DS1620R Self-Heating Temperature Sensor www.dalsemi.com FEATURES PIN ASSIGNMENT Requires no external components 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 temperature to digital word in 200 ms, typically Thermostatic settings are user-definable and nonvolatile Internal 50-ohm resistor provides self heating 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 16-pin SOIC package DQ 1 16 VDD CLK/CONV 2 15 TH NC 3 14 NC RST 4 13 TL GND 5 12 TCOM RA 6 11 RB NC 7 10 NC NC 8 9 NC DS1620R 16-Pin SOIC (300-MIL) PIN DESCRIPTION DQ - 3-Wire Input/Output CLK/CONV - 3-Wire Clock Input and Standalone Convert Input - 3-Wire Reset Input RST GND - Ground RA - Connection to Internal 50 Resistor RB - Connection to Internal 50 Resistor THIGH - High Temperature Trigger TLOW - Low Temperature Trigger TCOM - High/Low Combination Trigger VDD - Power Supply Voltage (+5V) DESCRIPTION The DS1620R Self-Heating Temperature Sensor provides 9-bit temperature readings which indicate the temperature of the device. The internal 50-ohm resistor acts as the self-heating element. Predictable self- heating characteristics allow users to model temperature rise of active components in their system, allowing monitoring of airflow and other thermal management parameters. With three thermal alarm outputs, the DS1620R can also act as a thermostat. THIGH is driven high if the DS1620R's temperature exceeds a user-defined temperature TH. TLOW is driven high if the DS1620R's temperature falls below 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. 1 of 11 102099 DS1620R User-defined temperature settings are stored in nonvolatile memory, so parts may 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 DS1620R over a simple 3-wire interface. OPERATION - READING TEMPERATURE The DS1620R measures temperatures through the use of an onboard proprietary temperature measurement technique. The temperature reading is provided in a 9-bit, two's complement reading. 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 DS1620R 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. Since data is transmitted over the 3-wire bus LSB first, temperature data may be written to/read from the DS1620R as either a 9-bit word (asserting RST after the 9th (MSB) bit), or as two transfers of 8-bit words, with the most significant 7 bits being ignored or set to 0, as illustrated in Table 1. Note that temperature is represented in the DS1620R 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 T = -25C TEMPERATURE/DATA RELATIONSHIPS Table 1 TEMP +125C +25C 1/2C 0C -1/2C -25C -55C DIGITAL OUTPUT (Binary) 00000000 11111010 00000000 00110010 00000000 00000001 00000000 00000000 00000001 11111111 00000001 11001110 00000001 10010010 DIGITAL OUTPUT (Hex) 00FA 0032h 0001h 0000h 01FFh 01CEh 0192h 2 of 11 102099 DS1620R DS1620R FUNCTIONAL BLOCK DIAGRAM Figure 1 DETAILED PIN DESCRIPTION Table 2 PIN 1 2 SYMBOL DQ CLK/ CONV 3 4 5 6 7 8 9 10 11 12 NC GND RA NC NC NC NC RB TCOM 13 14 15 16 TLOW NC THIGH VDD RST DESCRIPTION Data Input/Output pin for 3-wire communication port. Clock input pin for 3-wire communication port. When the DS1620 is used in a standalone 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. No internal connection Reset input pin for 3-wire communication port. Ground pin Connection to one side of internal 50 ohm resistor No internal connection No internal connection No internal connection No internal connection Connection to one side of internal 50 ohm resistor 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. No internal connection High Temperature Trigger. Goes high when temperature exceeds TH. Supply Voltage. 5V input power pin. OPERATION - THERMOSTAT CONTROLS Three thermally triggered outputs, THIGH, TLOW , and TCOM , are provided to allow the DS1620R to be used as a thermostat, as shown in Figure 2. When the DS1620R'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 DS1620R'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 it when the system temperature returns to tolerance. 3 of 11 102099 DS1620R The TLOW output functions similarly to the THIGH output. When the DS1620R's measured temperature equals or falls below the value stored in the low temperature register, the TLOW output becomes active. TLOW remains active until the DS1620R'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 it 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 exceeds TH, and will stay high until the temperature falls below TL. In this way, any amount of hysteresis may be obtained. THERMOSTAT OUTPUT OPERATION Figure 2 THIGH TLOW TCOM TH TL T(C) OPERATION AND CONTROL The DS1620R 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 DS1620R will use in a particular application and indicates 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 where DONE = Conversion Done bit. 1=Conversion complete, 0=Conversion in progress. In continuous conversion mode, the bit will always be 0. In one-shot mode, this bit should be checked prior to attempting to read the temperature to ensure that the conversion is complete. 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 from the 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 the 4 of 11 102099 DS1620R device. 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. This bit will be a 1 while a write to E2 memory is in progress; 0=nonvolatile memory not busy. A write to E2 memory typically takes 10 ms, but may take up to 50 ms at high temperatures. CPU = 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 DS1620 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. 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 perform temperature conversion. This bit is stored in nonvolatile E2 memory, capable of at least 50,000 writes. For typical thermostat operation, the DS1620R 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 MODE In applications where the DS1620R is used as a simple thermostat, no CPU is required save for programming the temperature limits. Since the temperature limits are nonvolatile, the DS1620R may be programmed prior to insertion in the system. In order to facilitate operation without a CPU, the CLK/CONV pin (pin 2) may 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. 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 con-versions 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. INTERNAL RESISTOR The internal 50-ohm resistor is connected between pins RA and RB. A typical application will use this resistor connected between 5V and ground, providing a 500-mW power dissipation in the resistor. In still air this will cause an approximately 40C temperature rise in the DS1620R. Under other airflow conditions this temperature rise will be different, giving some indication as to how much heat is conducted away from the device by the airflow. The actual temperature rise and thermostat settings for use in a particular system will therefore be dictated by the system's design and protection requirements and must be characterized by the user. Because the DS1620R measures the actual die temperature of the device, its measurement range is from -55C to +125C; however, since the internal resistor is causing a temperature rise in the device, the entire DS1620R is rated for operation in ambient temperatures of -40C to +85C only. 5 of 11 102099 DS1620R 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 3 and 4.) 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. Command bits and data bits are output on the falling edge of the clock and remain valid through the rising edge. When reading data from the DS1620R, 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. Write TH [01h] This command writes to the TH (HIGH TEMPERATURE) register. After issuing this command the next 9 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 the TLOW 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. 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 DS1620R will remain idle. In continuous mode this command will initiate continuous conversions. 6 of 11 102099 DS1620R Stop Convert T [22h] This command stops temperature conversion. No further data is required. This command may be used to halt a DS1620R in continuous conversion mode. After issuing this command the current temperature measurement will be completed and then the DS1620R 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. DS1620R COMMAND SET Table 3 INSTRUCTION Read Temperature Start Convert T Stop Convert T Write TH Write TL Read TH Read TL Write Config Read Config 3-WIRE BUS DATA AFTER ISSUING DESCRIPTION PROTOCOL PROTOCOL TEMPERATURE CONVERSION COMMANDS Reads last converted temperature Aah <read data> value from temperature register. Initiates temperature conversion. Eeh idle Halts temperature conversion. 22h idle THERMOSTAT COMMANDS Writes high temperature limit value 01h <write data> into TH register. Writes low temperature limit value 02h <write data> into TL register. Reads stored value of high A1h <read data> temperature limit from TH register. Reads stored value of low A2h <read data> temperature limit from TL register. Writes configuration data to 0Ch <write data> configuration register. Reads configuration data from ACh <read data> configuration register. NOTES 1 1 2 2 2 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 10 ms at room temperature. After issuing a write command no further writes should be requested for at least 10 ms. 7 of 11 102099 DS1620R FUNCTION EXAMPLE Example: CPU sets up DS1620R for continuous conversion and thermostatic function. DS1620R CPU MODE MODE DATA (LSB FIRST) COMMENTS (3-WIRE) TX RX Raise RST CPU raises RST to initiate transfer. TX RX 0Ch CPU issues Write Config command. TX RX 02h CPU sets DS1620R up for continuous conversion. TX RX Toggle RST CPU drops RST , then brings it high again to initiate new transfer. TX RX 01h CPU issues Write TH command. TX RX 0050h CPU sends data for TH limit of +40C. TX RX Toggle RST CPU drops RST , then brings it high again to initiate new transfer. TX RX 02h CPU issues Write TL command. TX RX 0014h CPU sends data for TL limit of +10C. TX RX CPU drops RST , then brings it high again to Toggle RST initiate new transfer. TX RX A1h CPU issues Read TH command. RX TX 0050h DS1620R sends back stored value of TH for CPU to verify. TX RX Toggle RST CPU drops RST , then brings it high again to initiate new transfer. TX RX A2h CPU issues Read TL command. RX TX 0014h DS1620R sends back stored value of TL for CPU to verify. TX RX Toggle RST CPU drops RST , then brings it high again to initiate new transfer. TX RX EEh CPU issues Start Convert T command. TX RX Drop RST CPU brings RST low, ending transfer. 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. 8 of 11 102099 DS1620R RECOMMENDED DC OPERATING CONDITIONS PARAMETER Supply Logic 1 Logic 0 SYMBOL VDD VIH VIL MIN 4.5 2.0 -0.3 TYP 5.0 DC ELECTRICAL CHARACTERISTICS PARAMETER Thermometer Error SYMBOL TERR MAX 5.5 VCC+0.3 +0.8 Logic 0 Output Logic 1 Output Input Resistance VOL VOH RI Active Supply Current Standby Supply Current ICC ISTBY NOTES 1 1 1 (-55C to +125C; VDD=4.5V to 5.5V) CONDITION 0C to +70C MIN -55C to +0C and 70C to 125C 105C, 1000 hours Long-term Stability UNITS V V V DQ, RST to GND, CLK to VDD 0C to +70C 0C to +70C MAX 1/2 UNITS C NOTES 10 See Typical Curve 0.1 C 0.4 V V M M mA A 2.4 1 1 1 1 3 2 4, 5 4, 5 SINGLE CONVERT TIMING DIAGRAM (STAND-ALONE MODE) tCNV AC ELECTRICAL CHARACTERISTICS PARAMETERS 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 (-55C to +125C; VDD=4.5V to 5.5V) MIN TYP 200 MAX 500 35 40 100 285 285 DC 1.75 500 100 40 125 250 ns 9 of 11 10 50 50 500 ms 50 UNITS ms ns ns ns ns ns MHz ns ns ns ns ns ns NOTES 6 6 6, 7, 8 6 6 6 6 6 6, 9 6 6 ms 102099 DS1620R AC ELECTRICAL CHARACTERISTICS PARAMETER Input Capacitance I/O Capacitance SYMBOL CI CI/O (-55C to +125C; VDD=4.5V to 5.5V) MIN TYP 5 10 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 0 voltages are specified at a sink current of 4 mA. 4. ICC specified with DQ pin open. 5. ICC specified with VCC at 5.0V and RST =GND. 6. Measured at VIH = 2.0V or VIL = 0.8V. 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 70C range. Thermometer error reflects sensor accuracy as tested during calibration. 11. Power rating derates linearly from 70C to 150C. READ DATA TRANSFER Figure 3 10 of 11 102099 DS1620R WRITE DATA TRANSFER Figure 4 TYPICAL PERFORMANCE CURVE DS1620R SELF HEATING TEMPERATURE SENSOR TEMPERATURE READING ERROR 11 of 11 102099