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2C Accurate, Micropower Digital Temperature Sensor ADT7302
FEATURES
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
FUNCTIONAL BLOCK DIAGRAM
BAND GAP TEMPERATURE SENSOR GND 13-BIT ANALOG/DIGITAL CONVERTER VDD
ADT7302
TEMPERATURE VALUE REGISTER
DOUT
APPLICATIONS
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
Figure 1.
GENERAL DESCRIPTION
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. 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.
PRODUCT HIGHLIGHTS
1. On-chip temperature sensor that allows an accurate measurement of the ambient temperature. The measurable temperature range is -40C to +125C. Supply voltage of 2.7 V to 5.25 V. Space-saving 6-lead SOT-23 and 8-lead MSOP packages. Maximum temperature accuracy of 2C. 13-bit temperature reading to 0.03125C resolution. Shutdown mode that reduces the power consumption to 4.88 W with VDD = 3.3 V at 1 SPS. Compatible with AD7814.
2. 3. 4. 5. 6. 7.
Rev. 0
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 Analog Devices, Inc. All rights reserved.
04662-001
SERIAL BUS INTERFACE
CS SCLK DIN
ADT7302 TABLE OF CONTENTS
Specifications..................................................................................... 3 Timing Characteristics ................................................................ 4 Absolute Maximum Ratings............................................................ 5 ESD Caution.................................................................................. 5 Pin Configurations and Function Descriptions ........................... 6 Typical Performance Characteristics ............................................. 7 Theory of Operation ........................................................................ 9 Converter Details.......................................................................... 9 Temperature Value Register .........................................................9 Serial Interface ............................................................................ 10 Applications..................................................................................... 12 Microprocessor Interfacing....................................................... 12 Mounting the ADT7302............................................................ 14 Supply Decoupling ..................................................................... 14 Outline Dimensions ....................................................................... 15 Ordering Guide .......................................................................... 15
REVISION HISTORY
10/05--Revision 0: Initial Version
Rev. 0 | Page 2 of 16
ADT7302 SPECIFICATIONS
TA = TMIN to TMAX, VDD = 2.7 V to 5.25 V, unless otherwise noted. All specifications for -40C to +125C, unless otherwise stated. Table 1.
Parameter TEMPERATURE SENSOR AND ADC Accuracy Min Typ 1 Max 2 2.5 3 Unit C C C C sec s sec V mA A mA A A A A W mW W W W W W W V V A pF 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 second.
Temperature Resolution Autoconversion Update Rate, tR Temperature Conversion Time Thermal Time Constant 1 SUPPLIES Supply Voltage Supply Current Normal Mode
0.03125 1 800 2 2.7 1.6 190 1.6 280 0.2 0.4 5.25 2.2 300 2.2 400 1 2 20
For specified performance. 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. VDD = 3.3 V. Auto conversion update, tR. VDD = 5 V. Auto conversion update, tR. VDD = 3.3 V. VDD = 5 V. VDD = 3.3 V. VDD = 5 V. VDD = 3.3 V. VDD = 5 V.
Shutdown Mode
Power Dissipation Normal Mode (Average) Shutdown Mode (Average) 2 1 SPS 10 SPS 100 SPS DIGITAL INPUT 3 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
1
631 1.41 4.88 7.4 42.9 65 423 641 2.5 0.8 1 10 VDD - 0.3 V 0.4 50
VIN = 0 V to VDD. All digital inputs. ISOURCE = ISINK = 200 A. IOL = 200 A.
V pF
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. Once the temperature conversion is complete, the ADT7302 is put back into shutdown mode. 3 Guaranteed by design and characterization, not production tested.
2
Rev. 0 | 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.
Parameter 1 t1 t2 t3 t4 2 t5 t6 t7 t82
1 2
Limit 5 25 25 35 20 5 5 40
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
IOL
TO OUTPUT PIN
1.6V CL 50pF
04662-002
200A
IOH
Figure 2. Load Circuit for Data Access Time and Bus Relinquish Time
Rev. 0 | Page 4 of 16
ADT7302 ABSOLUTE MAXIMUM RATINGS
Table 3.
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
1
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 WMAX = (TJ max - TA )/JA 190.4C/W WMAX = (TJ max - TA2)/JA 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
2
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
1.2
MAXIMUM POWER DISSIPATION (W)
1.0
0.8
SOT-23
0.6
0.4
MSOP
0.2
TEMPERATURE (C)
Figure 3. Maximum Power Dissipation vs. Temperature
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.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. 0 | Page 5 of 16
04662-003
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
-40
-30 -20 -10
0
ADT7302 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
GND 1
6
DOUT
NC 1 DOUT 2 CS 3
04662-004
8
NC GND DIN VDD
04662-005
ADT7302
DIN 2 VDD 3
5 CS TOP VIEW (Not to Scale) 4
ADT7302
TOP VIEW (Not to Scale)
7 6 5
SCLK 4
SCLK
NC = NO CONNECT
Figure 4. SOT-23 Pin Configuration
Figure 5. MSOP Pin Configuration
Table 4. Pin Function Descriptions
SOT-23 Pin No. 1 2 3 4 5 6 MSOP Pin No. 7 6 5 4 3 2 1, 8 Mnemonic GND DIN VDD SCLK CS DOUT 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. 0 | Page 6 of 16
ADT7302 TYPICAL PERFORMANCE CHARACTERISTICS
215 210 5.5V
SHUTDOWN CURRENT (nA)
500 450 400 350 300 250 200 150 100
04662-006
205 200 195 190 185 180 175 170 -45 5 55 TEMPERATURE (C) 105 3.3V
CURRENT (A)
50 0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 5.5
155
6.0
Figure 6. Average Operating Supply Current vs. Temperature
205
Figure 8. Shutdown Current vs. Supply Voltage @ 30C
20 250mV p-p RIPPLE @ VDD = 5V
200 TEMPERATURE ERROR (C)
15
CURRENT (A)
195
10
190
5
185
0
180
04662-007
-5
04662-009
175 2.5
3.0
3.5
4.0 4.5 5.0 SUPPLY VOLTAGE (V)
5.5
6.0
-10 10k
100k
1M FREQUENCY (Hz)
10M
100M
Figure 7. Average Operating Supply Current vs. Supply Voltage @ 30C
Figure 9. Temperature Accuracy vs. Supply Ripple Frequency
Rev. 0 | Page 7 of 16
04662-008
ADT7302
140
4 3
TEMPERATURE ERROR (C)
120
UPPER TEMPERATURE ERROR LIMIT
2 1 0 -1 -2
04662-012
TEMPERATURE (C)
100 80 60 40 20 0 0 5 10 15 20 25 30 TIME (SEC) 35 40 45
04662-010
-3 -4 -40
LOWER TEMPERATURE ERROR LIMIT -20 0 20 40 60 TEMPERATURE (C) 80 100 120
50
Figure 10. Response to Thermal Shock
Figure 12. Temperature Accuracy @ 5 V
4 3 UPPER TEMPERATURE ERROR LIMIT
TEMPERATURE ERROR (C)
2 1 0 -1 -2
04662-011
-3 -4 -40
LOWER TEMPERATURE ERROR LIMIT
-20
0
20
40
60
80
100
120
TEMPERATURE (C)
Figure 11. Temperature Accuracy @ 3.3 V
Rev. 0 | Page 8 of 16
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. 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
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 second. At this time, the part powers up its analog circuitry and performs a temperature conversion. This temperature conversion typically takes 800 s, after which the analog circuitry of the part automatically shuts down. The analog circuitry powers up again when the 1-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 800 s 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 800 s
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. 0 | Page 9 of 16
ADT7302
01, 0010, 1100, 0000
DIGITAL OUTPUT
00, 1001, 0110, 0000
75C
00, 0000, 0000, 0001 -0.03125C -40C -30C
11, 1111, 1111, 1111
TEMPERATURE (C)
150C
11, 1100, 0100, 0000
11, 1011, 0000, 0000
Figure 13. Temperature to Digital Transfer Function
CS
t1
SCLK 1 2
04662-013
t2
3 4 15 16
t7
t3 t4
DOUT LEADING ZEROS DB13 DB12 DB0 DB1 DB0
t8
t5
DIN
t6
POWERDOWN
04662-014
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. 0 | 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. 0 | Page 11 of 16
ADT7302 APPLICATIONS
MICROPROCESSOR INTERFACING
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. 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*
SCLK DOUT DIN CS P1.1 P1.0 P1.2
04662-016 04662-017
8051*
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.
ADT7302*
SCLK DOUT DIN CS MC68HC11* SCLK MISO MOSI
04662-015
P1.3
*ADDITIONAL PINS OMITTED FOR CLARITY
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*
PIC16C6x/7x* SCLK SDO SDI RA1
PC1
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 15. ADT7302 to MC68HC11 Interface
SCLK DOUT
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.
DIN CS
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 17. ADT7302 to PIC16C6x/7x Interface
Rev. 0 | Page 12 of 16
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 PortA.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; do{ delay_ms(10); Output_low(CS); delay_us(10); MSByte = SPI_Read(0); LSByte = SPI_Read(0); delay_us(10); Output_High(CS); ADC_Temp_Code = make16(MSByte,LSByte); ADC_Temp_Code_dec = (float)ADC_Temp_Code; if ((0x2000 & ADC_Temp_Code) == 0x2000) { TempVal = (ADC_Temp_Code_dec - 16384)/32; } else { TempVal = (ADC_Temp_Code_dec/32); } }while(True); }
//Pic is set up as Master device. //Idle state of clock is high.
//Allow time for conversions. //Pull CS low. //CS to SCLK setup time. //The first byte is clocked in. //The second byte is clocked in. //SCLK to CS setup time. //Bring CS high. //16bit ADC code is stored ADC_Temp_Code. //Covert to float for division. //Check sign bit for negative value. //Conversion formula if negative temperature.
//Conversion formula if positive temperature.
//Temperature value stored in TempVal.
Rev. 0 | Page 13 of 16
ADT7302
ADT7302 to ADSP-21xx Interface
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: 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 ADSP21xx 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.
ADT7302*
SCLK DOUT DIN CS ADSP-21xx* SCLK DR DT RFS
04662-018
MOUNTING THE ADT7302
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. 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. 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
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.
TFS *ADDITIONAL PINS OMITTED FOR CLARITY
Figure 18. ADT7302 to ADSP-21xx Interface
Rev. 0 | Page 14 of 16
ADT7302 OUTLINE DIMENSIONS
2.90 BSC
3.00 BSC
6 5 4
1.60 BSC
1 2 3
2.80 BSC
3.00 BSC
8
5
PIN 1 INDICATOR 0.95 BSC 1.30 1.15 0.90 1.90 BSC
4.90 BSC
4
PIN 1 0.65 BSC 1.10 MAX 8 0 0.80 0.60 0.40
1.45 MAX
0.22 0.08 10 4 0 0.60 0.45 0.30
0.15 0.00 0.38 0.22 COPLANARITY 0.10
0.15 MAX
0.50 0.30
SEATING PLANE
0.23 0.08 SEATING PLANE
COMPLIANT TO JEDEC STANDARDS MO-178-AB
COMPLIANT TO JEDEC STANDARDS MO-187AA
Figure 19. 6-Lead Small Outline Transistor Package [SOT-23] (RJ-6) Dimensions shown in millimeters
Figure 20. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters
ORDERING GUIDE
Model ADT7302ARTZ-500RL7 2 ADT7302ARTZ-REEL72 ADT7302ARMZ2 ADT7302ARMZ-REEL72
1 2
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Temperature Accuracy 1 2C 2C 2C 2C
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
Temperature accuracy is over 0C to 70C temperature range. Z = Pb-free part.
Rev. 0 | Page 15 of 16
ADT7302 NOTES
(c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04662-0-10/05(0)
Rev. 0 | Page 16 of 16

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