 1-Wire Digital Thermometer 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.
PAGE 19
DS18B20 Programmable Resolution 1-Wire Digital Thermometer Ordering Information PART TEMP RANGE PIN-PACKAGE TOP MARK DS18B20 -55°C to +125°C 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°C 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 FSOP 18B20 DS18B20U+ -55°C t
PAGE 20
DS18B20 Programmable Resolution 1-Wire Digital Thermometer Revision History REVISION DATE PAGES CHANGED DESCRIPTION In the Absolute Maximum Ratings section, removed the reflow oven temperature value of +220°C. Reference to JEDEC specification for reflow remains. 19 In the Operation—Alarm Signaling section, added “or equal to” in the description for a TH alarm condition 5 In the Memory section, removed incorrect text describing memory.