DS18S20 High-Precision 1-Wire Digital Thermometer: Features Pin Configurations
DS18S20 High-Precision 1-Wire Digital Thermometer: Features Pin Configurations
DS18S20 High-Precision 1-Wire Digital Thermometer: Features Pin Configurations
DS18S20
High-Precision
1-Wire Digital Thermometer
www.maxim-ic.com
FEATURES PIN CONFIGURATIONS
®
Unique 1-Wire Interface Requires Only One
Port Pin for Communication DALLAS
Each Device has a Unique 64-Bit Serial Code DS1820
Stored in an On-Board ROM
Multidrop Capability Simplifies Distributed 1 2 3
Temperature Sensing Applications
Requires No External Components N.C. 1 8 N.C.
Can Be Powered from Data Line. Power
DS1820
N.C. 2 7 N.C.
Supply Range is 3.0V to 5.5V
Measures Temperatures from -55°C to VDD 3 6 N.C.
+125°C (-67°F to +257°F)
GND
0.5C Accuracy from -10°C to +85°C DQ 4 5
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 0.5C 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.
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DS18S20
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
PIN
NAME FUNCTION
TO-92 SO
1 5 GND Ground
Data Input/Output. Open-drain 1-Wire interface pin. Also provides
2 4 DQ power to the device when used in parasite power mode (see the
Powering the DS18S20 section.)
Optional VDD. VDD must be grounded for operation in parasite
3 3 VDD
power mode.
1, 2, 6, 7,
— N.C. No Connection
8
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 (TH and TL). The TH and TL 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 (CPP), 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 VDD.
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DS18S20
VPU
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 0.5C 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 0.5C bit
(bit 0) from the temperature data (see Figure 2). The extended resolution temperature can then be
calculated using the following equation:
COUNT _ PER _ C COUNT _ REMAIN
TEMPERATURE TEMP _ READ 0.25
COUNT _ PER _ C
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DS18S20
OPERATION—ALARM SIGNALING
After the DS18S20 performs a temperature conversion, the temperature value is compared to the user-
defined two’s complement alarm trigger values stored in the 1-byte TH and TL registers (see Figure 3).
The sign bit (S) indicates if the value is positive or negative: for positive numbers S = 0 and for negative
numbers S = 1. The TH and TL registers are nonvolatile (EEPROM) so they will retain data when the
device is powered down. TH and TL can be accessed through bytes 2 and 3 of the scratchpad as explained
in the Memory section.
Figure 3. TH and TL Register Format
Only bits 8 through 1 of the temperature register are used in the TH and TL comparison since TH and TL
are 8-bit registers. If the measured temperature is lower than or equal to TL or higher than TH, an alarm
condition exists and an alarm flag is set inside the DS18S20. 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 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.
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DS18S20
In parasite power mode, the 1-Wire bus and CPP can provide sufficient current to the DS18S20 for most
operations as long as the specified timing and voltage requirements are met (see the DC Electrical
Characteristics and the AC Electrical Characteristics). However, when the DS18S20 is performing
temperature conversions or copying data from the scratchpad memory to EEPROM, the operating current
can be as high as 1.5mA. This current can cause an unacceptable voltage drop across the weak 1-Wire
pullup resistor and is more current than can be supplied by CPP. To assure that the DS18S20 has sufficient
supply current, it is necessary to provide a strong pullup on the 1-Wire bus whenever temperature
conversions are taking place or data is being copied from the scratchpad to EEPROM. This can be
accomplished by using a MOSFET to pull the bus directly to the rail as shown in Figure 4. The 1-Wire
bus must be switched to the strong pullup within 10s (max) after a Convert T [44h] or Copy Scratchpad
[48h] command is issued, and the bus must be held high by the pullup for the duration of the conversion
(tCONV) or data transfer (tWR = 10ms). No other activity can take place on the 1-Wire bus while the pullup
is enabled.
The DS18S20 can also be powered by the conventional method of connecting an external power supply to
the VDD pin, as shown in Figure 5. The advantage of this method is that the MOSFET pullup is not
required, and the 1-Wire bus is free to carry other traffic during the temperature conversion time.
The use of parasite power is not recommended for temperatures above 100C since the DS18S20 may not
be able to sustain communications due to the higher leakage currents that can exist at these temperatures.
For applications in which such temperatures are likely, it is strongly recommended that the DS18S20 be
powered by an external power supply.
In some situations the bus master may not know whether the DS18S20s on the bus are parasite powered
or powered by external supplies. The master needs this information to determine if the strong bus pullup
should be used during temperature conversions. To get this information, the master can issue a Skip ROM
[CCh] command followed by a Read Power Supply [B4h] command followed by a “read-time slot”.
During the read-time slot, parasite powered DS18S20s will pull the bus low, and externally powered
DS18S20s will let the bus remain high. If the bus is pulled low, the master knows that it must supply the
strong pullup on the 1-Wire bus during temperature conversions.
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DS18S20
DS18S20
GND DQ VDD
VPU
P
4.7k
TO OTHER
1-Wire BUS
1-WIRE DEVICES
6 of 23
DS18S20
MEMORY
The DS18S20’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).
Note that if the DS18S20 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 DS18S20 Function Commands section.
Byte 0 and byte 1 of the scratchpad contain the LSB and the MSB of the temperature register,
respectively. These bytes are read-only. Bytes 2 and 3 provide access to TH and TL registers. Bytes 4 and
5 are reserved for internal use by the device and cannot be overwritten; these bytes will return all 1s when
read. Bytes 6 and 7 contain the COUNT REMAIN and COUNT PER ºC registers, which can be used to
calculate extended resolution results as explained in the Operation—Measuring Temperature section.
Byte 8 of the scratchpad is read-only and contains the CRC code for bytes 0 through 7 of the scratchpad.
The DS18S20 generates this CRC using the method described in the CRC Generation section.
Data is written to bytes 2 and 3 of the scratchpad using the Write Scratchpad [4Eh] command; the data
must be transmitted to the DS18S20 starting with the least significant bit of byte 2. To verify data
integrity, the scratchpad can be read (using the Read Scratchpad [BEh] command) after the data is
written. When reading the scratchpad, data is transferred over the 1-Wire bus starting with the least
significant bit of byte 0. To transfer the TH and TL data from the scratchpad to EEPROM, the master must
issue the Copy Scratchpad [48h] command.
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
2
the scratchpad at any time using the Recall E [B8h] command. The master can issue “read-time slots”
(see the 1-Wire Bus System section) following the Recall E2 command and the DS18S20 will indicate the
status of the recall by transmitting 0 while the recall is in progress and 1 when the recall is done.
Figure 7. DS18S20 Memory Map
SCRATCHPAD
(POWER-UP STATE)
Byte 0 Temperature LSB (AAh)
(85°C)
Byte 1 Temperature MSB (00h) EEPROM
Byte 2 TH Register or User Byte 1* TH Register or User Byte 1
Byte 3 TL Register or User Byte 2* TL Register or User Byte 2
Byte 4 Reserved (FFh)
Byte 5 Reserved (FFh)
Byte 6 COUNT REMAIN (0Ch)
Byte 7 COUNT PER °C (10h)
Byte 8 CRC*
*Power-up state depends on value(s) stored in EEPROM.
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DS18S20
CRC GENERATION
CRC bytes are provided as part of the DS18S20’s 64-bit ROM code and in the 9th byte of the scratchpad
memory. The ROM code CRC is calculated from the first 56 bits of the ROM code and is contained in the
most significant byte of the ROM. The scratchpad CRC is calculated from the data stored in the
scratchpad, and therefore it changes when the data in the scratchpad changes. The CRCs provide the bus
master with a method of data validation when data is read from the DS18S20. To verify that data has been
read correctly, the bus master must re-calculate the CRC from the received data and then compare this
value to either the ROM code CRC (for ROM reads) or to the scratchpad CRC (for scratchpad reads). If
the calculated CRC matches the read CRC, the data has been 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 DS18S20 that prevents a command sequence from proceeding if the DS18S20
CRC (ROM or scratchpad) does not match the value generated by the bus master.
(MSB) (LSB)
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DS18S20
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 9.
The 1-Wire bus requires an external pullup resistor of approximately 5k; thus, the idle state for the
1-Wire bus is high. If for any reason a transaction needs to be suspended, the bus MUST be left in the idle
state if the transaction is to resume. Infinite recovery time can occur between bits so long as the 1-Wire
bus is in the inactive (high) state during the recovery period. If the bus is held low for more than 480s,
all components on the bus will be reset.
Figure 9. Hardware Configuration
VPU
DS18S20 1-Wire PORT
4.7k DQ
PIN
1-Wire BUS Rx
Rx
5μA
TYP TX
Tx 100
MOSFET
Rx = RECEIVE
Tx = TRANSMIT
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DS18S20
TRANSACTION SEQUENCE
The transaction sequence for accessing the DS18S20 is as follows:
Step 1. Initialization
Step 2. ROM Command (followed by any required data exchange)
Step 3. DS18S20 Function Command (followed by any required data exchange)
It is very important to follow this sequence every time the DS18S20 is accessed, as the DS18S20 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. After issuing either of these ROM commands, the
master must return to Step 1 in the sequence.
INITIALIZATION
All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence
consists of a reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the
slave(s). The presence pulse lets the bus master know that slave devices (such as the DS18S20) are on the
bus and are ready to operate. Timing for the reset and presence pulses is detailed in the 1-Wire Signaling
section.
ROM COMMANDS
After the bus master has detected a presence pulse, it can issue a ROM command. These commands
operate on the unique 64-bit ROM codes of each slave device and allow the master to single out a specific
device if many are present on the 1-Wire bus. These commands also allow the master to determine how
many and what types of devices are present on the bus or if any device has experienced an alarm
condition. There are five ROM commands, and each command is 8 bits long. The master device must
issue an appropriate ROM command before issuing a DS18S20 function command. A flowchart for
operation of the ROM commands is shown in Figure 14.
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. If the device is being used in parasite power mode, within 10s (max) after this
command is issued the master must enable a strong pullup on the 1-Wire bus for the duration of the
conversion (tCONV) as described in the Powering the DS18S20 section. If the DS18S20 is powered by an
external supply, the master can issue read-time slots 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. In parasite power mode this notification technique cannot be used since the bus is pulled high by
the strong pullup during the conversion.
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DS18S20
RECALL E2 [B8h]
This command recalls the alarm trigger values (TH and TL) from EEPROM and places the data in bytes 2
and 3, respectively, in the scratchpad memory. The master device can issue read-time slots following the
Recall E2 command and the DS18S20 will indicate the status of the recall by transmitting 0 while the
recall is in progress and 1 when the recall is done. The recall operation happens automatically at power-
up, so valid data is available in the scratchpad as soon as power is applied to the device.
READ POWER SUPPLY [B4h]
The master device issues this command followed by a read-time slot to determine if any DS18S20s on the
bus are using parasite power. During the read-time slot, parasite powered DS18S20s will pull the bus low,
and externally powered DS18S20s will let the bus remain high. See the Powering the DS18S20 section
for usage information for this command.
Table 2. DS18S20 Function Command Set
1-Wire BUS ACTIVITY
COMMAND DESCRIPTION PROTOCOL
AFTER COMMAND IS NOTES
ISSUED
TEMPERATURE CONVERSION COMMANDS
Convert T Initiates temperature DS18S20 transmits conversion
conversion. status to master (not applicable
44h 1
for parasite-powered
DS18S20s).
MEMORY COMMANDS
Read Reads the entire DS18S20 transmits up to 9
Scratchpad scratchpad including the BEh data bytes to master. 2
CRC byte.
Write Writes data into Master transmits 2 data bytes
Scratchpad scratchpad bytes 2 and 3 4Eh to DS18S20. 3
(TH and TL).
Copy Copies TH and TL data None
Scratchpad from the scratchpad to 48h 1
EEPROM.
2
Recall E Recalls TH and TL data DS18S20 transmits recall
from EEPROM to the B8h status to master.
scratchpad.
Read Power Signals DS18S20 power DS18S20 transmits supply
Supply supply mode to the B4h status to master.
master.
Note 1: For parasite-powered DS18S20s, the master must enable a strong pullup on the 1-Wire bus during temperature
conversions and copies from the scratchpad to EEPROM. No other bus activity may take place during this time.
Note 2: The master can interrupt the transmission of data at any time by issuing a reset.
Note 3: Both bytes must be written before a reset is issued.
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DS18S20
1-WIRE SIGNALING
The DS18S20 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. All these
signals, with the exception of the presence pulse, are initiated by the bus master.
1-WIRE BUS
GND
READ-TIME SLOTS
The DS18S20 can only transmit data to the master when the master issues read-time slots. Therefore, the
master must generate read-time slots immediately after issuing a Read Scratchpad [BEh] or Read Power
Supply [B4h] command, so that the DS18S20 can provide the requested data. In addition, the master can
generate read-time slots after issuing Convert T [44h] or Recall E2 [B8h] commands to find out the status
of the operation as explained in the DS18S20 Function Commands section.
All read-time slots must be a minimum of 60s in duration with a minimum of a 1s recovery time
between slots. A read-time slot is initiated by the master device pulling the 1-Wire bus low for a
minimum of 1s and then releasing the bus (see Figure 11). After the master initiates the 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 15s after the falling edge that initiated the read-time slot. Therefore,
the master must release the bus and then sample the bus state within 15s from the start of the slot.
Figure 12 illustrates that the sum of TINIT, TRC, and TSAMPLE must be less than 15s for a read-time slot.
Figure 13 shows that system timing margin is maximized by keeping TINIT and TRC as short as possible
and by locating the master sample time during read-time slots towards the end of the 15s period.
Figure 11. Read/Write Time Slot Timing Diagram
START START
OF SLOT OF SLOT
1-WIRE BUS
GND
DS18S20 Samples DS18S20 Samples
MIN TYP MAX MIN TYP MAX
1-WIRE BUS
GND
Master samples > 1 s
Master samples
> 1s
15s 45s 15s
Resistor pullup
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DS18S20
VPU
GND
TINT > 1s TRC Master samples
15s
VPU
GND
15 of 23
DS18S20
Initialization MASTER TX
RESET PULSE
Sequence
DS18S20 TX
PRESENCE
PULSE
MASTER TX ROM
COMMAND
Y Y Y Y Y
MASTER TX
BIT 0
N N DEVICE(S)
BIT 0 BIT 0 N
MATCH? WITH ALARM
MATCH?
FLAG SET?
DS18S20 TX
SERIAL NUMBER Y Y Y
6 BYTES
DS18S20 TX BIT 1
DS18S20 TX MASTER TX
DS18S20 TX BIT 1
CRC BYTE BIT 1
MASTER TX BIT 1
N N
BIT 1 BIT 1
MATCH? MATCH?
Y
Y
DS18S20 TX BIT 63
N N
BIT 63 BIT 63
MATCH? MATCH?
Y Y
MASTER TX
FUNCTION
COMMAND
(FIGURE 15)
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DS18S20
44h 48h
MASTER TX CONVERT N COPY N
FUNCTION TEMPERATURE SCRATCHPAD
COMMAND ? ?
Y Y
N PARASITE Y N PARASITE Y
POWER POWER
? ?
MASTER MASTER
MASTER MASTER RX “0s” RX “1s”
RX “0s” RX “1s”
Y Y Y Y
MASTER TX TH BYTE
MASTER RX DATA BYTE TO SCRATCHPAD
N Y
PARASITE FROM SCRATCHPAD
POWERED MASTER BEGINS DATA
? RECALL FROM E2 PROM
MASTER TX TL BYTE
TO SCRATCHPAD
MASTER MASTER Y
RX “0s” RX “1s”
MASTER RX SCRATCHPAD
CRC BYTE
RETURN TO INITIALIZATION
SEQUENCE (FIGURE 14) FOR
NEXT TRANSACTION
17 of 23
DS18S20
18 of 23
DS18S20
19 of 23
DS18S20
These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
DC ELECTRICAL CHARACTERISTICS
(VDD = 3.0V to 5.5V, TA = -55°C to +125°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS NOTES
Supply Voltage VDD Local Power +3.0 +5.5 V 1
Pullup Supply Parasite Power +3.0 +5.5
VPU V 1, 2
Voltage Local Power +3.0 VDD
-10°C to +85°C ±0.5
Thermometer Error tERR °C 3
-55°C to +125°C ±2
Input Logic-Low VIL -0.3 +0.8 V 1, 4, 5
Local Power +2.2 The lower of
5.5
Input Logic-High VIH V 1, 6
or
Parasite Power +3.0 VDD + 0.3
Sink Current IL VI/O = 0.4V 4.0 mA 1
Standby Current IDDS 750 1000 nA 7, 8
Active Current IDD VDD = 5V 1 1.5 mA 9
DQ Input Current IDQ 5 A 10
Drift ±0.2 °C 11
NOTES:
1) All voltages are referenced to ground.
2) The Pullup Supply Voltage specification assumes that the pullup device is ideal, and therefore the high level of
the pullup is equal to VPU. In order to meet the VIH spec of the DS18S20, the actual supply rail for the strong
pullup transistor must include margin for the voltage drop across the transistor when it is turned on; thus:
VPU_ACTUAL = VPU_IDEAL + VTRANSISTOR.
3) See typical performance curve in Figure 16.
4) Logic-low voltages are specified at a sink current of 4mA.
5) To guarantee a presence pulse under low voltage parasite power conditions, VILMAX may have to be reduced to
as low as 0.5V.
6) Logic-high voltages are specified at a source current of 1mA.
7) Standby current specified up to +70C. Standby current typically is 3A at +125C.
8) To minimize IDDS, DQ should be within the following ranges: GND DQ GND + 0.3V or
VDD – 0.3V DQ VDD.
9) Active current refers to supply current during active temperature conversions or EEPROM writes.
10) DQ line is high (“high-Z” state).
11) Drift data is based on a 1000-hour stress test at +125°C with VDD = 5.5V.
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DS18S20
AC ELECTRICAL CHARACTERISTICS
(VDD = 3.0V to 5.5V; TA = -55°C to +125°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS NOTES
Temperature Conversion
tCONV 750 ms 1
Time
Start Convert T
Time to Strong Pullup On tSPON 10 s
Command Issued
Time Slot tSLOT 60 120 s 1
Recovery Time tREC 1 s 1
Write 0 Low Time tLOW0 60 120 s 1
Write 1 Low Time tLOW1 1 15 s 1
Read Data Valid tRDV 15 s 1
Reset Time High tRSTH 480 s 1
Reset Time Low tRSTL 480 s 1, 2
Presence-Detect High tPDHIGH 15 60 s 1
Presence-Detect Low tPDLOW 60 240 s 1
Capacitance CIN/OUT 25 pF
NOTES:
1) See the timing diagrams in Figure 17.
2) Under parasite power, if tRSTL > 960s, a power-on reset may occur.
0.5
0.4
+3s Error
0.3
0.2
0.1
0
0 10 20 30 40 50 60 70
-0.1
-0.2
-0.3
Mean Error
-0.4
-3s Error
-0.5
Temperature (°C)
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DS18S20
PACKAGE INFORMATION
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-”
in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
8 SO S8-2 21-0041 90-0096
3 TO-92
Q3-1 21-0248 —
(straight leads)
3 TO-92
Q3-4 21-0250 —
(formed leads)
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DS18S20
REVISION HISTORY
REVISION PAGES
DESCRIPTION
DATE CHANGED
In the Ordering Information table, added TO-92 straight-lead packages and
042208 included a note that the TO-92 package in tape and reel can be ordered with 2
either formed or straight leads.
Removed the Top Mark column from the Ordering Information table;
8/10 added the continuous power dissipation and lead and soldering 2, 20
temperatures to the Absolute Maximum Ratings section
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