±2°C Accurate, Micropower Digital
Temperature Sensor
ADT7302
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
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Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2005–2011 Analog Devices, Inc. All rights reserved.
FEATURES
13-bit temperature-to-digital converter
−40°C to +125°C operating temperature range
±2°C accuracy
0.03125°C temperature resolution
Shutdown current of 1 μA
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
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
FUNCTIONAL BLOCK DIAGRAM
SERIAL
BUS
INTERFACE
ADT7302
V
DD
SCLK
DIN
DOUT
GND
13-BIT
ANALOG/DIGITAL
CONVERTER
TEMPERATURE
VALUE
REGISTER
BAND GAP
TEMPERATURE
SENSOR
CS
04662-001
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 0.03125°C.
The ADT7302 has a flexible serial interface that allows easy
interfacing to most microcontrollers. The interface is compatible
with SPI®, QSPI™, and MICROWIRE™ 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 −40°C to +125°C.
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 ±2°C.
5. 13-bit temperature reading to 0.03125°C resolution.
6. Shutdown mode that reduces the power consumption to
4.88 μW with VDD = 3.3 V at 1 SPS.
7. Compatible with AD7814.
ADT7302
Rev. B | Page 2 of 16
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 2
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 Information .............................................................. 12
Microprocessor Interfacing ....................................................... 12
Mounting the ADT7302 ............................................................ 14
Supply Decoupling ..................................................................... 14
Outline Dimensions ....................................................................... 15
Ordering Guide .......................................................................... 15
REVISION HISTORY
6/11—Rev. A to Rev. B
Changed Temperature Conversion Time from 800 µs 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
ADT7302
Rev. B | Page 3 of 16
SPECIFICATIONS
TA = TMIN to TMAX, VDD = 2.7 V to 5.25 V, unless otherwise noted. All specifications are for −40°C to +125°C, unless otherwise stated.
Table 1.
Parameter Min Typ Max Unit Test Conditions/Comments
TEMPERATURE SENSOR AND ADC VDD = 3.3 V (±10%) and 5 V (±5%)
Accuracy ±1 ±2 °C TA = 0°C to 70°C
±2.5 °C TA = −20°C to +85°C
±3 °C TA = −40°C to +125°C
Temperature Resolution 0.03125 °C
Autoconversion Update Rate, tR 1.5 sec Temperature measurement every 1.5 second
Temperature Conversion Time 1.2 ms
Thermal Time Constant1 2 sec
SUPPLIES
Supply Voltage 2.7 5.25 V For specified performance
Supply Current
Normal Mode 1.6 2.2 mA VDD = 3.3 V, powered up and converting
190 300 µA VDD = 3.3 V, powered up and not converting
1.6 2.2 mA V
DD
= 5 V, powered up and converting
280 400 µA VDD = 5 V, powered up and not converting
Shutdown Mode 0.2 1 µA VDD = 3.3 V, TA = 0°C to 70°C
0.4 2 µA VDD = 5 V, TA = 0°C to 70°C
20 µA VDD = 2.7 V to 5.25 V, TA = −40°C to +125°C
Power Dissipation
Normal Mode (Average) 631 µW VDD = 3.3 V, autoconversion update, tR
1.41 mW VDD = 5 V, autoconversion update, tR
Shutdown Mode (Average)2
1 SPS 4.88 µW VDD = 3.3 V
7.4 µW VDD = 5 V
10 SPS 42.9 µW V
DD
= 3.3 V
65 µW VDD = 5 V
100 SPS 423 µW VDD = 3.3 V
641 µW VDD = 5 V
DIGITAL INPUT3
Input High Voltage, VIH 2.5 V
Input Low Voltage, VIL 0.8 V
Input Current, IIN ±1 µA VIN = 0 V to VDD
Input Capacitance, CIN 10 pF All digital inputs
DIGITAL OUTPUT3
Output High Voltage, VOH VDD − 0.3 V ISOURCE = ISINK = 200 µA
Output Low Voltage, VOL 0.4 V IOL = 200 µA
Output Capacitance, C
OUT
50 pF
1 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 0°C to 100°C, it typically takes 2 seconds for the ADT7302 to reach 63.2°C.
2 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.
ADT7302
Rev. B | Page 4 of 16
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 Limit Unit Comments
t1 5 ns min CS to SCLK setup time
t2 25 ns min SCLK high pulse width
t
3
25 ns min SCLK low pulse width
t42 35 ns max Data access time after SCLK falling edge
t5 20 ns min Data setup time prior to SCLK rising edge
t6 5 ns min Data hold time after SCLK rising edge
t7 5 ns min CS to SCLK hold time
t82 40 ns max CS to DOUT high impedance
1 See Figure 14 for the SPI timing diagram.
2 Measured with the load circuit of Figure 2.
1.6V
200µA
200µA I
OH
I
OL
TO
OUTPUT
PIN C
L
50pF
04662-002
Figure 2. Load Circuit for Data Access Time and Bus Relinquish Time
ADT7302
Rev. B | Page 5 of 16
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Rating
VDD to GND −0.3 V to +7 V
Digital Input Voltage to GND −0.3 V to VDD + 0.3 V
Digital Output Voltage to GND −0.3 V to VDD + 0.3 V
Operating Temperature Range −40°C to +125°C
Storage Temperature Range −65°C to +150°C
Junction Temperature 150°C
6-Lead SOT-23 (RJ-6)
Power Dissipation1WMAX = (TJ max − TA
2
Thermal Impedance
)/θJA
θJA, Junction-to-Ambient (Still Air) 190.4°C/W
8-Lead MSOP (RM-8)
Power Dissipation1 WMAX = (TJ max − TA2)/θJA
Thermal Impedance3
θJA, Junction-to-Ambient (Still Air) 205.9°C/W
θJC, Junction-to-Case 43.74°C/W
IR Reflow Soldering
Peak Temperature 220°C (0°C/5°C)
Time at Peak Temperature 10 sec to 20 sec
Ramp-Up Rate 3°C/sec max
Ramp-Down Rate −6°C/sec
Time 25°C to Peak Temperature 6 minutes max
IR Reflow Soldering—Pb-Free Package
Peak Temperature 260°C (0°C)
Time at Peak Temperature 20 sec to 40 sec
Ramp-Up Rate 3°C/sec max
Ramp-Down Rate −6°C/sec max
Time 25°C to Peak Temperature 8 minutes max
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, PCB-
mounted components.
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.
04662-003
TEMPERATURE (°C)
–40
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
–10
–20
–30
MAXIMUM POWER DISSIPATION (W)
1.2
1.0
0.8
0.6
0.4
0.2
0
SOT-23
MSOP
Figure 3. Maximum Power Dissipation vs. Temperature
ESD CAUTION
ADT7302
Rev. B | Page 6 of 16
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
GND 1
DIN 2
VDD 3
DOUT
6
CS
5
SCLK
4
ADT7302
TOP VIEW
(Not to Scale)
04662-004
Figure 4. SOT-23 Pin Configuration
NC 1
DOUT 2
CS 3
SCLK 4
NC
8
GND
7
DIN
6
VDD
5
NC = NO CONNECT
ADT7302
TOP VIEW
(Not to Scale)
04662-005
Figure 5. MSOP Pin Configuration
Table 4. Pin Function Descriptions
SOT-23
Pin No.
MSOP
Pin No. Mnemonic Description
1 7 GND Analog and Digital Ground.
2 6 DIN 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.
3 5 VDD Positive Supply Voltage, 2.7 V to 5.25 V.
4 4 SCLK 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.
5 3 CS Chip Select Input. Logic input. The device is selected when this input is low. The SCLK input is
disabled when this pin is high.
6 2 DOUT 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.
1, 8 NC No Connect.
ADT7302
Rev. B | Page 7 of 16
TYPICAL PERFORMANCE CHARACTERISTICS
TEMPERATURE (°C)
CURRENT (µA)
215
210
205
195
190
185
200
180
170
175
–45 5 55 105 155
04662-006
5.5V
3.3V
Figure 6. Average Operating Supply Current vs. Temperature
SUPPLY VOLTAGE (V)
CURRENT (µA)
205
200
190
185
195
175
180
2.5 3.0 3.5 5.04.0 4.5 5.5 6.0
04662-007
Figure 7. Average Operating Supply Current vs. Supply Voltage @ 30°C
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (nA)
500
450
250
300
200
150
350
400
0
100
50
2.5 3.0 3.5 5.04.0 4.5 5.5 6.0
04662-008
Figure 8. Shutdown Current vs. Supply Voltage @ 30°C
Figure 9. Temperature Accuracy vs. Supply Ripple Frequency
ADT7302
Rev. B | Page 8 of 16
TIME (SEC)
TEMPERATURE (°C)
140
60
80
40
100
120
0
20
0 105 15 2520 403530 45 50
04662-010
Figure 10. Response to Thermal Shock
04662-011
TEMPERATURE ERROR (°C)
4
3
2
1
0
–4
–3
–2
–1
–40 –20 0 20 40 60 80 100 120
TEMPERATURE (°C)
UPPER TEMPERATURE
ERROR LIMIT
LOWER TEMPERATURE
ERROR LIMIT
Figure 11. Temperature Accuracy @ 3.3 V
UPPER TEMPERATURE
ERROR LIMIT
LOWER TEMPERATURE
ERROR LIMIT
4
3
2
1
0
–4
–3
–2
–1
–40 –20 0 20 40 60 80 100 120
04662-012
TEMPERATURE ERROR (°C)
TEMPERATURE (°C)
Figure 12. Temperature Accuracy @ 5 V
ADT7302
Rev. B | Page 9 of 16
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 −40°C to +125°C. 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 auto-
matically 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 255°C temperature
span. The internal temperature sensor is guaranteed to a low
value limit of −40°C and a high limit of +125°C. The temperature
data format is shown in Table 5, which also shows the
temperature measurement range of the device (−40°C to
+125°C). A typical performance curve is shown in Figure 11.
Table 5. Temperature Data Format
Temperature Digital Output DB13…DB0
−40°C 11, 1011 0000 0000
−30°C 11, 1100 0100 0000
−25°C 11, 1100 1110 0000
−10°C 11, 1110 1100 0000
−0.03125°C 11, 1111 1111 1111
0°C 00, 0000 0000 0000
+0.03125°C 00, 0000 0000 0001
+10°C 00, 0001 0100 0000
+25°C 00, 0011 0010 0000
+50°C 00, 0110 0100 0000
+75°C 00, 1001 0110 0000
+100°C 00, 1100 1000 0000
+125°C 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 ADC Code uses all 14 bits of the data byte, including the sign bit.
2 DB13 (the sign bit) is removed from the ADC code.
ADT7302
Rev. B | Page 10 of 16
DIGITAL OUTPUT
–40°C–0.03125°C
–30°C
11, 1111, 1111, 1111
11, 1100, 0100, 0000
11, 1011, 0000, 0000
TEMPERATURE (°C)
75°C
150°C
01, 0010, 1100, 0000
00, 1001, 0110, 0000
00, 0000, 0000, 0001
04662-013
Figure 13. Temperature to Digital Transfer Function
SCLK
DOUT
DIN POWER-
DOWN
LEADING ZEROS DB13 DB0
12 3 4 15 16
t1t2
t3t4
t6
t5
t7
t8
DB12 DB1 DB0
CS
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 inter-
face 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 temper-
ature 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.
ADT7302
Rev. B | Page 11 of 16
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.
ADT7302
Rev. B | Page 12 of 16
APPLICATIONS INFORMATION
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 power-
down 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.
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
MC68HC11*
SCLK
MISO
MOSI
PC1
*ADDITIONAL PINS OMITTED FOR CLARITY
CS
04662-015
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.
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
8051*
P1.1
P1.0
P1.2
P1.3
*ADDITIONAL PINS OMITTED FOR CLARITY
CS
04662-016
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*
SCLK
DOUT
DIN
PIC16C6x/7x*
SCLK
SDO
SDI
RA1
*ADDITIONAL PINS OMITTED FOR CLARITY
CS
04662-017
Figure 17. ADT7302 to PIC16C6x/7x Interface
ADT7302
Rev. B | Page 13 of 16
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); //Pic is set up as Master device.
CKP = 1; //Idle state of clock is high.
do{
delay_ms(10); //Allow time for conversions.
Output_low(CS); //Pull CS low.
delay_us(10); //CS to SCLK setup time.
MSByte = SPI_Read(0); //The first byte is clocked in.
LSByte = SPI_Read(0); //The second byte is clocked in.
delay_us(10); //SCLK to CS setup time.
Output_High(CS); //Bring CS high.
ADC_Temp_Code = make16(MSByte,LSByte); //16bit ADC code is stored ADC_Temp_Code.
ADC_Temp_Code_dec = (float)ADC_Temp_Code; //Convert to float for division.
if ((0x2000 & ADC_Temp_Code) == 0x2000) //Check sign bit for negative value.
{
TempVal = (ADC_Temp_Code_dec - 16384)/32; //Conversion formula if negative temperature.
}
else
{
TempVal = (ADC_Temp_Code_dec/32); //Conversion formula if positive temperature.
}
}while(True);
//Temperature value stored in TempVal.
}
ADT7302
Rev. B | Page 14 of 16
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
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.
ADT7302*
SCLK
DOUT
DIN
ADSP-21xx*
SCLK
DR
DT
RFS
*ADDITIONAL PINS OMITTED FOR CLARITY
TFS
CS
04662-018
Figure 18. ADT7302 to ADSP-21xx Interface
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 0.1°C 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 µF ceramic
capacitor between VDD and GND. This is particularly important
if the ADT7302 is mounted remote from the power supply.
ADT7302
Rev. B | Page 15 of 16
OUTLINE DIMENSIONS
COMPLIANT TO JEDEC STANDARDS MO-178-AB
10°
4°
0°
SEATING
PLANE
1.90
BSC
0.95 BSC
0.60
BSC
6 5
1 2 3
4
3.00
2.90
2.80
3.00
2.80
2.60
1.70
1.60
1.50
1.30
1.15
0.90
0.15 MAX
0.05 MIN
1.45 MAX
0.95 MIN
0.20 MAX
0.08 MIN
0.50 MAX
0.30 MIN
0.55
0.45
0.35
PIN 1
INDICATOR
12-16-2008-A
Figure 19. 6-Lead Small Outline Transistor Package [SOT-23]
(RJ-6)
Dimensions shown in millimeters
COMPLIANT TO JEDEC STANDARDS MO-187-AA
6°
0°
0.80
0.55
0.40
4
8
1
5
0.65 BSC
0.40
0.25
1.10 MAX
3.20
3.00
2.80
COPLANARITY
0.10
0.23
0.09
3.20
3.00
2.80
5.15
4.90
4.65
PIN 1
IDENTIFIER
15° MAX
0.95
0.85
0.75
0.15
0.05
10-07-2009-B
Figure 20. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model1 Temperature Range Temperature Accuracy2 Package Description Package Option Branding
ADT7302ARTZ-500RL7 −40°C to +125°C ±2°C 6-Lead SOT-23 RJ-6 T02
ADT7302ARTZ-REEL7 −40°C to +125°C ±2°C 6-Lead SOT-23 RJ-6 T02
ADT7302ARMZ −40°C to +125°C ±2°C 8-Lead MSOP RM-8 T02
ADT7302ARMZ-REEL7 −40°C to +125°C ±2°C 8-Lead MSOP RM-8 T02
1 Z = RoHS-Compliant Part.
2 Temperature accuracy is over 0°C to 70°C temperature range.
ADT7302
Rev. B | Page 16 of 16
NOTES
©2005–2011 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D04662–0–6/11(B)