2C Accurate, Micropower Digital Temperature Sensor ADT7302 FUNCTIONAL BLOCK DIAGRAM 13-bit temperature-to-digital converter -40C to +125C operating temperature range 2C accuracy 0.03125C temperature resolution Shutdown current of 1 A Power dissipation of 0.631 mW at VDD = 3.3 V SPI- and DSP-compatible serial interface Shutdown mode Space-saving SOT-23 and MSOP packages Compatible with AD7814 BAND GAP TEMPERATURE SENSOR 13-BIT ANALOG/DIGITAL CONVERTER GND VDD TEMPERATURE VALUE REGISTER ADT7302 SERIAL BUS INTERFACE CS SCLK DIN DOUT APPLICATIONS 04662-001 FEATURES Figure 1. Medical equipment Automotive Environmental controls Oil temperature Hydraulic systems Cell phones Hard disk drives Personal computers Electronic test equipment Office equipment Domestic appliances Process control GENERAL DESCRIPTION PRODUCT HIGHLIGHTS The ADT7302 is a complete temperature monitoring system available in SOT-23 and MSOP packages. It contains a band gap temperature sensor and a 13-bit ADC to monitor and digitize the temperature reading to a resolution of 0.03125C. 1. On-chip temperature sensor that allows an accurate measurement of the ambient temperature. The measurable temperature range is -40C to +125C. 2. Supply voltage of 2.7 V to 5.25 V. 3. Space-saving 6-lead SOT-23 and 8-lead MSOP packages. 4. Maximum temperature accuracy of 2C. 5. 13-bit temperature reading to 0.03125C resolution. 6. Shutdown mode that reduces the power consumption to 4.88 W with VDD = 3.3 V at 1 SPS. 7. Compatible with AD7814. The ADT7302 has a flexible serial interface that allows easy interfacing to most microcontrollers. The interface is compatible with SPI(R), QSPITM, and MICROWIRETM protocols as well as DSPs. The part features a standby mode that is controlled via the serial interface. The ADT7302's wide supply voltage range, low supply current, and SPI-compatible interface make it ideal for a variety of applications, including PCs, office equipment, automotive, and domestic appliances. Rev. B Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2005-2011 Analog Devices, Inc. All rights reserved. ADT7302 TABLE OF CONTENTS Features .............................................................................................. 1 Typical Performance Characteristics ..............................................7 Applications ....................................................................................... 1 Theory of Operation .........................................................................9 Functional Block Diagram .............................................................. 1 Converter Details ..........................................................................9 General Description ......................................................................... 1 Temperature Value Register .........................................................9 Product Highlights ........................................................................... 1 Serial Interface ............................................................................ 10 Revision History ............................................................................... 2 Applications Information .............................................................. 12 Specifications..................................................................................... 3 Microprocessor Interfacing ....................................................... 12 Timing Characteristics ................................................................ 4 Mounting the ADT7302 ............................................................ 14 Absolute Maximum Ratings ............................................................ 5 Supply Decoupling ..................................................................... 14 ESD Caution .................................................................................. 5 Outline Dimensions ....................................................................... 15 Pin Configurations and Function Descriptions ........................... 6 Ordering Guide .......................................................................... 15 REVISION HISTORY 6/11--Rev. A to Rev. B Changed Temperature Conversion Time from 800 s to 1.2 ms.. 3 Changed Temperature Conversion Time in Converter Details Section .................................................................................. 9 3/10--Rev. 0 to Rev. A Change to Autoconversion Update Rate Parameter, Table 1 ...... 3 Changes to Converter Details Section ........................................... 9 Updated Outline Dimensions ....................................................... 15 10/05--Revision 0: Initial Version Rev. B | Page 2 of 16 ADT7302 SPECIFICATIONS TA = TMIN to TMAX, VDD = 2.7 V to 5.25 V, unless otherwise noted. All specifications are for -40C to +125C, unless otherwise stated. Table 1. Parameter TEMPERATURE SENSOR AND ADC Accuracy Temperature Resolution Autoconversion Update Rate, tR Temperature Conversion Time Thermal Time Constant 1 SUPPLIES Supply Voltage Supply Current Normal Mode Min Max Unit 1 2 2.5 3 C C C C sec ms sec 0.03125 1.5 1.2 2 2.7 Power Dissipation Normal Mode (Average) Shutdown Mode (Average)2 1 SPS 10 SPS 100 SPS Test Conditions/Comments VDD = 3.3 V (10%) and 5 V (5%) TA = 0C to 70C TA = -20C to +85C TA = -40C to +125C Temperature measurement every 1.5 second 5.25 V For specified performance 2.2 300 2.2 400 1 2 20 mA A mA A A A A VDD = 3.3 V, powered up and converting VDD = 3.3 V, powered up and not converting VDD = 5 V, powered up and converting VDD = 5 V, powered up and not converting VDD = 3.3 V, TA = 0C to 70C VDD = 5 V, TA = 0C to 70C VDD = 2.7 V to 5.25 V, TA = -40C to +125C 631 1.41 W mW VDD = 3.3 V, autoconversion update, tR VDD = 5 V, autoconversion update, tR 4.88 7.4 42.9 65 423 641 W W W W W W VDD = 3.3 V VDD = 5 V VDD = 3.3 V VDD = 5 V VDD = 3.3 V VDD = 5 V 0.8 1 10 V V A pF VIN = 0 V to VDD All digital inputs 0.4 50 V pF 1.6 190 1.6 280 0.2 0.4 Shutdown Mode DIGITAL INPUT3 Input High Voltage, VIH Input Low Voltage, VIL Input Current, IIN Input Capacitance, CIN DIGITAL OUTPUT3 Output High Voltage, VOH Output Low Voltage, VOL Output Capacitance, COUT Typ 2.5 VDD - 0.3 V 1 ISOURCE = ISINK = 200 A IOL = 200 A The thermal time constant is the time it takes for a temperature delta to change to 63.2% of its final value. For example, if the ADT7302 experiences a thermal shock from 0C to 100C, it typically takes 2 seconds for the ADT7302 to reach 63.2C. The ADT7302 is taken out of shutdown mode and a temperature conversion is immediately performed after this write operation. When the temperature conversion is complete, the ADT7302 is put back into shutdown mode. 3 Guaranteed by design and characterization, not production tested. 2 Rev. B | Page 3 of 16 ADT7302 TIMING CHARACTERISTICS Guaranteed by design and characterization, not production tested. All input signals are specified with tR = tF = 5 ns (10% to 90% of VDD) and timed from a voltage level of 1.6 V. TA = TMIN to TMAX, VDD = 2.7 V to 5.25 V, unless otherwise noted. Table 2. Parameter1 t1 t2 t3 t42 t5 t6 t7 t8 2 2 Unit ns min ns min ns min ns max ns min ns min ns min ns max Comments CS to SCLK setup time SCLK high pulse width SCLK low pulse width Data access time after SCLK falling edge Data setup time prior to SCLK rising edge Data hold time after SCLK rising edge CS to SCLK hold time CS to DOUT high impedance See Figure 14 for the SPI timing diagram. Measured with the load circuit of Figure 2. 200A TO OUTPUT PIN IOL 1.6V CL 50pF 200A IOH 04662-002 1 Limit 5 25 25 35 20 5 5 40 Figure 2. Load Circuit for Data Access Time and Bus Relinquish Time Rev. B | Page 4 of 16 ADT7302 ABSOLUTE MAXIMUM RATINGS Table 3. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Rating -0.3 V to +7 V -0.3 V to VDD + 0.3 V -0.3 V to VDD + 0.3 V -40C to +125C -65C to +150C 150C 1.2 2 205.9C/W 43.74C/W 220C (0C/5C) 10 sec to 20 sec 3C/sec max -6C/sec 6 minutes max 260C (0C) 20 sec to 40 sec 3C/sec max -6C/sec max 8 minutes max SOT-23 0.6 MSOP 0.4 0.2 0 TEMPERATURE (C) Figure 3. Maximum Power Dissipation vs. Temperature ESD CAUTION 1 Values relate to the package being used on a standard 2-layer PCB. Refer to Figure 3 for a plot of maximum power dissipation vs. ambient temperature (TA). 2 TA = ambient temperature. 3 Junction-to-case resistance is applicable to components featuring a preferential flow direction, for example, components mounted on a heat sink. Junction-to-ambient resistance is more useful for air-cooled, PCBmounted components. Rev. B | Page 5 of 16 04662-003 WMAX = (TJ max - TA2)/JA 0.8 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 190.4C/W 1.0 -40 WMAX = (TJ max - TA )/JA MAXIMUM POWER DISSIPATION (W) Parameter VDD to GND Digital Input Voltage to GND Digital Output Voltage to GND Operating Temperature Range Storage Temperature Range Junction Temperature 6-Lead SOT-23 (RJ-6) Power Dissipation 1 Thermal Impedance JA, Junction-to-Ambient (Still Air) 8-Lead MSOP (RM-8) Power Dissipation1 Thermal Impedance 3 JA, Junction-to-Ambient (Still Air) JC, Junction-to-Case IR Reflow Soldering Peak Temperature Time at Peak Temperature Ramp-Up Rate Ramp-Down Rate Time 25C to Peak Temperature IR Reflow Soldering--Pb-Free Package Peak Temperature Time at Peak Temperature Ramp-Up Rate Ramp-Down Rate Time 25C to Peak Temperature ADT7302 GND 1 6 NC 1 DOUT DOUT 2 ADT7302 TOP VIEW (Not to Scale) VDD 3 5 4 CS 3 CS SCLK SCLK 4 04662-004 DIN 2 ADT7302 TOP VIEW (Not to Scale) 8 NC 7 GND 6 DIN 5 VDD NC = NO CONNECT Figure 4. SOT-23 Pin Configuration 04662-005 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS Figure 5. MSOP Pin Configuration Table 4. Pin Function Descriptions SOT-23 Pin No. 1 2 MSOP Pin No. 7 6 Mnemonic GND DIN 3 4 5 4 VDD SCLK 5 3 CS 6 2 DOUT 1, 8 NC Description Analog and Digital Ground. Serial Data Input. Serial data to be loaded to the part's control register is provided on this input. Data is clocked into the control register on the rising edge of SCLK. Positive Supply Voltage, 2.7 V to 5.25 V. Serial Clock Input. This is the clock input for the serial port. The serial clock is used to clock data out of the ADT7302's temperature value register and to clock data into the ADT7302's control register. Chip Select Input. Logic input. The device is selected when this input is low. The SCLK input is disabled when this pin is high. Serial Data Output. Logic output. Data is clocked out of the temperature value register at this pin. Data is clocked out on the falling edge of SCLK. No Connect. Rev. B | Page 6 of 16 ADT7302 TYPICAL PERFORMANCE CHARACTERISTICS 500 215 450 210 5.5V SHUTDOWN CURRENT (nA) 200 195 190 3.3V 185 180 400 350 300 250 200 150 04662-006 100 175 170 -45 5 55 TEMPERATURE (C) 105 04662-008 CURRENT (A) 205 50 0 2.5 155 Figure 6. Average Operating Supply Current vs. Temperature 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 5.5 6.0 Figure 8. Shutdown Current vs. Supply Voltage @ 30C 205 20 200 15 TEMPERATURE ERROR (C) 195 190 185 180 5 0 -5 04662-007 175 2.5 10 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 5.5 -10 10k 6.0 Figure 7. Average Operating Supply Current vs. Supply Voltage @ 30C Rev. B | Page 7 of 16 04662-009 CURRENT (A) 250mV p-p RIPPLE @ VDD = 5V 100k 1M FREQUENCY (Hz) 10M 100M Figure 9. Temperature Accuracy vs. Supply Ripple Frequency ADT7302 140 4 3 100 80 60 40 0 0 5 10 15 20 25 30 TIME (SEC) 35 40 45 UPPER TEMPERATURE ERROR LIMIT 1 0 -1 -2 LOWER TEMPERATURE ERROR LIMIT -20 0 20 40 60 04662-011 TEMPERATURE ERROR (C) 2 -4 -40 80 0 -1 -2 LOWER TEMPERATURE ERROR LIMIT -20 0 20 40 60 TEMPERATURE (C) 80 100 Figure 12. Temperature Accuracy @ 5 V 4 -3 1 -4 -40 50 Figure 10. Response to Thermal Shock 3 2 -3 04662-010 20 UPPER TEMPERATURE ERROR LIMIT 04662-012 TEMPERATURE ERROR (C) TEMPERATURE (C) 120 100 120 TEMPERATURE (C) Figure 11. Temperature Accuracy @ 3.3 V Rev. B | Page 8 of 16 120 ADT7302 THEORY OF OPERATION The ADT7302 is a 13-bit digital temperature sensor with a 14th bit that acts as a sign bit. The part houses an on-chip temperature sensor, a 13-bit ADC, a reference circuit, and serial interface logic functions in SOT-23 and MSOP packages. The ADC section consists of a conventional successive approximation converter based around a capacitor DAC. The parts can run on a 2.7 V to 5.25 V power supply. The on-chip temperature sensor allows an accurate measurement of the ambient device temperature to be made. The specified measurement range of the ADT7302 is -40C to +125C. The structural integrity of the device can start to deteriorate when continuously operated at absolute maximum voltage and temperature specifications. CONVERTER DETAILS The conversion clock for the part is internally generated. No external clock is required except when reading from and writing to the serial port. In normal mode, an internal clock oscillator runs an automatic conversion sequence. During this automatic conversion sequence, a conversion is initiated every 1.5 second. At this time, the part powers up its analog circuitry and performs a temperature conversion. This temperature conversion typically takes 1.2 ms, after which the analog circuitry of the part automatically shuts down. The analog circuitry powers up again when the 1.5 second timer times out and the next conversion begins. Since the serial interface circuitry never shuts down, the result of the most recent temperature conversion is always available in the serial output register. The ADT7302 can be placed into shutdown mode via the control register. This means that the on-chip oscillator is shut down and no further conversions are initiated until the ADT7302 is taken out of shutdown mode. The ADT7302 can be taken out of shutdown mode by writing all zeros into the control register. The conversion result from the last conversion prior to shutdown can still be read from the ADT7302 even when it is in shutdown mode. In normal conversion mode, the internal clock oscillator is reset after every read or write operation. This causes the device to start a temperature conversion, the result of which is typically available 1.2 ms later. Similarly, when the part is taken out of shutdown mode, the internal clock oscillator is started and a conversion is initiated. The conversion result is available 1.2 ms later, typically. Every result is stored in a buffer register and is only loaded into the temperature value register at the first falling SCLK edge of every serial port activity. Serial port activity does not interfere with the conversion process and every conversion completes its process even during a read operation. A conversion has to be completed before a read occurs, otherwise its result does not get loaded into the temperature value register and instead goes into the buffer register. A new conversion is triggered at the end of each serial port activity except when a conversion is already in progress. TEMPERATURE VALUE REGISTER The temperature value register is a 14-bit read-only register that stores the temperature reading from the ADC in 13-bit twos complement format plus a sign bit. The MSB (DB13) is the sign bit. The ADC can theoretically measure a 255C temperature span. The internal temperature sensor is guaranteed to a low value limit of -40C and a high limit of +125C. The temperature data format is shown in Table 5, which also shows the temperature measurement range of the device (-40C to +125C). A typical performance curve is shown in Figure 11. Table 5. Temperature Data Format Temperature -40C -30C -25C -10C -0.03125C 0C +0.03125C +10C +25C +50C +75C +100C +125C Digital Output DB13...DB0 11, 1011 0000 0000 11, 1100 0100 0000 11, 1100 1110 0000 11, 1110 1100 0000 11, 1111 1111 1111 00, 0000 0000 0000 00, 0000 0000 0001 00, 0001 0100 0000 00, 0011 0010 0000 00, 0110 0100 0000 00, 1001 0110 0000 00, 1100 1000 0000 00, 1111 1010 0000 Temperature Conversion Equations Positive Temperature = ADC Code(d)/32 Negative Temperature = (ADC Code(d)1 - 16384)/32 Negative Temperature = (ADC Code(d)2 - 8192)/32 1 2 ADC Code uses all 14 bits of the data byte, including the sign bit. DB13 (the sign bit) is removed from the ADC code. Rev. B | Page 9 of 16 ADT7302 DIGITAL OUTPUT 01, 0010, 1100, 0000 00, 1001, 0110, 0000 75C 00, 0000, 0000, 0001 -0.03125C 11, 1111, 1111, 1111 -40C -30C TEMPERATURE (C) 150C 04662-013 11, 1100, 0100, 0000 11, 1011, 0000, 0000 Figure 13. Temperature to Digital Transfer Function CS t1 SCLK t7 t2 1 2 3 15 4 16 t3 t8 t4 LEADING ZEROS DB13 t5 DIN DB12 DB0 DB1 DB0 t6 04662-014 DOUT POWERDOWN Figure 14. Serial Interface Timing Diagram SERIAL INTERFACE The serial interface on the ADT7302 consists of four wires: CS, SCLK, DIN, and DOUT. The interface can be operated in 3-wire mode with DIN tied to ground, in which case the interface has read-only capability, with data being read from the data register via the DOUT line. It is advisable to always use CS to create a communications window, as shown in Figure 13, because this improves synchronization between the ADT7302 and the master device. The DIN line is used to write the part into standby mode, if required. The CS line is used to select the device when more than one device is connected to the serial clock and data lines. The part operates in slave mode and requires an externally applied serial clock to the SCLK input to access data from the data register. The serial interface on the ADT7302 allows the part to be interfaced to systems that provide a serial clock synchronized to the serial data, such as the 80C51, 87C51, 68HC11, 68HC05, and PIC16Cxx microcontrollers as well as DSP processors. A read operation from the ADT7302 accesses data from the temperature value register while a write operation to the part writes data to the control register. Read Operation Figure 14 shows the timing diagram for a serial read from the ADT7302. The CS line enables the SCLK input. Thirteen bits of data plus a sign bit are transferred during a read operation. Read operations occur during streams of 16 clock pulses. The first two bits out are leading zeros and the next 14 bits contain the temperature data. If CS remains low and 16 more SCLK cycles are applied, the ADT7302 loops around and outputs the two leading zeros plus the 14 bits of data that are in the temperature value register. When CS returns high, the DOUT line goes into three-state. Data is clocked out onto the DOUT line on the falling edge of SCLK. Rev. B | Page 10 of 16 ADT7302 Write Operation Figure 14 also shows the timing diagram for a serial write to the ADT7302. The write operation takes place at the same time as the read operation. Only the third bit in the data stream provides a user-controlled function. This third bit is the power-down bit, which, when set to 1, puts the ADT7302 into shutdown mode. In addition to the power-down bit, all bits in the input data stream should be 0 to ensure correct operation of the ADT7302. Data is loaded into the control register on the 16th rising SCLK edge; the data takes effect at this time. Therefore, if the part is programmed to go into shutdown, it does so at this point. If CS is brought high before this 16th SCLK edge, the control register is not loaded and the power-down status of the part does not change. Data is clocked into the ADT7302 on the rising edge of SCLK. Rev. B | Page 11 of 16 ADT7302 APPLICATIONS INFORMATION The serial data transfer to and from the ADT7302 requires a 16-bit read operation. Many 8-bit microcontrollers have 8-bit serial ports, and this 16-bit data transfer is handled as two 8-bit transfers. Other microcontrollers and DSP processors transfer 16 bits of data in a serial data operation. In the example, the ADT7302 is connected to the serial port of the 8051. Because the serial interface of the 8051 contains only one data line, the DIN line of the ADT7302 is tied low in Figure 16. For applications that require the ADT7302 power-down feature, the serial interface should be implemented using data port lines on the 8051. This allows a full-duplex serial interface to be implemented. The method involves "bit-banging" a port line to generate a serial clock while using two other port lines to shift data in and out with the fourth port line connecting to CS. Port lines 1.0 through 1.3 (with P1.1 configured as an input) can be used to connect to SCLK, DOUT, DIN, and CS, respectively, to implement this scheme. ADT7302 to MC68HC11 Interface Figure 15 shows an interface between the ADT7302 and the MC68HC11 microcontroller. The MC68HC11 is configured in master mode with its CPOL and CPHA bits set to a Logic 1. When the MC68HC11 is configured like this, its SCLK line idles high between data transfers. Data is transferred to and from the ADT7302 in two 8-bit serial data operations. Figure 15 shows the full (4-wire) interface. PC1 of the MC68HC11 is configured as an output and is used to drive the CS input. MC68HC11* SCLK SCLK DOUT MISO DIN MOSI CS PC1 *ADDITIONAL PINS OMITTED FOR CLARITY 04662-015 ADT7302* 8051* ADT7302* SCLK P1.1 DOUT P1.0 DIN P1.2 CS P1.3 *ADDITIONAL PINS OMITTED FOR CLARITY 04662-016 The ADT7302's serial interface allows easy interface to most microcomputers and microprocessors. Figure 15 through Figure 18 show some typical interface circuits. The serial interface on the ADT7302 consists of four wires: CS, DIN, DOUT, and SCLK. All interface circuits shown use all four interface lines. However, it is possible to operate the interface with three wires. If the application does not require the powerdown facility offered by the ADT7302, the DIN line can be tied low permanently. Thus, the interface can be operated from just three wires: SCLK, CS, and DOUT. Figure 16. ADT7302 to 8051 Interface ADT7302 to PIC16C6x/7x and PIC16F873 Interface Figure 17 shows an interface circuit between the ADT7302 and the PIC16C6x/7x microcontroller. The PIC16C6x/7x synchronous serial port (SSP) is configured as an SPI master with the clock polarity bit set to a Logic 1. In this mode, the serial clock line of the PIC16C6x/7x idles high between data transfers. Data is transferred to and from the ADT7302 in two 8-bit serial data operations. In the example shown, port line RA1 is being used to generate the CS for the ADT7302. ADT7302* Figure 15. ADT7302 to MC68HC11 Interface ADT7302 to 8051 Interface Figure 16 shows an interface circuit between the ADT7302 and the microcontroller. The 8051 is configured in its Mode 0 serial interface mode. The serial clock line of the 8051 (on P3.1) idles high between data transfers. Data is transferred to and from the ADT7302 in two 8-bit serial data operations. The ADT7302 outputs the MSB of its data stream as the first valid bit while the 8051 expects the LSB first. Thus, the data read into the serial buffer needs to be rearranged before the correct data-word from the ADT7302 is available in the accumulator. Rev. B | Page 12 of 16 PIC16C6x/7x* SCLK SCLK DOUT SDO DIN SDI CS RA1 *ADDITIONAL PINS OMITTED FOR CLARITY Figure 17. ADT7302 to PIC16C6x/7x Interface 04662-017 MICROPROCESSOR INTERFACING ADT7302 The following software program shows how to program a PIC16F873 to communicate with the ADT7302. The PIC16F873 is configured as an SPI master with the Port A.1 pin used as CS. Any microchip microcontroller can use this program by simply exchanging the include file for the device that is being used. #include <16F873.h> #device adc=8 #use delay(clock=4000000) #fuses NOWDT,XT, PUT, NOPROTECT, BROWNOUT, LVP #BIT CKP = 0x14.4 #define CS PIN_A1 void main(){ int MSByte,LSByte; long int ADC_Temp_Code; float TempVal,ADC_Temp_Code_dec; setup_spi(spi_master); CKP = 1; //Pic is set up as Master device. //Idle state of clock is high. do{ delay_ms(10); //Allow time for conversions. Output_low(CS); delay_us(10); MSByte = SPI_Read(0); LSByte = SPI_Read(0); //Pull CS low. //CS to SCLK setup time. //The first byte is clocked in. //The second byte is clocked in. delay_us(10); Output_High(CS); //SCLK to CS setup time. //Bring CS high. ADC_Temp_Code = make16(MSByte,LSByte); ADC_Temp_Code_dec = (float)ADC_Temp_Code; //16bit ADC code is stored ADC_Temp_Code. //Convert to float for division. if ((0x2000 & ADC_Temp_Code) == 0x2000) { TempVal = (ADC_Temp_Code_dec - 16384)/32; } else { TempVal = (ADC_Temp_Code_dec/32); } }while(True); //Check sign bit for negative value. //Conversion formula if negative temperature. //Conversion formula if positive temperature. //Temperature value stored in TempVal. } Rev. B | Page 13 of 16 ADT7302 ADT7302 to ADSP-21xx Interface MOUNTING THE ADT7302 Figure 18 shows an interface between the ADT7302 and the ADSP-21xx DSP processor. To ensure correct operation of the interface, the SPORT control register should be set up as follows: The ADT7302 can be used for surface- or air-temperature sensing applications. If the device is cemented to a surface with thermally conductive adhesive, the die temperature will be within about 0.1C of the surface temperature, because of the ADT7302's low power consumption. Care should be taken to insulate the back and leads of the device from the air if the ambient air temperature is different from the surface temperature being measured. TFSW = RFSW = 1, alternate framing INVRFS = INVTFS = 1, active low framing signal DTYPE = 00, right justify data SLEN = 1111, 16-bit data-words ISCLK = 1, internal serial clock TFSR = RFS = 1, frame every word IRFS = 0, RFS configured as input ITFS = 1, TFS configured as output The interface requires an inverter between the SCLK line of the ADSP-21xx and the SCLK input of the ADT7302. The ADSP-21xx has the TFS and RFS of the SPORT tied together, with TFS set as an output and RFS set as an input. The DSP operates in alternate framing mode, and the SPORT control register is set up as described previously. ADSP-21xx* SCLK SCLK DOUT DR DIN DT CS RFS TFS *ADDITIONAL PINS OMITTED FOR CLARITY As with any IC, the ADT7302 and its associated wiring and circuits must be kept free from moisture to prevent leakage and corrosion, particularly in cold conditions where condensation is more likely to occur. Water-resistant varnishes and conformal coatings can be used for protection. The small size of the ADT7302 allows it to be mounted inside sealed metal probes, which provide a safe environment for the device. SUPPLY DECOUPLING 04662-018 ADT7302* The ground pin provides the best thermal path to the die, therefore the temperature of the die is close to that of the printed circuit ground track. Care should be taken to ensure that this is in good thermal contact with the surface being measured. The ADT7302 should be decoupled with a 0.1 F ceramic capacitor between VDD and GND. This is particularly important if the ADT7302 is mounted remote from the power supply. Figure 18. ADT7302 to ADSP-21xx Interface Rev. B | Page 14 of 16 ADT7302 OUTLINE DIMENSIONS 3.00 2.90 2.80 1.70 1.60 1.50 6 5 4 1 2 3 3.00 2.80 2.60 PIN 1 INDICATOR 0.95 BSC 1.90 BSC 1.30 1.15 0.90 0.20 MAX 0.08 MIN 0.15 MAX 0.05 MIN 10 4 0 SEATING PLANE 0.50 MAX 0.30 MIN 0.60 BSC 0.55 0.45 0.35 12-16-2008-A 1.45 MAX 0.95 MIN COMPLIANT TO JEDEC STANDARDS MO-178-AB Figure 19. 6-Lead Small Outline Transistor Package [SOT-23] (RJ-6) Dimensions shown in millimeters 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5.15 4.90 4.65 5 4 PIN 1 IDENTIFIER 0.65 BSC 0.95 0.85 0.75 15 MAX 1.10 MAX 0.40 0.25 6 0 0.80 0.55 0.40 0.23 0.09 COMPLIANT TO JEDEC STANDARDS MO-187-AA 10-07-2009-B 0.15 0.05 COPLANARITY 0.10 Figure 20. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters ORDERING GUIDE Model1 ADT7302ARTZ-500RL7 ADT7302ARTZ-REEL7 ADT7302ARMZ ADT7302ARMZ-REEL7 1 2 Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C Temperature Accuracy2 2C 2C 2C 2C Z = RoHS-Compliant Part. Temperature accuracy is over 0C to 70C temperature range. Rev. B | Page 15 of 16 Package Description 6-Lead SOT-23 6-Lead SOT-23 8-Lead MSOP 8-Lead MSOP Package Option RJ-6 RJ-6 RM-8 RM-8 Branding T02 T02 T02 T02 ADT7302 NOTES (c)2005-2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04662-0-6/11(B) Rev. B | Page 16 of 16