AD7414ARMZ-0REEL - Analog Devices, Inc.

±0.5°C Accurate, 10-Bit Digital

Temperature Sensors in SOT-23

AD7414/AD7415

Rev. F

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

FEATURES

10-bit temperature-to-digital converter

Temperature range: −40°C to +125°C

Typical accuracy of ±0.5°C at +40°C

SMBus/I2C®-compatible serial interface

3 μA power-down current

Temperature conversion time: 29 μs 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 I2C addresses (AD7414)

2 versions allow 6 I2C addresses (AD7415)

APPLICATIONS

Hard disk drives

Personal computers

Electronic test equipment

Office equipment

Domestic appliances

Process control

Cellular phones

GENERAL DESCRIPTION

The AD7414/AD7415 are complete temperature monitoring

systems in 6-lead and 5-lead SOT-23 packages. They contain 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 provide a 2-wire serial interface that is

compatible with SMBus and I2C interfaces. The parts come 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 I2C addresses while the two AD7415 versions allow up to

six I2C addresses to be used.

The AD7414/AD7415’s 2.7 V supply voltage, low supply current,

serial interface, and small package size make them 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

FUNCTIONAL BLOCK DIAGRAM

SDA

SCL

SMBus/I

INTERFACE

10-BIT

ANALOG-DIGITAL

CONVERTER

BAND GAP

TEMPERATURE

SENSOR

CONFIGURATION

TEMPERATURE

VALUE

AD7415

GND

SDA

SCL

LOW

SETPOINT

COMPARATOR ALERT

AD7414

SMBus/I

INTERFACE

10-BIT

ANALOG-DIGITAL

CONVERTER

BAND GAP

TEMPERATURE

SENSOR

CONFIGURATION

VALUE

HIGH

SETPOINT

02463-001

Figure 1.

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.

PRODUCT HIGHLIGHTS

1. On-chip temperature sensor. The sensor allows an accurate

measurement of the ambient temperature to be made. It is

capable of ±0.5°C temperature accuracy.

2. SMBus/I2C-compatible serial interface. The interface offers 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. Overtemperature indicator. This indicator can be software

disabled. It is used as an interrupt of SMBus alert.

7. One-shot and automatic temperature conversion rates.

AD7414/AD7415

Rev. F | Page 2 of 20

TABLE OF CONTENTS

Specifications ..................................................................................... 3

Absolute Maximum Ratings ............................................................ 5

ESD Caution .................................................................................. 5

Pin Configurations and Function Descriptions ............................ 6

Theory of Operation ......................................................................... 7

Circuit Information ...................................................................... 7

Functional Description................................................................. 7

Measurement Technique .............................................................. 7

Temperature Data Format ............................................................ 8

Internal Register Structure ............................................................... 9

Address Pointer Register .............................................................. 9

Configuration Register (Address 0X01) ..................................... 9

Temperature Value Register (Address 0X00) ........................... 10

AD7414 THIGH Register (Address 0X02) ................................... 10

AD7414 TLOW Register (Address 0X03) .................................... 10

Serial Interface ................................................................................. 12

Serial Bus Address ....................................................................... 12

Write Mo de .................................................................................. 12

Read Mode ................................................................................... 12

SMBUS ALERT............................................................................. 13

Power-On Defaults ..................................................................... 13

Operating Modes ........................................................................ 13

Power vs. Throughput ................................................................ 14

Mounting the AD7414/AD7415 ............................................... 14

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

Temperature Accuracy vs. Supply ............................................. 15

Typical Temperature Error Graph ............................................ 15

Outline Dimensions ........................................................................ 16

Ordering Guide ........................................................................... 18

REVISION HISTORY

11/10—Rev. E to Rev. F

Added Data Hold Time, t7 Parameter, Table 1 .............................. 4

Changes to Figure 2 ........................................................................... 4

Updated to Outline Dimensions ................................................... 16

Changes to Ordering Guide ........................................................... 18

4/05—Rev. D to Rev. E

Updated Format .................................................................. Universal

Changes to Absolute Maximum Ratings ........................................ 6

Changes to Figure 6 ........................................................................... 7

Changes to Ordering Guide ........................................................... 17

9/04—Rev. C to Rev. D.

Changes to Absolute Maximum Ratings ........................................ 3

Updated Ordering Guide ................................................................. 4

8/03—Rev. B to Rev. C.

Change to Temperature Range ......................................... Universal

Updated Features ............................................................................... 1

Updated Specifications ..................................................................... 2

Updated Absolute Maximum Ratings ............................................ 3

Updated Ordering Guide ................................................................. 4

Updated Circuit Information .......................................................... 5

Updated Temperature Data Format................................................ 6

Updated Temperature Value Register ............................................. 8

Updated Figure 14 ........................................................................... 11

Updated Outline Dimensions ........................................................ 12

11/02—Rev. A to Rev. B.

Changes to Absolute Maximum Ratings........................................ 3

10/02—Rev. 0 to Rev. A.

Changes to Specifications ................................................................ 2

Changes to Pin Function Descriptions .......................................... 3

Changes to Absolute Maximum Ratings........................................ 3

Ordering Guide Updated ................................................................. 4

Change to Figure 2 ............................................................................ 5

Added to Typical Temperature

Error Graph section ........................................................................ 11

Added Figure 15 .............................................................................. 11

Outline Dimensions updated ........................................................ 12

7/01—Revision 0: Initial Version

AD7414/AD7415

Rev. F | Page 3 of 20

SPECIFICATIONS

TA = TMIN to TMAX, VDD = 2.7 V to 5.5 V, unless otherwise noted. Temperature range as follows: A version = −40°C to +125°C.

Table 1.

Parameter A Version Unit Test Conditions/Comments

TEMPERATURE SENSOR AND ADC

Accuracy1 ±0.5 °C typ VDD = 3 V @ +40°C

−0.87 to +0.822 °C max VDD = 3 V @ +40°C

±1.5 °C max VDD = 3 V @ −40°C to +70°C

±2.0 °C max VDD = 3 V @ −40°C to +85°C

±3.0 °C max VDD = 3 V @ −40°C to +125°C

±2.0 °C typ VDD = 3 V @ −40°C to +125°C

±1.872 °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 VDD = 5.5 V @ −40°C to +85°C

±3.0 °C typ VDD = 5.5 V @ −40°C to +125°C

Resolution 10 Bits

Update Rate, tR 800 ms typ

Temperature Conversion Time 25 μs typ

POWER SUPPLIES

Supply Current3

Peak Supply Current4 1.2 mA typ Current during conversion

Supply Current – Nonconverting 900 μA max Peak current between conversions

Inactive Serial Bus5

Normal Mode @ 3 V 169 μA typ Supply current with serial bus inactive. Part not

converting and D7 of configuration register = 0.

Normal Mode @ 5 V 188 μA typ

Active Serial Bus6

Normal Mode @ 3 V 180 μA typ Supply current with serial bus active. Part not

converting and D7 of configuration register = 0.

D7 of configuration register = 1. Typical values

are 0.04 μA at 3 V and 0.5 μA at 5 V.

Normal Mode @ 5 V 214 μA typ

Shutdown Mode 3 μA max

DIGITAL INPUT

Input High Voltage, VIH 2.4 V min

Input Low Voltage, VIL 0.8 V max

Input Current, IIN7 ±1 μA max VIN = 0 V to VDD

Input Capacitance, CIN 10 pF max All digital inputs

DIGITAL OUTPUT (OPEN-DRAIN)

Output High Voltage, VOH 2.4 V min

Output Low Voltage, VOL 0.4 V max IOL = 1.6 mA

Output High Current, IOH 1 μA max VOH = 5 V

Output Capacitance, COUT 10 pF max Typ = 3 pF

ALERT Output Saturation Voltage 0.8 V max IOUT = 4 mA

AD7414/AD7415

Rev. F | Page 4 of 20

Parameter A Version Unit Test Conditions/Comments

AC ELECTRICAL CHARACTERISTICS8, 9

Serial Clock Period, t1 2.5 μs min See Figure 2

Data In Setup Time to SCL High, t2 50 ns min See Figure 2

Data Out Stable after SCL Low, t3 0 ns min See Figure 2

SDA Low Setup Time to SCL Low

(Start Condition), t4

50 ns min See Figure 2

SDA High Hold Time after SCL High

(Stop Condition), t5

50 ns min See Figure 2

SDA and SCL Fall Time, t6 90 ns max See Figure 2

Data Hold Time, t7 35 ns min See Figure 2

Power-Up Time 4 μs typ

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

full VDD supply range.

2 100% production tested at 40°C to these limits.

3 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.

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

5 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.

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

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

8 The SDA and SCL timing is measured with the input filters turned on so as to meet the fast mode I2C specification. Switching off the input filters improves the transfer

rate but has a negative effect on the EMC behavior of the part.

9 Guaranteed by design. Not tested in production.

SCL

SDA

DATA IN

SDA

DATA OUT

02463-002

Figure 2. Diagram for Serial Bus Timing

AD7414/AD7415

Rev. F | Page 5 of 20

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

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 Dissipation1, 2 WMAX = (TJMAX − TA)/θJA

Thermal Impedance3

θJA, Junction-to-Ambient (still air) 240°C/W

6-Lead SOT-23 (RJ-6)

Power Dissipation1, 2 W

MAX = (TJMAX − TA)/θJA

Thermal Impedance3

θJA, Junction-to-Ambient (still air) 190.4°C/W

8-Lead MSOP (RM-8)

Power Dissipation1, 2 W

MAX = (TJMAX − TA)/θJA

Thermal Impedance3

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/s max

Ramp-down Rate −6°C/s max

Ramp from 25°C to Peak Temperature 6 minutes max

IR Reflow Soldering in Pb-Free Package

Peak Temperature 260°C (0°C)

Time at Peak Temperature 20 sec to 40 sec

Ramp Rate 3°C/s max

Ramp-Down Rate −6°C/s max

Ramp from 25°C to Peak Temperature 8 minutes max

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

2 TA = ambient temperature.

3 Junction-to-case resistance is applicable to components featuring a

preferential flow direction, such as components mounted on a heat sink.

Junction-to-ambient resistance is more useful for air-cooled, PCB-mounted

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.

ESD CAUTION

AD7414/AD7415

Rev. F | Page 6 of 20

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

AS SDA

SCL

GND 2 5ALERT

AD7414

Top View

(Not to Scale)

02463-003

Figure 3. AD7414 Pin Configuration (SOT-23)

02463-004

SCL V

NC NC

LER

GND

SDA 2 7AS

NC = NO CONNECT

AD7414

Top View

(Not to Scale)

Figure 4. AD7414 Pin Configuration (MSOP)

AS SDA

SCL

GND 2

AD7415

Top View

(Not to Scale)

02463-005

Figure 5. AD7415 Pin Configuration (SOT-23)

Table 3. Pin Function Descriptions

Mnemonic Description

AS Logic Input. Address select input that selects one

of three I2C addresses for the AD7414/AD7415 (see

Table 4). Recommend a pull-up or pull-down

resistor of 1 kΩ.

GND Analog and Digital Ground.

VDD 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 THIGH. Open-drain output.

SCL Digital Input. Serial bus clock.

Table 4. I2C Address Selection

Part Number AS Pin I2C Address

AD7414-0 Float 1001 000

AD7414-0 GND 1001 001

AD7414-0 VDD 1001 010

AD7414-1 Float 1001 100

AD7414-1 GND 1001 101

AD7414-1 VDD 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 VDD 1001 010

AD7415-1 Float 1001 100

AD7415-1 GND 1001 101

AD7415-1 VDD 1001 110

AD7414/AD7415

Rev. F | Page 7 of 20

THEORY OF OPERATION

CIRCUIT INFORMATION

The AD7414/AD7415 are standalone digital temperature

sensors. The on-chip temperature sensor allows an accurate

measurement of the ambient device temperature to be made.

The 10-bit analog-to-digital converter converts the temperature

measured into a twos complement format for storage in the

temperature register. The ADC is made up of a conventional

successive-approximation converter based around a capacitor

digital-to-analog (DAC). The serial interface is I2C-and SMBus-

compatible. The AD7414/AD7415 require a 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 two 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 power-up 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 I2C

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

1 starts a temperature conversion directly after the write

operation. The track-and-hold goes into hold approximately

4 μs (monostable time out) 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 tempera-

ture limit, stored in an 8-bit read/write register. This is applica-

ble only to the AD7414, because 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 1 by a write operation, and when

the temperature measured is less than the value in the TLOW

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 the ALERT pin polarity

SUPPLY

2.7V TO

5.5V 10μF 1kΩ0.1μF

SDA

SCL

ALERT

GND

AD7414

02463-006

10kΩ10kΩ10kΩ

Figure 6. 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 VBE, which varies from device to

device. The technique used in the AD7414/AD7415 is to

measure the change in VBE when the device is operated at two

different currents. This is given by

(

)

NlnqKTVBE

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.

AD7414/AD7415

Rev. F | Page 8 of 20

OUT

–

TO ADC

SENSING

TRANSISTOR

SENSING

TRANSISTOR

II×N

02463-007

Figure 7. Temperature Measurement Technique

Figure 7 shows the method the AD7414/AD7415 use to

measure the ambient device temperature. To measure ΔVBE,

the sensor (substrate transistor) is switched between operating

currents of I and N × I. The resulting waveform is passed

through a chopper stabilized amplifier that performs the

functions of amplification and rectification of the waveform to

produce a dc voltage proportional to ΔVBE. This voltage is

measured by the ADC to give a temperature output in 10-bit,

twos complement format.

TEMPERATURE DATA FORMAT

The temperature resolution of the ADC is 0.25°C, which

corresponds to 1 LSB of the ADC. The ADC can theoretically

measure a temperature span of 255°C; the lowest practical value

is limited to −40°C due to the device maximum ratings. The

A grade can measure a temperature range of −40°C to +125°C.

(Temperature data format is shown in Table 5.)

Table 5. A Grade Temperature Data Format

Temperature Digital Output DB9…DB0

−55°C 11 0010 0100

−50°C 11 0011 1000

−25°C 11 1001 1100

−0.25°C 11 1111 1111

0°C 00 0000 0000

+0.25°C 00 0000 0001

+10°C 00 0010 1000

+25°C 00 0110 0100

+50°C 00 1100 1000

+75°C 01 0010 1100

+100°C 01 1001 0000

+125°C 01 1111 0100

The grade temperature conversion formula follows:

)(dCodeADC

eTemperaturPositive =

512)(

−

=dCodeADC

eTemperaturNegative

Note that DB9 is removed from the ADC code in the negative

temperature formula.

AD7414/AD7415

Rev. F | Page 9 of 20

INTERNAL REGISTER STRUCTURE

The AD7414 has five internal registers, as shown in Figure 8.

Four are data registers, and one is an address pointer register.

SDA

SCL

TEMPERATURE

VALUE

CONFIGURATION

HIGH

LOW

ADDRESS

POINTER

SERIAL BUS INTERFACE

02463-008

Figure 8. AD7414 Register Structure

The AD7415 has three internal registers, as shown in Figure 9.

Two are data registers, and one is an address pointer register.

SDA

SCL

TEMPERATURE

VALUE

CONFIGURATION

ADDRESS

POINTER

02463-009

Figure 9. AD7415 Register Structure

Each data register has an address pointed to by the address

pointer register when communicating with it. The temperature

value register is the only data register that is read-only.

ADDRESS POINTER REGISTER

The address pointer register is an 8-bit register that stores an

address that points to one of the four data registers of the

AD7414 and one of the two data registers of the AD7415. The

first byte of every serial write operation to the AD7414/AD7415

is the address of one of the data registers, which is stored in the

address pointer register and selects the data register to which

subsequent data bytes are written. Only the 2 LSBs of this

Table 6. Address Pointer Register

P7 P6 P5 P4 P3 P2 P1 P0

0 0 0 0 0 0 Register Select

Table 7. AD7414 Register Address

P1 P0 Register

0 0 Temperature value register (read-only)

0 1 Configuration register (read/write)

1 0 THIGH register (read/write)

1 1 TLOW register (read/write)

Table 8. AD7415 Register Address

P1 P0 Registers

0 0 Temperature value register (read-only)

0 1 Configuration register (read/write)

Table 9. AD7414 Configuration Register

D7 D6 D5 D4 D3 D2 D1 D0

PD FLTR ALERT

ALERT

POLARITY

ALERT

RESET

ONE

SHOT

TEST

MODE

01 1

1 0

1 0s1

1 Default settings at power-up.

CONFIGURATION REGISTER (ADDRESS 0X01)

The configuration register is an 8-bit read/write register that is

used to set the operating modes of the AD7414/AD7415. In the

AD7414, six of the MSBs are used (D7 to D2) to set the

operating modes (see Table 10). D0 and D1 are used for factory

settings and must have zeros written to them during normal

operation.

Table 10. AD7414 Configuration Register Settings

D7 Full power-down if = 1.

D6 Bypass SDA and SCL filtering if = 0.

D5 Disable ALERT if = 1.

D4 ALERT is active low if D4 = 0, ALERT is active high if D4 = 1.

D3 Reset the ALERT pin if set to 1. The next temperature

conversion has the ability to activate the ALERT function.

The bit status is not stored; thus this bit is 0 if read.

D2 Initiate a one shot temperature conversion if set to a 1.

The bit status is not stored; thus this bit is 0 if read.

Table 11. AD7415 Configuration Register

D7 D6 D5 D4 D3 D2 D1 D0

PD FLTR TEST MODE

0s1

ONE SHOT TEST MODE

01 11 0s1 0s1

1 Default settings at power-up.

AD7414/AD7415

Rev. F | Page 10 of 20

In the AD7415, only three of the bits are used (D7, D6, and D2)

to set the operating modes (see Table 12). D0, D1, and D3 to D5

are used for factory settings and must have zeros written to

them during normal operation.

Table 12. AD7415 Configuration Register Settings

D7 Full power-down if = 1.

D6 Bypass SDA and SCL filtering if = 0.

D2 Initiate a one-shot temperature conversion if set to 1.

The bit status is not stored; thus this bit is 0 if read.

If the AD7414/AD7415 are in power-down mode (D7 = 1), a

temperature conversion can still be initiated by the one-shot

operation. This involves a write operation to the configuration

the AD7414/AD7415 to power up, perform a single conversion,

and power down again. This is a very power efficient mode.

TEMPERATURE VALUE REGISTER (ADDRESS 0X00)

The temperature value register is a 10-bit, read-only register

that stores the temperature reading from the ADC in twos

complement format. Two reads are necessary to read data from

this register. Table 13 shows the contents of the first byte to be

read, while Table 14 and Tabl e 15 show the contents of the

second byte to be read from the AD7414 and AD7415,

respectively. In Tabl e 14, D3 to D5 of the second byte are used

as flag bits and are obtained from other internal registers. They

function as follows:

ALERT_Flag: The state of this bit is the same as that of the

ALERT pin.

THIGH_Flag: This flag is set to 1 when the temperature

measured goes above the THIGH limit. It is reset

when the second temperature byte (Table 14) is

read. If the temperature is still greater than the

THIGH limit after the read operation, the flag is

again.

TLOW_Flag: This flag is set to 1 when the temperature

measured goes below the TLOW limit. It is reset

when the second temperature byte (Table 14) is

read. If the temperature is still less than the TLOW

limit after the read operation, the flag is set again.

The full theoretical span of the ADC is 255°C, but in practice

the temperature measurement range is limited to the operating

range of the device, −40°C to +125°C for the A grade.

Table 13. Temperature Value Register (First Read)

D15 D14 D13 D12 D11 D10 D9 D8

MSB B8 B7 B6 B5 B4 B3 B2

Table 14. AD7414 Temperature Value Register (Second Read)

D7 D6 D5 D4 D3 D2 D1 D0

B1 LSB ALERT_Flag THIGH_Flag TLOW_Flag 0 0 0

Table 15. AD7415 Temperature Value Register (Second Read)

D7 D6 D5 D4 D3 D2 D1 D0

B1 LSB N/A N/A N/A N/A N/A N/A

AD7414 THIGH REGISTER (ADDRESS 0X02)

The THIGH register (see Table 16) is an 8-bit, read/write register

that stores the upper limit that activates the ALERT output.

Therefore, if the value in the temperature value register is

greater than the value in the THIGH register, the ALERT pin is

activated (that is, if ALERT is enabled in the configuration

resolution is 1°C.

Table 16. THIGH Register

D7 D6 D5 D4 D3 D2 D1 D0

MSB B6 B5 B4 B3 B2 B1 B0

AD7414 TLOW REGISTER (ADDRESS 0X03)

The TLOW register (see Table 17) is an 8-bit read/write register

that stores the lower limit that deactivates the ALERT output.

Therefore, if the value in the temperature value register is less

than the value in the TLOW register, the ALERT pin is

deactivated (that is, if ALERT is enabled in the configuration

Because it is an 8-bit register, the temperature resolution is 1°C.

Table 17. TLOW Register

D7 D6 D5 D4 D3 D2 D1 D0

MSB B6 B5 B4 B3 B2 B1 B0

AD7414/AD7415

Rev. F | Page 11 of 20

02463-010

FRAME 1

SERIAL BUS ADDRESS BYTE FRAME 2

ADDRESS POINTER REGISTER BYTE

SCL

1A2 A1 A0 P7 P6 P5 P4 P3 P2 P1 P0

ACK. BY

AD7414/AD7415 STOP BY

MASTER

START BY

MASTER

ACK. BY

AD7414/AD7415

00R/W

Figure 10. Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation

FRAME 3

DATA BYTE

D7 D6 D5 D4 D3 D2 D1 D0

ACK. BY

AD7414/AD7415 STOP BY

MASTER

SCL (CONTINUED)

SDA (CONTINUED)

SCL

SDA 1A2 A1 A0 P7 P6 P5 P4 P3 P2 P1 P0

ACK. BY

AD7414/AD7415

START B

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE FRAME 2

ADDRESS POINTER REGISTER BYTE

ACK. BY

AD7414/AD7415

191

•••

02463-011

R/W

Figure 11. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Register

SDA

NO ACK. BY

MASTER

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE FRAME 2

SINGLE DATA BYTE FROM AD7414/AD7415

ACK. BY

AD7414/AD7415

D7 D6 D5 D4 D3 D2 D1 D0A0A1A210

SCL

STOP BY

MASTER

0R/W

02463-012

Figure 12. Reading a Single Byte of Data from a Selected Register

D7 D6 D5 D4 D3 D2 D1 D0

NO ACK. BY

MASTER STOP BY

MASTER

FRAME 3

LEAST SIGNIFICANT DATA BYTE FROM AD7414/AD7415

SCL (CONTINUED)

SDA (CONTINUED)

SCL

SDA 1A2 A1 A0 D15 D14 D13 D12 D10 D11 D9 D8

ACK. BY

MASTER

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE FRAME 2

MOST SIGNIFICANT DATA BYTE FROM AD7414/AD7415

ACK. BY

AD7414/AD7415

•••

02463-013

R/W

Figure 13. Reading Two Bytes of Data from the Temperature Value Register

AD7414/AD7415

Rev. F | Page 12 of 20

SERIAL INTERFACE

Control of the AD7414/AD7415 is carried out via the I2C-

compatible serial bus. The AD7414/AD7415 are connected to

this bus as slave device, under the control of a master device,

such as the processor.

SERIAL BUS ADDRESS

Like all I2C-compatible devices, the AD7414/AD7415 have a

7-bit serial address. The four MSBs of this address for the

AD7414/AD7415 are set to 1001. The AD7414/AD7415 are

available in four versions: AD7414/AD7415-0, AD7414/

AD7415-1, AD7414-2, and AD7414-3. The first two versions

have three different I2C addresses available, which are selected

by either tying the AS pin to GND, to VDD, or letting the pin

float (see Table 4 ). By giving different addresses for the four

versions, up to eight AD7414s or six AD7415s can be connected

to a single serial bus, or the addresses can be set to avoid

conflicts with other devices on the bus.

The serial bus protocol operates as follows.

The master initiates data transfer by establishing a START

condition, defined as a high-to-low transition on the serial data

line SDA, while the serial clock line SCL remains high. This

indicates that an address/data stream follows. All slave periph-

erals connected to the serial bus respond to the START condi-

tion and shift in the next eight bits, consisting of a 7-bit address

(MSB first) plus an R/W bit, which determines the direction of

the data transfer and whether data is written to or read from the

slave device.

The peripheral whose address corresponds to the transmitted

address responds by pulling the data line low during the low

period before the ninth clock pulse, known as the acknowledge

bit. All other devices on the bus remain idle while the selected

device waits for data to be read from or written to it. If the R/W

bit is 0, the master writes to the slave device. If the R/W bit is 1,

the master reads from the slave device.

Data is sent over the serial bus in sequences of nine clock

pulses, eight bits of data followed by an acknowledge bit from

the receiver of data. Transitions on the data line must occur

during the low period of the clock signal and remain stable

during the high period, because a low-to-high transition when

the clock is high may be interpreted as a STOP signal.

When all data bytes have been read or written, stop conditions

are established. In WRITE mode, the master pulls the data line

high during the 10th clock pulse to assert a STOP condition. In

READ mode, the master device pulls the data line high during

the low period before the ninth clock pulse. This is known as

No Acknowledge. The master then takes the data line low

during the low period before the 10th clock pulse, then high

during the 10th clock pulse to assert a STOP condition.

Any number of bytes of data may be transferred over the serial

bus in one operation, but it is not possible to mix read and write

in one operation. The type of operation is determined at the

beginning and cannot then be changed without starting a new

operation.

WRITE MODE

Depending on the register being written to, there are two

different writes for the AD7414/AD7415.

Writing to the Address Pointer Register for a Subsequent

Read

In order to read data from a particular register, the address

pointer register must contain the address of that register. If it

does not, the correct address must be written to the address

pointer register by performing a single-byte write operation, as

shown in Figure 10. The write operation consists of the serial

bus address followed by the address pointer byte. No data is

written to any of the data registers. A read operation is then

performed to read the register.

Writing a Single Byte of Data to the Configuration

All three registers are 8-bit registers, so only one byte of data

can be written to each register. Writing a single byte of data to

one of these registers consists of the serial bus address, the data

by the data byte written to the selected data register. This is

illustrated in Figure 11.

READ MODE

Reading data from the AD7414/AD7415 is a 1- or 2-byte

operation. Reading back the contents of the configuration

read operation, as shown in Figure 12. The register address was

previously set up by a single-byte write operation to the address

pointer register. Once the register address has been set up, any

number of reads can subsequently be performed from that

again. To read from another register, the address pointer

address.

Reading data from the temperature value register is a 2-byte

operation, as shown in Figure 13. The same rules apply for a

2-byte read as a 1-byte read.

AD7414/AD7415

Rev. F | Page 13 of 20

SMBUS ALERT

The AD7414 ALERT output is an SMBus interrupt line for

devices that want to trade their ability to master for an extra

pin. The AD7414 is a slave-only device and uses the SMBus

ALERT to signal to the host device that it wants to talk. The

SMBus ALERT on the AD7414 is used as an overtemperature

indicator.

The ALERT pin has an open-drain configuration that allows the

ALERT outputs of several AD7414s to be wire-AND’ed together

when the ALERT pin is active low. Use D4 of the configuration

power-up default is active low. The ALERT function can be

disabled or enabled by setting D5 of the configuration register

to 1 or 0, respectively.

The host device can process the ALERT interrupt and

simultaneously access all SMBus ALERT devices through the

alert response address. Only the device that pulled the ALERT

low acknowledges the Alert Response Address (ARA). If more

than one device pulls the ALERT pin low, the highest priority

(lowest address) device wins communication rights via standard

I2C arbitration during the slave address transfer.

The ALERT output becomes active when the value in the

temperature value register exceeds the value in the THIGH

value stored in the TLOW register.

The ALERT output requires an external pull-up resistor. This

can be connected to a voltage different from VDD, provided the

maximum voltage rating of the ALERT output pin is not

exceeded. The value of the pull-up resistor depends on the

application, but it should be as large as possible to avoid

excessive sink currents at the ALERT output, which can heat the

chip and affect the temperature reading.

POWER-ON DEFAULTS

The AD7414/AD7415 always power up with these defaults:

Address pointer register pointing to the temperature value

THIGH register loaded with 7Fh.

TLOW register loaded with 80h.

Configuration register loaded with 40h.

Note that the AD7415 does not have any THIGH or TLOW registers.

OPERATING MODES

Mode 1

This is the power-on default mode of the AD7414/AD7415. In

this mode, the AD7414/AD7415 does a temperature conversion

every 800 ms and then partially powers down until the next

conversion occurs.

If a one-shot operation (setting D2 of the configuration register

to a 1) is performed between automatic conversions, a conver-

sion is initiated right after the write operation. After this

conversion, the part returns to performing a conversion every

800 ms.

Depending on where a serial port access occurs during a

conversion, that conversion might be aborted. If the conversion

is completed before the part recognizes a serial port access, the

temperature register is updated with the new conversion. If the

conversion is completed after the part recognizes a serial port

access, the internal logic prevents the temperature register from

being updated, because corrupt data could be read.

A temperature conversion can start anytime during a serial port

access (other than a one-shot operation), but the result of that

conversion is loaded into the temperature register only if the

serial port access is not active at the end of the conversion.

Mode 2

The only other mode in which the AD7414/AD7415 operates is

the full power-down mode. This mode is usually used when

temperature measurements are required at a very slow rate. The

power consumption of the part can be greatly reduced in this

mode by writing to the part to go to a full power-down. Full

power-down is initiated right after D7 of the configuration

When a temperature measurement is required, a write

operation can be performed to power up the part and put it into

one-shot mode (setting D2 of the configuration register to a 1).

The power-up takes approximately 4 μs. The part then performs

a conversion and is returned to full power-down. The

temperature value can be read in the full power-down mode,

because the serial interface is still powered up.

AD7414/AD7415

Rev. F | Page 14 of 20

POWER VS. THROUGHPUT

The two modes of operation for the AD7414/AD7415 produce

different power vs. throughput performances. Mode 2 is the

sleep mode of the part, and it achieves the optimum power

performance.

Mode 1

In this mode, continuous conversions are performed at a rate of

approximately one every 800 ms. Figure 14 shows the times and

currents involved with this mode of operation for a 5 V supply.

At 5 V, the current consumption for the part when converting is

1.1 mA typically, and the quiescent current is 188 μA typically.

The conversion time of 25 μs plus power-up time of typically

4 μs contributes 199.3 nW to the overall power dissipation in

the following way:

(29 μs/800 ms) × (5 × 1.1 mA) = 199.3 nW

The contribution to the total power dissipated by the remaining

time is 939.96 μW.

(799.97 ms/800 ms) × (5 × 1.1 μA) = 199.3 μW

Thus the total power dissipated during each cycle is

199.3 nW + 939.96 μW = 940.16 μW

TIME

1.1mA

188μA

800ms 29μs

02463-014

Figure 14. Mode 1 Power Dissipation

Mode 2

In this mode, the part is totally powered down. All circuitry

except the serial interface is switched off. The most power

efficient way of operating in this mode is to use the one-shot

method. Write to the configuration register and set the one-shot

bit to a 1. The part powers up in approximately 4 μs and then

performs a conversion. Once the conversion is finished, the

device powers down again until the PD bit in the configuration

the same timing as Figure 14 in mode 1; a one-shot is initiated

every 800 ms. If we take the voltage supply to be 5 V, we can

work out the power dissipation in the following way. The

current consumption for the part when converting is 1.1 mA

typically, and the quiescent current is 800 nA typically. The

conversion time of 25 μs plus the power-up time of typically

4 μs contributes 199.3 nW to the overall power dissipation in

the following way:

(29 μs/800 ms) × (5 V × 1.1 mA) = 199.3 nW

The contribution to the total power dissipated by the remaining

time is 3.9 μW.

(799.971 ms/800 ms) × (5 V × 800 nA) = 3.9 μW

Thus the total power dissipated during each cycle is:

199.3 nW + 3.9 μW = 940.16 μW

IDD

TIME

1.1mA

800nA

800ms 29μs

02463-015

Figure 15. Mode 2 Power Dissipation

MOUNTING THE AD7414/AD7415

The AD7414/AD7415 can be used for surface or air tempera-

ture sensing applications. If the device is cemented to a surface

with thermally conductive adhesive, the die temperature is

within about 0.1°C of the surface temperature, due to the

device’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.

The ground pin provides the best thermal path to the die, so 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 surface being measured.

As with any IC, the AD7414/AD7415 and their 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 AD7414/AD7415 packages allows them to be

mounted inside sealed metal probes, which provide a safe

environment for the devices.

SUPPLY DECOUPLING

The AD7414/AD7415 should at least be decoupled with a 0.1μF

ceramic capacitor between VDD and GND. This is particularly

important if the AD7414/AD7415 are mounted remote from

the power supply.

AD7414/AD7415

Rev. F | Page 15 of 20

TYPICAL TEMPERATURE ERROR GRAPH

TEMPERATURE ACCURACY VS. SUPPLY

Figure 18 shows the typical temperature error plots for one

device with VDD at 3.3 V and at 5.5 V.

The temperature accuracy specifications are guaranteed for

voltage supplies of 3 V and 5.5 V only. Figure 16 gives the

typical performance characteristics of a large sample of parts

over the full voltage range of 2.7 V to 5.5 V. Figure 17 gives the

typical performance characteristics of one part over the full

voltage range of 2.7 V to 5.5 V.

02463-018

TEMPERATURE ERROR (°C)

–4

–3

–2

–1

5.5V

3.3V

–40–30–20 –10 0 10 20 30 40 50 60 70 80 90 95 100 110 125

TEMPERATURE (°C)

SUPPLYVOLTAGE(V)

2.7

TEMPERATURE ERROR (°C)

–4

5.5

–3

–2

–1

3.0

–40°C

+40°C

+85°C

02463-016

Figure 18. Typical Temperature Error @ 3.3 V and 5.5 V

Figure 19 shows a histogram of the temperature error at

ambient temperature (40°C) over approximately 6,000 units.

Figure 19 shows that over 70% of the AD7414/AD7415 devices

tested have a temperature error within ±0.3°C.

Figure 16. Typical Temperature Error vs. Supply for Large Sample of Parts

100

200

300

400

500

600

700

800

900

NUMBER OF UNITS

02463-019

–1.08 –0.81 –0.54 –0.27 0 0.27 0.54 0.81 1.08

TEMPERATURE ERROR (°C)

AMBIENT TEMPERATURE = 40°C

3.3 5.0

SUPPLYVOLTAGE(V)

2.7

TEMPERATURE ERROR (°C)

–4

5.5

–3

–2

–1

–40°C

+40°C

+85°C

02463-017

Figure 19. Ambient Temperature Error @ 3 V

Figure 17. Typical Temperature Error vs. Supply for One Part

AD7414/AD7415

Rev. F | Page 16 of 20

OUTLINE DIMENSIONS

COMP LIANT TO JEDEC S TANDARDS MO - 178- AB

121608-A

10°

4°

0°

SEATING

PLANE

1.90

BSC

0.95 BSC

0.60

BSC

123

3.00

2.90

2.80

3.00

2.80

2.60

1.70

1.60

1.50

1.30

1.15

0.90

.15 MAX

.05 MIN

1.45 MAX

0.95 MIN

0.20 MAX

0.08 MIN

0.50 MAX

0.30 MIN

0.55

0.45

0.35

PIN 1

INDICATOR

Figure 20. 6-Lead Small Outline Transistor Package [SOT-23]

(RJ-6)

Dimensions shown in millimeters

COMPLIANT TO JEDEC STANDARDS MO-187-AA

6°

0°

0.80

0.55

0.40

0.65 BSC

0.40

0.25

1.10 MAX

3.20

3.00

2.80

COPLANARITY

0.10

0.23

0.09

3.20

3.00

2.80

5.15

4.90

4.65

PIN 1

IDENTIFIER

15° MAX

0.95

0.85

0.75

0.15

0.05

10-07-2009-B

Figure 21. 8-Lead Mini Small Outline Package [MSOP]

(RM-8)

Dimensions shown in millimeters

AD7414/AD7415

Rev. F | Page 17 of 20

COMPLIANT TO JEDEC STANDARDS MO-178-AA

10°

5°

0°

SEATING

PLANE

1.90

BSC

0.95 BSC

0.60

BSC

123

3.00

2.90

2.80

3.00

2.80

2.60

1.70

1.60

1.50

1.30

1.15

0.90

.15 MAX

.05 MIN

1.45 MAX

0.95 MIN

0.20 MAX

0.08 MIN

0.50 MAX

0.35 MIN

0.55

0.45

0.35

11-01-2010-A

Figure 22. 5-Lead Small Outline Transistor Package [SOT-23]

(RJ-5)

Dimensions shown in millimeters

AD7414/AD7415

Rev. F | Page 18 of 20

ORDERING GUIDE

Model1 Temperature Range

Typ Temperature

Error @ 3 V

Package

Option Package Description Branding

Ordering

Quantity

AD7414ARTZ-0REEL7 −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 #CHA 3,000

AD7414ARTZ-0REEL −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 #CHA 10,000

AD7414ARTZ-0500RL7 −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 #CHA 500

AD7414ARMZ-0REEL7 −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOL 3,000

AD7414ARMZ-0REEL −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOL 10,000

AD7414ARMZ-0 −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOL 50

AD7414ARTZ-1REEL7 −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 TOH 3,000

AD7414ARTZ-1REEL −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 TOH 10,000

AD7414ARTZ-1500RL7 −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 TOH 500

AD7414ARTZ-2REEL7 −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 TOJ 3,000

AD7414ARTZ-2REEL −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 TOJ 10,000

AD7414ARTZ-3REEL7 −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 TOK 3,000

AD7414ARTZ-3REEL −40°C to +125°C ±2°C RJ-6 6-Lead SOT-23 TOK 10,000

AD7415ARTZ-0REEL7 −40°C to +125°C ±2°C RJ-5 5-Lead SOT-23 #CGA 3,000

AD7415ARTZ-0REEL −40°C to +125°C ±2°C RJ-5 5-Lead SOT-23 #CGA 10,000

AD7415ARTZ-0500RL7 −40°C to +125°C ±2°C RJ-5 5-Lead SOT-23 #CGA 500

AD7415ARTZ-1REEL7 −40°C to +125°C ±2°C RJ-5 5-Lead SOT-23 #CGB 3,000

AD7415ARTZ-1REEL −40°C to +125°C ±2°C RJ-5 5-Lead SOT-23 #CGB 10,000

AD7415ARTZ-1500RL7 −40°C to +125°C ±2°C RJ-5 5-Lead SOT-23 #CGB 500

EVAL-AD7414/15EBZ Evaluation Board

1 Z = RoHS Compliant Part.

AD7414/AD7415

Rev. F | Page 19 of 20

NOTES

AD7414/AD7415

Rev. F | Page 20 of 20

NOTES

I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors).

registered trademarks are the property of their respective owners.

D02463-0-11/10(F)