DS1822-PAR_07 DALLAS [Dallas Semiconductor], DS1822-PAR_07 Datasheet - Page 2

• Manufacturer Part Number: DS1822-PAR_07
• Description: Econo 1-Wire Parasite-Power Digital Thermometer
• Manufacturer: DALLAS [Dallas Semiconductor]

DETAILED PIN DESCRIPTIONS Table 1
OVERVIEW
The DS1822-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 DS1822-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 data sheet.
An important feature of the DS1822-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 (C
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 DS1822-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 (T
are NV (EEPROM), so they will retain their data when the device is powered down.
DS1822-PAR BLOCK DIAGRAM Figure 1
PIN
4.7K
1
2
3
V
GND
PU
DQ
SYMBOL
GND
DQ
NC
PARASITE POWER
DESCRIPTION
Ground.
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.)
No Connect. Doesn’t connect to internal circuit.
CIRCUIT
C
INTERNAL V
PP
DD
64-BIT ROM
1-wire PORT
2 of 19
AND
PP
), which then supplies power to the device when the
SCRATCHPAD
MEMORY CONTROL
LOGIC
H
and T
L
). The T
CONFIGURATION REGISTER
ALARM HIGH TRIGGER (T
ALARM LOW TRIGGER (T
DS1822-PAR
TEMPERATURE SENSOR
REGISTER (EEPROM)
REGISTER (EEPROM)
8-BIT CRC GENERATOR
(EEPROM)
H
and T
DS1822-PAR
L
registers
L
H
)
)