Analog Devices AD7814 Datasheet

REV. B

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a

AD7814

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] World Wide Web Site: http://www.analog.com
Fax: [phone] © Analog Devices, Inc., 2000

10-Bit Digital Temperature Sensor

in 6-Lead SOT-23

FUNCTIONAL BLOCK DIAGRAM

SERIAL

BUS

INTERFACE

AD7814

V

DD

CS

SCLK
DIN

DOUT

GND

TEMPERATURE

VALUE

REGISTER

10-BIT

ANALOG/DIGITAL

CONVERTER

BANDGAP

TEMPERATURE

SENSOR

FEATURES
10-Bit Temperature-to-Digital Converter
–55ⴗC to +125ⴗC Operating Temperature Range
ⴞ2ⴗC Accuracy
SPI- and DSP-Compatible Serial Interface
Shutdown Mode
Space-Saving SOT-23 Package

APPLICATIONS
Hard Disk Drives
Personal Computers
Electronic Test Equipment
Office Equipment
Domestic Appliances
Process Control

GENERAL DESCRIPTION

The AD7814 is a complete temperature monitoring system in
an SOT-23 package or 8-lead µSOIC package. It contains a
bandgap temperature sensor and 10-bit ADC to monitor and
digitize the temperature reading to a resolution of +0.25°C.

The AD7814 has a flexible serial interface that allows easy inter­facing to most microcontrollers. The interface is compatible
with SPI™, QSPI and MICROWIRE™ protocol and is also
compatible with DSPs. The part features a standby mode that is
controlled via the serial interface.

The AD7814’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, and
domestic appliances.

SPI is a trademark of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor, Inc.

PRODUCT HIGHLIGHTS

1. The AD7814 has an on-chip temperature sensor that allows
an accurate measurement of the ambient temperature. The
measurable temperature range is –55°C to +125°C, with a
± 2°C temperature accuracy.

2. Supply voltage of +2.7 V to +5.5 V.

3. Space-saving 6-lead SOT-23 package and 8-lead µSOIC
package.

4. 10-bit temperature reading to +0.25°C resolution.

5. The AD7814 features a standby mode that reduces the
current consumption to 1 µA.

REV. B

–2–

AD7814–SPECIFICATIONS

1, 2

Parameter Min Typ Max Units Test Conditions/Comments

TEMPERATURE SENSOR AND ADC

Accuracy ± 2.0 °CT

A

= 0°C to +85°C. VDD = +3 V to +5.5 V

3

± 2.5 °CT

A

= –40°C to 0°C. VDD = +3 V to +5.5 V

3

± 2.0 ± 3.5 °CT

A

= –55°C to +125°C. VDD = +3 V to +5.5 V
Resolution 10 Bits
Update Rate, t

R

400 µs

Temperature Conversion Time 25 µs

SUPPLIES

Supply Voltage 2.7 5.5 V For Specified Performance
Supply Current

Normal Mode 250 400 µA
Shutdown Mode 1 3 µA

Power Dissipation 80 µWV

DD

= +3 V. Using Normal Mode

Power Dissipation V

DD

= +3 V. Using Shutdown Mode
1 sps 3 µW
10 sps 3.3 µW
100 sps 6 µW

DIGITAL INPUT

Input High Voltage, V

IH

2.4 V

Input Low Voltage, V

IL

0.8 V

Input Current, I

IN

± 1 µAV

IN

= 0 V to V

DD

Input Capacitance, C

IN

10 pF All Digital Inputs

DIGITAL OUTPUT

Output High Voltage, V

OH

VDD – 0.3 V I

SOURCE

= I

SINK

= 200 µA

Output Low Voltage, V

OL

0.4 V IOL = 200 µA

Output Capacitance, C

OUT

50 pF

NOTES

1

All specifications apply for –55°C to +125°C unless otherwise stated.

2

Guaranteed by design and characterization, not production tested.

3

For VDD = +2.7 V to +3 V and TA = –40°C to +85°C, the typical temperature error is ±2°C.

Specifications subject to change without notice.

TIMING CHARACTERISTICS

1, 2, 3

Parameter Limit Units Comments

t

1

0 ns min CS to SCLK Setup Time

t

2

50 ns min SCLK High Pulsewidth

t

3

50 ns min SCLK Low Pulsewidth

t

4

4

35 ns max Data Access Time After SCLK Falling Edge

t

5

20 ns min Data Setup Time Prior to SCLK Rising Edge

t

6

0 ns min Data Hold Time After SCLK Rising Edge

t

7

0 ns min CS to SCLK Hold Time

t

8

4

40 ns max CS to DOUT High Impedance

NOTES

1

Guaranteed by design and characterization, not production tested.

2

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.

3

See Figure 2.

4

Measured with the load circuit of Figure 1.

(TA = T

MIN

to T

MAX

, VDD = +2.7 V to +5.5 V, unless otherwise noted)

(TA = T

MIN

to T

MAX

, VDD = +2.7 V to +5.5 V, unless otherwise noted)

REV. B

AD7814

–3–

ORDERING GUIDE

Temperature Temperature Package Branding Package

Model Range Error* Description Information Option

AD7814ART –55°C to +125°C ± 2°C 6-Lead SOT-23 CAA RT-6
AD7814ARM –55°C to +125°C ± 2°C 8-Lead µSOIC CAA RM-8

*Temperature error is over 0°C to +85°C temperature range.

ABSOLUTE MAXIMUM RATINGS*

VDD to GND . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V

Digital Input Voltage to GND . . . . . . . –0.3 V to V

DD

+ 0.3 V

Digital Output Voltage to GND . . . . . –0.3 V to V

DD

+ 0.3 V

Operating Temperature Range . . . . . . . . . . –55°C to +125°C

Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C

Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . +150°C

SOT-23, Power Dissipation . . . . . . . . . . . . . . . . . . . . 450 mW

θ

JA

Thermal Impedance . . . . . . . . . . . . . . . . . . . . 240°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . +215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . +220°C

µSOIC Package, Power Dissipation . . . . . . . . . . . . . . 450 mW

θ

JA

Thermal Impedance . . . . . . . . . . . . . . . . . . . . 206°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . +215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . +220°C

*Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent 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.

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 the AD7814 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.

WARNING!

ESD SENSITIVE DEVICE

+1.6V

I

OL

200␮A

200␮A

I

OH

TO

OUTPUT

PIN

C

L

50pF

Figure 1. Load Circuit for Data Access Time and Bus
Relinquish Time