DS18S20 查看數據表（PDF） - Dallas Semiconductor -> Maxim Integrated
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DS18S20 Datasheet PDF : 27 Pages
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DS18S20
DETAILED PIN DESCRIPTION
PIN
PIN
8-PIN SOIC TO92 SYMBOL DESCRIPTION
5
1
GND Ground.
4
2
DQ
Data Input/Output pin. For 1-Wire operation: Open drain.
(See “Parasite Power” section.)
3
3
VDD Optional VDD pin. See “Parasite Power” section for details of
connection. VDD must be grounded for operation in parasite
power mode.
DS18S20Z (8-pin SOIC): All pins not specified in this table are not to be connected.
OVERVIEW
The block diagram of Figure 1 shows the major components of the DS18S20. The DS18S20 has three
main data components: 1) 64–bit lasered ROM, 2) temperature sensor, 3) nonvolatile temperature alarm
triggers TH and TL. The device derives its power from the 1–Wire communication line by storing energy
on an internal capacitor during periods of time when the signal line is high and continues to operate off
this power source during the low times of the 1–Wire line until it returns high to replenish the parasite
(capacitor) supply. As an alternative, the DS18S20 may also be powered from an external 3 volt – 5 volt
supply.
Communication to the DS18S20 is via a 1–Wire port. With the 1–Wire port, the memory and control
functions will not be available before the ROM function protocol has been established. The master must
first provide one of five ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4)
Skip ROM, or 5) Alarm Search. These commands operate on the 64–bit lasered ROM portion of each
device and can single out a specific device if many are present on the 1–Wire line as well as indicate to
the bus master how many and what types of devices are present. After a ROM function sequence has
been successfully executed, the memory and control functions are accessible and the master may then
provide any one of the six memory and control function commands.
One control function command instructs the DS18S20 to perform a temperature measurement. The result
of this measurement will be placed in the DS18S20’s scratch-pad memory, and may be read by issuing a
memory function command which reads the contents of the scratchpad memory. The temperature alarm
triggers TH and TL consist of 1-byte EEPROM each. If the alarm search command is not applied to the
DS18S20, these registers may be used as general purpose user memory. Writing TH and TL is done
using a memory function command. Read access to these registers is through the scratchpad. All data is
read and written least significant bit first.
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