Datasheet AD7414 Datasheet (Analog Devices)

Page 1
0.5C Accurate, 10-Bit Digital
Temperature Sensors in SOT-23
AD7414/AD7415
FEATURES 10-Bit Temperature-to-Digital Converter Temperature Range: –40C to +125ⴗC Typical Accuracy of 0.5C at +40ⴗC SMBus/I
2C®
-Compatible Serial Interface 3 A Power-Down Current Temperature Conversion Time: 29 s Typ Space-Saving 6-Lead (AD7414) and 5-Lead (AD7415)
SOT-23 Packages Pin Selectable Addressing via AS Overtemperature Indicator (AD7414 Only) SMBus Alert Function (AD7414 Only) 4 Versions Allow 8 I 2 Versions Allow 6 I
2
C Addresses (AD7414)
2
C Addresses (AD7415)
APPLICATIONS Hard Disk Drives Personal Computers Electronic Test Equipment Office Equipment Domestic Appliances Process Control Cellular Phones

GENERAL DESCRIPTION

The AD7414/AD7415 is a complete temperature monitoring system in 6-lead and 5-lead SOT-23 packages. It contains a band gap temperature sensor and a 10-bit ADC to monitor and digitize the temperature reading to a resolution of 0.25°C.
The AD7414/AD7415 provides a 2-wire serial interface that is compatible with SMBus and I
2
C interfaces. The part comes in four versions: the AD7414/AD7415-0, AD7414/AD7415-1, AD7414-2, and AD7414-3. The AD7414/AD7415-0 and AD7414/AD7415-1 versions provide a choice of three different SMBus addresses for each version. All four AD7414 versions give the possibility of eight different I AD7415 versions allow up to six I
2
C addresses while the two
2
C addresses to be used.
The AD7414/AD7415’s 2.7 V supply voltage, low supply current, serial interface, and small package size make it ideal for a variety of applications, including personal computers, office equipment, cellular phones, and domestic appliances.
In the AD7414, on-chip registers can be programmed with high and low temperature limits, and an open-drain overtemperature indicator output (ALERT) becomes active when a programmed limit is exceeded. A configuration register allows programming of the state of the ALERT output (active high or active low). This output can be used as an interrupt or as an SMBus alert.
REV. D
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

FUNCTIONAL BLOCK DIAGRAM

GND
AS
GND
AS
BAND GAP
TEMPERATURE
SENSOR
CONFIGURATION
REGISTER
SETPOINT
T
HIGH
REGISTER
T
SETPOINT
LOW
REGISTER
AD7414
AD7415
BAND GAP
TEMPERATURE
SENSOR
CONFIGURATION
REGISTER
SMBus/I2C
INTERFACE
SMBus/I2C
INTERFACE
10-BIT
ANALOG-DIGITAL
CONVERTER
TEMPERATURE
VALUE
REGISTER
SETPOINT
COMPARATOR
10-BIT
ANALOG-DIGITAL
CONVERTER
TEMPERATURE
VALUE
REGISTER
V
DD
ALERT
SCL
SDA
V
DD
SCL
SDA

PRODUCT HIGHLIGHTS

1. The AD7414/AD7415 has an on-chip temperature sensor that allows an accurate measurement of the ambient temperature to be made. It is capable of 0.5°C temperature accuracy.
2. SMBus/I
2
C-compatible serial interface with pin selectable choice of three addresses per version of the AD7414/AD7415, eight address options in total for the AD7414, and six in total for the AD7415.
3. Supply voltage of 2.7 V to 5.5 V.
4. Space-saving 5-lead and 6-lead SOT-23 packages.
5. 10-bit temperature reading to 0.25°C resolution.
6. The AD7414 has an overtemperature indicator that can be software disabled. Used as an interrupt of SMBus alert.
7. One-shot and automatic temperature conversion rates.
Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.
Page 2
1
AD7414/AD7415–SPECIFICATIONS
(TA = T
Parameter A Version Unit Test Conditions/Comments
TEMPERATURE SENSOR AND ADC
Accuracy
2
± 0.5 °C typ VDD = 3 V @ +40°C –0.87 to +0.823°C max VDD = 3 V @ +40°C
± 1.5 °C max VDD = 3 V @ –40°C to +70°C ± 2.0 °C max V ± 3.0 °C max VDD = 3 V @ –40°C to +125°C ± 2.0 °C typ V
3
± 1.87
°C max VDD = 5.5 V @ +40°C ± 2.0 °C typ VDD = 5.5 V @ –40°C to +85°C ± 3.0 °C max V ± 3.0 °C typ VDD = 5.5 V @ –40°C to +125°C
Resolution 10 Bits Update Rate, t
R
800 ms typ
Temperature Conversion Time 25 µs typ
POWER SUPPLIES
Supply Current
Peak Supply Current Supply Current – Nonconverting 900 µA max Peak Current between Conversions Inactive Serial Bus
4
5
6
1.2 mA typ Current during Conversion
Normal Mode @ 3 V 169 µA typ Supply Current with Serial Bus Inactive. Part not Normal Mode @ 5 V 188 µA typ converting and D7 of Configuration Register = 0.
Active Serial Bus
7
Normal Mode @ 3 V 180 µA typ Supply Current with Serial Bus Active. Part not Normal Mode @ 5 V 214 µA typ converting and D7 of Configuration Register = 0.
Shutdown Mode 3 µA max D7 of Configuration Register = 1. Typical values
DIGITAL INPUT
Input High Voltage, V Input Low Voltage, V Input Current, I Input Capacitance, C
IL
8
IN
IN
IH
2.4 V min
0.8 V max ± 1 µA max VIN = 0 V to V 10 pF max All Digital Inputs
DIGITAL OUTPUT (OPEN-DRAIN)
Output High Voltage, V Output Low Voltage, V Output High Current, I Output Capacitance, C
OL
OH
OUT
OH
2.4 V min
0.4 V max IOL = 1.6 mA 1 µA max VOH = 5 V 10 pF max Typ = 3 pF
ALERT Output Saturation Voltage 0.8 V max I
AC ELECTRICAL CHARACTERISTICS
Serial Clock Period, t
1
Data In Setup Time to SCL High, t Data Out Stable after SCL Low, t
9, 10
2.5 µs min See Figure 1
2
3
50 ns min See Figure 1 0 ns min See Figure 1
SDA Low Setup Time to SCL Low
(Start Condition), t
4
50 ns min See Figure 1
SDA High Hold Time after SCL High
(Stop Condition), t
5
SDA and SCL Fall Time, t
6
50 ns min See Figure 1 90 ns max See Figure 1
Power-Up Time 4 µs typ
NOTES
1
Temperature range as follows: A Version = –40°C to +125°C.
2
Accuracy specifications apply only to voltages listed under Test Conditions. See Temperature Accuracy vs. Supply section for typical accuracy performance over the full V supply range.
3
100% production tested at 40°C to these limits.
4
These current values can be used to determine average power consumption at different one-shot conversion rates. Average power consumption at the automatic conversion rate of 1.25 kHz is 940 µW.
5
This peak supply current is required for 29 µs (the conversion time plus power-up time) out of every 800 µs (the conversion rate).
6
These current values are derived by not issuing a stop condition at the end of a write or read, thus preventing the part from going into a conversion.
7
The current is derived assuming a 400 kHz serial clock being active continuously.
8
On power-up, the initial input current, IIN, on the AS pin is typically 50 µA.
9
The SDA and SCL timing is measured with the input filters turned on so as to meet the Fast Mode I but has a negative effect on the EMC behavior of the part.
10
Guaranteed by design. Not tested in production.
Specifications subject to change without notice.
to T
MIN
, VDD = 2.7 V to 5.5 V, unless otherwise noted.)
MAX
= 3 V @ –40°C to +85°C
DD
= 3 V @ –40°C to +125°C
DD
= 5.5 V @ –40°C to +85°C
DD
are 0.04 µA at 3 V and 0.5 µA at 5 V.
DD
= 4 mA
OUT
DD
2
C specification. Switching off the input filters improves the transfer rate
REV. D–2–
Page 3
AD7414/AD7415

PIN FUNCTION DESCRIPTIONS

Mnemonic Description
AS Logic Input. Address select input that selects one
of three I2C addresses for the AD7414/AD7415 (see Table I). Recommend a pull-up or pull-down resistor of 1 kΩ.
GND Analog and Digital Ground
V
DD
Positive Supply Voltage, 2.7 V to 5.5 V
SDA Digital I/O. Serial bus bidirectional data. Open-
drain output.
ALERT AD7414 Digital Output. Overtemperature indicator
becomes active when temperature exceeds T
HIGH
.
Open-drain output.
SCL Digital Input. Serial bus clock.

ABSOLUTE MAXIMUM RATINGS

1
VDD to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V
SDA Input Voltage to GND . . . . . . . . . . . . . . –0.3 V to +7 V
SDA Output Voltage to GND . . . . . . . . . . . . . –0.3 V to +7 V
SCL Input Voltage to GND . . . . . . . . . . . . . . –0.3 V to +7 V
ALERT Output Voltage to GND . . . . . . . . . . –0.3 V to +7 V
Operating Temperature Range . . . . . . . . . . –40°C to +125°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 150°C
5-Lead SOT-23 (RJ-5)
Power Dissipation Thermal Impedance
2
. . . . . . . . . . . . . . . . .
4
W
MAX
= (T
JMAX
– T
3
)/
A
JA
␪JA, Junction-to-Ambient (still air) . . . . . . . . . . . 240°C/W
6-Lead SOT-23 (RJ-6)
Power Dissipation Thermal Impedance
2
. . . . . . . . . . . . . . . . .
4
W
MAX
= (T
JMAX
– T
3
)/
A
JA
␪JA, Junction-to-Ambient (still air) . . . . . . . . . . 190.4°C/W
8-Lead MSOP (RM-8)
Power Dissipation Thermal Impedance
2
. . . . . . . . . . . . . . . . .
4
W
MAX
= (T
JMAX
– T
3
)/
A
JA
␪JA, Junction-to-Ambient (still air) . . . . . . . . . . 205.9°C/W
, Junction-to-Case . . . . . . . . . . . . . . . . . . . .43.74°C/W
JC
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause perma­nent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
2
Values relate to package being used on a standard 2-layer PCB.
3
TA = ambient temperature.
4
Junction-to-case resistance is applicable to components featuring a preferential
flow direction, e.g., components mounted on a heat sink. Junction-to-ambient resistance is more useful for air-cooled, PCB-mounted components.
t
SCL
SDA
DATA IN
SDA
DATA OUT
t
4
1
t
2
t
3
t
5
t
6

PIN CONFIGURATIONS

SOT-23
SDA
AS
GND 2
V
DD
1
AD7414
Top View
(Not to Scale)
6
5
ALERT
SCL34
MSOP
NCNC18
AD7414
SDA 2 7 AS
ALERT GND36
SCL V
Top View
(Not to Scale)
45
NC = NO CONNECT
DD
SOT-23
15
AS
AD7415
Top View
2
GND
V
DD
(Not to Scale)
3
SDA
SCL
4
Table I. I2C Address Selection
Part Number AS Pin I2C Address
AD7414-0 Float 1001 000 AD7414-0 GND 1001 001 AD7414-0 V
DD
1001 010
AD7414-1 Float 1001 100 AD7414-1 GND 1001 101 AD7414-1 V
DD
1001 110
AD7414-2 N/A 1001 011
AD7414-3 N/A 1001 111
AD7415-0 Float 1001 000 AD7415-0 GND 1001 001 AD7415-0 V
DD
1001 010
AD7415-1 Float 1001 100 AD7415-1 GND 1001 101 AD7415-1 V
DD
1001 110
REV. D
Figure 1. Diagram for Serial Bus Timing
–3–
Page 4
AD7414/AD7415

ORDERING GUIDE

Temperature Typ Temperature Package Package Minimum
Model Range Error @ 3 V Option Description Branding Quantities/Reel
AD7414ART-0REEL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHA 3,000 AD7414ART-0REEL –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHA 10,000 AD7414ART-0500RL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHA 500 AD7414ARM-0REEL7 –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHA 3,000 AD7414ARM-0REEL –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHA 10,000 AD7414ARM-0 –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHA
AD7414ART-1REEL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHB 3,000 AD7414ART-1REEL –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHB 10,000 AD7414ART-1500RL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHB 500 AD7414ARM-1REEL7 –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHB 3,000 AD7414ARM-1REEL –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHB 10,000 AD7414ARM-1 –40°C to +125°C ± 2°C RM-8 8-Lead MSOP CHB
AD7414ART-2REEL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHC 3,000 AD7414ART-2REEL –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHC 10,000
AD7414ART-3REEL7 –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHD 3,000 AD7414ART-3REEL –40°C to +125°C ± 2°C RT-6 6-Lead SOT-23 CHD 10,000
AD7415ART-0REEL7 –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGA 3,000 AD7415ART-0REEL –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGA 10,000 AD7415ART-0500RL7 –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGA 500
AD7415ART-1REEL7 –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 3,000 AD7415ART-1REEL –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 10,000 AD7415ART-1500RL7 –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 500
AD7415ARTZ-500RL7* –40°C to +125°C ±2°C RT-5 5-Lead SOT-23 CGB 500 AD7415ARTZ-0REEL* –40°C to +125°C ±2°C RT-5 5-Lead SOT-23 CGB 500 AD7415ARTZ-0REEL7* –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 500 AD7415ARTZ-1500RL7* –40°C to +125°C ±2°C RT-5 5-Lead SOT-23 CGB 500 AD7415ARTZ-1REEL* –40°C to +125°C ±2°C RT-5 5-Lead SOT-23 CGB 500 AD7415ARTZ-1REEL7* –40°C to +125°C ± 2°C RT-5 5-Lead SOT-23 CGB 500
EVAL-AD7414/AD7415EB Evaluation Board
*Z = Pb-free part.
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD7414/AD7415 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
REV. D–4–
Page 5
AD7414/AD7415
TO ADC
V
OUT
+
V
OUT
SENSING
TRANSISTOR
V
DD
I
NI
SENSING
TRANSISTOR

CIRCUIT INFORMATION

The AD7414/AD7415 is a standalone digital temperature sensor. The on-chip temperature sensor allows an accurate measurement of the ambient device temperature to be made. The 10-bit A/D converter converts the temperature measured into a twos comple­ment format for storage in the temperature register. The A/D converter is made up of a conventional successive-approximation converter based around a capacitor DAC. The serial interface is
2
C and SMBus compatible. The AD7414/AD7415 requires a
I
2.7 V to 5.5 V power supply. The temperature sensor has a working measurement range of –40°C to +125°C.

FUNCTIONAL DESCRIPTION

Temperature measurement is initiated by a couple of methods. The first uses an internal clock countdown of 800 ms, and a conversion is performed. The internal oscillator is the only circuit that is powered up between conversions, and once it times out, every 800 ms, a wake-up signal is sent to power up the rest of the circuitry. A monostable is activated at the beginning of the wake-up signal to ensure that sufficient time is given to the power­up process. The monostable typically takes 4 µs to time out. It then takes typically 25 µs for each conversion to be completed. The new temperature value is loaded into the temperature value register and ready for reading by the I
2
C interface.
A temperature measurement is also initiated every time the one-shot method is used. This method requires the user to write to the one-shot bit in the configuration register when a temperature measurement is needed. Setting the one-shot bit to a 1 will start a temperature conversion directly after the write operation. The track-and-hold goes into hold approxi­mately 4 µs (monostable timeout) after the STOP condition and a conversion is then initiated. Typically 25 µs later, the conversion is complete and the temperature value register is loaded with a new temperature value.
The measurement modes are compared with a high temperature limit, stored in an 8-bit read/write register. This is applicable only to the AD7414 since the AD7415 does not have an ALERT pin and subsequently does not have an overtemperature monitoring function. If the measurement is greater than the high limit, the ALERT pin is activated (if it has already been enabled in the configuration register). There are two ways to deactivate the ALERT pin again: when the alert reset bit in the configuration register is set to a 1 by a write operation, and when the tempera­ture measured is less than the value in the T
register. This
LOW
ALERT pin is compatible with the SMBus SMBALERT option.
Configuration functions consist of
Switching between normal operation and full power-down
Enabling or disabling the SCL and SDA filters
Enabling or disabling the ALERT function
Setting ALERT pin polarity
SUPPLY
2.7V TO
5.5V 10F
0.1F
1k
V
AS
GND
AD7414
DD
SDA
SCL
ALERT
C/P
Figure 2. Typical Connection Diagram

MEASUREMENT TECHNIQUE

A common method of measuring temperature is to exploit the negative temperature coefficient of a diode, or the base-emitter voltage of a transistor, operated at constant current. Unfortu­nately, this technique requires calibration to null the effect of the absolute value of V
, which varies from device to device.
BE
The technique used in the AD7414/AD7415 is to measure the change in V
when the device is operated at two different currents.
BE
This is given by
VKTqnN
BE
1
()
where:
K is Boltzmann’s constant. q is the charge on the electron (1.6 × 10
–19
Coulombs).
T is the absolute temperature in Kelvins. N is the ratio of the two currents.
Figure 3. Temperature Measurement Technique
Figure 3 shows the method the AD7414/AD7415 uses to measure the ambient device temperature. To measure V
, the sensor
BE
(substrate transistor) is switched between operating currents of I and N × I. The resulting waveform is passed through a chopper­stabilized amplifier that performs the functions of amplification and rectification of the waveform to produce a dc voltage propor­tional to V
. This voltage is measured by the ADC to give a
BE
temperature output in 10-bit twos complement format.
REV. D
–5–
Page 6
AD7414/AD7415

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 practical lowest 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 II.)
Table II. A Grade Temperature Data Format
Digital Output
Temperature 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
A Grade Temperature Conversion Formula:
Positive Temperature
Negative Temperature
*DB9 is removed from the ADC Code.
ADC Code
=
4
ADC Code
* – 512
()
=
4

INTERNAL REGISTER STRUCTURE

The AD7414 has five internal registers as shown in Figure 4. Four are data registers and one is an address pointer register.
TEMPERATURE
VALUE
REGISTER
CONFIGURATION
ADDRESS
POINTER
REGISTER
REGISTER
T
HIGH
REGISTER
D A T A
The AD7415 has three internal registers as shown in Figure 5. Two are data registers and one is an address pointer register.
TEMPERATURE
VALUE
ADDRESS
POINTER
REGISTER
SERIAL BUS INTERFACE
REGISTER
CONFIGURATION
REGISTER
D A T A
SDA
SCL
Figure 5. 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 regis­ter are used to select a data register.
Table III. Address Pointer Register
P7 P6 P5 P4 P3 P2 P1 P0
00000 0Register Select
Table IV. AD7414 Register Address
P1 P0 Registers
00Temperature Value Register (Read-Only) 01Configuration Register (Read/Write) 10T 11T
Register (Read/Write)
HIGH
Register (Read/Write)
LOW
Table V. AD7415 Register Address
P1 P0 Registers
00Temperature Value Register (Read-Only) 01Configuration Register (Read/Write)
T
LOW
REGISTER
SERIAL BUS INTERFACE
Figure 4. AD7414 Register Structure
SDA
SCL
Table VI. AD7414 Configuration Register
D7 D6 D5 D4 D3 D2 D1 D0
PD FLTR ALERT ALERT ALERT ONE TEST
EN POLARITY RESET SHOT MODE
0* 1* 0* 0* 0* 0* 0s*
*Default settings at power-up.
REV. D–6–
Page 7
AD7414/AD7415

CONFIGURATION REGISTER (ADDRESS 01H)

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 VII). D0 and D1 are used for factory settings and must have zeros written to them during normal operation.
Table VII. AD7414 Configuration Register Setting
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 will have the ability to activate the ALERT function. The bit status is not stored; thus this bit will be 0 if read.
D2 Initiate a temperature conversion if set to a 1. The bit
status is not stored; thus this bit will be 0 if read.
Table VIII. AD7415 Configuration Register
D7 D6 D5 D4 D3 D2 D1 D0
PD FLTR TEST MODE ONE TEST
SHOT MODE
0* 1* 0s* 0s* 0s*
*Default settings at power-up.
In the AD7415, only three of the bits are used (D7, D6, and D2) to set the operating modes (see Table IX). D0, D1, and D3 to D5 are used for factory settings and must have zeros written to them during normal operation.
Table IX. AD7415 Configuration Register Settings
D7 Full Power-Down if = 1. D6 Bypass SDA and SCL filtering if = 0. D2 Initiate a temperature conversion if set to a 1. The bit
status is not stored; thus this bit will be 0 if read.
If the AD7414/AD7415 is 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 a 1 (D2 = 1), which will cause the AD7414/AD7415 to power up, perform a single conversion, and power down again. This is a very power efficient mode.
9
P0
ACK. BY
AD7414/AD7415
STOP BY
MASTER
SCL
SDA
START BY
MASTER
19
1
001A2
FRAME 1
SERIAL BUS ADDRESS BYTE
A0
A1
R/W
ACK. BY
AD7414/AD7415
1
P6
P7
P5
ADDRESS POINTER REGISTER BYTE
P4
P3
FRAME 2
P1
P2
Figure 6. Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation
SCL
SDA
START BY
MASTER
191
001A2
1
SERIAL BUS ADDRESS BYTE
FRAME 1
SCL (CONTINUED)
SDA (CONTINUED)
R/W
A0
A1
ACK. BY
AD7414/AD7415
19
D7
P7
D6
P6
P5
ADDRESS POINTER REGISTER BYTE
D5
D4
DATA BYTE
P4
D3
FRAME 3
P3
FRAME 2
D2
P1 P0
P2
D1
D0
AD7414/AD7415
AD7414/AD7415
ACK. BY
ACK. BY
9
STOP BY MASTER
Figure 7. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Register
REV. D
–7–
Page 8
AD7414/AD7415

TEMPERATURE VALUE REGISTER (ADDRESS 00H)

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 X shows the contents of the first byte to be read, while Table XI and Table XII show the contents of the second byte to be read from AD7414 and AD7415, respec­tively. In Table XI, 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.
T
_Flag: This flag is set to a 1 when the temperature
HIGH
measured goes above the T
HIGH
limit. It is reset when the second temperature byte (Table XI) is read. If the temperature is still greater than the T
limit after the read
HIGH
operation, the flag will be set again.
T
_Flag: This flag is set to a 1 when the temperature
LOW
measured goes below the T
limit. It is
LOW
reset when the second temperature byte (Table XI) is read. If the temperature is still less than the T
limit after the read operation,
LOW
the flag will be 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 A grade.
Table X. Temperature Value Register (First Read)
D15 D14 D13 D12 D11 D10 D9 D8
MSB B8 B7B6B5B4B3B2
Table XI. AD7414 Temperature Value Register (Second Read)
D7 D6 D5 D4 D3 D2 D1 D0
B1 LSB ALERT_ T
HIGH
_T
LOW
_0 0 0
Flag Flag Flag
Table XII. 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 (Address 02h)
HIGH
register is an 8-bit read/write register that stores the upper limit that will activate the ALERT output. Therefore, if the value in the temperature value register is greater than the value in the T
register, the ALERT pin is activated (that is,
HIGH
if ALERT is enabled in the configuration register). Since it is an 8-bit register, the temperature resolution is 1°C.
Table XIII. T
HIGH
Register
D7 D6 D5 D4 D3 D2 D1 D0
MSB B6 B5 B4 B3 B2 B1 B0
AD7414 T
The T
REGISTER (Address 03h)
LOW
register is an 8-bit read/write register that stores the
LOW
lower limit that will deactivate the ALERT output. Therefore, if the value in the temperature value register is less than the value in the T
register, the ALERT pin is deactivated (that
LOW
is, if ALERT is enabled in the configuration register). Since it is an 8-bit register, the temperature resolution is 1°C.
SCL
SDA
START BY
MASTER
SCL
SDA
START BY
MASTER
191 9
0
FRAME 1
SERIAL BUS ADDRESS BYTE
A0A1A2101
R/W
AD7414/AD7415
D7 D6 D5 D4 D3 D2 D1 D0
ACK. BY
SINGLE DATA BYTE FROM AD7414/AD7415
FRAME 2
NO ACK. BY
MASTER
STOP BY MASTER
Figure 8. Reading a Single Byte of Data from a Selected Register
19
001A2
1
SERIAL BUS ADDRESS BYTE
FRAME 1
SCL (CONTINUED)
SDA (CONTINUED)
A0
A1
R/W
ACK. BY
AD7414/AD7415
1
D14
D15
MOST SIGNIFICANT DATA BYTE FROM AD7414/AD7415
19
D6
D7
LEAST SIGNIFICANT DATA BYTE FROM AD7414/AD7415
D5
D13
D4
D12
D3
FRAME 3
D10
FRAME 2
D2
D11
D1
D9 D8
D0
NO ACK. BY
MASTER
9
ACK. BY MASTER
STOP BY MASTER
Figure 9. Reading Two Bytes of Data from the Temperature Value Register
REV. D–8–
Page 9
AD7414/AD7415
Table XIV. T
Register
LOW
D7 D6 D5 D4 D3 D2 D1 D0
MSB B6 B5 B4 B3 B2 B1 B0

AD7414/AD7415 SERIAL INTERFACE

Control of the AD7414/AD7415 is carried out via the I2C­compatible serial bus. The AD7414/AD7415 is connected to this bus as a slave device, under the control of a master device, e.g., the processor.

SERIAL BUS ADDRESS

Like all I2C-compatible devices, the AD7414/AD7415 has a 7-bit serial address. The four MSBs of this address for the AD7414/ AD7415 are set to 1001. The AD7414/AD7415 comes in four versions: AD7414/AD7415-0, AD7414/AD7415-1, AD7414-2, and AD7414-3. The first two versions have three different I
2
C addresses available, which are selected by either tying the AS pin to GND, to V
, or letting the pin float (see Table I). By
DD
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:
1. 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 will follow. 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/W bit, which deter­mines the direction of the data transfer, i.e., whether data will be 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 now remain idle while the selected device waits for data to be read from or written to it. If the R/W bit is a 0, the master will write to the slave device. If the R/W bit is a 1, the master will read from the slave device.
2. 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, since a low to high transition when the clock is high may be interpreted as a STOP signal.
3. When all data bytes have been read or written, stop conditions
are established. In WRITE mode, the master will pull the data line high during the 10th clock pulse to assert a STOP condition. In READ mode, the master device will pull the data line high during the low period before the ninth clock pulse. This is known as No Acknowledge. The master will then take 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 because the type of operation is determined at the beginning and cannot be changed subsequently without starting a new operation.

WRITING TO THE AD7414/AD7415

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 6. 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
Register, or T
HIGH
Register
LOW
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 7.

READING DATA FROM THE AD7414/AD7415

Reading data from the AD7414/AD7415 is a 1- or 2-byte opera­tion. Reading back the contents of the configuration register, T
HIGH
register, or T
register is a single-byte read operation,
LOW
as shown in Figure 8. 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 done from that register without having to write to the address pointer register again. To read from another register, the address pointer register will have to be written to again to set up the relevant register address.
Reading data from the temperature value register is a 2-byte operation, as shown in Figure 9. The same rules apply for a 2-byte read as a single-byte read.

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 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.
REV. D
–9–
Page 10
AD7414/AD7415
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 will acknowledge the ARA (Alert Response Address). If more than one device pulls the ALERT pin low, the highest priority (lowest address) device will win communication rights via stan-
2
C arbitration during the slave address transfer.
dard I
The ALERT output becomes active when the value in the temperature value register exceeds the value in the T
HIGH
register. It is reset when a write operation to the configuration register sets D3 to a 1 or when the temperature falls below the value stored in the T
LOW
register.
The ALERT output requires an external pull-up resistor. This can be connected to a voltage different from V
provided the
DD
maximum voltage rating of the ALERT output pin is not exceeded. The value of the pull-up resistor depends on the application, but 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 powers up with the following defaults:
Address pointer register pointing to the temperature value register. T
register loaded with 7Fh.
HIGH
T
register loaded with 80h.
LOW
Configuration register loaded with 40h.
Note that the AD7415 does not have any T
OPERATING MODES Mode 1
HIGH
or T
LOW
registers.
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 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 conversion, that conversion might or might not be aborted. If the conversion is completed before the part recognizes a serial port access, the temperature register will be updated with the new conversion. If the conversion is completed after the part recognizes a serial port access, the internal logic will prevent the temperature register from being updated since 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 will only be loaded into the temperature register 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 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 ms. 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 since the serial interface is still powered up.

POWER VS. THROUGHPUT

The two modes of operation for the AD7414/AD7415 will 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 10 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:
29 800 5 1 1 199 3µsms mA nW/..
()
××
()
=
The contribution to the total power dissipated by the remaining time is 939.96 µW.
799 97 800 5 1 1 199 3./ . .ms ms A W
()
××
()
=µµ
Thus the total power dissipated during each cycle is:
199 3 939 96 940 16.. .nW W W+=µµ
1.1mA
I
DD
Figure 10. Mode 1 Power Dissipation

Mode 2

188␮A
800ms
29␮s
TIME
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 will power up in approximately 4 ms and then perform a conversion. Once the conversion is finished, the device will power down again until the PD bit in the configuration register is set to a 0 or the one-shot bit is set to 1. Figure 11 shows the same timing as Figure 10 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 ms contributes
199.3 nW to the overall power dissipation in the following way:
29 800 5 1 1 199 3µs/ ms V . mA . n W
()
××
()
=
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 mW
()
××
()
=
Thus the total power dissipated during each cycle is:
199 3 3 9 940 16.. .nW W W+=µµ
REV. D–10–
Page 11
1.1mA
0
100
200
300
400
500
600
700
800
900
0.810 0.27 0.54 1.08
NUMBER OF UNITS
AMBIENT TEMPERATURE = 40ⴗC
1.08 0.54ⴚ0.81 0.27
TEMPERATURE ERROR (ⴗC)
I
DD
800nA
800ms
29␮s
TIME
Figure 11. Mode 2 Power Dissipation

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 will be 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 will be 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 its 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 device.

SUPPLY DECOUPLING

The AD7414/AD7415 should at least be decoupled with a 0.1 µF ceramic capacitor between V
and GND. This is particularly
DD
important if the AD7414/AD7415 is mounted remote from the power supply.
AD7414/AD7415
4
3
2
1
0
2.7
+40C
3.3
–1
–2
TEMPERATURE ERROR (ⴗC)
–3
–4
Figure 13. Typical Temperature Error vs. Supply for One Part

TYPICAL TEMPERATURE ERROR GRAPH

Figure 14 shows the typical temperature error plots for one device with V
TEMPERATURE ERROR (ⴗC)
at 3.3 V and at 5.5 V.
DD
4
3
2
1
0
–1
–2
–3
–4
–40
01020304050607080 90–30 –20–10 100 110 12585
–40C
+85C
5.0
SUPPLY VOLTAGE (V)
5.5V
3.3V
TEMPERATURE (ⴗC)
5.5

TEMPERATURE ACCURACY VS. SUPPLY

The temperature accuracy specifications are guaranteed for voltage supplies of 3 V and 5.5 V only. Figure 12 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 13 gives the typical performance characteristics of one part over the full voltage range of 2.7 V to 5.5 V.
REV. D
4
3
2
1
0
–1
–2
TEMPERATURE ERROR (ⴗC)
–3
–4
2.7 SUPPLY VOLTAGE (V)
3.0
–40C
+40C
+85C
5.5
Figure 12. Typical Temperature Error vs. Supply for Large Sample of Parts
Figure 14. Typical Temperature Error @ 3.3 V and 5.5 V
Figure 15 shows a histogram of the temperature error at ambient temperature (40°C) over approximately 6,000 units. Figure 15 shows that over 70% of the AD7414/AD7415 devices tested have a temperature error within 0.3°C.
Figure 15. Ambient Temperature Error @ 3 V
–11–
Page 12
AD7414/AD7415

OUTLINE DIMENSIONS

6-Lead Small Outline Transistor Package [SOT-23]
(RT-6)
Dimensions shown in millimeters
2.90 BSC
2
1.90
BSC
0.50
0.30
4 5
2.80 BSC
0.95 BSC
1.45 MAX
SEATING PLANE
0.22
0.08 10
0.60
4
0.45
0
0.30
1.60 BSC
PIN 1
INDICATOR
1.30
1.15
0.90
0.15 MAX
6
1 3
COMPLIANT TO JEDEC STANDARDS MO-178AB
5-Lead Small Outline Transistor Package [SOT-23]
Dimensions shown in millimeters
(RT-5)
8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
3.00 BSC
85
3.00 BSC
1
PIN 1
0.65 BSC
0.15
0.00
0.38
0.22
COPLANARITY
0.10
COMPLIANT TO JEDEC STANDARDS MO-187AA
4
SEATING PLANE
4.90 BSC
1.10 MAX
0.23
0.08
8 0
0.80
0.60
0.40
1.60 BSC
1.30
1.15
0.90
0.15 MAX
2.90 BSC
4 5
2.80 BSC
1 3
2
PIN 1
COMPLIANT TO JEDEC STANDARDS MO-178AA
1.90 BSC
0.50
0.30
0.95 BSC
1.45 MAX
SEATING PLANE
0.22
0.08 10
5 0
0.60
0.45
0.30
REV. D–12–
Page 13
AD7414/AD7415

Revision History

Location Page
9/04—Data Sheet Changed from REV. C to REV. D.
Changes to ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Updated ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
8/03—Data Sheet Changed from 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—Data Sheet Changed from REV. A to REV. B.
Changes to ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
10/02—Data Sheet Changed from 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
REV. D
–13–
Page 14
–14–
Page 15
–15–
Page 16
C02463–0–9/04(D)
–16–
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