ANALOG DEVICES ADT7302 Service Manual

±2°C Accurate, Micropower Digital

www.BDTIC.com/ADI

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 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

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
in

terfacing 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.

= 3.3 V

DD

Temperature Sensor

ADT7302

FUNCTIONAL BLOCK DIAGRAM

BAND GAP

TEMPERATURE

SENSOR

GND

ADT7302

INTERFACE

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. S

upply voltage of 2.7 V to 5.25 V.

pace-saving 6-lead SOT-23 and 8-lead MSOP packages.

3. S

4. M

aximum temperature accuracy of ±2°C.

5. 13-b

it temperature reading to 0.03125°C resolution.

13-BIT

ANALOG/DIGITAL

CONVERTER

TEMPERATURE

VALUE

REGISTER

SERIAL

BUS

Figure 1.

V

DD

CS
SCLK
DIN
DOUT

04662-001

The ADT7302’s wide supply voltage range, low supply current,

nd SPI-compatible interface make it ideal for a variety of

a
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.

hutdown mode that reduces the power consumption to

6. S

4.88 μW with V

ompatible with AD7814.

7. C

= 3.3 V at 1 SPS.

DD

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2005 Analog Devices, Inc. All rights reserved.

ADT7302

www.BDTIC.com/ADI

TABLE OF CONTENTS

Specifications..................................................................................... 3

Temperature Value Register.........................................................9

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

REVISION HISTORY

10/05—Revision 0: Initial Version

Serial Interface............................................................................ 10

Applications..................................................................................... 12

Microprocessor Interfacing....................................................... 12

Mounting the ADT7302............................................................ 14

Supply Decoupling ..................................................................... 14

Outline Dimensions ....................................................................... 15

Ordering Guide .......................................................................... 15

Rev. 0 | Page 2 of 16

ADT7302

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SPECIFICATIONS

TA = T

Table 1.

Parameter Min Typ Max Unit Test Conditions/Comments

TEMPERATURE SENSOR AND ADC VDD = 3.3 V (±10%) and 5 V (±5%).

±2.5 °C T
±3 °C T

SUPPLIES

190 300 μA VDD = 3.3 V. Powered up and not converting.

1.6 2.2 mA VDD = 5 V. Powered up and converting.
280 400 μA VDD = 5 V. Powered up and not converting.

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.

7.4 μW VDD = 5 V.

65 μW VDD = 5 V.

641 μW VDD = 5 V.
DIGITAL INPUT

DIGITAL OUTPUT

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. Once the temperature conversion is

complete, the ADT7302 is put back into shutdown mode.

3

Guaranteed by design and characterization, not production tested.

MIN

to T

, VDD = 2.7 V to 5.25 V, unless otherwise noted. All specifications for –40°C to +125°C, unless otherwise stated.

MAX

Accuracy ±1 ±2 °C TA = 0°C to 70°C.

= −20°C to +85°C.

A

= −40°C to +125°C.

A

Temperature Resolution 0.03125 °C
Autoconversion Update Rate, t

R

1 sec Temperature measurement every 1 second.
Temperature Conversion Time 800 μs
Thermal Time Constant

1

2 sec

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.

Shutdown Mode 0.2 1 μA VDD = 3.3 V, TA = 0°C to 70°C.

Power Dissipation

Normal Mode (Average) 631 μW VDD = 3.3 V. Auto conversion update, tR.

1.41 mW VDD = 5 V. Auto conversion update, tR.

Shutdown Mode (Average)

2

1 SPS 4.88 μW VDD = 3.3 V.

10 SPS 42.9 μW VDD = 3.3 V.

100 SPS 423 μW VDD = 3.3 V.

3

Input High Voltage, V
Input Low Voltage, V
Input Current, I
Input Capacitance, C

IL

IN

IN

3

Output High Voltage, V
Output Low Voltage, V
Output Capacitance, C

IH

OH

OL

OUT

2.5 V

0.8 V

±1 μA V

= 0 V to VDD.

IN

10 pF All digital inputs.

VDD − 0.3 V I

SOURCE

= I

= 200 μA.

SINK

0.4 V IOL = 200 μA.

50 pF

Rev. 0 | Page 3 of 16

ADT7302

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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.

T

= T

to T

A

MIN

Table 2.

Parameter

t

1

t

2

t

3

2

t

4

t

5

t

6

t

7

2

t

8

1

See Figure 14 for the SPI timing diagram.

2

Measured with the load circuit of Figure 2.

, VDD = 2.7 V to 5.25 V, unless otherwise noted.

MAX

1

Limit Unit Comments

5 ns min
25 ns min SCLK High Pulse Width

25 ns min SCLK Low Pulse Width
35 ns max Data Access Time After SCLK Falling Edge
20 ns min Data Setup Time Prior to SCLK Rising Edge
5 ns min Data Hold Time After SCLK Rising Edge
5 ns min

40 ns max

CS

to SCLK Setup Time

CS

to SCLK Hold Time

CS

to DOUT High Impedance

I

OL

1.6V

OH

04662-002

TO

OUTPUT

PIN

50pF

200μA

C

L

200μAI

Figure 2. Load Circuit for Data Access Time and Bus Relinquish Time

Rev. 0 | Page 4 of 16

ADT7302

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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 Dissipation

1

W

= (TJ max − T

MAX

2

)/θ

A

JA

Thermal Impedance

θJA, Junction-to-Ambient (Still Air) 190.4°C/W

8-Lead MSOP (RM-8)

Power Dissipation

1

Thermal Impedance

W

= (TJ max − T

3

MAX

2

)/θ

A

JA

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, PCB­mounted 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

1.2

1.0

0.8

0.6

0.4

0.2

MAXIMUM POWER DISSIPATION (W)

0

–40

0

–10

–20

–30

Figure 3. Maximum Power Dissipation vs. Temperature

SOT-23

MSOP

60

50

40

30

20

10

TEMPERATURE (°C)

90

80

70

100

110

120

130

140

150

04662-003

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