DS1620 ,Digital Thermometer and ThermostatPIN DESCRIPTIONDQ - 3-Wire Input/OutputCLK/ CONV - 3-Wire Clock Input andStand-alone Convert InputR ..
DS1620+ ,Digital Thermometer and ThermostatDS1620Digital Thermometer andThermostat
DS1620S ,Digital Thermometer and ThermostatPIN DESCRIPTIONDQ - 3-Wire Input/OutputCLK/ CONV - 3-Wire Clock Input andStand-alone Convert InputR ..
DS1620S+ ,Digital Thermometer and ThermostatApplications include thermostatic controls,54industrial systems, consumer products, GND TCOMthermom ..
DS1621 ,Digital Thermometer and ThermostatPIN DESCRIPTIONPIN SYMBOL DESCRIPTION1 SDA Data input/output pin for 2-wire serial communication po ..
DS1621+ ,Digital Thermometer and ThermostatFEATURES PIN ASSIGNMENT Temperature measurements require no8SDA 1 VDDexternal components2 7 Measu ..
DTD123TK , 500mA / 40V Digital transistors (with built-in resistors)
DTD123YKT146 , DTD123YK
DTD123YS , Digital transistors (built-in resistors)
DTD133HK , Digital transistors (Includes resistors)
DTD143E ,Tech Electronics LTD - Digital transistors (built-in resistors)
DTD143EK ,Tech Electronics LTD - Digital transistors (built-in resistors)
DS1620
Digital Thermometer and Thermostat
FEATURESRequires no external componentsSupply voltage range covers from 2.7V to5.5VMeasures temperatures from -55°C to +125°C
in 0.5°C increments; Fahrenheit equivalent is
-67°F to +257°F in 0.9°F incrementsTemperature is read as a 9-bit valueConverts temperature to digital word in 1
second (max)Thermostatic settings are user-definable and
nonvolatileData is read from/written via a 3-wire serial
interface (CLK, DQ, RST)Applications include thermostatic controls,
industrial systems, consumer products,
thermometers, or any thermally sensitive
system8-pin DIP or SOIC (208-mil) packages
PIN ASSIGNMENT
PIN DESCRIPTIONDQ- 3-Wire Input/Output
CLK/CONV- 3-Wire Clock Input and
Stand-alone Convert Input
RST- 3-Wire Reset Input
GND- Ground
THIGH- High Temperature Trigger
TLOW- Low Temperature TriggerTCOM- High/Low Combination Trigger
VDD- Power Supply Voltage (3V - 5V)
DESCRIPTIONThe DS1620 Digital Thermometer and Thermostat provides 9–bit temperature readings which indicate
the temperature of the device. With three thermal alarm outputs, the DS1620 can also act as a thermostat.THIGH is driven high if the DS1620’s temperature is greater than or equal to a user–defined temperature
TH. TLOW is driven high if the DS1620’s temperature is less than or equal to a user–defined temperature
TL. TCOM is driven high when the temperature exceeds TH and stays high until the temperature falls
below that of TL.
DS1620
Digital Thermometer and
ThermostatCLK/CONV
RST
GND
VDD
THIGH
TLOW
TCOM
DS1620S 8-Pin SOIC (208-miil)
See Mech Drawings Section
CLK/CONV
RST
GND
VDD
THIGH
TLOW
TCOM
DS1620 8-Pin DIP (300-mil)
See Mech Drawings Section
DS1620
User–defined temperature settings are stored in nonvolatile memory, so parts can be programmed prior to
insertion in a system, as well as used in standalone applications without a CPU. Temperature settings and
temperature readings are all communicated to/from the DS1620 over a simple 3–wire interface.
OPERATION-MEASURING TEMPERATUREA block diagram of the DS1620 is shown in Figure 1. The DS1620 measures temperatures through theuse of an onboard proprietary temperature measurement technique. A block diagram of the temperature
measurement circuitry is shown in Figure 2.
The DS1620 measures temperature by counting the number of clock cycles that an oscillator with a low
temperature coefficient goes through during a gate period determined by a high temperature coefficient
oscillator. The counter is preset with a base count that corresponds to –55�C. If the counter reaches 0
before the gate period is over, the temperature register, which is also preset to the –55�C value, is
incremented, indicating that the temperature is higher than –55�C.
At the same time, the counter is then preset with a value determined by the slope accumulator circuitry.
This circuitry is needed to compensate for the parabolic behavior of the oscillators over temperature. The
counter is then clocked again until it reaches 0. If the gate period is still not finished, then this process
repeats.
The slope accumulator is used to compensate for the nonlinear behavior of the oscillators over
temperature, yielding a high-resolution temperature measurement. This is done by changing the number
of counts necessary for the counter to go through for each incremental degree in temperature. To obtain
the desired resolution, therefore, both the value of the counter and the number of counts per degree C (thevalue of the slope accumulator) at a given temperature must be known.
DS1620 FUNCTIONAL BLOCK DIAGRAM Figure 1
DS1620
TEMPERATURE MEASURING CIRCUITRY Figure 2This calculation is done inside the DS1620 to provide 0.5�C resolution. The temperature reading is
provided in a 9–bit, two’s complement reading by issuing a READ TEMPERATURE command. Table 1describes the exact relationship of output data to measured temperature. The data is transmitted serially
through the 3–wire serial interface, LSB first. The DS1620 can measure temperature over the range of
-55�C to +125�C in 0.5�C increments. For Fahrenheit usage, a lookup table or conversion factor must be
used.
TEMPERATURE/DATA RELATIONSHIPS Table 1Since data is transmitted over the 3–wire bus LSB first, temperature data can be written to/read from the
DS1620
words, with the most significant 7 bits being ignored or set to 0, as illustrated in Table 1. After the MSB,
the DS1620 will output 0s.
Note that temperature is represented in the DS1620 in terms of a ½�C LSB, yielding the following 9–bitformat:
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 + CCOUNT_PER_
DETAILED PIN DESCRIPTION Table 2
OPERATION–THERMOSTAT CONTROLSThree thermally triggered outputs, THIGH, TLOW, and TCOM, are provided to allow the DS1620 to be usedas a thermostat, as shown in Figure 3. When the DS1620’s temperature meets or exceeds the value stored
in the high temperature trip register, the output THIGH becomes active (high) and remains active until the
DS1620’s measured temperature becomes less than the stored value in the high temperature register, TH.
The THIGH output can be used to indicate that a high temperature tolerance boundary has been met or
exceeded, or it can be used as part of a closed loop system to activate a cooling system and deactivate itwhen the system temperature returns to tolerance.
The TLOW output functions similarly to the THIGH output. When the DS1620’s measured temperature
LSB
T = -25°C
MSB
DS1620
boundary has been met or exceeded, or as part of a closed loop system it can be used to activate a heating
system and deactivate it when the system temperature returns to tolerance.
The TCOM output goes high when the measured temperature meets or exceeds TH, and will stay high untilthe temperature equals or falls below TL. In this way, any amount of hysteresis can be obtained.
THERMOSTAT OUTPUT OPERATION Figure 3
OPERATION AND CONTROLThe DS1620 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 DS1620 willuse in a particular application and indicates the status of the temperature conversion operation. The
configuration register is defined as follows:
CONFIGURATION/STATUS REGISTER
where
DONE=Conversion Done Bit. 1=conversion complete, 0=conversion in progress.
THF=Temperature High Flag. This bit will be set to 1 when the temperature is greater than or equal
to the value of TH. It will remain 1 until reset by writing 0 into this location or by removing power fromthe device. This feature provides a method of determining if the DS1620 has ever been subjected to
temperatures above TH while power has been applied.
TLF=Temperature Low Flag. This bit will be set to 1 when the temperature is less than or equal to
the value of TL. It will remain 1 until reset by writing 0 into this location or by removing power from thedevice. This feature provides a method of determining if the DS1620 has ever been subjected to
temperatures below TL while power has been applied.
NVB=Nonvolatile Memory Busy Flag. 1=write to an E2 memory cell in progress. 0=nonvolatile
memory is not busy. A copy to E2 may take up to 10 ms.THT(°C)
DS1620
operation of the CLK/CONV pin is as a normal clock in concert with DQ and RST. This bit is stored in
nonvolatile E2 memory, capable of at least 50,000 writes. The DS1620 is shipped with CPU=0.
1SHOT=One–Shot Mode. If 1SHOT is 1, the DS1620 will perform one temperature conversion upon
reception of the Start Convert T protocol. If 1SHOT is 0, the DS1620 will continuously performtemperature conversion. This bit is stored in nonvolatile E2 memory, capable of at least 50,000 writes.
The DS1620 is shipped with 1SHOT=0.
For typical thermostat operation, the DS1620 will operate in continuous mode. However, for applications
where only one reading is needed at certain times or to conserve power, the one–shot mode may be used.Note that the thermostat outputs (THIGH, TLOW, TCOM) will remain in the state they were in after the last
valid temperature conversion cycle when operating in one–shot mode.
OPERATION IN STAND–ALONE MODEIn applications where the DS1620 is used as a simple thermostat, no CPU is required. Since the
temperature limits are nonvolatile, the DS1620 can be programmed prior to insertion in the system. In
order to facilitate operation without a CPU, the CLK/CONV pin (pin 2) can be used to initiate
conversions. Note that the CPU bit must be set to 0 in the configuration register to use this mode ofoperation. Whether CPU=0 or 1, the 3–wire port is active. Setting CPU=1 disables the stand–alone mode.
To use the CLK/CONV pin to initiate conversions, RST must be low and CLK/CONV must be high. If
CLK/CONV is driven low and then brought high in less than 10 ms, one temperature conversion will be
performed and then the DS1620 will return to an idle state. If CLK/CONV is driven low and remains low,
continuous conversions will take place until CLK/CONV is brought high again. With the CPU bit set to 0,
the CLK/CONV will override the 1SHOT bit if it is equal to 1. This means that even if the part is set for
one–shot mode, driving CLK/CONV low will initiate conversions.
3–WIRE COMMUNICATIONSThe 3–wire bus is comprised of three signals. These are the RST (reset) signal, the CLK (clock) signal,
and the DQ (data) signal. All data transfers are initiated by driving the RST input high. Driving the RST
input low terminates communication. (See Figures 4 and 5.) A clock cycle is a sequence of a falling edge
followed by a rising edge. For data inputs, the data must be valid during the rising edge of a clock cycle.Data bits are output on the falling edge of the clock and remain valid through the rising edge.
When reading data from the DS1620, the DQ pin goes to a high-impedance state while the clock is high.
Taking RST low will terminate any communication and cause the DQ pin to go to a high-impedance
state.
Data over the 3–wire interface is communicated LSB first. The command set for the 3–wire interface as
shown in Table 3 is as follows.
Read Temperature [AAh]This command reads the contents of the register which contains the last temperature conversion result.
The next nine clock cycles will output the contents of this register.
DS1620
Write TH [01h]This command writes to the TH (HIGH TEMPERATURE) register. After issuing this command the next
nine clock cycles clock in the 9–bit temperature limit which will set the threshold for operation of the
THIGH output.
Write TL [02h]This command writes to the TL (LOW TEMPERATURE) register. After issuing this command the next
nine clock cycles clock in the 9–bit temperature limit which will set the threshold for operation of theTLOW output.
Read TH [A1h]This command reads the value of the TH (HIGH TEMPERATURE) register. After issuing this command
the next nine clock cycles clock out the 9–bit temperature limit which sets the threshold for operation of
the THIGH output.
Read TL [A2h]This command reads the value of the TL (LOW TEMPERATURE) register. After issuing this command
the next nine clock cycles clock out the 9–bit temperature limit which sets the threshold for operation of
the TLOW output.
Read Counter [A0h]This command reads the value of the counter byte. The next nine clock cycles will output the contents ofthis register.
Read Slope [A9h]This command reads the value of the slope counter byte from the DS1620. The next nine clock cycles
will output the contents of this register.
Start Convert T [EEh]This command begins a temperature conversion. No further data is required. In one–shot mode thetemperature conversion will be performed and then the DS1620 will remain idle. In continuous mode this
command will initiate continuous conversions.
Stop Convert T [22h]This command stops temperature conversion. No further data is required. This command may be used to
halt a DS1620 in continuous conversion mode. After issuing this command the current temperaturemeasurement will be completed and then the DS1620 will remain idle until a Start Convert T is issued to
resume continuous operation.
Write Config [0Ch]This command writes to the configuration register. After issuing this command the next eight clock cycles
clock in the value of the configuration register.
Read Config [ACh]This command reads the value in the configuration register. After issuing this command the next eight
clock cycles output the value of the configuration register.
