Datasheet

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Pin Congurations

General Description

The DS18S20 digital thermometer provides 9-bit Celsius

temperature measurements and has an alarm function

with nonvolatile user-programmable upper and lower trig-

ger points. The DS18S20 communicates over a 1-Wire

bus that by definition requires only one data line (and

ground) for communication with a central microproces-

sor. 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.

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

● Maximize System Accuracy in Broad Range of

Thermal Management Applications

• 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 Resolution

• No External Components Required

● Parasite 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) and 3-Pin TO-92

Packages

Ordering Information appears at end of data sheet.

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

19-5474; Rev 2; 1/15

BOTTOM VIEW

N.C.

GND

N.C.

GND

DS18S20

SO (150 mils)

(DS18S20Z)

DS18S20

1 2 3

GND DQ

2 3

TOP VIEW

TO-92

(DS18S20)

DS18S20 High-Precision 1-Wire Digital Thermometer

Summary of content (21 pages)

PAGE 1
DS18S20 High-Precision 1-Wire Digital Thermometer General 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.
PAGE 2
DS18S20 High-Precision 1-Wire Digital Thermometer Absolute Maximum Ratings Voltage Range on Any Pin Relative to Ground.....-0.5V to +6.0V Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 5.9mW/°C above +70°C)...............470.6mW 3-Pin TO-92 (derate 6.3mW/°C above +70°C).............500mW Operating Temperature Range.......................... -55°C to +125°C Storage Temperature Range............................. -55°C to +125°C Lead Temperature (soldering, 10s)..................................
PAGE 3
DS18S20 High-Precision 1-Wire Digital Thermometer DS18S20 TYPICAL ERROR CURVE 0.5 THERMOMETER ERROR (°C) 0.4 0.3 +3s ERROR 0.2 0.1 0 -0.1 -3s ERROR -0.2 -0.3 MEAN ERROR -0.4 -0.5 0 10 20 30 40 50 60 70 TEMPERATURE (°C) Figure 1. Typical Performance Curve AC Electrical Characteristics—NV Memory (VDD = 3.0V to 5.5V, TA = -55°C to +100°C, unless otherwise noted.
PAGE 4
DS18S20 High-Precision 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 tPDHIGH tPDLOW Figure 2. Timing Diagrams Pin Description PIN NAME FUNCTION TO-92 SO 1 5 GND 2 4 DQ Data Input/Output. Open-drain 1-Wire interface pin.
PAGE 5
DS18S20 High-Precision 1-Wire Digital Thermometer Overview Figure 3 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 (TH and TL).
PAGE 6
DS18S20 High-Precision 1-Wire Digital Thermometer Operation—Alarm Signaling 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 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
DS18S20 High-Precision 1-Wire Digital Thermometer The master device can check the alarm flag status of all DS18S20s on the bus by issuing an Alarm Search [ECh] command. Any DS18S20s with a set alarm flag will respond to the command, so the master can determine exactly which DS18S20s 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 8
DS18S20 High-Precision 1-Wire Digital Thermometer 64-Bit Lasered ROM Code Each DS18S20 contains a unique 64-bit code (see Figure 8) stored in ROM. The least significant 8 bits of the ROM code contain the DS18S20’s 1-Wire family code: 10h. 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. A detailed explanation of the CRC bits is provided in the CRC Generation section.
PAGE 9
DS18S20 High-Precision 1-Wire Digital Thermometer Data in the EEPROM registers is retained when the device is powered down; at power-up the EEPROM data is reloaded into the corresponding scratchpad locations. Data can also be reloaded from EEPROM to the scratchpad at any time using the Recall E2 [B8h] command.
PAGE 10
DS18S20 High-Precision 1-Wire Digital Thermometer Hardware Configuration The 1-Wire bus has by definition only a single data line. Each device (master or slave) interfaces to the data line via an open drain or 3-state port. This allows each device to “release” the data line when the device is not transmitting data so the bus is available for use by another device. The 1-Wire port of the DS18S20 (the DQ pin) is open drain with an internal circuit equivalent to that shown in Figure 11.
PAGE 11
DS18S20 High-Precision 1-Wire Digital Thermometer Match ROM [55h] Alarm Search [ECh] The match ROM command followed by a 64-bit ROM code sequence allows the bus master to address a specific slave device on a multidrop or single-drop bus. Only the slave that exactly matches the 64-bit ROM code sequence will respond to the function command issued by the master; all other slaves on the bus will wait for a reset pulse.
PAGE 12
DS18S20 High-Precision 1-Wire Digital Thermometer Convert T [44h] This command initiates a single temperature conversion. 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 low-power idle state.
PAGE 13
DS18S20 High-Precision 1-Wire Digital Thermometer Initialization Procedure—Reset And Presence Pulses Write Time Slots All communication with the DS18S20 begins with an initialization sequence that consists of a reset pulse from the master followed by a presence pulse from the DS18S20. This is illustrated in Figure 12. When the DS18S20 sends the presence pulse in response to the reset, it is indicating to the master that it is on the bus and ready to operate.
PAGE 14
DS18S20 High-Precision 1-Wire Digital Thermometer START OF SLOT START OF SLOT MASTER WRITE “0” SLOT MASTER WRITE “1” SLOT 1µs < TREC < ∞ 60µs < Tx “0” < 120µs > 1µs VPU 1-Wire BUS GND DS18S20 SAMPLES TYP MIN 15µS 15µS DS18S20 SAMPLES MIN MAX 30µS 15µS 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 DS18S20 PULLING LOW RESISTOR PULLUP Figure
PAGE 15
DS18S20 High-Precision 1-Wire Digital Thermometer Read-Time Slots read-time slot, the DS18S20 will begin transmitting a 1 or 0 on bus. The DS18S20 transmits a 1 by leaving the bus high and transmits a 0 by pulling the bus low. When transmitting a 0, the DS18S20 will release the bus by the end of the time slot, and the bus will be pulled back to its high idle state by the pullup resister. Output data from the DS18S20 is valid for 15µs after the falling edge that initiated the read-time slot.
PAGE 16
DS18S20 High-Precision 1-Wire Digital Thermometer MASTER Tx RESET PULSE INITIALIZATION SEQUENCE DS18S20 Tx PRESENCE PULSE MASTER Tx ROM COMMAND 33h READ ROM COMMAND N 55h MATCH ROM COMMAND F0h SEARCH ROM COMMAND N Y Y Y MASTER Tx BIT 0 DS18S20 Tx FAMILY CODE 1 BYTE DS18S20 Tx SERIAL NUMBER 6 BYTES DS18S20 Tx CRC BYTE N BIT 0 MATCH? N CCh SKIP ROM COMMAND N Y DS18S20 Tx BIT 0 DS18S20 Tx BIT 0 DS18S20 Tx BIT 0 MASTER Tx BIT 0 MASTER Tx BIT 0 BIT 0 MATCH? DEVICE(S) WITH ALARM FLAG SET
PAGE 17
DS18S20 High-Precision 1-Wire Digital Thermometer 44h CONVERT TEMPERATURE ? MASTER Tx FUNCTION COMMAND 48h COPY SCRATCHPAD ? N Y Y N PARASITE POWER ? DS18S20 BEGINS CONVERSION Y MASTER ENABLES STRONG PULL- UP ON DQ COPY IN PROGRESS ? N N B8h RECALL E2 ? Y MASTER DISABLES STRONG PULLUP MASTER Rx “1s” BEh READ SCRATCH PAD ? N Y Y PARASITE POWERED ? N MASTER Rx “0s” MASTER Rx “1s” B4h READ POWER SUPPLY ? DATA COPIED FROM SCRATCHPAD TO EEPROM Y MASTER DISABLES STRONG PULLUP MASTE
PAGE 18
DS18S20 High-Precision 1-Wire Digital Thermometer Ds18S20 Operation Example 1 In this example there are multiple DS18S20s on the bus and they are using parasite power. The bus master initiates a temperature conversion in a specific DS18S20 and then reads its scratchpad and recalculates the CRC to verify the data. MASTER MODE DATA (LSB FIRST) Tx Reset Rx Presence Tx 55h Tx 64-bit ROM code Master sends DS18S20 ROM code. Tx 44h Master issues Convert T command.
PAGE 19
DS18S20 High-Precision 1-Wire Digital Thermometer DS18S20 Operation Example 3 In this example there is only one DS18S20 on the bus and it is using parasite power. The bus master initiates a temperature conversion then reads the DS18S20 scratchpad and calculates a higher resolution result using the data from the temperature, COUNT REMAIN and COUNT PER °C registers. MASTER MODE DATA (LSB FIRST) Tx Reset Tx Presence Tx CCh Master issues Skip ROM command. Tx 44h Master issues Convert T command.
PAGE 20
DS18S20 High-Precision 1-Wire Digital Thermometer Ordering Information PART TEMP RANGE Package Information 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
PAGE 21
DS18S20 High-Precision 1-Wire Digital Thermometer Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 4/08 In the Ordering Information table, added TO-92 straight-lead packages and included a note that the TO-92 package in tape and reel can be ordered with either formed or straight leads 2 1 8/10 Removed the Top Mark column from the Ordering Information table; added the continuous power dissipation and lead and soldering temperatures to the Absolute Maximum Ratings section