DS18S20-PAR Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS18S20-PAR

1-Wire® Parasite-Power Digital Thermometer

Dallas Semiconductor -> Maxim Integrated 

DS18S20-PAR

DETAILED PIN DESCRIPTIONS Table 1

PIN SYMBOL

DESCRIPTION

1

GND Ground.

2

DQ Data Input/Output pin. Open-drain 1-wire interface pin. Also provides power

to the device when used in parasite power mode (see “Parasite Power” section.)

3

NC

No Connect. Doesn’t connect to internal circuit.

OVERVIEW

The DS18S20-PAR uses Dallas’ 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-PAR). 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 of this datasheet.

An important feature of the DS18S20-PAR is its 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.”

Figure 1 shows a block diagram of the DS18S20-PAR, and pin descriptions are given in Table 1. 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 their data when the device is powered down.

DS18S20-PAR BLOCK DIAGRAM Figure 1

VPU

4.7K

DQ

PARASITE POWER

CIRCUIT

INTERNAL VDD

CPP

64-BIT ROM

AND

1-wire PORT

GND

MEMORY CONTROL DS18S20-PAR

LOGIC

SCRATCHPAD

TEMPERATURE SENSOR

ALARM HIGH TRIGGER (TH)

REGISTER (EEPROM)

ALARM LOW TRIGGER (TL)

REGISTER (EEPROM)

8-BIT CRC GENERATOR

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