DS1621 Digital Thermometer and Thermostat www.dalsemi.com PIN ASSIGNMENT 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 (2byte 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) SDA 1 8 VDD SCL 2 7 A0 TOUT 3 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 SCL GND TOUT A0 A1 A2 VDD - 2-Wire Serial Data Input/Output - 2-Wire Serial Clock - Ground - Thermostat Output Signal - Chip Address Input - Chip Address Input - Chip Address Input - 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. 1 of 16 102299 DS1621 DETAILED PIN DESCRIPTION Table 1 PIN 1 2 3 SYMBOL SDA SCL TOUT 4 5 6 7 8 GND A2 A1 A0 VDD DESCRIPTION Data input/output pin for 2-wire serial communication port. Clock input/output pin for 2-wire serial communication port. Thermostat output. Active when temperature exceeds TH; will reset when temperature falls below TL. Ground pin. Address input pin. Address input pin. Address input pin. Supply voltage input power pin. (2.7V – 5.5V) OPERATION Measuring Temperature A block diagram of the DS1621 is shown in Figure 1. The DS1621 measures temperatures through the use of an onboard proprietary temperature measurement technique. A block diagram of the temperature measurement circuitry is shown in Figure 2. The DS1621 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 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, both the value of the counter and the number of counts per °C (the value of the slope accumulator) at a given temperature must be known. This calculation is done inside the DS1621 to provide 0.5°C resolution. The temperature reading is provided in a 9–bit, two’s complement reading by issuing the READ TEMPERATURE command. Table 2 describes the exact relationship of output data to measured temperature. The data is transmitted through the 2–wire serial interface, MSB first. The DS1621 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. 2 of 16 102299 DS1621 DS1621 FUNCTIONAL BLOCK DIAGRAM Figure 1 STATUS REGISTER & CONTROL LOGIC SCL SDA TEMPERATURE SENSOR ADDRESS AND I/O CONTROL HIGH TEMP TRIGGER, TH A0 A1 A2 LOW TEMP TRIGGER, TL DIGITAL COMPARATOR/LOGIC 3 of 16 TOUT 102299 DS1621 TEMPERATURE MEASURING CIRCUITRY Figure 2 SLOPE ACCUMULATOR PRESET COMPARE LOW TEMPERATURE COEFFICIENT OSCILLATOR COUNTER SET/CLEAR LSB PRESET INC TEMPERATURE REGISTER =0 HIGH TEMPERATURE COEFFICIENT OSCILLATOR COUNTER STOP =0 TEMPERATURE/DATA RELATIONSHIPS Table 2 TEMPERATURE DIGITAL OUTPUT (Binary) 01111101 00000000 00011001 00000000 00000001 00000000 00000000 00000000 11111111 10000000 11100111 00000000 11001001 00000000 +125°C +25°C +½°C +0°C -½°C -25°C -55°C DIGITAL OUTPUT (Hex) 7B00h 1900h 0080h 0000h FF80h E700h C900h Since data is transmitted over the 2–wire bus MSB first, temperature data may be written to/read from the DS1621 as either a single byte (with temperature resolution of 1°C) or as two bytes. The second byte would contain the value of the least significant (0.5°C) bit of the temperature reading as shown in Table 1. Note that the remaining 7 bits of this byte are set to all "0"s. Temperature is represented in the DS1621 in terms of a ½°C LSB, yielding the following 9–bit format: MSB 1 LSB 1 1 0 0 1 1 1 0 0 T = -25°C 4 of 16 0 0 0 0 0 0 102299 DS1621 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. 5 of 16 102299 DS1621 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 removing power from the device. This feature provides a method of determining if the DS1621 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 removing power from the device. This feature provides a method of determining if the DS1621 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. POL = Output Polarity Bit. “1” = active high, “0” = active low. This bit is nonvolatile. 1SHOT = One Shot Mode. If 1SHOT is “1”, the DS1621 will perform one temperature conversion upon receipt of the Start Convert T protocol. If 1SHOT is “0”, the DS1621 will continuously perform temperature conversions. This bit is nonvolatile. For typical thermostat operation the DS1621 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 output (TOUT) will remain in the state it was in after the last valid temperature conversion cycle when operating in one–shot mode. 2–WIRE SERIAL DATA BUS The DS1621 supports a bidirectional 2–wire bus and data transmission protocol. A device that sends data onto the bus is defined as a transmitter, and a device receiving data as a receiver. The device that controls the message is called a “master." The devices that are controlled by the master are “slaves." The bus must be controlled by a master device which generates the serial clock (SCL), controls the bus access, and generates the START and STOP conditions. The DS1621 operates as a slave on the 2–wire bus. Connections to the bus are made via the open–drain I/O lines SDA and SCL. The following bus protocol has been defined (See Figure 4): • Data transfer may be initiated only when the bus is not busy. • During data transfer, the data line must remain stable whenever the clock line is HIGH. Changes in the data line while the clock line is high will be interpreted as control signals. Accordingly, the following bus conditions have been defined: Bus not busy: Both data and clock lines remain HIGH. Start data transfer: A change in the state of the data line, from HIGH to LOW, while the clock is HIGH, defines a START condition. Stop data transfer: A change in the state of the data line, from LOW to HIGH, while the clock line is HIGH, defines the STOP condition. 6 of 16 102299 DS1621 Data valid: The state of the data line represents valid data when, after a START condition, the data line is stable for the duration of the HIGH period of the clock signal. The data on the line must be changed during the LOW period of the clock signal. There is one clock pulse per bit of data. Each data transfer is initiated with a START condition and terminated with a STOP condition. The number of data bytes transferred between START and STOP conditions is not limited and is determined by the master device. The information is transferred byte–wise and each receiver acknowledges with a ninth–bit. Within the bus specifications a regular mode (100 kHz clock rate) and a fast mode (400 kHz clock rate) are defined. The DS1621 works in both modes. Acknowledge: Each receiving device, when addressed, is obliged to generate an acknowledge after the reception of each byte. The master device must generate an extra clock pulse which is associated with this acknowledge bit. A device that acknowledges must pull down the SDA line during the acknowledge clock pulse in such a way that the SDA line is stable LOW during the HIGH period of the acknowledge related clock pulse. Of course, setup and hold times must be taken into account. A master must signal an end of data to the slave by not generating an acknowledge bit on the last byte that has been clocked out of the slave. In this case, the slave must leave the data line HIGH to enable the master to generate the STOP condition. DATA TRANSFER ON 2–WIRE SERIAL BUS Figure 4 Figure 4 details how data transfer is accomplished on the 2–wire bus. Depending upon the state of the R/W bit, two types of data transfer are possible: 1. Data transfer from a master transmitter to a slave receiver. The first byte transmitted by the master is the slave address. Next follows a number of data bytes. The slave returns an acknowledge bit after each received byte. 2. Data transfer from a slave transmitter to a master receiver. The first byte, the slave address, is transmitted by the master. The slave then returns an acknowledge bit. Next follows a number of data bytes transmitted by the slave to the master. The master returns an acknowledge bit after all received bytes other than the last byte. At the end of the last received byte, a ‘not acknowledge’ is returned. 7 of 16 102299 DS1621 The master device generates all of the serial clock pulses and the START and STOP conditions. A transfer is ended with a STOP condition or with a repeated START condition. Since a repeated START condition is also the beginning of the next serial transfer, the bus will not be released. The DS1621 may operate in the following two modes: 1. Slave receiver mode: Serial data and clock are received through SDA and SCL. After each byte is received an acknowledge bit is transmitted. START and STOP conditions are recognized as the beginning and end of a serial transfer. Address recognition is performed by hardware after reception of the slave address and direction bit. 2. Slave transmitter mode: The first byte is received and handled as in the slave receiver mode. However, in this mode the direction bit will indicate that the transfer direction is reversed. Serial data is transmitted on SDA by the DS1621 while the serial clock is input on SCL. START and STOP conditions are recognized as the beginning and end of a serial transfer. SLAVE ADDRESS A control byte is the first byte received following the START condition from the master device. The control byte consists of a 4-bit control code; for the DS1621, this is set as 1001 binary for read and write operations. The next 3 bits of the control byte are the device select bits (A2, A1, A0). They are used by the master device to select which of eight devices are to be accessed. These bits are in effect the 3 least significant bits of the slave address. The last bit of the control byte (R/ W ) defines the operation to be performed. When set to a “1” a read operation is selected, when set to a “0” a write operation is selected. Following the START condition the DS1621 monitors the SDA bus checking the device type identifier being transmitted. Upon receiving the 1001 code and appropriate device select bits, the slave device outputs an acknowledge signal on the SDA line. 8 of 16 102299 DS1621 2-WIRE SERIAL COMMUNICATION WITH DS1621 Figure 5 9 of 16 102299 DS1621 COMMAND SET Data and control information is read from and written to the DS1621 in the format shown in Figure 5. To write to the DS1621, the master will issue the slave address of the DS1621 and the R/ W bit will be set to “0”. After receiving an acknowledge, the bus master provides a command protocol. After receiving this protocol, the DS1621 will issue an acknowledge and then the master may send data to the DS1621. If the DS1621 is to be read, the master must send the command protocol as before and then issue a repeated START condition and the control byte again, this time with the R/ W bit set to “1” to allow reading of the data from the DS1621. The command set for the DS1621 as shown in Table 3 is as follows: Read Temperature [AAh] This command reads the last temperature conversion result. The DS1621 will send 2 bytes, in the format described earlier, which are the contents of this register. Access TH [A1h] If R/ W is “0” this command writes to the TH (HIGH TEMPERATURE) register. After issuing this command, the next 2 bytes written to the DS1621, in the same format as described for reading temperature, will set the high temperature threshold for operation of the TOUT output. If R/ W is “1” the value stored in this register is read back. Access TL [A2h] If R/ W is “0” this command writes to the TL (LOW TEMPERATURE) register. After issuing this command, the next 2 bytes written to the DS1621, in the same format as described for reading temperature, will set the high temperature threshold for operation of the TOUT output. If R/ W is “1” the value stored in this register is read back. Access Config [ACh] If R/ W is “0” this command writes to the configuration register. After issuing this command, the next data byte is the value to be written into the configuration register. If R/ W is “1” the next data byte read is the value stored in the configuration register. Read Counter [A8h] This command reads the value of the counter byte. This command is valid only if R/ W is “1”. Read Slope [A9h] This command reads the value of the slope counter byte from the DS1621. This command is valid only if R/ W is “1”. 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 DS1621 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 DS1621 in continuous conversion mode. After issuing this command, the current temperature 10 of 16 102299 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 2-WIRE BUS DATA AFTER ISSUING PROTOCOL INSTRUCTION DESCRIPTION PROTOCOL TEMPERATURE CONVERSION COMMANDS Read Temperature Read last converted temperature AAh <read 2 bytes data> value from temperature register. Read Counter Reads value of count remaining A8h <read data> from counter. Read Slope Reads value of the slope A9h <read data> accumulator. Start Convert T Initiates temperature EEh idle conversion. Stop Convert T Halts temperature conversion. 22h idle THERMOSTAT COMMANDS Access TH Reads or writes high A1h <write data> temperature limit value into TH register. Access TL Reads or writes low A2h <write data> temperature limit value into TL register. Access Config 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. 11 of 16 102299 DS1621 MEMORY FUNCTION EXAMPLE Example: Bus master sets up DS1621 for continuous conversion and thermostatic function. BUS MASTER MODE TX TX RX TX RX TX DS1621 MODE RX RX TX RX TX RX DATA (MSB FIRST) START <address,0> ACK ACh ACK 02h RX TX TX RX TX RX TX TX RX RX TX RX TX RX ACK START <address,0> ACK A1h ACK 28h RX TX TX RX ACK 00h RX TX TX RX TX RX TX TX RX RX TX RX TX RX ACK START <address,0> ACK A2h ACK 0Ah RX TX TX RX ACK 00h RX TX TX RX TX RX TX TX RX RX TX RX TX RX ACK START <address,0> ACK EEh ACK STOP COMMENTS Bus Master initiates a START condition. Bus Master sends DS1621 address; R/ W = 0. DS1621 generates acknowledge bit. Bus Master sends Access Config command protocol. DS1621 generates acknowledge bit. Bus Master sets up DS1621 for output polarity active high, continuous conversion. DS1621 generates acknowledge bit. Bus Master generates a repeated START condition. Bus Master sends DS1621 address; R/ W = 0. DS1621 generates acknowledge bit. Bus Master sends Access TH command. DS1621 generates acknowledge bit. Bus Master sends first byte of data for TH limit of +40°C. DS1621 generates acknowledge bit. Bus Master sends second byte of data for TH limit of +40°C. DS1621 generates acknowledge bit. Bus Master generates a repeated START condition. Bus Master sends DS1621 address; R/ W = 0. DS1621 generates acknowledge bit. Bus Master sends Access TL command. DS1621 generates acknowledge bit. Bus Master sends first byte of data for TL limit of +10°C. DS1621 generates acknowledge bit. Bus Master sends second byte of data for TL limit of +10°C. DS1621 generates acknowledge bit. Bus Master generates a repeated START condition. Bus Master sends DS1621 address; R/ W = 0. DS1621 generates acknowledge bit. Bus Master sends Start Convert T command protocol. DS1621 generates acknowledge bit. Bus Master initiates STOP condition. 12 of 16 102299 DS1621 ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature –0.5V to +7.0V –55°C to +125°C –55°C to +125°C 260°C 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. RECOMMENDED DC OPERATING CONDITIONS PARAMETER Supply Voltage SYMBOL VDD MIN 2.7 DC ELECTRICAL CHARACTERISTICS PARAMETER Thermometer Error Low Level Input Voltage High Level Input Voltage Pulse width of spikes which must be suppressed by the input filter Low Level Output Voltage SYMBOL TERR Active Supply Current Standby Supply Current Thermostat Output (TOUT) Output Voltage MAX 5.5 UNITS V NOTES 1 (-55°C to +125°C; VDD=2.7V to 5.5V) MIN TYP MAX ±½ UNITS °C NOTES 11 See Typical Curve VIL 0.5 0.3 VDD V VIH 0.7 VDD VDD+0.5 V tSP Fast Mode 0 50 ns VOL1 3 mA Sink Current 6 mA Sink Current 0.4<VI/O<0.9VDD 0 0.4 V 0 0.6 V -10 10 µA 10 pF 1000 400 100 µA 3, 4 1 µA 3, 4 0.4 V V VOL2 Input Current each I/O Pin I/O Capacitance CONDITION 0°C to 70°C -55°C to + 0°C and 70°C to 125°C TYP CI/O ICC Temperature Conversion E2 Write Communication Only ISTBY VOH VOL 1 mA Source 4 mA Sink 13 of 16 2.4 2 102299 DS1621 AC ELECTRICAL CHARACTERISTICS PARAMETER Temperature Conversion Time NV Write Cycle Time SCL Clock Frequency Bus Free Time Between a STOP and START Condition Hold Time (Repeated) START Condition Low Period of SCL Clock High Period of SCL Clock Setup Time for a Repeated START Condition Data Hold Time Data Setup Time SYMBOL TTC CONDITION tWR 0°C to 70°C fSCL Fast Mode Standard Mode Fast Mode Standard Mode 0 0 1.3 4.7 tHD:STA Fast Mode Standard Mode 0.6 4.0 µs TLOW Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode 1.3 4.7 0.6 4.0 0.6 4.7 µs Fast Mode Standard Mode Fast Mode Standard Mode Fast Mode Standard Mode 0 0 100 250 20+0.1CB tBUF THIGH tSU:STA tHD:DAT tSU:DAT Rise Time of Both tR SDA and SCL Signals Fall Time of both tF Fast Mode SDA and SCL Standard Mode Signals Setup time for tSU:STO Fast Mode STOP Condition Standard Mode Capacitative Load Cb for each Bus Line All values referred to VIH=0.9 VDD and VIL=0.1 VDD. AC ELECTRICAL CHARACTERISTICS PARAMETER Input Capacitance (-55°C to +125°C; VDD=2.7V to 5.5V) SYMBOL CI MIN 14 of 16 MIN TYP 0.4 MAX 1 UNITS s NOTES 10 50 ms 10 400 100 KHz µs 5 µs µs 0.9 20+0.1CB µs 6, 7 ns 8 300 1000 ns 9 300 300 ns 9 0.6 4.0 µs 400 pF (-55°C to +125°C; VDD=2.7V to 5.5V) TYP 5 MAX UNITS pF NOTES 102299 DS1621 NOTES: 1. All voltages are referenced to ground. 2. I/O pins of fast mode devices must not obstruct the SDA and SCL lines if VDD is switched off. 3. ICC specified with TOUT pin open. 4. ICC specified with VCC at 5.0V and SDA, SCL = 5.0V, 0°C to 70°C. 5. After this period, the first clock pulse is generated. 6. A device must internally provide a hold time of at least 300 ns for the SDA signal (referred to the VIH MIN of the SCL signal) in order to bridge the undefined region of the falling edge of SCL. 7. The maximum tHD:DAT has only to be met if the device does not stretch the LOW period (tLOW) of the SCL signal. 8. A fast mode device can be used in a standard mode system, but the requirement tSU:DAT >250 ns must then be met. This will automatically be the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit to the SDA line tRMAX+tSU:DAT = 1000+250 = 1250 ns before the SCL line is released. 9. Cb – total capacitance of one bus line in pF. 10. Writing to the nonvolatile memory should only take place in the 0°C to 70°C temperature range. 11. See typical curve for specification limits outside 0°C to 70°C range. Thermometer error reflects sensor accuracy as tested during calibration. TIMING DIAGRAM 15 of 16 102299 DS1621 TYPICAL PERFORMANCE CURVE DS1621 DIGITAL THERMOMETER AND THERMOSTAT TEMPERATURE READING ERROR TEMPERATURE (deg. C) 16 of 16 102299