±2°C Accurate, Micropower Digital
Temperature Sensor
ADT7302
FUNCTIONAL BLOCK DIAGRAM
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
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 0.03125°C.
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.
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.
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
© 2005 Analog Devices, Inc. All rights reserved.
ADT7302
TABLE OF CONTENTS
Specifications..................................................................................... 3
Temperature Value Register .........................................................9
Timing Characteristics ................................................................ 4
Serial Interface ............................................................................ 10
Absolute Maximum Ratings............................................................ 5
Applications..................................................................................... 12
ESD Caution.................................................................................. 5
Microprocessor Interfacing....................................................... 12
Pin Configurations and Function Descriptions ........................... 6
Mounting the ADT7302............................................................ 14
Typical Performance Characteristics ............................................. 7
Supply Decoupling ..................................................................... 14
Theory of Operation ........................................................................ 9
Outline Dimensions ....................................................................... 15
Converter Details.......................................................................... 9
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 –40°C to +125°C, 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
μs
sec
0.03125
1
800
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 = 0°C to 70°C.
TA = −20°C to +85°C.
TA = −40°C to +125°C.
Temperature measurement every 1 second.
5.25
V
For specified performance.
2.2
300
2.2
400
1
2
20
mA
μA
mA
μA
μA
μA
μA
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 = 0°C to 70°C.
VDD = 5 V, TA = 0°C to 70°C.
VDD = 2.7 V to 5.25 V, TA = −40°C to 125°C.
631
1.41
μW
mW
VDD = 3.3 V. Auto conversion update, tR.
VDD = 5 V. Auto conversion update, tR.
4.88
7.4
42.9
65
423
641
μW
μW
μW
μW
μW
μW
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
μA
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 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
Typ
2.5
VDD − 0.3 V
1
ISOURCE = ISINK = 200 μA.
IOL = 200 μA.
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.
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
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.
200μA
TO
OUTPUT
PIN
IOL
1.6V
CL
50pF
200μA
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. 0 | 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
−40°C to +125°C
−65°C to +150°C
150°C
1.2
2
WMAX = (TJ max − TA )/θJA
MSOP
0.4
0.2
0
TEMPERATURE (°C)
Figure 3. Maximum Power Dissipation vs. Temperature
260°C (0°C)
20 sec to 40 sec
3°C/sec max
−6°C/sec max
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, 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
220°C (0°C/5°C)
10 sec to 20 sec
3°C/sec max
−6°C/sec
6 minutes max
SOT-23
0.6
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
205.9°C/W
43.74°C/W
0.8
–30
–20
–10
WMAX = (TJ max − TA2)/θJA
1.0
–40
190.4°C/W
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
θJA, Junction-to-Ambient (Still Air)
8-Lead MSOP (RM-8)
Power Dissipation1
Thermal Impedance 3
θJA, Junction-to-Ambient (Still Air)
θJC, Junction-to-Case
IR Reflow Soldering
Peak Temperature
Time at Peak Temperature
Ramp-up Rate
Ramp-down Rate
Time 25°C to Peak Temperature
IR Reflow Soldering—Pb-Free Package
Peak Temperature
Time at Peak Temperature
Ramp-Up Rate
Ramp-Down Rate
Time 25°C to Peak Temperature
ADT7302
GND 1
6
NC 1
DOUT
DOUT 2
ADT7302
5 CS
TOP VIEW
(Not to Scale)
VDD 3
4
SCLK
CS 3
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. 0 | 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 (μA)
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 @ 30°C
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 @ 30°C
Rev. 0 | Page 7 of 16
04662-009
CURRENT (μA)
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
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. 0 | Page 8 of 16
100
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 −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 second. At this time, the part powers up its analog circuitry
and performs a temperature conversion. This temperature
conversion typically takes 800 μs, 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 μs 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 μs
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
−40°C
−30°C
−25°C
−10°C
−0.03125°C
0°C
+0.03125°C
+10°C
+25°C
+50°C
+75°C
+100°C
+125°C
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. 0 | Page 9 of 16
ADT7302
DIGITAL OUTPUT
01, 0010, 1100, 0000
00, 1001, 0110, 0000
75°C
00, 0000, 0000, 0001
–0.03125°C
11, 1111, 1111, 1111
–40°C
–30°C
TEMPERATURE (°C)
150°C
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
DB0
DB12
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. 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
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. 0 | 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 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;
//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.
//Covert 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. 0 | 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 0.1°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.
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.
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 μF 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. 0 | Page 14 of 16
ADT7302
OUTLINE DIMENSIONS
2.90 BSC
3.00
BSC
6
5
4
1
2
3
2.80 BSC
1.60 BSC
8
5
4.90
BSC
3.00
BSC
PIN 1
INDICATOR
4
0.95 BSC
1.30
1.15
0.90
PIN 1
1.90
BSC
0.65 BSC
1.45 MAX
0.15 MAX
0.50
0.30
SEATING
PLANE
1.10 MAX
0.15
0.00
0.22
0.08
10°
4°
0°
0.38
0.22
COPLANARITY
0.10
0.60
0.45
0.30
0.23
0.08
0.80
0.60
0.40
8°
0°
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
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
Temperature Accuracy 1
±2°C
±2°C
±2°C
±2°C
Temperature accuracy is over 0°C to 70°C temperature range.
Z = Pb-free part.
Rev. 0 | 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
© 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