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PDF DS1621 Data sheet ( Hoja de datos )
| Número de pieza | DS1621 | |
| Descripción | Digital Thermometer and Thermostat | |
| Fabricantes | Dallas | |
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DS1621
Digital Thermometer and Thermostat
FEATURES
§ Temperature measurements require no
external components
§ Measures temperatures from –55°C to
+125°C in 0.5°C increments. Fahrenheit
equivalent is –67°F to 257°F in 0.9°F
increments
§ Temperature is read as a 9–bit value (2-
byte transfer)
§ Wide power supply range (2.7V to 5.5V)
§ Converts temperature to digital word in 1
second
§ Thermostatic settings are user definable
and nonvolatile
§ Data is read from/written via a two–wire
serial interface (open drain I/O lines)
§ Applications include thermostatic
controls, industrial systems, consumer
products, thermometers, or any thermal
sensitive system
§ 8–pin DIP or SOIC package (150-MIL and
208-MIL)
PIN ASSIGNMENT
SDA
1
8 VDD
SCL
TOUT
2
3
7 A0
6 A1
GND
4
5 A2
DS1621S 8-PIN SOIC (150-MIL)
DS1621V 8-PIN SOIC (208-MIL)
See Mech Drawings Section
SDA 1
8 VDD
SCL 2
7 A0
TOUT
3
6 A1
GND
4
5 A2
DS1621 8-PIN DIP (300-MIL)
See Mech Drawings Section
PIN DESCRIPTION
SDA
- 2-Wire Serial Data Input/Output
SCL - 2-Wire Serial Clock
GND
- Ground
TOUT
A0
- Thermostat Output Signal
- Chip Address Input
A1 - Chip Address Input
A2 - Chip Address Input
VDD - Power Supply Voltage
DESCRIPTION
The DS1621 Digital Thermometer and Thermostat provides 9–bit temperature readings which indicate
the temperature of the device. The thermal alarm output, TOUT, is active when the temperature of the
device exceeds a user–defined temperature TH. The output remains active until the temperature drops
below user defined temperature TL, allowing for any hysteresis necessary.
User-defined temperature settings are stored in nonvolatile memory so parts may be programmed prior to
insertion in a system. Temperature settings and temperature readings are all communicated to/from the
DS1621 over a simple two–wire serial interface.
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Higher resolutions may be obtained by reading the temperature and truncating the 0.5°C bit (the LSB)
from the read value. This value is TEMP_READ. The value left in the counter may then be read by
issuing a READ COUNTER command. This value is the count remaining (COUNT_REMAIN) after the
gate period has ceased. By loading the value of the slope accumulator into the count register (using the
READ SLOPE command), this value may then be read, yielding the number of counts per degree C
(COUNT_PER_C) at that temperature. The actual temperature may be then be calculated by the user
using the following:
TEMPERATURE=TEMP_READ-0.25 + (COUNT _ PER _ C − COUNT _ REMAIN)
COUNT _ PER _ C
Thermostat Control
In its operating mode, the DS1621 functions as a thermostat with programmable hysteresis as shown in
Figure 3. The thermostat output updates as soon as a temperature conversion is complete.
When the DS1621’s temperature meets or exceeds the value stored in the high temperature trip register
(TH), the output becomes active and will stay active until the temperature falls below the temperature
stored in the low temperature trigger register (TL). In this way, any amount of hysteresis may be
obtained.
The active state for the output is programmable by the user so that an active state may either be a logic
"1" (VDD) or a logic "0" (0V).
THERMOSTAT OUTPUT OPERATION Figure 3
DQ (Thermostat output, Active=High)
TL TH T (°C)
OPERATION AND CONTROL
The DS1621 must have temperature settings resident in the TH and TL registers for thermostatic
operation. A configuration/status register also determines the method of operation that the DS1621 will
use in a particular application, as well as indicating the status of the temperature conversion operation.
The configuration register is defined as follows:
DONE THF TLF NVB
1
0 POL 1SHOT
where
DONE = Conversion Done bit. “1” = Conversion complete, “0” = Conversion in progress.
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DS1621
measurement will be completed and the DS1621 will remain idle until a Start Convert T is issued to
resume continuous operation.
DS1621 COMMAND SET Table 3
INSTRUCTION
Read Temperature
Read Counter
Read Slope
Start Convert T
Stop Convert T
Access TH
Access TL
Access Config
2-WIRE BUS DATA
AFTER ISSUING
DESCRIPTION
PROTOCOL
PROTOCOL
TEMPERATURE CONVERSION COMMANDS
Read last converted temperature
AAh
<read 2 bytes data>
value from temperature register.
Reads value of count remaining
A8h
<read data>
from counter.
Reads value of the slope
A9h <read data>
accumulator.
Initiates temperature
EEh idle
conversion.
Halts temperature conversion.
22h
idle
THERMOSTAT COMMANDS
Reads or writes high
A1h <write data>
temperature limit value into TH
register.
Reads or writes low
A2h <write data>
temperature limit value into TL
register.
Reads or writes configuration
ACh
<write data>
data to configuration register.
NOTES
1
1
2
2
2
NOTES:
1. In continuous conversion mode a Stop Convert T command will halt continuous conversion. To
restart the Start Convert T command must be issued. In one–shot mode a Start Convert T command
must be issued for every temperature reading desired.
2. Writing to the E2 typically requires 10ms at room temperature. After issuing a write command, no
further writes should be requested for at least 10 ms.
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet DS1621.PDF ] | |
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