Datasheet AD7415 Datasheet (ANALOG DEVICES)

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±0.5°C Accurate, 10-Bit Digital

FEATURES

10-bit temperature-to-digital converter Temperature range: −40°C to +125°C Typical accuracy of ±0.5°C at +40°C SMBus/I 3 µA power-down current Temperature conversion time: 29 µs typ Space-saving 6-lead (AD7414) and 5-lead (AD7415)

Pin selectable addressing via AS Overtemperature indicator (AD7414 Only) SMBus alert function (AD7414 only) 4 versions allow 8 I 2 versions allow 6 I

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 I 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 six I

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

Rev. E

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.

C®-compatible serial interface

SOT-23 packages

C addresses (AD7414)

C addresses (AD7415)

C interfaces. The parts come in four

C addresses while the two AD7415 versions allow up to

C addresses to be used.

Temperature Sensors in SOT-23

AD7414/AD7415

FUNCTIONAL BLOCK DIAGRAM

GND

SENSOR

CONFIGURATION

SETPOINT

HIGH

SETPOINT

LOW

AD7414

AD7415

BAND GAP

TEMPERATURE

SENSOR

CONFIGURATION

SMBus/I2C

INTERFACE

SMBus/I2C

INTERFACE

Figure 1.

BAND GAP

TEMPERATURE

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/I 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.

C-compatible serial interface. The interface offers pin

10-BIT

ANALOG-DIGITAL

CONVERTER

TEMPERATURE

VALUE

SETPOINT

COMPARATOR

10-BIT

ANALOG-DIGITAL

CONVERTER

TEMPERATURE

VALUE

ALERT

SCL SDA

02463-001

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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 T

HIGH

LOW

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

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

Writ e M o 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...........................................................................17

REVISION HISTORY

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.

hanges 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

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

. A to REV. B.

Rev. E | Page 2 of 20

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SPECIFICATIONS

TA = T

Table 1.

Parameter A Version Unit Test Conditions/Comments

TEMPERATURE SENSOR AND ADC

POWER SUPPLIES

DIGITAL INPUT

DIGITAL OUTPUT (OPEN-DRAIN)

AC ELECTRICAL CHARACTERISTICS

MIN

Accuracy

to T

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

MAX

±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, t

800 ms typ

Temperature Conversion Time 25 µs typ

Supply Current

Peak Supply Current

1.2 mA typ Current during conversion Supply Current – Nonconverting 900 µA max Peak current between conversions Inactive Serial Bus

Normal Mode @ 3 V 169 µA typ Normal Mode @ 5 V 188 µA typ

Active Serial Bus

Normal Mode @ 3 V 180 µA typ Normal Mode @ 5 V 214 µA typ

Shutdown Mode 3 µA max

Supply current with serial bus inactive. Part not converting and D7 of configuration register = 0.

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.

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

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

OUT

ALERT Output Saturation Voltage 0.8 V max I

8, 9

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

2.4 V min

0.8 V max

±1 µA max VIN = 0 V to V

10 pF max All digital inputs

2.4 V min

0.4 V max IOL = 1.6 mA

1 µA max VOH = 5 V 10 pF max Typ = 3 pF

= 4 mA

OUT

2.5 µs min See Figure 2

50 ns min See Figure 2 0 ns min See Figure 2

Rev. E | Page 3 of 20

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Parameter A Version Unit Test Conditions/Comments

SDA Low Setup Time to SCL Low

(Start Condition), t

SDA High Hold Time after SCL High

(Stop Condition), t

SDA and SCL Fall Time, t

Power-Up Time 4 µs typ

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.

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

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.

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

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.

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

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

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.

Guaranteed by design. Not tested in production.

50 ns min See Figure 2

90 ns max See Figure 2

SCL

SDA

DATA IN

SDA

DATA OUT

02463-002

Figure 2. Diagram for Serial Bus Timing

Rev. E | Page 4 of 20

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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 Dissipation Thermal Impedance

θJA, Junction-to-Ambient

1, 2

= (T

JMAX

− TA)/θ

MAX

240°C/W

(still air)

6-Lead SOT-23 (RJ-6)

Power Dissipation

1, 2

= (T

JMAX

− TA)/θ

MAX

Thermal Impedance3

θJA, Junction-to-Ambient

190.4°C/W

(still air)

8-Lead MSOP (RM-8)

Power Dissipation

1, 2

= (T

JMAX

− TA)/θ

MAX

Thermal Impedance3

θJA, Junction-to-Ambient

205.9°C/W

(still air) 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

Ramp from 25°C to Peak

−6°C/s max 6 minutes max

Temperature

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

Ramp from 25°C to Peak

−6°C/s max 8 minutes max

Temperature

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

TA = ambient temperature.

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

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. E | Page 5 of 20

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PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

SDA

GND 2

AD7414

Top View

(Not to Scale)

ALERT

SCL

02463-003

Figure 3. AD7414 Pin Configuration (SOT-23)

Table 3. Pin Function Descriptions

Mnemonic Description

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. V

SDA

Positive Supply Voltage, 2.7 V to 5.5 V.

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

drain output. ALERT

AD7414 Digital Output. Overtemperature

indicator becomes active when temperature

exceeds T

. Open-drain output.

HIGH

SCL Digital Input. Serial bus clock.

AD7414

SDA 2

LER

SCL V

Top View

(Not to Scale)

NC = NO CONNECT

GND

02463-004

Figure 4. AD7414 Pin Configuration (MSOP)

Table 4. I

C Address Selection

Part Number AS Pin I2C Address

AD7414-0 Float 1001 000 AD7414-0 GND 1001 001 AD7414-0 V AD7414-1 Float 1001 100 AD7414-1 GND 1001 101 AD7414-1 V 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 AD7415-1 Float 1001 100 AD7415-1 GND 1001 101 AD7415-1 V

SDA

GND 2

AD7415

Top View

(Not to Scale)

SCL

02463-005

Figure 5. AD7415 Pin Configuration (SOT-23)

1001 010

1001 110

1001 010

1001 110

Rev. E | Page 6 of 20

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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 I

C-and SMBuscompatible. 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 I 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 temperature limit, stored in an 8-bit read/write register. This is applicable 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 T register. This ALERT pin is compatible with the SMBus SMBALERT option.

LOW

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

VDDVDDV

10kΩ 10kΩ 10kΩ

GND

Figure 6. Typical Connection Diagram

SDA

SCL

ALERT

AD7414

µC/µ

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

different currents. This is given by

NlnqKTV

where:

K is Boltzmann’s constant.

q is the charge on the electron (1.6 × 10

T is the absolute temperature in Kelvins.

N is the ratio of the two currents.

, which varies from device to

when the device is operated at two

)

–19

Coulombs).

02463-006

Rev. E | Page 7 of 20

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SENSING

TRANSISTOR

II× N

SENSING TRANSISTOR

Figure 7. Temperature Measurement Technique

OUT

TO ADC

–

OUT

02463-007

Figure 7 shows the method the AD7414/AD7415 use to measure the ambient device temperature. To measure ΔV

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 ΔV

. 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:

eTemperaturPositive =

eTemperaturNegative

)(dCodeADC

dCodeADC

512)(

Note that DB9 is removed from the ADC code in the negative temperature formula.

Rev. E | Page 8 of 20

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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.

TEMPERATURE

VALUE

CONFIGURATION

ADDRESS

POINTER

HIGH

LOW

SERIAL BUS INTERFACE

Figure 8. AD7414 Register Structure

D A T A

SDA SCL

The AD7415 has three internal registers, as shown in Figure 9. Two are data registers, and one is an address pointer register.

02463-008

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 T 1 1 T

HIGH

LOW

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 EN

011

Default settings at power-up.

ALERT POLARITY

ALERT RESET

ONE SHOT

TEST MODE

TEMPERATURE

VALUE

ADDRESS

POINTER

Figure 9. AD7415 Register Structure

CONFIGURATION

D A T A

SDA SCL

02463-009

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 register are used to select a data register.

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.

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 ONE SHOT TEST MODE

011

Default settings at power-up.

TEST MODE

0s1 0s

0s1

Rev. E | Page 9 of 20

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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 register and setting the one-shot bit to 1 (D2 = 1), which causes 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 Table 15 show the contents of the second byte to be read from the AD7414 and AD7415, respectively. In Table 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

ALER

T pin.

_Flag: This flag is set to 1 when the temperature

HIGH

measured goes above the T when the second temperature byte (Table 14) is read. If the temperature is still greater than the T

limit after the read operation, the flag is

HIGH

again.

_Flag: This flag is set to 1 when the temperature

LOW

measured goes below the T when the second temperature byte (Table 14) is read. If the temperature is still less than the T limit after the read operation, the flag is set again.

limit. It is reset

HIGH

limit. It is reset

LOW

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 T

_Flag T

HIGH

_Flag 0 0 0

LOW

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 T

The T

HIGH

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 T

HIGH

activated (that is, if ALERT is enabled in the configuration register). Because it is an 8-bit register, the temperature resolution is 1°C.

Table 16. T

D7 D6 D5 D4 D3 D2 D1 D0

MSB B6 B5 B4 B3 B2 B1 B0

HIGH

AD7414 T

The T

LOW

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 T

LOW

deactivated (that is, if ALERT is enabled in the configuration register).

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

Table 17. T

D7 D6 D5 D4 D3 D2 D1 D0

MSB B6 B5 B4 B3 B2 B1 B0

LOW

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

he temperature measurement range is limited to the operating

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

Rev. E | Page 10 of 20

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SCL

START BY

MASTER

SERIAL BUS ADDRESS BYTE

FRAME 1

R/W

ACK. BY

AD7414/AD7415

ADDRESS POINTER REGISTER BYTE

FRAME 2

ACK. BY

AD7414/AD7415

STOP BY MASTER

02463-010

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

ACK. BY

AD7414/AD7415

STOP BY MASTER

•••

02463-011

SCL

SDA

START B

MASTER

SERIAL BUS ADDRESS BYTE

FRAME 1

SDA (CONTINUED)

SCL (CONTINUED)

R/W

ACK. BY

AD7414/AD7415

•••

191

ADDRESS POINTER REGISTER BYTE

DATA BYTE

FRAME 3

FRAME 2

P1 P0

ACK. BY

AD7414/AD7415

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

SCL

SDA

START BY

MASTER

SERIAL BUS ADDRESS BYTE

R/W

AD7414/AD7415

FRAME 1

ACK. BY

D7 D6 D5 D4 D3 D2 D1 D0A0A1A210

SINGLE DATA BYTE FROM AD7414/AD7415

FRAME 2

NO ACK. BY

MASTER

STOPBY MASTER

02463-012

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

SCL

SDA

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

SDA (CONTINUED)

SCL (CONTINUED)

R/W

ACK. BY

AD7414/AD7415

•••

LEAST SIGNIFICANT DATA BYTE FROM AD7414/AD7415

D14

D15

MOST SIGNIFICANT DATA BYTE FROM AD7414/AD7415

D13

D12

FRAME 3

D10

FRAME 2

D11

D9 D8

NO ACK. BY

MASTER

ACK. BY

STOP BY MASTER

•••

02463-013

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

Rev. E | Page 11 of 20

Page 12

AD7414/AD7415

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SERIAL INTERFACE

Control of the AD7414/AD7415 is carried out via the I2Ccompatible 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 I by either tying the AS pin to GND, to V 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 co

ndition, 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 peripherals connected to the serial bus respond to the START condition and shift in the next eight bits, consisting of a 7-bit address (MSB first) plus an R/

the data transfer and whether data is written to or read from the slave device.

The peripheral whose address corresponds to the transmitted addr

ess 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/

bit is 0, the master writes to the slave device. If the R/ the master reads from the slave device.

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

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

p 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 a

re 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.

C addresses available, which are selected

, or letting the pin

bit, which determines the direction of

bit is 1,

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

us 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 Register,T

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 register address written to the address pointer register, followed by the data byte written to the selected data register. This is illustrated in Figure 11.

HIGH

LOW

READ MODE

Reading data from the AD7414/AD7415 is a 1- or 2-byte operation. Reading back the contents of the configuration register, the T 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 register without having to write to the address pointer register again. To read from another register, the address pointer register has to be written to again to set up the relevant register address.

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

peration, as shown in Figure 13. The same rules apply for a 2-byte read as a 1-byte read.

HIGH

LOW

Rev. E | Page 12 of 20

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AD7414/AD7415

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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 ALER

T outputs of several AD7414s to be wire-AND’ed together when the ALERT pin is active low. Use D4 of the configuration register to set the active polarity of the ALERT output. The 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 sim

ultaneously 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

C arbitration during the slave address transfer.

The ALERT output becomes active when the value in the

emperature value register exceeds the value in the T

t register. It is reset when a write operation to the configuration register sets D3 to 1 or when the temperature falls below the value stored in the T

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

n be connected to a voltage different from V

ca 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.

LOW

HIGH

, provided the

POWER-ON DEFAULTS

The AD7414/AD7415 always power up with these defaults:

Address pointer register pointing to the temperature value

gister.

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 t

o a 1) is performed between automatic conversions, a conversion 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 co

nversion, 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 acces

s (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 register is set to 1.

When a temperature measurement is required, a write o

peration 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 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.

µs. The part then performs

HIGH

LOW

Configuration register loaded with 40h.

Note that the AD7415 does not have any T

HIGH

or T

registers.

LOW

Rev. E | Page 13 of 20

Page 14

AD7414/AD7415

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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

1.1mA

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 performs a conversion. Once the conversion is finished, the device powers down again until the PD bit in the configuration register is set to 0 or the one-shot bit is set to 1. Figure 15 shows 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

800ms

188µA

29µs

TIME

µs and then

02463-014

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

1.1mA

Figure 15. Mode 2 Power Dissipation

800ms

800nA

29µs

TIME

MOUNTING THE AD7414/AD7415

The AD7414/AD7415 can be used for surface or air temperature 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 V important if the AD7414/AD7415 are mounted remote from the power supply.

and GND. This is particularly

02463-015

Rev. E | Page 14 of 20

Page 15

AD7414/AD7415

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TEMPERATURE ACCURACY VS. SUPPLY

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.

–1

–2

TEMPERATURE ERROR (°C)

–3

–40°C

+40°C

+85°C

TYPICAL TEMPERATURE ERROR GRAPH

Figure 18 shows the typical temperature error plots for one device with V

–1

–2

TEMPERATURE ERROR (°C)

–3

–4

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

at 3.3 V and at 5.5 V.

5.5V

3.3V

TEMPERATURE (°C)

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

02463-018

–4

2.7

3.0

SUPPLYVOLTAGE (V)

5.5

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

–1

–2

TEMPERATURE ERROR (°C)

–3

–4

2.7

+40°C

3.3 5.0

SUPPLYVOLTAGE (V)

–40°C

+85°C

5.5

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

02463-016

02463-017

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.

900

AMBIENT TEMPERATURE = 40°C

800

700

600

500

400

300

NUMBER OF UNITS

200

100

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

Figure 19. Ambient Temperature Error @ 3 V

TEMPERATURE ERROR (°C)

02463-019

Rev. E | Page 15 of 20

Page 16

AD7414/AD7415

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OUTLINE DIMENSIONS

2.90 BSC

1.60 BSC

1 3452

PIN 1

INDICATOR

1.30

1.15

0.90

0.15MAX

1.90 BSC

0.50

0.30

COMPLIANT TO JEDEC STANDARDS MO-178AB

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

Dimensions shown in millimeters

2.80 BSC

0.95 BSC

1.45 MAX

SEATING PLANE

(RT-6)

0.22

0.08 10°

3.00 BSC

3.00

BSC

PIN 1

0.65 BSC

0.15

0.60

4°

0.45

0°

0.30

0.00

0.38

0.22

COPLANARITY

0.10 COMPLIANT TO JEDEC STANDARDS MO-187-AA

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

4.90 BSC

1.10 MAX

8° 0°

SEATING PLANE

0.23

0.08

(RM-8)

Dimensions shown in millimeters

0.80

0.60

0.40

2.90 BSC

4 5

0.50

0.30

2.80 BSC

0.95 BSC

1.45 MAX

SEATING PLANE

0.22

0.08 10°

5° 0°

0.60

0.45

0.30

1.60 BSC

1.30

1.15

0.90

0.15MAX

PIN 1

1.90 BSC

COMPLIANT TO JEDEC STANDARDS MO-178AA

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

(RT-5)

Dimensions shown in millimeters

Rev. E | Page 16 of 20

Page 17

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ORDERING GUIDE

Temperature

Model

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 AD7414ARTZ-0REEL7 AD7414ARTZ-0REEL1 −40°C to +125°C ±2°C RT-6 6-Lead SOT-23 #CHA 10,000 AD7414ARTZ-0500RL71 −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 AD7414ARMZ-0REEL71 −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOL 3,000 AD7414ARMZ-0REEL1 −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOL 10,000 AD7414ARMZ-01 −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOL 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 AD7414ARTZ-1REEL71 −40°C to +125°C ±2°C RT-6 6-Lead SOT-23 TOH 3,000 AD7414ARTZ-1REEL1 −40°C to +125°C ±2°C RT-6 6-Lead SOT-23 TOH 10,000 AD7414ARTZ-1500RL71 −40°C to +125°C ±2°C RT-6 6-Lead SOT-23 TOH 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 AD7414ARMZ-1REEL71 −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOH 3,000 AD7414ARMZ-1REEL1 −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOH 10,000 AD7414ARMZ-11 −40°C to +125°C ±2°C RM-8 8-Lead MSOP TOH 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 AD7414ARTZ-2REEL71 −40°C to +125°C ±2°C RT-6 6-Lead SOT-23 TOJ 3,000 AD7414ARTZ-2REEL1 −40°C to +125°C ±2°C RT-6 6-Lead SOT-23 TOJ 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 AD7414ARTZ-3REEL71 −40°C to +125°C ±2°C RT-6 6-Lead SOT-23 TOK 3,000 AD7414ARTZ-3REEL1 −40°C to +125°C ±2°C RT-6 6-Lead SOT-23 TOK 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 AD7415ARTZ-0REEL71 −40°C to +125°C ±2°C RT-5 5-Lead SOT-23 #CGA 3,000 AD7415ARTZ-0REEL1 −40°C to +125°C ±2°C RT-5 5-Lead SOT-23 #CGA 10,000 AD7415ARTZ-0500RL71 −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-1REEL71 −40°C to +125°C ±2°C RT-5 5-Lead SOT-23 #CGB 3,000 AD7415ARTZ-1REEL1 −40°C to +125°C ±2°C RT-5 5-Lead SOT-23 #CGB 10,000 AD7415ARTZ-1500RL71 −40°C to +125°C ±2°C RT-5 5-Lead SOT-23 #CGB 500 EVAL-AD7414/15EB

Z = Pb-free part.

Range

−40°C to +125°C ±2°C RT-6 6-Lead SOT-23 #CHA 3,000

Typ Temperature Error @ 3

Package Option

Package Description

Evaluation Board

Minimum

Branding

Quantities/Reel

Rev. E | Page 17 of 20

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NOTES

Rev. E | Page 18 of 20

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NOTES

Rev. E | Page 19 of 20

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AD7414/AD7415

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NOTES

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.

C02463-0-4/05(E)

Rev. E | Page 20 of 20