DS1822-PAR Digital Thermometer Datasheet

DS1822-PAR Datasheet, PDF, Equivalent


Part Number

DS1822-PAR

Description

Econo 1-Wire Parasite-Power Digital Thermometer

Manufacture

Maxim Integrated

Total Page 19 Pages
Datasheet
Download DS1822-PAR Datasheet


DS1822-PAR
www.maxim-ic.com
FEATURES
ƒ Unique 1-Wire® interface requires only one
port pin for communication
ƒ Derives power from data line (“parasite
power”)—does not need a local power supply
ƒ Multidrop capability simplifies distributed
temperature sensing applications
ƒ Requires no external components
ƒ ±2.0°C accuracy from -10°C to +85°C
ƒ Measures temperatures from -55°C to +100°C
(-67°F to +212°F)
ƒ Thermometer resolution is user-selectable
from 9 to 12 bits
ƒ Converts temperature to 12-bit digital word in
750ms (max.)
ƒ User-definable temperature alarm settings
ƒ Alarm search command identifies and
addresses devices whose temperature is
outside of programmed limits (temperature
alarm condition)
ƒ Software compatible with the DS18B20-PAR
ƒ Ideal for use in remote sensing applications
(e.g., temperature probes) that do not have a
local power source
DS1822-PAR
Econo 1-Wire Parasite-Power
Digital Thermometer
PIN ASSIGNMENT
DALLAS
1822P
123
12 3
(BOTTOM VIEW)
TO-92
(DS1822-PAR)
PIN DESCRIPTION
GND - Ground
DQ - Data In/Out
NC - No Connect
DESCRIPTION
The DS1822-PAR digital thermometer provides 9- to 12-bit centigrade temperature measurements and
has an alarm function with nonvolatile (NV) user-programmable upper and lower trigger points. The
DS1822-PAR does not need an external power supply because it derives power directly from the data line
(“parasite power”). The DS1822-PAR communicates over a 1-Wire bus, which 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 +100°C and is accurate to ±2.0°C over a range of -10°C to +85°C.
Each DS1822-PAR has a unique 64-bit identification code, which allows multiple DS1822-PARs to
function on the same 1-Wire bus; thus, it is simple to use one microprocessor to control many
DS1822-PARs 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 Dallas Semiconductor.
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101107

DS1822-PAR
DS1822-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 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 (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 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 (TH and TL). The TH and TL registers
are NV (EEPROM), so they will retain their data when the device is powered down.
DS1822-PAR BLOCK DIAGRAM Figure 1
VPU
4.7K
DQ
GND
PARASITE POWER
CIRCUIT
INTERNAL VDD
CPP
64-BIT ROM
AND
1-wire PORT
DS1822-PARMEMORY CONTROL
LOGIC
SCRATCHPAD
TEMPERATURE SENSOR
ALARM HIGH TRIGGER (TH)
REGISTER (EEPROM)
ALARM LOW TRIGGER (TL)
REGISTER (EEPROM)
CONFIGURATION REGISTER
(EEPROM)
8-BIT CRC GENERATOR
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Features www.maxim-ic.com FEATURES ƒ Unique 1-Wi re® interface requires only one port p in for communication ƒ Derives power f rom data line (“parasite power”)— does not need a local power supply ƒ M ultidrop capability simplifies distribu ted temperature sensing applications ƒ Requires no external components ƒ ±2 .0°C accuracy from -10°C to +85°C ƒ Measures temperatures from -55°C to + 100°C (-67°F to +212°F) ƒ Thermomet er resolution is user-selectable from 9 to 12 bits ƒ Converts temperature to 12-bit digital word in 750ms (max.) ƒ User-definable temperature alarm settin gs ƒ Alarm search command identifies a nd addresses devices whose temperature is outside of programmed limits (temper ature alarm condition) ƒ Software comp atible with the DS18B20-PAR ƒ Ideal fo r use in remote sensing applications (e .g., temperature probes) that do not ha ve a local power source GND DQ NC DS1 822-PAR Econo 1-Wire Parasite-Power Dig ital Thermometer PIN ASSIGNMENT DALLAS 1822P 123 12 3 (BOTTOM VIEW) TO-92 (DS1822-PAR) PIN.
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