Analog Devices AD7414 5 d Datasheet

ⴞ0.5ⴗC Accurate, 10-Bit Digital

Temperature Sensors in SOT-23

AD7414/AD7415

FEATURES
10-Bit Temperature-to-Digital Converter
Temperature Range: –40ⴗC to +125ⴗC
Typical Accuracy of ⴞ0.5ⴗC at +40ⴗC
SMBus/I

2C®

-Compatible Serial Interface
3 ␮A Power-Down Current
Temperature Conversion Time: 29 ␮s Typ
Space-Saving 6-Lead (AD7414) and 5-Lead (AD7415)

SOT-23 Packages
Pin Selectable Addressing via AS
Overtemperature Indicator (AD7414 Only)
SMBus Alert Function (AD7414 Only)
4 Versions Allow 8 I
2 Versions Allow 6 I

2

C Addresses (AD7414)

2

C Addresses (AD7415)

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

GENERAL DESCRIPTION

The AD7414/AD7415 is a complete temperature monitoring
system in 6-lead and 5-lead SOT-23 packages. It contains a
band gap temperature sensor and a 10-bit ADC to monitor and
digitize the temperature reading to a resolution of 0.25°C.

The AD7414/AD7415 provides a 2-wire serial interface that is
compatible with SMBus and I

2

C interfaces. The part comes in
four versions: the AD7414/AD7415-0, AD7414/AD7415-1,
AD7414-2, and AD7414-3. The AD7414/AD7415-0 and
AD7414/AD7415-1 versions provide a choice of three different
SMBus addresses for each version. All four AD7414 versions
give the possibility of eight different I
AD7415 versions allow up to six I

2

C addresses while the two

2

C addresses to be used.

The AD7414/AD7415’s 2.7 V supply voltage, low supply
current, serial interface, and small package size make it ideal for
a variety of applications, including personal computers, office
equipment, cellular phones, and domestic appliances.

In the AD7414, on-chip registers can be programmed with high
and low temperature limits, and an open-drain overtemperature
indicator output (ALERT) becomes active when a programmed limit
is exceeded. A configuration register allows programming of the
state of the ALERT output (active high or active low). This
output can be used as an interrupt or as an SMBus alert.

REV. D

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. 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.

FUNCTIONAL BLOCK DIAGRAM

GND

AS

GND

AS

BAND GAP

TEMPERATURE

SENSOR

CONFIGURATION

REGISTER

SETPOINT

T

HIGH

REGISTER

T

SETPOINT

LOW

REGISTER

AD7414

AD7415

BAND GAP

TEMPERATURE

SENSOR

CONFIGURATION

REGISTER

SMBus/I2C

INTERFACE

SMBus/I2C

INTERFACE

10-BIT

ANALOG-DIGITAL

CONVERTER

TEMPERATURE

VALUE

REGISTER

SETPOINT

COMPARATOR

10-BIT

ANALOG-DIGITAL

CONVERTER

TEMPERATURE

VALUE

REGISTER

V

DD

ALERT

SCL

SDA

V

DD

SCL

SDA

PRODUCT HIGHLIGHTS

1. The AD7414/AD7415 has an on-chip temperature sensor that
allows an accurate measurement of the ambient temperature
to be made. It is capable of ⫾0.5°C temperature accuracy.

2. SMBus/I

2

C-compatible serial interface with pin selectable
choice of three addresses per version of the AD7414/AD7415,
eight address options in total for the AD7414, and six in
total for the AD7415.

3. Supply voltage of 2.7 V to 5.5 V.

4. Space-saving 5-lead and 6-lead SOT-23 packages.

5. 10-bit temperature reading to 0.25°C resolution.

6. The AD7414 has an overtemperature indicator that can be
software disabled. Used as an interrupt of SMBus alert.

7. One-shot and automatic temperature conversion rates.

Purchase of licensed I2C components of Analog Devices or one of its sublicensed
Associated Companies conveys a license for the purchaser under the Philips I2C
Patent Rights to use these components in an I2C system, provided that the system
conforms to the I2C Standard Specification as defined by Philips.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

1

AD7414/AD7415–SPECIFICATIONS

(TA = T

Parameter A Version Unit Test Conditions/Comments

TEMPERATURE SENSOR AND ADC

Accuracy

2

± 0.5 °C typ VDD = 3 V @ +40°C
–0.87 to +0.823°C max VDD = 3 V @ +40°C

± 1.5 °C max VDD = 3 V @ –40°C to +70°C
± 2.0 °C max V
± 3.0 °C max VDD = 3 V @ –40°C to +125°C
± 2.0 °C typ V

3

± 1.87

°C max VDD = 5.5 V @ +40°C
± 2.0 °C typ VDD = 5.5 V @ –40°C to +85°C
± 3.0 °C max V
± 3.0 °C typ VDD = 5.5 V @ –40°C to +125°C

Resolution 10 Bits
Update Rate, t

R

800 ms typ

Temperature Conversion Time 25 µs typ

POWER SUPPLIES

Supply Current

Peak Supply Current
Supply Current – Nonconverting 900 µA max Peak Current between Conversions
Inactive Serial Bus

4

5

6

1.2 mA typ Current during Conversion

Normal Mode @ 3 V 169 µA typ Supply Current with Serial Bus Inactive. Part not
Normal Mode @ 5 V 188 µA typ converting and D7 of Configuration Register = 0.

Active Serial Bus

7

Normal Mode @ 3 V 180 µA typ Supply Current with Serial Bus Active. Part not
Normal Mode @ 5 V 214 µA typ converting and D7 of Configuration Register = 0.

Shutdown Mode 3 µA max D7 of Configuration Register = 1. Typical values

DIGITAL INPUT

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

IL

8

IN

IN

IH

2.4 V min

0.8 V max
± 1 µA max VIN = 0 V to V
10 pF max All Digital Inputs

DIGITAL OUTPUT (OPEN-DRAIN)

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

OL

OH

OUT

OH

2.4 V min

0.4 V max IOL = 1.6 mA
1 µA max VOH = 5 V
10 pF max Typ = 3 pF

ALERT Output Saturation Voltage 0.8 V max I

AC ELECTRICAL CHARACTERISTICS

Serial Clock Period, t

1

Data In Setup Time to SCL High, t
Data Out Stable after SCL Low, t

9, 10

2.5 µs min See Figure 1

2

3

50 ns min See Figure 1
0 ns min See Figure 1

SDA Low Setup Time to SCL Low

(Start Condition), t

4

50 ns min See Figure 1

SDA High Hold Time after SCL High

(Stop Condition), t

5

SDA and SCL Fall Time, t

6

50 ns min See Figure 1
90 ns max See Figure 1

Power-Up Time 4 µs typ

NOTES

1

Temperature range as follows: A Version = –40°C to +125°C.

2

Accuracy specifications apply only to voltages listed under Test Conditions. See Temperature Accuracy vs. Supply section for typical accuracy performance over the full V
supply range.

3

100% production tested at 40°C to these limits.

4

These current values can be used to determine average power consumption at different one-shot conversion rates. Average power consumption at the automatic conversion rate
of 1.25 kHz is 940 µW.

5

This peak supply current is required for 29 µs (the conversion time plus power-up time) out of every 800 µs (the conversion rate).

6

These current values are derived by not issuing a stop condition at the end of a write or read, thus preventing the part from going into a conversion.

7

The current is derived assuming a 400 kHz serial clock being active continuously.

8

On power-up, the initial input current, IIN, on the AS pin is typically 50 µA.

9

The SDA and SCL timing is measured with the input filters turned on so as to meet the Fast Mode I
but has a negative effect on the EMC behavior of the part.

10

Guaranteed by design. Not tested in production.

Specifications subject to change without notice.

to T

MIN

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

MAX

= 3 V @ –40°C to +85°C

DD

= 3 V @ –40°C to +125°C

DD

= 5.5 V @ –40°C to +85°C

DD

are 0.04 µA at 3 V and 0.5 µA at 5 V.

DD

= 4 mA

OUT

DD

2

C specification. Switching off the input filters improves the transfer rate

REV. D–2–

AD7414/AD7415

PIN FUNCTION DESCRIPTIONS

Mnemonic Description

AS Logic Input. Address select input that selects one

of three I2C addresses for the AD7414/AD7415
(see Table I). Recommend a pull-up or pull-down
resistor of 1 kΩ.

GND Analog and Digital Ground

V

DD

Positive Supply Voltage, 2.7 V to 5.5 V

SDA Digital I/O. Serial bus bidirectional data. Open-

drain output.

ALERT AD7414 Digital Output. Overtemperature indicator

becomes active when temperature exceeds T

HIGH

.

Open-drain output.

SCL Digital Input. Serial bus clock.

ABSOLUTE MAXIMUM RATINGS

1

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

SDA Input Voltage to GND . . . . . . . . . . . . . . –0.3 V to +7 V

SDA Output Voltage to GND . . . . . . . . . . . . . –0.3 V to +7 V

SCL Input Voltage to GND . . . . . . . . . . . . . . –0.3 V to +7 V

ALERT Output Voltage to GND . . . . . . . . . . –0.3 V to +7 V

Operating Temperature Range . . . . . . . . . . –40°C to +125°C

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

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

5-Lead SOT-23 (RJ-5)

Power Dissipation
Thermal Impedance

2

. . . . . . . . . . . . . . . . .

4

W

MAX

= (T

JMAX

– T

3

)/␪

A

JA

␪JA, Junction-to-Ambient (still air) . . . . . . . . . . . 240°C/W

6-Lead SOT-23 (RJ-6)

Power Dissipation
Thermal Impedance

2

. . . . . . . . . . . . . . . . .

4

W

MAX

= (T

JMAX

– T

3

)/␪

A

JA

␪JA, Junction-to-Ambient (still air) . . . . . . . . . . 190.4°C/W

8-Lead MSOP (RM-8)

Power Dissipation
Thermal Impedance

2

. . . . . . . . . . . . . . . . .

4

W

MAX

= (T

JMAX

– T

3

)/␪

A

JA

␪JA, Junction-to-Ambient (still air) . . . . . . . . . . 205.9°C/W

␪

, Junction-to-Case . . . . . . . . . . . . . . . . . . . .43.74°C/W

JC

NOTES

1

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.

2

Values relate to package being used on a standard 2-layer PCB.

3

TA = ambient temperature.

4

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.

t

SCL

SDA

DATA IN

SDA

DATA OUT

t

4

1

t

2

t

3

t

5

t

6

PIN CONFIGURATIONS

SOT-23

SDA

AS

GND 2

V

DD

1

AD7414

Top View

(Not to Scale)

6

5

ALERT

SCL34

MSOP

NCNC18

AD7414

SDA 2 7 AS

ALERT GND36

SCL V

Top View

(Not to Scale)

45

NC = NO CONNECT

DD

SOT-23

15

AS

AD7415

Top View

2

GND

V

DD

(Not to Scale)

3

SDA

SCL

4

Table I. I2C Address Selection

Part Number AS Pin I2C Address

AD7414-0 Float 1001 000
AD7414-0 GND 1001 001
AD7414-0 V

DD

1001 010

AD7414-1 Float 1001 100
AD7414-1 GND 1001 101
AD7414-1 V

DD

1001 110

AD7414-2 N/A 1001 011

AD7414-3 N/A 1001 111

AD7415-0 Float 1001 000
AD7415-0 GND 1001 001
AD7415-0 V

DD

1001 010

AD7415-1 Float 1001 100
AD7415-1 GND 1001 101
AD7415-1 V

DD

1001 110

REV. D

Figure 1. Diagram for Serial Bus Timing

–3–

AD7414/AD7415

ORDERING GUIDE

Temperature Typ Temperature Package Package Minimum

Model Range Error @ 3 V Option Description Branding Quantities/Reel

AD7414ART-0REEL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHA 3,000
AD7414ART-0REEL –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHA 10,000
AD7414ART-0500RL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHA 500
AD7414ARM-0REEL7 –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHA 3,000
AD7414ARM-0REEL –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHA 10,000
AD7414ARM-0 –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHA

AD7414ART-1REEL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHB 3,000
AD7414ART-1REEL –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHB 10,000
AD7414ART-1500RL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHB 500
AD7414ARM-1REEL7 –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHB 3,000
AD7414ARM-1REEL –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHB 10,000
AD7414ARM-1 –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHB

AD7414ART-2REEL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHC 3,000
AD7414ART-2REEL –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHC 10,000

AD7414ART-3REEL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHD 3,000
AD7414ART-3REEL –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHD 10,000

AD7415ART-0REEL7 –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGA 3,000
AD7415ART-0REEL –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGA 10,000
AD7415ART-0500RL7 –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGA 500

AD7415ART-1REEL7 –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 3,000
AD7415ART-1REEL –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 10,000
AD7415ART-1500RL7 –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 500

AD7415ARTZ-500RL7* –40°C to +125°C ±2°C RT-5 5-Lead SOT-23 CGB 500
AD7415ARTZ-0REEL* –40°C to +125°C ±2°C RT-5 5-Lead SOT-23 CGB 500
AD7415ARTZ-0REEL7* –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 500
AD7415ARTZ-1500RL7* –40°C to +125°C ±2°C RT-5 5-Lead SOT-23 CGB 500
AD7415ARTZ-1REEL* –40°C to +125°C ±2°C RT-5 5-Lead SOT-23 CGB 500
AD7415ARTZ-1REEL7* –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 500

EVAL-AD7414/AD7415EB Evaluation Board

*Z = Pb-free part.

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
AD7414/AD7415 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. D–4–

AD7414/AD7415

TO ADC

V

OUT

+

V

OUT

–

SENSING

TRANSISTOR

V

DD

I

NⴛI

SENSING

TRANSISTOR

CIRCUIT INFORMATION

The AD7414/AD7415 is a standalone digital temperature sensor.
The on-chip temperature sensor allows an accurate measurement
of the ambient device temperature to be made. The 10-bit A/D
converter converts the temperature measured into a twos comple­ment format for storage in the temperature register. The A/D
converter is made up of a conventional successive-approximation
converter based around a capacitor DAC. The serial interface is

2

C and SMBus compatible. The AD7414/AD7415 requires a

I

2.7 V to 5.5 V power supply. The temperature sensor has a
working measurement range of –40°C to +125°C.

FUNCTIONAL DESCRIPTION

Temperature measurement is initiated by a couple of methods.
The first uses an internal clock countdown of 800 ms, and a
conversion is performed. The internal oscillator is the only circuit
that is powered up between conversions, and once it times out,
every 800 ms, a wake-up signal is sent to power up the rest of
the circuitry. A monostable is activated at the beginning of the
wake-up signal to ensure that sufficient time is given to the power­up process. The monostable typically takes 4 µs to time out. It
then takes typically 25 µs for each conversion to be completed.
The new temperature value is loaded into the temperature value
register and ready for reading by the I

2

C interface.

A temperature measurement is also initiated every time the
one-shot method is used. This method requires the user to
write to the one-shot bit in the configuration register when a
temperature measurement is needed. Setting the one-shot bit
to a 1 will start a temperature conversion directly after the
write operation. The track-and-hold goes into hold approxi­mately 4 µs (monostable timeout) after the STOP condition
and a conversion is then initiated. Typically 25 µs later, the
conversion is complete and the temperature value register is
loaded with a new temperature value.

The measurement modes are compared with a high temperature
limit, stored in an 8-bit read/write register. This is applicable only
to the AD7414 since the AD7415 does not have an ALERT pin
and subsequently does not have an overtemperature monitoring
function. If the measurement is greater than the high limit, the
ALERT pin is activated (if it has already been enabled in the
configuration register). There are two ways to deactivate the
ALERT pin again: when the alert reset bit in the configuration
register is set to a 1 by a write operation, and when the tempera­ture measured is less than the value in the T

register. This

LOW

ALERT pin is compatible with the SMBus SMBALERT
option.

Configuration functions consist of

• Switching between normal operation and full power-down

• Enabling or disabling the SCL and SDA filters

• Enabling or disabling the ALERT function

• Setting ALERT pin polarity

SUPPLY

2.7V TO

5.5V
10␮F

0.1␮F

1k⍀

V

AS

GND

AD7414

DD

SDA

SCL

ALERT

␮C/␮P

Figure 2. Typical Connection Diagram

MEASUREMENT TECHNIQUE

A common method of measuring temperature is to exploit the
negative temperature coefficient of a diode, or the base-emitter
voltage of a transistor, operated at constant current. Unfortu­nately, this technique requires calibration to null the effect of
the absolute value of V

, which varies from device to device.

BE

The technique used in the AD7414/AD7415 is to measure the
change in V

when the device is operated at two different currents.

BE

This is given by

∆VKTqnN

=×

BE

1

()

where:

K is Boltzmann’s constant.
q is the charge on the electron (1.6 × 10

–19

Coulombs).

T is the absolute temperature in Kelvins.
N is the ratio of the two currents.

Figure 3. Temperature Measurement Technique

Figure 3 shows the method the AD7414/AD7415 uses to measure
the ambient device temperature. To measure ∆V

, the sensor

BE

(substrate transistor) is switched between operating currents of
I and N × I. The resulting waveform is passed through a chopper­stabilized amplifier that performs the functions of amplification
and rectification of the waveform to produce a dc voltage propor­tional to ∆V

. This voltage is measured by the ADC to give a

BE

temperature output in 10-bit twos complement format.

REV. D

–5–