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PDF DS1822 Data sheet ( Hoja de datos )
| Número de pieza | DS1822 | |
| Descripción | Econo 1-Wire Digital Thermometer | |
| Fabricantes | Dallas | |
| Logotipo |  |
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FEATURES
§ Unique 1-Wire® interface requires only one
port pin for communication.
§ Each device has a unique 64-bit serial code
stored in an on-board ROM.
§ Multidrop capability simplifies distributed
temperature-sensing applications.
§ Requires no external components.
§ Can be powered from data line. Power supply
range is 3.0V to 5.5V.
§ Measures temperatures from -55°C to +125°C
(-67°F to +257°F).
§ ±2.0°C accuracy from -10°C to +85°C.
§ Thermometer resolution is user-selectable
from 9 to 12 bits.
§ Converts temperature to 12-bit digital word in
750ms (max.)
§ User-definable nonvolatile (NV) alarm
settings.
§ Alarm search command identifies and
addresses devices whose temperature is
outside of programmed limits (temperature
alarm condition).
§ Software compatible with the DS18B20.
§ Applications include thermostatic controls,
industrial systems, consumer products,
thermometers, or any thermally sensitive
system.
DS1822
Econo 1-Wire Digital
Thermometer
PIN ASSIGNMENT
DALLAS
1822
123
NC 1
NC 2
VDD
3
DQ 4
8 NC
7 NC
6 NC
5 GND
8-Pin 150mil SO
(DS1822Z)
12 3
(BOTTOM VIEW)
TO-92
(DS1822)
PIN DESCRIPTION
GND - Ground
DQ - Data In/Out
VDD - Power Supply Voltage
NC - No Connect
DESCRIPTION
The DS1822 digital thermometer provides 9- to 12-bit centigrade temperature measurements and has an
alarm function with NV user-programmable upper and lower trigger points. The DS1822 communicates
over a 1-Wire bus that 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 +125°C and is accurate to
±2.0°C over the range of –10°C to +85°C. In addition, the DS1822 can derive power directly from the
data line (“parasite power”), eliminating the need for an external power supply.
Each DS1822 has a unique 64-bit serial code, which allows multiple DS1822s to function on the 1-Wire
bus; thus, it is simple to use one microprocessor to control many DS1822s 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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061002
1 page  
DS1822
The use of parasite power is not recommended for temperatures above 100°C since the DS1822 may not
be able to sustain communications due to the higher leakage currents that can exist at these temperatures.
For applications in which such temperatures are likely, it is strongly recommended that the DS1822 be
powered by an external power supply.
In some situations the bus master may not know whether the DS1822s on the bus are parasite powered or
powered by external supplies. The master needs this information to determine if the strong bus pullup
should be used during temperature conversions. To get this information, the master can issue a Skip ROM
[CCh] command followed by a Read Power Supply [B4h] command followed by a “read-time slot”.
During the read time slot, parasite powered DS1822s will pull the bus low, and externally powered
DS1822s will let the bus remain high. If the bus is pulled low, the master knows that it must supply the
strong pullup on the 1-Wire bus during temperature conversions.
SUPPLYING THE PARASITE-POWERED DS1822 DURING TEMPERATURE
CONVERSIONS Figure 4
VPU
Micro-
processor
VPU
4.7k
DS1822
GND DQ VDD
1-Wire Bus
To Other
1-Wire Devices
POWERING THE DS1822 WITH AN EXTERNAL SUPPLY Figure 5
Micro-
processor
VPU
4.7k
DS1822
GND DQ VDD
1-Wire Bus
VDD (External Supply)
To Other
1-Wire Devices
64-BIT LASERED ROM CODE
Each DS1822 contains a unique 64–bit code (see Figure 6) stored in ROM. The least significant 8 bits of
the ROM code contain the DS1822’s 1-Wire family code: 22h. The next 48 bits contain a unique serial
number. The most significant 8 bits contain a cyclic redundancy check (CRC) byte that is calculated from
the first 56 bits of the ROM code. A detailed explanation of the CRC bits is provided in the CRC
GENERATION section. The 64-bit ROM code and associated ROM function control logic allow the
DS1822 to operate as a 1-Wire device using the protocol detailed in the 1-WIRE BUS SYSTEM section
of this data sheet.
64-BIT LASERED ROM CODE Figure 6
8-BIT CRC
48-BIT SERIAL NUMBER
8-BIT FAMILY CODE (22h)
MSB
LSB MSB
LSB MSB
LSB
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DS1822
issued the master must enable a strong pullup on the 1-Wire bus for at least 10ms as described in the
POWERING THE DS1822 section.
RECALL E2 [B8h]
This command recalls the alarm trigger values (TH and TL) and configuration data from EEPROM and
places the data in bytes 2, 3, and 4, respectively, in the scratchpad memory. The master device can issue
read time slots following the Recall E2 command and the DS1822 will indicate the status of the recall by
transmitting 0 while the recall is in progress and 1 when the recall is done. The recall operation happens
automatically at power-up, so valid data is available in the scratchpad as soon as power is applied to the
device.
READ POWER SUPPLY [B4h]
The master device issues this command followed by a read time slot to determine if any DS1822s on the
bus are using parasite power. During the read time slot, parasite powered DS1822s will pull the bus low,
and externally powered DS1822s will let the bus remain high. Refer to the POWERING THE DS1822
section for usage information for this command.
DS1822 FUNCTION COMMAND SET Table 4
1-Wire Bus Activity
Command
Description
Protocol After Command is Issued
TEMPERATURE CONVERSION COMMANDS
Convert T
Initiates temperature
44h DS1822 transmits conversion
conversion.
status to master (not applicable
for parasite-powered DS1822s).
MEMORY COMMANDS
Read Scratchpad Reads the entire scratchpad
BEh DS1822 transmits up to 9 data
including the CRC byte.
bytes to master.
Write Scratchpad Writes data into scratchpad
4Eh Master transmits 3 data bytes to
bytes 2, 3, and 4 (TH, TL,
and configuration registers).
DS1822.
Copy Scratchpad Copies TH, TL, and
configuration register data
48h None
from the scratchpad to
Recall E2
EEPROM.
Recalls TH, TL, and
configuration register data
B8h DS1822 transmits recall status to
master.
from EEPROM to the
scratchpad.
Read Power
Signals DS1822 power
B4h DS1822 transmits supply status
Supply
supply mode to the master.
to master.
Notes
1
2
3
1
NOTES:
1. For parasite-powered DS1822s, the master must enable a strong pullup on the 1-Wire bus during
temperature conversions and copies from the scratchpad to EEPROM. No other bus activity may take
place during this time.
2. The master can interrupt the transmission of data at any time by issuing a reset.
3. All three bytes must be written before a reset is issued.
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| PDF Descargar | [ Datasheet DS1822.PDF ] | |
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