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
For situations where the bus master does not know whether the DS18S20s on the bus are parasite
powered or supplied with external VDD, a provision is made in the DS18S20 to signal the power supply
scheme used. The bus master can determine if any DS18S20s are on the bus which require the strong
pullup by sending a Skip ROM protocol, then issuing the read power supply command. After this
command is issued, the master then issues read time slots. The DS18S20 will send back “0” on the
1-Wire bus if it is parasite powered; it will send back a “1” if it is powered from the VDD pin. If the
master receives a “0,” it knows that it must supply the strong pullup on the DQ line during temperature
conversions. See “Memory Command Functions” section for more detail on this command protocol.
STRONG PULL-UP FOR SUPPLYING DS18S20 DURING TEMPERATURE
CONVERSION Figure 2
+3V - +5V
DS18S20
+3V - +5V
µP
4.7k
GND
VDD
I/O
USING VDD TO SUPPLY TEMPERATURE CONVERSION CURRENT Figure 3
DS18S20
TO OTHER
1-WIRE DEVICES
+3V - +5V
4.7k
µP
GND
I/O
VDD
EXTERNAL +3V - +5V
SUPPLY
4 of 27
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