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| DS1720 PRELIMINARY DS1720 Econo - Digital Thermometer and Thermostat FEATURES PIN ASSIGNMENT DQ CLK/CONV RST GND 1 2 3 4 8 7 6 5 VDD THIGH TLOW TCOM * Requires no external components * Supply voltage range covers from 2.7V to 5.5V * Measures temperatures from -55C to +125C in 0.5C increments. Fahrenheit equivalent is -67F to +257F in 0.9F increments * Temperature is read as a 9-bit value * Converts (max) temperature to digital word in 1 second DQ CLK/CONV DS1720S 8-PIN SOIC (208 MIL) See Mech Drawings Section PIN DESCRIPTION - 3-Wire Input/Output - 3-Wire Clock Input and Stand-alone Convert Input - 3-Wire Reset Input - Ground - High Temperature Trigger - Low Temperature Trigger - High/Low Combination Trigger - Power Supply Voltage (3V - 5V) * Thermostatic settings are user-definable and non- volatile * Data 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 system * 8-pin SOIC (208 mil) package RST GND THIGH TLOW TCOM VDD DESCRIPTION The DS1720 Digital Thermometer and Thermostat provides 9-bit temperature readings which indicate the temperature of the device. With three thermal alarm outputs, the DS1720 can also act as a thermostat. THIGH is driven high if the DS1720's temperature is greater than or equal to a user-defined temperature TH. TLOW is driven high if the DS1720'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. User-defined temperature settings are stored in non- volatile memory, so parts can be programmed prior to insertion in a system, as well as used in stand-alone applications without a CPU. Temperature settings and temperature readings are all communicated to/from the DS1720 over a simple 3-wire interface. 030598 1/12 DS1720 OPERATION-MEASURING TEMPERATURE A block diagram of the DS1720 is shown in Figure 1. The DS1720 measures temperatures through the use of an on-board proprietary temperature measurement technique. A block diagram of the temperature measurement circuitry is shown in Figure 2. The DS1720 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 -55C. If the counter reaches zero before the gate period is over, the temperature register, which is also preset to the -55C value, is incremented, indicating that the temperature is higher than -55C. 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 zero. 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 (the value of the slope accumulator) at a given temperature must be known. DS1720 FUNCTIONAL BLOCK DIAGRAM Figure 1 STATUS REGISTER AND CONTROL LOGIC CLK ADDRESS AND RESET DQ TEMPERATURE SENSOR HIGH TEMP TRIGGER, TH RST THIGH LOW TEMP TRIGGER, TL TLOW DIGITAL COMPARATOR/LOGIC TCOM 030598 2/12 DS1720 TEMPERATURE MEASURING CIRCUITRY Figure 2 SLOPE ACCUMULATOR PRESET COMPARE LOW TEMPERATURE COEFFICIENT OSCILLATOR COUNTER PRESET SET/CLEAR LSB =0 INC TEMPERATURE REGISTER HIGH TEMPERATURE COEFFICIENT OSCILLATOR COUNTER =0 STOP This calculation is done inside the DS1720 to provide 0.5C resolution. The temperature reading is provided in a 9-bit, two's complement reading by issuing a READ TEMPERATURE command. Table 1 describes the exact relationship of output data to measured temperature. The data is transmitted serially through the 3-wire serial interface, LSB first. The DS1720 can measure temperature over the range of -55C to +125C in 0.5C increments. For Fahrenheit usage, a lookup table or conversion factor must be used. 9th (MSB) bit), or as two transfers of 8-bit words, with the most significant 7 bits being ignored or set to zero, as illustrated in Table 1. After the MSB, the DS1720 will output 0s. Note that temperature is represented in the DS1720 in terms of a 1/2C LSB, yielding the following 9-bit format: MSB X X X X X X X 1 LSB 1 1 0 0 1 1 1 0 TEMPERATURE/DATA RELATIONSHIPS Table 1 DIGITAL OUTPUT (Binary) 0 10101010 0 00110010 0 00000001 0 00000000 1 11111111 1 11001110 DIGITAL OUTPUT (Hex) 00AA 0032h 0001h 0000h 01FFh 01CEh T = -25C TEMP +85C +25C +1/2C +0C -1/2C -25C Higher resolutions may be obtained by reading the temperature, and truncating the 0.5C 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 Since data is transmitted over the 3-wire bus LSB first, temperature data can be written to/read from the DS1720 as either a 9-bit word (taking RST low after the 030598 3/12 DS1720 DETAILED PIN DESCRIPTION Table 2 PIN 1 2 SYMBOL DQ CLK/CONV DESCRIPTION Data Input/Output pin for 3-wire communication port. Clock input pin for 3-wire communication port. When the DS1720 is used in a stand-alone application with no 3-wire port, this pin can be used as a convert pin. Temperature conversion will begin on the falling edge of CONV. Reset input pin for 3-wire communication port. Ground pin. High/Low Combination Trigger. Goes high when temperature exceeds TH; will reset to low when temperature falls below TL. Low Temperature Trigger. Goes high when temperature falls below TL. High Temperature Trigger. Goes high when temperature exceeds TH. Supply Voltage. 2.7V - 5.5V input power pin. falls below the value stored in the low temperature register, the TLOW output becomes active. TLOW remains active until the DS1720's temperature becomes greater than the value stored in the low temperature register, TL. The TLOW output can be used to indicate that a low temperature tolerance boundary has been met or exceeded, or as part of a closed loop system, can be used to activate a heating system and to 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 until the temperature equals or falls below TL. In this way, any amount of hysteresis can be obtained. 3 4 5 6 7 8 RST GND TCOM TLOW THIGH VDD OPERATION-THERMOSTAT CONTROLS Three thermally triggered outputs, THIGH, TLOW, and TCOM, are provided to allow the DS1720 to be used as a thermostat, as shown in Figure 3. When the DS1720'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 DS1720'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 as part of a closed loop system can be used to activate a cooling system and to deactivate it when the system temperature returns to tolerance. The TLOW output functions similarly to the THIGH output. When the DS1720's measured temperature equals or THERMOSTAT OUTPUT OPERATION Figure 3 THIGH TLOW TCOM TL TH T (C) 030598 4/12 DS1720 OPERATION AND CONTROL The DS1720 must have temperature settings resident in the TH and TL registers for thermostatic operation. A configuration/status register is also used to determine the method of operation that the DS1720 will use in a particular application, as well as indicating the status of the temperature conversion operation. The configuration register is defined as follows: CONFIGURATION/STATUS REGISTER DONE THF TLF NVB 1 0 CPU 1SHOT conversion upon reception of the Start Convert T protocol. If 1SHOT is 0, the DS1720 will continuously perform temperature conversion. This bit is stored in nonvolatile E2 memory, capable of at least 50,000 writes. The DS1720 is shipped with 1SHOT=0. For typical thermostat operation, the DS1720 will operate in continuous mode. However, for applications where only one reading is needed at certain times, and 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. where DONE = THF = Conversion Done bit. 1=conversion complete, 0=conversion in progress. 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 from the device. This feature provides a method of determining if the DS1720 has ever been subjected to temperatures above TH while power has been applied. 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 the device. This feature provides a method of determining if the DS1720 has ever been subjected to temperatures below TL while power has been applied. 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. CPU use bit. If CPU=0, the CLK/CONV pin acts as a conversion start control, when RST is low. If CPU is 1, the DS1720 will be used with a CPU communicating to it over the 3-wire port, and the 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 DS1720 is shipped with CPU=0. One-Shot Mode. If 1SHOT is 1, the DS1720 will perform one temperature OPERATION IN STAND-ALONE MODE In applications where the DS1720 is used as a simple thermostat, no CPU is required. Since the temperature limits are nonvolatile, the DS1720 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 of operation. 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 DS1720 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 1-shot 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. TLF = NVB = CPU = 3-WIRE COMMUNICATIONS The 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 1SHOT = 030598 5/12 DS1720 falling edge of the clock, and remain valid through the rising edge. When reading data from the DS1720, 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; only these protocols should be written to the DS1720, as writing other protocols to the device may result in permanent damage to the part. 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 of this register. Read Slope [A9h] This command reads the value of the slope counter byte from the DS1720. The next nine clock cycles will output the contents of this register. 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. Start Convert T [EEh] This command begins a temperature conversion. No further data is required. In one-shot mode, the temperature conversion will be performed and then the DS1720 will remain idle. In continuous mode, this command will initiate continuous conversions. 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. Stop Convert T [22h] This command stops temperature conversion. No further data is required. This command may be used to halt a DS1720 in continuous conversion mode. After issuing this command, the current temperature measurement will be completed, and then the DS1720 will remain idle until a Start Convert T is issued to resume continuous operation. 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 the TLOW output. 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 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 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. 030598 6/12 DS1720 DS1720 COMMAND SET Table 3 3-WIRE BUS DATA AFTER ISSUING PROTOCOL INSTRUCTION DESCRIPTION PROTOCOL NOTES TEMPERATURE CONVERSION COMMANDS Read Temperature Read Counter Read Slope Start Convert T Stop Convert T Reads last converted temperature value from temperature register Reads value of count remaining from counter Reads value of the slope accumulator Initiates temperature conversion Halts temperature conversion AAh A0h A9h EEh 22h THERMOSTAT COMMANDS Write TH Write TL Read TH Read TL Write Config Read Config Writes high temperature limit value into TH register Writes low temperature limit value into TL register Reads stored value of high temperature limit from TH register Reads stored value of low temperature limit from TL register Writes configuration data to configuration register Reads configuration data from configuration register 01h 02h A1h A2h 0Ch ACh 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 10 ms at room temperature. After issuing a write command, no further writes should be requested for at least 10 ms. 030598 7/12 DS1720 FUNCTION EXAMPLE Example: CPU sets up DS1720 for continuous conversion and thermostatic function. CPU MODE TX TX TX TX TX TX TX TX TX TX RX TX TX RX TX TX TX DS1720 MODE (3-WIRE) RX RX RX RX RX RX RX RX RX RX TX RX RX TX RX RX RX DATA (LSB FIRST) 0Ch 00h Toggle RST 01h 0050h Toggle RST 02h 0014h Toggle RST A1h 0050h Toggle RST A2h 0014h Toggle RST EEh Toggle RST COMMENTS CPU issues Write Config command CPU sets DS1720 up for continuous conversion CPU issues Reset to DS1720 CPU issues Write TH command CPU sends data for TH limit of +40C CPU issues Reset to DS1720 CPU issues Write TL command CPU sends data for TL limit of +10C CPU issues Reset to DS1720 CPU issues Read TH command DS1720 sends back stored value of TH for CPU to verify CPU issues Reset to DS1720 CPU issues Read TL command DS1720 sends back stored value of TL for CPU to verify CPU issues Reset to DS1720 CPU issues Start Convert T command CPU issues Reset to DS1720 030598 8/12 DS1720 READ DATA TRANSFER Figure 4 RST tCC tCCH CLK tCDH tDC DQ 0 1 7 LSB DATA tCDD tCDZ MSB DATA tRDZ PROTOCOL WRITE DATA TRANSFER Figure 5 tCWH RST tCC tCL CLK tCDH tDC DQ 0 1 tCH tDC tDCH 7 LSB DATA MSB DATA tCCH tR tF PROTOCOL NOTE: tCL, tCH, tR, and tF apply to both read and write data transfer. RELATED APPLICATION NOTES The following Application Notes can be applied to the DS1720. These notes can be obtained from the Dallas Semiconductor "Application Note Book", via our website at http:\\www.dalsemi.com/, or through our faxback service at (972) 371-4441. Application Note 67: "Applying and Using the DS1620 in Temperature Control Applications" Application Note 85: "Interfacing the DS1620 to the Motorola SPI Bus" Application Note 105: "High Resolution Temperature Measurement with Dallas Direct-to-Digital Temperature Sensors" Sample DS1720 subroutines that can be used in conjunction with AN105 can be downloaded from the website or our Anonymous FTP Site. 030598 9/12 DS1720 ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature -0.5V to +7.0V -55C to +125C -55C to +125C 260C for 10 seconds * This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. The Dallas Semiconductor DS1720 is built to the highest quality standards and manufactured for long term reliability. All Dallas Semiconductor devices are made using the same quality materials and manufacturing methods. However, the DS1720 is not exposed to environmental stresses, such as burn-in, that some industrial applications require. For specific reliability information on this product, please contact the factory in Dallas at (972) 371-4448. RECOMMENDED DC OPERATING CONDITIONS PARAMETER Supply Logic 1 Logic 0 SYMBOL VDD VIH VIL MIN 2.7 2.0 -0.3 TYP MAX 5.5 VCC+0.3 +0.6 UNITS V V V NOTES 1 1 1 DC ELECTRICAL CHARACTERISTICS PARAMETER Thermometer Error SYMBOL TERR CONDITION 0C to 85C -55C to +125C Logic 0 Output Logic 1 Output Input Resistance Active Supply Current Standby Supply Current VOL VOH RI ICC ISTBY RST to GND DQ,CLK to VDD 0C to +70C 0C to +70C (-55C to +125C; VDD=2.7V to 5.5V) MIN MAX 2.5 UNITS C NOTES 10, 11 See Typical Curve 0.4 2.4 2 2 1 1 V V M M mA A 4, 5 4, 5 3 2 SINGLE CONVERT TIMING DIAGRAM (STAND-ALONE MODE) CONV tCNV 030598 10/12 DS1720 AC ELECTRICAL CHARACTERISTICS PARAMETER Temperature Conversion Time Data to CLK Setup CLK to Data Hold CLK to Data Delay CLK Low Time CLK High Time CLK Frequency CLK Rise and Fall RST to CLK Setup CLK to RST Hold RST Inactive Time CLK High to I/O High-Z RST Low to I/O High-Z Convert Pulse Width NV Write Cycle Time SYMBOL TTC tDC tCDH tCDD tCL tCH fCLK tR, tF tCC tCCH tCWH tCDZ tRDZ tCNV tWR 250 ns 10 100 40 125 285 285 DC 35 40 MIN TYP 400 (-55C to +125C; VDD=2.7V to 5.5V) MAX 1000 UNITS ms ns ns 100 ns ns ns 1.75 500 MHz ns ns ns ns 50 50 500 ms 50 ms 12 ns ns 6 6 6, 9 6 6 6 6 6, 7, 8 6 6 6 NOTES AC ELECTRICAL CHARACTERISTICS PARAMETER Input Capacitance I/O Capacitance SYMBOL CI CI/O MIN TYP 5 10 (-55C to +125C; VDD=2.7V to 5.5V) MAX UNITS pF pF NOTES NOTES: 1. All voltages are referenced to ground. 2. Logic one voltages are specified at a source current of 1 mA. 3. Logic zero voltages are specified at a sink current of 4 mA. 4. ICC specified with DQ pin open and CLK pin at VDD. 5. ICC specified with VCC at 3.3V and RST=GND. 6. Measured at VIH = 2.0V or VIL = 0.6V. 7. Measured at VOH = 2.4V or VOL = 0.4V. 8. Load capacitance = 50 pF. 9. tCWH must be 10 ms minimum following any write command that involves the E2 memory. 10. See typical curve for specification limits outside 0C to 85C range. 11. Thermometer error reflects temperature accuracy as tested during calibration. 12. Writing to the nonvolatile memory should only take place in the 0C to 70C temperature range. 030598 11/12 DS1720 DS1720 TYPICAL THERMOMETER ERROR DS1720 TYPICAL THERMOMETER ERROR 4 3 UPPER SPEC LIMIT 2 1 TYPICAL ERROR THERMOMETER ERROR (C) -55 -25 -10 5 20 45 60 75 90 100 125 -1 -2 -3 LOWER SPEC LIMIT -4 -5 -6 AMBIENT TEMPERATURE (C) 030598 12/12 |
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