FEATURES
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
BAND GAP
TEMPERATURE
SENSOR
13-BIT
ANALOG/DIGITAL
CONVERTER
GND
VDD
TEMPERATURE
VALUE
REGISTER
ADT7302
SERIAL
BUS
INTERFACE
CS
SCLK
DIN
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
04662-C-001
Preliminary Technical Data
±2°C Accurate, MicroPower Digital
Temperature Sensor in 6-Lead SOT-23
ADT7302
Figure 1. Functional Block Diagram
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.
The ADT7302 has an on-chip temperature sensor that
allows an accurate measurement of the ambient temperature. The measurable temperature range is −40°C to
+125°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.
2.
Supply voltage of 2.7 V to 5.5 V.
3.
Space-saving 6-lead SOT-23 and 8-lead MSOP packages.
4.
Temperature accuracy of ±2°C.
5.
13-bit temperature reading to 0.03125°C resolution.
6.
The ADT7302 features a shutdown mode that reduces the
power consumption to 4.88 µW with VDD = 3.3 V @ 1 SPS.
The ADT7302’s wide supply voltage range, low supply current,
and SPI compatible interface make it ideal for a variety of
applications, including personal computers, office equipment,
automotive, and domestic appliances.
Rev. PrE
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.
www.analog.com
Tel: 781.329.4700
© 2004 Analog Devices, Inc. All rights reserved.
Fax: 781.326.8703
ADT7302
Preliminary Technical Data
TABLE OF CONTENTS
Specifications.....................................................................................3
Temperature Value Register ........................................................ 8
Timing Characteristics.................................................................4
Serial Interface .............................................................................. 9
Absolute Maximum Ratings............................................................5
Microprocessor Interfacing....................................................... 10
ESD Caution..................................................................................5
Mounting The ADT7302........................................................... 12
Pin Configurations and Function Descriptions............................6
Supply Decoupling ..................................................................... 12
Typical Performance Characteristics..............................................7
Outline Dimensions ....................................................................... 13
Circuit Information ..........................................................................8
Ordering Guide............................................................................... 14
Converter Details..........................................................................8
REVISION HISTORY
Revision PrE: Preliminary Version
Rev. PrE | Page 2 of 14
Preliminary Technical Data
ADT7302
SPECIFICATIONS
TA = TMIN to TMAX, VDD = 2.7 V to 5.5 V, unless otherwise noted. All specifications apply for –40°C to +125°C, unless otherwise stated
Table 1.
Parameter
TEMPERATURE SENSOR AND ADC
Accuracy
Temperature Resolution
Auto Conversion Update Rate, tR
Temperature Conversion Time
Thermal Time Constant1
SUPPLIES
Supply Voltage
Supply Current
Normal Mode
Min
Max
Unit
TBD
TBD
TBD
0.03125
1
2
2
±2
±2.5
±3
°C
°C
°C
°C
sec
ms
sec
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 (±10%)
TA = 0°C to 70°C.
TA = −20°C to +85°C.
TA = −40°C to +125°C.
Temperature measurement every 1 second
5.5
V
For Specified performance.
2.2
300
2.2
400
1
1
mA
µA
mA
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.
VDD = 5 V.
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
0.2
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 µA
IOL = 200 µA
Thermal Time Constant is the time it takes for a starting temperature difference to change to 36.8% of it’s starting value. For example if the ADT7302 experienced a
thermal shock from 0°C to 100°C, it would take typically 2 secs 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. PrE | Page 3 of 14
ADT7302
Preliminary Technical Data
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. See Figure 3.
TA = TMIN to TMAX, VDD = 2.7 V to 5.5 V, unless otherwise noted.
Table 2.
Parameter
t1
t2
t3
t4 1
t5
t6
t7
t 81
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
Measured with the load circuit of Figure 2.
200µA
TO
OUTPUT
PIN
IOL
1.6V
CL
50pF
200µA
IOH
02884-0-002
1
Limit
5
25
25
35
20
5
5
40
Figure 2. Load Circuit for Data Access Time and Bus Relinquish Time
Rev. PrE | Page 4 of 14
Preliminary Technical Data
ADT7302
ABSOLUTE MAXIMUM RATINGS
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
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
190.4°C/W
WMAX = (TJMAX - TA2)/θJA
205.9°C/W
43.74°C/W
1.0
0.8
SOT-23
0.6
MSOP
0.4
0.2
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
–10
–20
0
–30
+220°C (−0/+5°C)
10 s to 20 s
2°C/s to 3°C/s
−6°C/sec
MAXIMUM POWER DISSIPATION (W)
WMAX = (TJMAX - TA2)/θJA
–40
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 Dissipation1
Thermal Impedance
θJA, Junction-to-Ambient (Still Air)
8-Lead MSOP (RM-8)
Power Dissipation1
Thermal Impedance3
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
TEMPERATURE (°C)
1
Values relate to the package being used on a standard 2-layer PCB. Reference
Figure 3 for a plot of maximum power dissipation versus ambient
temperature (TA).
2
TA = ambient temperature
3
Junction-to-case resistance is applicable to components featuring a
preferential flow direction, e.g., components mounted on a heat sink.
Junction-to-ambient resistance is more useful for air-cooled, PCB mounted
components.
Figure 3. Plot of Maximum Power Dissipation vs. Temperature
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. PrE | Page 5 of 14
02884-0-003
Table 3. ADT7302 Stress Ratings
ADT7302
Preliminary Technical Data
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
TOP VIEW 5 CS
(Not to Scale)
4 SCLK
VDD 3
DOUT 2
04662-C-004
DIN 2
NC 1
6 DOUT
ADT7302
CS 3
SCLK 4
Figure 4. SOT-23
8 NC
ADT7302
TOP VIEW
(Not to Scale)
7 GND
6 DIN
5 VDD
04662-C-005
GND 1
Figure 5. MSOP
Table 4. Pin Function Description
Mnemonic
GND
DIN
SOT-23
Pin No.
1
2
VDD
SCLK
3
4
CS
5
DOUT
6
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 5.5 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.
Rev. PrE | Page 6 of 14
Preliminary Technical Data
ADT7302
TYPICAL PERFORMANCE CHARACTERISTICS
–000
500E-9
400E-9
–000
TBD
–000
350E-9
Shutdown Current (A)
ALL CAPS (Initial caps)
450E-9
300E-9
250E-9
200E-9
150E-9
–000
100E-9
50E-9
–000
–000
–000
–000
ALL CAPS (Initial caps)
–000
000E+0
–000
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Supply Voltage (V)
Figure 6. Temperature Accuracy @ 3.3 V and 5 V
Figure 9. Shutdown Current vs. Supply Voltage @ 30°C
215.0E-6
20
250 mv p-p ripple @ Vdd = 5 V
210.0E-6
5.5 V
15
Temperature Error (°C)
205.0E-6
Current (A)
200.0E-6
195.0E-6
190.0E-6
3.3 V
185.0E-6
10
5
0
10E+3
100E+3
1E+6
100E+6
-5
180.0E-6
175.0E-6
-10
Frequency (Hz)
170.0E-6
-45
10E+6
5
55
105
155
Figure 10. Temperature Accuracy vs. Supply Ripple Frequency
Temperature (°C)
140
Figure 7. Average Operating Supply Current vs. Temperature
120
205E-6
100
Temperature (°C)
200E-6
Current (A)
195E-6
80
60
40
190E-6
20
185E-6
0
0
5
10
15
20
25
30
35
Time (sec)
180E-6
Figure 11. Response to Thermal Shock
175E-6
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Supply Voltage (V)
Figure 8. Average Operating Supply Current vs. Supply Voltage @ 30°C
Rev. PrE | Page 7 of 14
40
45
50
ADT7302
Preliminary Technical Data
CIRCUIT INFORMATION
TEMPERATURE VALUE REGISTER
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 A/D converter, a reference circuit, and
serial interface logic functions in SOT-23 and MSOP packages.
The A/D converter section consists of a conventional
successive-approximation converter based around a capacitor
DAC. The parts are capable of running on a 2.7 V to 5.5 V
power supply.
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 shows the
temperature measurement range of the device (–40°C to
+125°C). A typical performance curve is shown in Figure 6.
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 starts to
deteriorate when operated at voltage and temperature
maximum specifications.
Table 5. Temperature Data Format
The ADT7302 can be placed in a shutdown mode via the control register, in which case 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. Reading from the device before a conversion is
complete causes the ADT7302 to stop converting; the part starts
again when serial communication is finished. This read
operation provides the previous result.
Temperature Conversion Formula
1. Positive Temperature = ADC Code(d)/32
2.
Negative Temperature = (ADC Code*(d) – 16384)/32
*Using all 14 bits of the data byte, includes the sign bit.
Negative Temperature = (ADC Code(d)* – 8192)/32
*DB13 (sign bit) is removed from the ADC code
01, 0010, 1100, 0000
00, 1001, 0110, 0000
75°C
00, 0000, 0000, 0001
–0.03125 °C
–40°C
–30°C
11, 1111, 1111, 1111
TEMPERATURE (°C)
11, 1100, 0100, 0000
11, 1011, 0000, 0000
Figure 12. Temperature to Digital Transfer Function
Rev. PrE | Page 8 of 14
125°C
04662-C-006
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 time 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. The result of the most recent
temperature conversion is always available in the serial output
register because the serial interface circuitry never shuts down.
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
DIGITAL OUTPUT
CONVERTER DETAILS
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
Preliminary Technical Data
ADT7302
CS
t1
SCLK
t7
t2
1
2
3
15
4
16
t3
t8
t4
LEADING ZEROS
t5
DIN
DB1
DB12
DB13
DB0
t6
04662-C-007
DOUT
POWERDOWN
Figure 13. 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 2wire mode with CS and 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 utilize CS,
which 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 a 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 13 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.
Write Operation
Figure 13 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 powerdown bit, which, when set to a 1, puts the ADT7302 into
shutdown mode. Besides the power-down bit, all bits in the
input data stream should be zero 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, i.e., 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. PrE | Page 9 of 14
ADT7302
Preliminary Technical Data
MICROPROCESSOR INTERFACING
The serial data transfer to and from the ADT7302 requires a 16bit 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 shown, 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 the interface example given in Figure 15.
For applications that require the ADT7302’s 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.
Figure 14 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. The
diagram 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
SCLK
P3.1
DOUT
P3.0
DIN
P1.2
CS
P1.3
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 15. ADT7302 to 8051 Interface
ADT7302 to PIC16C6x/7x and PIC16F873 Interface
Figure 16 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.
04662-C-008
ADT7302*
8051*
ADT7302*
ADT7302 to MC68HC11 Interface
04662-C-009
The ADT7302’s serial interface allows for easy interface to most
microcomputers and microprocessors. Figure 14 through
Figure 17 show some typical interface circuits. The serial
interface on the ADT7302 consists of four wires: CS, DIN,
DOUT and SCLK. All interface circuits shown utilize 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
permanently low. Thus, the interface can be operated from just
three wires: SCLK, CS, and DOUT.
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 14. ADT7302 to MC68HC11 Interface
PIC16C6x/7x*
SCLK
SCK
DOUT
SDO
DIN
SDI
CS
RA1
04662-C-010
ADT7302*
ADT7302 to 8051 Interface
An interface circuit between the ADT7302 and the microcontroller is shown in Figure 15. 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 dataword from the ADT7302 is available in the accumulator.
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 16. ADT7302 to PIC16C6x/7x Interface
The following software program shows how to program an
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’s being used.
Rev. PrE | Page 10 of 14
Preliminary Technical Data
ADT7302
#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.
MSByte = 0x03;
LSByte = 0x20;
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. PrE | Page 11 of 14
ADT7302
Preliminary Technical Data
ADT7302 to ADSP-21xx Interface
MOUNTING THE ADT7302
Figure 17 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, thanks to 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 ground pin provides the best thermal path to the die, so the
temperature of the die will be 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 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.
SCK
DOUT
DR
DIN
DT
CS
SUPPLY DECOUPLING
ADSP-21xx*
SCLK
RFS
TFS
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.
04662-C-011
ADT7302*
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.
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 17. ADT7302 to ADSP-21 Interface
Rev. PrE | Page 12 of 14
Preliminary Technical Data
ADT7302
OUTLINE DIMENSIONS
2.90 BSC
6
5
4
1
2
3
2.80 BSC
1.60 BSC
PIN 1
0.95 BSC
1.90
BSC
1.30
1.15
0.90
1.45 MAX
0.50
0.30
0.15 MAX
0.22
0.08
10°
4°
0°
SEATING
PLANE
0.60
0.45
0.30
COMPLIANT TO JEDEC STANDARDS MO-178AB
Figure 18. 6-Lead Small Outline Transistor Package [SOT-23]
(RJ-6)
Dimensions shown in millimeters
3.00
BSC
8
5
4.90
BSC
3.00
BSC
4
PIN 1
0.65 BSC
1.10 MAX
0.15
0.00
0.38
0.22
COPLANARITY
0.10
0.23
0.08
8°
0°
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MO-187AA
Figure 19. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
Rev. PrE | Page 13 of 14
0.80
0.60
0.40
ADT7302
Preliminary Technical Data
ORDERING GUIDE
Model
ADT7302ART-500RL7
ADT7302ART-REEL7
ADT7302ART-REEL
ADT7302ARM
ADT7302ARM-REEL7
ADT7302ARM-REEL
ADT7302ARTZ-500RL72
ADT7302ARTZ-REEL72
ADT7302ARTZ-REEL2
ADT7302ARMZ2
ADT7302ARMZ-REEL72
ADT7302ARMZ-REEL2
1
2
Temperature Range
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
Temperature
Accuracy1
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
Temperature accuracy is over 0°C to 70°C temperature range.
Z = Pb-free.
© 2004 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
PR04662-0-8/04(PrE)
Rev. PrE | Page 14 of 14
Package
Description
6-Lead SOT-23
6-Lead SOT-23
6-Lead SOT-23
8-Lead MSOP
8-Lead MSOP
8-Lead MSOP
6-Lead SOT-23
6-Lead SOT-23
6-Lead SOT-23
8-Lead MSOP
8-Lead MSOP
8-Lead MSOP
Samples Branding
Information
T01
T01
T01
Package
Option
RJ-6
RJ-6
RJ-6
RM-8
RM-8
RM-8
RJ-6
RJ-6
RJ-6
RM-8
RM-8
RM-8