±1°C Accurate, 13-Bit,
Digital Temperature Sensor
ADT7301
FUNCTIONAL BLOCK DIAGRAM
13-bit temperature-to-digital converter
−40°C to +150°C operating temperature range
±0.5°C typical 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
ADT7301
SERIAL
BUS
INTERFACE
CS
SCLK
DIN
DOUT
APPLICATIONS
02884-0-001
FEATURES
Figure 1.
Medical equipment
Automotive
Environmental controls
Oil temperature
Hydraulic systems
Cellular phones
Hard disk drives
Personal computers
Electronic test equipment
Office equipment
Domestic appliances
Process control
GENERAL DESCRIPTION
PRODUCT HIGHLIGHTS
The ADT7301 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 +150°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.
Typical temperature accuracy of ±0.5°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 @ 1 SPS.
7.
Compatible with AD7814.
The ADT7301 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 ADT7301’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. The
ADT7301 is rated for operation over the −40°C to +150°C
temperature range. It is not recommended to operate the device
at temperatures above +125°C for greater than a total of 5%
(5,000 hours) of the lifetime of the device. Exposure beyond this
limit affects device reliability.
Rev. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2005–2011 Analog Devices, Inc. All rights reserved.
ADT7301
TABLE OF CONTENTS
Features .............................................................................................. 1
Typical Performance Characteristics ..............................................7
Applications ....................................................................................... 1
Theory of Operation .........................................................................9
Functional Block Diagram .............................................................. 1
Converter Details ..........................................................................9
General Description ......................................................................... 1
Temperature Value Register ...................................................... 10
Product Highlights ........................................................................... 1
Serial Interface ............................................................................ 11
Revision History ............................................................................... 2
Applications Information .............................................................. 12
Specifications..................................................................................... 3
Microprocessor Interfacing ....................................................... 12
Timing Characteristics ................................................................ 4
Mounting the ADT7301 ............................................................ 14
Absolute Maximum Ratings ............................................................ 5
Supply Decoupling ..................................................................... 14
ESD Caution .................................................................................. 5
Outline Dimensions ....................................................................... 15
Pin Configurations and Function Descriptions ........................... 6
Ordering Guide .......................................................................... 15
REVISION HISTORY
6/11—Rev. A to Rev. B
Changed Temperature Conversion Time from 800 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
Rev. B | Page 2 of 16
ADT7301
SPECIFICATIONS
TA = TMIN to TMAX, VDD = 2.7 V to 5.25 V, unless otherwise noted. All specifications are for −40°C to +150°C, unless otherwise noted.
Table 1. A Grade Specifications
Parameter
TEMPERATURE SENSOR AND ADC
Accuracy 1
Temperature Resolution
Autoconversion Update Rate, tR
Temperature Conversion Time
Thermal Time Constant3
SUPPLIES
Supply Voltage
Supply Current
Normal Mode
Min
Max
Unit
±0.5
±1
±2
±3
±42
°C
°C
°C
°C
°C
sec
ms
sec
0.03125
1.5
1.2
2
2.7
Power Dissipation
Normal Mode (Average)
Shutdown Mode (Average)4
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
TA = −40°C to +150°C
Temperature measurement every 1.5 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 +150°C
631
1.41
µW
mW
VDD = 3.3 V, autoconversion update, tR
VDD = 5 V, autoconversion 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 INPUT5
Input High Voltage, VIH
Input Low Voltage, VIL
Input Current, IIN
Input Capacitance, CIN
DIGITAL OUTPUT5
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 accuracy specifications for 0°C to 70°C are specified to 3.5-Σ performance.
It is not recommended to operate the device at temperatures above 125°C for greater than a total of 5% (5,000 hours) of the lifetime of the device. Any exposure
beyond this limit affects device reliability.
3
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 ADT7301 experiences a thermal shock
from 0°C to 100°C, it would take typically 2 seconds for the ADT7301 to reach 63.2°C.
4
The ADT7301 is taken out of shutdown mode and a temperature conversion is immediately performed after this write operation. When the temperature conversion is
complete, the ADT7301 is put back into shutdown mode.
5
Guaranteed by design and characterization, not production tested.
2
Rev. B | Page 3 of 16
ADT7301
TIMING CHARACTERISTICS
Guaranteed by design and characterization, not production tested. All input signals are specified with tR = tF = 5 ns (10% to 90% of VDD)
and timed from a voltage level of 1.6 V. TA = TMIN to TMAX, VDD = 2.7 V to 5.25 V, unless otherwise noted.
Table 2.
Parameter1
t1
t2
t3
t4 2
t5
t6
t7
t8 2
2
Unit
ns min
ns min
ns min
ns max
ns min
ns min
ns min
ns max
Comments
CS to SCLK setup time
SCLK high pulse width
SCLK low pulse width
Data access time after SCLK falling edge
Data setup time prior to SCLK rising edge
Data hold time after SCLK rising edge
CS to SCLK hold time
CS to DOUT high Impedance
See Figure 14 for the SPI timing diagram.
Measured with the load circuit of Figure 2.
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. B | Page 4 of 16
ADT7301
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 +150°C
−65°C to +150°C
150°C
1.2
205.9°C/W
43.74°C/W
MSOP
0.4
0.2
0
220°C (0°C/5°C)
10 sec to 20 sec
3°C/s max
−6°C/s max
6 minutes max
260°C (0°C)
20 sec to 40 sec
3°C/s max
−6°C/s max
8 minutes max
SOT-23
0.6
TEMPERATURE (°C)
Figure 3. Plot of Maximum Power Dissipation vs. Temperature
ESD CAUTION
1
It is not recommended to operate the ADT7301 at temperatures above
125°C for greater than a total of 5% (5,000 hours) of the lifetime of the
device. Any exposure beyond this limit affects device reliability.
2
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).
3
TA = ambient temperature.
4
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.
Rev. B | Page 5 of 16
02884-003
WMAX = (TJ max − TA3)/θJA
0.8
–30
–20
–10
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
190.4°C/W
1.0
–40
WMAX = (TJ max − TA3)/θJA
MAXIMUM POWER DISSIPATION (W)
Parameter
VDD to GND
Digital Input Voltage to GND
Digital Output Voltage to GND
Operating Temperature Range1
Storage Temperature Range
Junction Temperature
6-Lead SOT-23 (RJ-6)
Power Dissipation2
Thermal Impedance
θJA, Junction-to-Ambient
(Still Air)
8-Lead MSOP (RM-8)
Power Dissipation2
Thermal Impedance4
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
ADT7301
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
NC 1
6 DOUT
DOUT 2
TOP VIEW 5 CS
(Not to Scale)
4 SCLK
VDD 3
CS 3
02884-0-004
DIN 2
ADT7301
SCLK 4
8 NC
ADT7301
TOP VIEW
(Not to Scale)
7 GND
6 DIN
5 VDD
02884-0-005
GND 1
Figure 5. MSOP Pin Configuration
Figure 4. SOT-23 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 ADT7301’s temperature value register and to clock data into the ADT7301’s control register.
Chip Select Input. Logic input. The device is selected when this input is low. The SCLK input is
disabled when this pin is high.
Serial Data Output. Logic output. Data is clocked out of the temperature value register at this pin.
Data is clocked out on the falling edge of SCLK.
No Connect.
Rev. B | Page 6 of 16
ADT7301
TYPICAL PERFORMANCE CHARACTERISTICS
20
215
250mV p-p RIPPLE @ VDD = 5V
210
15
5.5V
TEMPERATURE ERROR (°C)
CURRENT (µA)
205
200
195
190
3.3V
185
180
10
5
0
170
–45
5
55
TEMPERATURE (°C)
105
–10
10k
155
1M
FREQUENCY (Hz)
10M
100M
Figure 9. Temperature Accuracy vs. Supply Ripple Frequency
205
140
120
TEMPERATURE (°C)
195
190
185
180
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
5.5
450
400
350
300
250
200
150
02884-020
100
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
5.5
40
0
500
0
2.5
60
0
6.0
Figure 7. Average Operating Supply Current vs. Supply Voltage @ 30°C
50
80
20
02884-019
175
2.5
100
02884-022
CURRENT (µA)
100k
Figure 6. Average Operating Supply Current vs. Temperature
200
SHUTDOWN CURRENT (nA)
02884-021
02884-018
–5
175
6.0
Figure 8. Shutdown Current vs. Supply Voltage @ 30°C
Rev. B | Page 7 of 16
5
10
15
20
25
30
TIME (SEC)
35
40
Figure 10. Response to Thermal Shock
45
50
ADT7301
5
5
4
2
1
0
–1
–2
02884-006
1
0
–1
–2
LOWER TEMPERATURE
ERROR LIMIT
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 11. Temperature Accuracy of 40 ADT7301s @ 3.3 V
Figure 12. Temperature Accuracy of 40 ADT7301s @ 5 V
Rev. B | Page 8 of 16
140
130
120
110
90
100
80
70
60
50
40
30
20
0
10
–10
–20
–5
–30
–4
–40
140
130
120
110
90
100
80
70
60
50
40
30
20
0
10
–10
–20
–30
–4
–5
2
–3
LOWER TEMPERATURE
ERROR LIMIT
150
–3
UPPER TEMPERATURE
ERROR LIMIT
3
02884-023
TEMPERATURE ERROR (°C)
3
150
UPPER TEMPERATURE
ERROR LIMIT
–40
TEMPERATURE ERROR (°C)
4
ADT7301
THEORY OF OPERATION
The ADT7301 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
ADC section consists of a conventional successive approximation
converter based around a capacitor DAC. The parts 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 ADT7301 is −40°C to
+150°C. Greater than 125°C, the ADT7301 is limited to 5%
of its 55°C operational lifetime. The structural integrity of the
device may start to deteriorate when continuously operated at
absolute maximum voltage and temperature specifications.
CONVERTER DETAILS
The conversion clock for the part is internally generated. No
external clock is required except when reading from and writing
to the serial port. In normal mode, an internal clock oscillator
runs an automatic conversion sequence. During this automatic
conversion sequence, a conversion is initiated every 1.5 second.
At this time, the part powers up its analog circuitry and performs
a temperature conversion. This temperature conversion typically
takes 1.2 ms, after which the analog circuitry of the part automatically shuts down. The analog circuitry powers up again when
the 1.5 second timer times out and the next conversion begins.
Since the serial interface circuitry never shuts down, the result
of the most recent temperature conversion is always available in
the serial output register.
The ADT7301 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 ADT7301 is taken
out of shutdown mode. The ADT7301 can be taken out of
shutdown mode by writing all 0s into the control register. The
conversion result from the last conversion prior to shutdown
can still be read from the ADT7301 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. Every
result is stored in a buffer register and is loaded into the
temperature value register only at the first falling SCLK edge of
every serial port activity. Serial port activity does not interfere
with conversion processes, and every conversion is completed,
even during a read operation. A conversion has to be completed
before a read occurs, otherwise its result is not loaded into the
temperature value register and instead is loaded 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.
Rev. B | Page 9 of 16
ADT7301
Temperature Conversion Equations
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 +150°C. The temperature
data format is shown in Table 5, which shows the temperature
measurement range of the device (−40°C to +150°C). The
typical performance curve is shown in Figure 11.
Positive Temperature = ADC Code(d)/32
Negative Temperature = (ADC Code(d)1 − 16384)/32
Negative Temperature = (ADC Code(d)2 − 8192)/32
01, 0010, 1100, 0000
00, 1001, 0110, 0000
DIGITAL OUTPUT
TEMPERATURE VALUE REGISTER
75°C
Table 5. Temperature Data Format
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
01, 0010 1100 0000
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 13. Temperature-to-Digital Transfer Function
1
2
ADC code uses all 14 bits of the data byte, including the sign bit.
DB13 (the sign bit) is removed from the ADC code.
Rev. B | Page 10 of 16
150°C
02884-0-006
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
+150°C
ADT7301
CS
t1
SCLK
t7
t2
1
2
3
15
4
16
t3
t8
t4
LEADING ZEROS
DB13
t5
DIN
DB12
DB0
DB1
DB0
t6
02884-0-007
DOUT
POWERDOWN
Figure 14. Serial Interface Timing Diagram
SERIAL INTERFACE
Read Operation
The serial interface on the ADT7301 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 14; this
improves synchronization between the ADT7301 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 ADT7301 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.
Figure 14 shows the timing diagram for a serial read from the
ADT7301. 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 2 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 ADT7301 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.
A read operation from the ADT7301 accesses data from the
temperature value register, while a write operation to the part
writes data to the control register.
Write Operation
Figure 14 also shows the timing diagram for a serial write to the
ADT7301. 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 ADT7301 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 ADT7301.
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 ADT7301 on the rising edge
of SCLK.
Rev. B | Page 11 of 16
ADT7301
APPLICATIONS INFORMATION
The serial data transfer to and from the ADT7301 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 shown in Figure 16, the ADT7301 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 ADT7301
is tied low in Figure 16.
For applications that require the ADT7301 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 generating a serial clock on
one port line while using two other port lines to shift data
in and out with the fourth port line connecting to CS. Port
lines 1.0 to 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.
ADT7301-to-MC68HC11 Interface
Figure 15 shows an interface circuit between the ADT7301 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
ADT7301 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
02884-0-008
ADT7301*
*ADDITIONAL PINS OMITTED FOR CLARITY
8051*
ADT7301*
SCLK
P3.1
DOUT
P3.0
DIN
P1.2
CS
P1.3
02884-0-009
The ADT7301 serial interface allows easy interface to most
microcomputers and microprocessors. Figure 15 to Figure 18
show some typical interface circuits. The serial interface on the
ADT7301 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 ADT7301, the DIN line can be tied low permanently.
Thus, the interface can be operated from just three wires: SCLK,
CS, and DOUT.
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 16. ADT7301-to-8051 Interface
ADT7301-to-PIC16C6x/7x Interface
Figure 17 shows an interface circuit between the ADT7301 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 ADT7301 in two 8-bit serial data
operations. In the example shown in Figure 17, port line RA1 is
being used to generate the CS for the ADT7301.
Figure 15. ADT7301-to-MC68HC11 Interface
ADT7301*
PIC16C6x/7x*
ADT7301-to-8051 Interface
SCLK
SCK
Figure 16 shows an interface circuit between the ADT7301 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
ADT7301 in two 8-bit serial data operations. The ADT7301
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 ADT7301 is available in the accumulator.
DOUT
SDO
Rev. B | Page 12 of 16
DIN
SDI
CS
RA1
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 17. ADT7301-to-PIC16C6x/7x Interface
02884-0-010
MICROPROCESSOR INTERFACING
ADT7301
The following software program shows how to program a
PIC16F873 to communicate with the ADT7301. The
PIC16F873 is configured as an SPI master with the Port A.1 pin
used as CS. Any microchip microcontroller can use this
program by simply exchanging the include file for the device
that is being used.
#include <16F873.h>
#device adc = 8
#use delay(clock = 4000000)
#fuses NOWDT,XT, PUT, NOPROTECT, BROWNOUT, LVP
#BIT CKP = 0x14.4
#define CS PIN_A1
void main(){
int MSByte,LSByte;
long int ADC_Temp_Code;
float TempVal,ADC_Temp_Code_dec;
setup_spi(spi_master);
CKP = 1;
//Pic is set up as master device.
//Idle state of clock is high.
do{
delay_ms(10);
//Allow time for conversions.
Output_low(CS);
delay_us(10);
MSByte = SPI_Read(0);
LSByte = SPI_Read(0);
//Pull CS low.
//CS to SCLK set-up time.
//The first byte is clocked in.
//The second byte is clocked in.
delay_us(10);
Output_High(CS);
//SCLK to CS set-up time.
//Bring CS high.
ADC_Temp_Code = make16(MSByte,LSByte);
ADC_Temp_Code_dec = (float)ADC_Temp_Code;
//16 bit ADC code is stored ADC_Temp_Code.
//Convert to float for division.
if ((0x2000 & ADC_Temp_Code) == 0x2000)
{
TempVal = (ADC_Temp_Code_dec - 16384)/32;
}
else
{
TempVal = (ADC_Temp_Code_dec/32);
}
}while(True);
//Check sign bit for negative value.
//Conversion formula if negative temperature.
//Conversion formula if positive temperature.
//Temperature value stored in TempVal.
}
Rev. B | Page 13 of 16
ADT7301
ADT7301-to-ADSP-21xx Interface
MOUNTING THE ADT7301
Figure 18 shows an interface between the ADT7301 and the
ADSP-21xx DSP processor. To ensure correct operation of the
interface, the SPORT control register should be set up as follows:
The ADT7301 can be used for surface or air temperature
sensing applications. If the device is cemented to a surface with
a thermally conductive adhesive, the die temperature will be
within about 0.1°C of the surface temperature because of the
ADT7301’s low power consumption. Care should be taken to
insulate the back and leads of the device 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 ADT7301. On the
ADSP-21xx interface, the TFS and RFS of the SPORT are tied
together; TFS is set as an output, and RFS is set as an input. The
DSP operates in alternate framing mode and the SPORT control
register is set up as described in this section.
ADSP-21xx*
SCLK
SCK
DOUT
DR
DIN
DT
CS
RFS
TFS
As in any IC, the ADT7301 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
ADT7301 allows it to be mounted inside sealed metal probes,
which provide a safe environment for the device.
SUPPLY DECOUPLING
02884-0-011
ADT7301*
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 measured surface.
The ADT7301 should be decoupled with a 0.1 µF ceramic
capacitor between VDD and GND. This is particularly important
if the ADT7301 mount is remote from the power supply.
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 18. ADT7301-to-ADSP-21xx Interface
Rev. B | Page 14 of 16
ADT7301
OUTLINE DIMENSIONS
3.00
2.90
2.80
1.70
1.60
1.50
6
5
4
1
2
3
3.00
2.80
2.60
PIN 1
INDICATOR
0.95 BSC
1.90
BSC
1.30
1.15
0.90
0.20 MAX
0.08 MIN
0.15 MAX
0.05 MIN
10°
4°
0°
SEATING
PLANE
0.50 MAX
0.30 MIN
0.60
BSC
0.55
0.45
0.35
12-16-2008-A
1.45 MAX
0.95 MIN
COMPLIANT TO JEDEC STANDARDS MO-178-AB
Figure 19. 6-Lead Small Outline Transistor Package [SOT-23]
(RJ-6)
Dimensions shown in millimeters
3.20
3.00
2.80
8
3.20
3.00
2.80
5.15
4.90
4.65
5
1
4
PIN 1
IDENTIFIER
0.65 BSC
0.95
0.85
0.75
15° MAX
1.10 MAX
0.40
0.25
6°
0°
0.23
0.09
COMPLIANT TO JEDEC STANDARDS MO-187-AA
0.80
0.55
0.40
10-07-2009-B
0.15
0.05
COPLANARITY
0.10
Figure 20. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
ADT7301ARTZ-500RL7
ADT7301ARTZ-REEL7
ADT7301ARMZ
ADT7301ARMZ-REEL7
EVAL-ADT7301EBZ
1
2
Temperature Range
−40°C to +150°C
−40°C to +150°C
−40°C to +150°C
−40°C to +150°C
Temperature Accuracy2
±1°C
±1°C
±1°C
±1°C
Z = RoHS Compliant Part.
Temperature accuracy is over a 0°C to 70°C temperature range.
Rev. B | Page 15 of 16
Package Description
6-Lead SOT-23
6-Lead SOT-23
8-Lead MSOP
8-Lead MSOP
Evaluation Board
Package Option
RJ-6
RJ-6
RM-8
RM-8
Branding
T1H
T1H
T1H
T1H
ADT7301
NOTES
©2005–2011 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D02884–0–6/11(B)
Rev. B | Page 16 of 16