AD7314 [ADI]
Low-Voltage, 10-Bit Digital Temperature Sensor in 8-Lead uSOIC; 低电压， 10位数字温度传感器采用8引脚uSOIC
| 型号： | AD7314 |
| 厂家： | 
ADI |
| 描述： | Low-Voltage, 10-Bit Digital Temperature Sensor in 8-Lead uSOIC |
| 文件： | 总8页 (文件大小：98K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Low-Voltage, 10-Bit Digital Temperature
a
Sensor in 8-Lead SOIC
AD7314
FUNCTIONAL BLOCK DIAGRAM
FEATURES
10-Bit Temperature-to-Digital Converter
–35؇C to +85؇C Operating Temperature Range
؎2؇C Accuracy
SPI™- and DSP-Compatible Serial Interface
Shutdown Mode
BANDGAP
TEMPERATURE
SENSOR
10-BIT
ANALOG/DIGITAL
CONVERTER
ID
Space-Saving SOIC Package
GND
V
TEMPERATURE
VALUE
REGISTER
DD
AD7314
APPLICATIONS
Hard Disk Drives
CE
Personal Computers
Electronic Test Equipment
Office Equipment
Domestic Appliances
Process Control
SERIAL
BUS
INTERFACE
SCLK
SDI
SDO
Mobile Phones
GENERAL DESCRIPTION
PRODUCT HIGHLIGHTS
The AD7314 is a complete temperature monitoring system in
an 8-lead µSOIC package. It contains a bandgap temperature
sensor and 10-bit ADC to monitor and digitize the temperature
reading to a resolution of 0.25°C.
1. The AD7314 has an on-chip temperature sensor that allows
an accurate measurement of the ambient temperature. The
measurable temperature range is –35°C to +85°C, with a
2°C temperature accuracy.
The AD7314 has a flexible serial interface that allows easy
interfacing to most microcontrollers. The interface is compat-
ible with SPI, QSPI and MICROWIRE™ protocol and is also
compatible with DSPs. The part features a standby mode that
is controlled via the serial interface.
2. Supply voltage of 2.65 V to 2.9 V.
3. Space-saving 8-lead µSOIC package.
4. 10-bit temperature reading to 0.25°C resolution.
5. The AD7314 features a standby mode that reduces the
current consumption to 1 µA max.
The AD7314’s low supply current and SPI-compatible interface,
make it ideal for a variety of applications, including personal
computers, office equipment, and domestic appliances.
SPI is a trademark of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corporation.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
www.analog.com
© Analog Devices, Inc., 2001
AD7314–SPECIFICATIONS1
(TA = TMIN to TMAX, VDD = 2.65 V to 2.9 V, unless otherwise noted.)
Parameter
Min
Typ
Max
Unit
Test Conditions/Comments
TEMPERATURE SENSOR AND ADC
Accuracy
Resolution
Update Rate, tR
Temperature Conversion Time
2.0
°C
Bits
µs
TA = –35°C to +85°C.
10
400
25
µs
SUPPLIES
Supply Voltage
Supply Current
Normal Mode (Inactive)
Normal Mode (Active)
Shutdown Mode
Power Dissipation
2.65
2.9
300
1
V
For Specified Performance
250
1
µA
Part not Converting
Part Converting
mA
µA
860
µW
VDD = 2.65 V. Using Normal Mode
(Auto Conversion)
Power Dissipation
1 sps
10 sps
VDD = 2.65 V. Using Shutdown Mode
3
3.3
6
µW
µW
µW
100 sps
DIGITAL INPUT
Input High Voltage, VIH
Input Low Voltage, VIL
Input Current, IIN
1.85
2.4
V
V
µA
pF
VDD = 2.65 V to 2.9 V
VDD = 2.65 V to 2.9 V
VIN = 0 V to VDD
0.53
1
10
Input Capacitance, CIN
All Digital Inputs
DIGITAL OUTPUT
Output High Voltage, VOH
Output Low Voltage, VOL
Output Capacitance, COUT
V
V
pF
ISOURCE = ISINK = 200 µA
IOL = 200 µA
0.4
50
NOTES
1All specifications apply for –35°C to +85°C unless otherwise noted.
Specifications subject to change without notice.
1,2
3
TIMINGCHARACTERISTICS
(TA = TMIN to TMAX, VDD = 2.65 V to 2.9 V, unless otherwise noted. See Figure 1.)
Parameter
Limit
Unit
Comments
t1
t2
0
ns min
ns min
ns min
ns max
ns min
ns min
ns min
ns max
CE to SCLK Setup Time
SCLK High Pulsewidth
SCLK Low Pulsewidth
Data Access Time After SCLK Rising Edge
Data Setup Time Prior to SCLK Falling Edge
Data Hold Time After SCLK Falling Edge
CE to SCLK Hold Time
50
50
35
20
0
0
40
t34
t4
t5
t6
t74
t8
CE to SDO High Impedance
NOTES
1Guaranteed by design and characterization, not production tested.
2All input signals are specified with tr = tf = 5 ns (10% to 90% of VDD) and timed from a voltage level of 1.6 V.
3All specifications apply for –35°C to +85°C unless otherwise noted.
4Measured with the load circuit of Figure 2.
Specifications subject to change without notice.
–2–
REV. 0
AD7314
CE
t7
t2
t1
SCLK
t3
t8
t4
SDO
SDI
t5
t6
Figure 1. Timing Diagram
ABSOLUTE MAXIMUM RATINGS1
200A
I
OL
VDD to GND . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V
Digital Input Voltage to GND . . . . . . . –0.3 V to VDD + 0.3 V
Digital Output Voltage to GND . . . . . –0.3 V to VDD + 0.3 V
Operating Temperature Range . . . . . . . . . . . –35°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . 150°C
SOT-23, Power Dissipation . . . . . . . . . . . . . . . . . . . . 450 mW
TO
OUTPUT
PIN
1.6V
C
50pF
L
θ
JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . 240°C/W
200A
I
OH
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
µSOIC Package, Power Dissipation . . . . . . . . . . . . . . 450 mW
Figure 2. Load Circuit for Data Access Time and Bus
Relinquish Time
θ
JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . 206°C/W
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
Latch-Up for ID Pin2 . . . . . . . . . . . . . . . . . . . . . . . . ≤ –70 mA
Latch-Up for All Other Pins . . . . . . . . . . . . . . . . . ≥ –110 mA
NOTES
1Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
2Correct usage of the ID pin will prevent any latch-up occurring. We recommend
that in an application the ID pin should be either tied via a 100 kΩ resistor to VDD
or left open circuit. If the application complies with our recommendation, the ID
pin will never see –70 mA.
ORDERING GUIDE
Temperature
Range
Temperature
Error
Package
Description
Package
Option
Branding
Information
Model
AD7314ARM
–35°C to +85°C
2°C
8-Lead µSOIC
RM-8
CKA
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 AD7314 features proprietary ESD protection circuitry, permanent damage may occur on
devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are
recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
REV. 0
–3–
AD7314
PIN FUNCTION DESCRIPTIONS
Pin No.
Mnemonic
Description
1
2
NC
CE
No Connect.
Chip Enable Input. The device is selected when this input is high. The SCLK input is disabled
when this pin is low.
3
SCLK
Serial Clock Input. This is the clock input for the serial port. The serial clock is used to clock
data out of the temperature value register of the AD7314 and also to clock data into the control
register on the part.
4
5
6
7
GND
SDO
SDI
ID
Analog and Digital Ground.
Serial Data Output. Logic output. Data is clocked out of the temperature value register at this pin.
Serial Data Input. Serial data to be loaded to the parts’s control register is provided on this input.
Identification. This pin can be used by a master device to identify the AD7314 in an SPI Bus
system. This pin has an internal pull-down resistor of 1 kΩ.
8
VDD
Positive Supply Voltage, 2.65 V to 2.9 V.
PIN CONFIGURATION
SOIC
V
NC
CE
1
2
3
4
8
7
6
5
DD
AD7314
TOPVIEW
(Not to Scale)
ID
SDI
SDO
SCLK
GND
NC = NO CONNECT
–4–
REV. 0
AD7314
CIRCUIT INFORMATION
Table I. Temperature Data Format
The AD7314 is a 10-bit digital temperature sensor. The part
houses an on-chip temperature sensor, a 10-bit A/D converter, a
reference and serial interface logic functions in an µSOIC package.
The A/D converter section consists of a conventional successive-
approximation converter based around a capacitor DAC. The
parts are capable of running on a 2.65 V to 2.9 V power supply.
Digital Output
DB9 . . . DB0
Temperature
–128°C
–125°C
–100°C
–75°C
–50°C
–25°C
–0.25°C
0°C
+0.25°C
+10°C
+25°C
+50°C
+75°C
+100°C
+125°C
+127°C
10 0000 0000
10 0000 1100
10 0111 0000
10 1101 0100
11 0011 1000
11 1001 1100
11 1111 1111
00 0000 0000
00 0000 0001
00 0010 1000
00 0110 0100
00 1100 1000
01 0010 1100
01 1001 0000
01 1111 0100
01 1111 1100
The on-chip temperature sensor allows an accurate measurement
of the ambient device temperature to be made. The working
measurement range of the AD7314 is –35°C to +85°C.
CONVERTER DETAILS
The conversion clock for the part is internally generated so no
external clock is required except when reading from and writing
to the serial port. In normal mode, an internal clock oscillator
runs the automatic conversion sequence. A conversion is initi-
ated every 400 µs. At this time, the part wakes up and performs
a temperature conversion. This temperature conversion typically
takes 25 µs, at which time the part automatically shuts down.
The result of the most recent temperature conversion is avail-
able in the serial output register at any time. The AD7314 can
be placed in a shutdown mode, via the Control Register, in
which case, the on-chip oscillator is shut down and no further
conversions are initiated until the AD7314 is taken out of shut-
down mode. The conversion result from the last conversion prior
to shutdown can still be read from the AD7314 even when it is
in shutdown mode.
Serial Interface
The serial interface on the AD7314 consists of four wires, CE,
SCLK, SDI and SDO. The interface can be operated in 3-wire
mode with SDI tied to Ground, in which case the interface has
read-only capability, with data being read from the data register
via the SDO line. The SDI line is used to write the part into
standby mode, if required. The CE line is used to select the
device when more than one device is connected to the serial
clock and data lines. To ensure that the serial port is reset prop-
erly after power-up, the CE must be at a logic low before the
first serial port access. The serial clock is active only when CE is
high. For correct data synchronization it is important that the
CE be low when the serial port is not been accessed.
In the automatic conversion mode, every time a read or write
operation takes place, the internal clock oscillator is restarted at
the end of the read or write operation. The result of the conver-
sion is available, typically 25 µs later. Similarly, when the part is
taken out of shutdown mode, the internal clock oscillator is
restarted and the conversion result is available, typically 25 µs
later. Reading from the device again before conversion is com-
plete will again provide the same set of data.
The part operates in a slave mode and requires an externally
applied serial clock to the SCLK input to access data from the
data register. The serial interface on the AD7314 is designed to
allow the part to be interfaced to systems that provide a serial
clock that is synchronized to the serial data, such as the 80C51,
87C51, 68HC11, 68HC05, and PIC16Cxx microcontrollers as
well as DSP processors.
Temperature Value Register
The temperature value register is a read-only register that stores
the temperature reading from the ADC in 10-bit twos comple-
ment format. The temperature data format is shown in Table I.
This shows the full theoretical range of the ADC from –128°C
to +127°C, but in practice the temperature measurement range
is limited to the operating temperature range of the device (–35°C
to +85°C).
A read operation from the AD7314 accesses data from the
Temperature Value Register while a write operation to the part
writes data to the Control Register. Input data is not loaded into
the Control Register until the rising edge of the fifteenth SCLK
cycle. Data on the SDI line is latched in on the falling edge of
the serial clock whilst data is updated on the SDO line on the
rising edge of the serial clock.
Read Operation
Figure 3 shows the interface diagram for a serial read from the
AD7314. The CE line enables the SCLK input. A leading zero
and ten bits of data are transferred during a read operation. Read
operations occur during streams of 16 clock pulses. Output data
is updated on the rising edge of SCLK. The serial data is accessed
in a number of bytes if ten bits of data are being read. At the
end of the read operation, the SDO line remains in the state of
the last bit of data clocked out of the AD7314 until CE returns
low, at which time the SDO line goes into three-state.
REV. 0
–5–
AD7314
CE
DATA-IN IS LOADED INTO
CONTROL REGISTER
ONTHIS EDGE
SCLK
SDO
3
12
15
16
1
2
11
4
t4
LEADING
ZERO
DB8
DB0
DB9
t6
DON'T
CARE
DON'T
CARE
POWER-
DOWN
SDI
Figure 3. Serial Interface Diagram
Write Operation
Figure 5 shows the recommended pull-up resistor value for the
ID pin. The recommended resistor value in Figure 5 minimizes
the additional power the AD7314 has to dissipate, thus reducing
any negative affects on the temperature sensor measurements.
Figure 3 also shows the interface diagram for a serial write to
the AD7314. The write operation takes place at the same time
as the read operation. Data is clocked into the Control Register
on the falling edge of SCLK. Only the third bit in the data stream
provides a user-controlled function. This third bit is the power-
down bit which, when set to a 1, puts the AD7314 into shutdown
mode. The first two bits of the data stream are don’t cares while
all other bits in the data stream other, than the power-down bit,
should be 0 to ensure correct operation of the AD7314. Data is
loaded into the Control Register on the fifteenth rising SCLK
edge. The data takes effect at this time i.e., if the part is pro-
grammed to go into shutdown, it does so at this point. If the CE
is brought low before this fifteenth SCLK edge, the Control
Register will not be loaded and the power-down status of the
part will not change.
2.9V
100k⍀
AD7314*
Controller*
ID
1k⍀
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 5. Typical ID Pin Interface
MICROCONTROLLER INTERFACING
The AD7314 serial interface allows for easy interface to most
microcontrollers and microprocessors. A typical interface circuit
is shown in Figure 4.
MOUNTING THE AD7314
The AD7314 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, thanks to the devices low
power consumption. Care should be taken to insulate the back
and leads of the device from the air, if the ambient air tempera-
ture is different from the surface temperature being measured.
Controller*
AD7314*
SCLK
SCLK
SDI
SDO
CE
DOUT
DIN
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.
CE
*ADDITIONAL PINS OMITTED FOR CLARITY
As with any IC, the AD7314 and its associated wiring and cir-
cuits 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 AD7314
package allows it to be mounted inside sealed metal probes,
which provide a safe environment for the device.
Figure 4. Typical Interface
The ID pin of the AD7314 can be used to distinguish the device
if used as a drop-in replacement temperature sensor. Connected
to Pin 7 (ID pin) is a 1 kΩ internal pull-down resistor. If a pull-
up resistor is used on Pin 7 to aid in identifying a device then we
recommend a pull-up value of 100 kΩ with VDD at 2.9 V nominal.
–6–
REV. 0
AD7314
SUPPLY DECOUPLING
The AD7314 should at least be decoupled with a 0.1 µF ceramic
capacitor between VDD and GND. This is particularly important
if the AD7314 is mounted remote from the power supply.
TYPICAL TEMPERATURE ERROR GRAPHS
Figure 6 shows a typical temperature error plot for one device
with VDD at 2.65 V.
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–55
–35
0
40
85
125
TEMPERATURE –
C
Figure 6. Typical Temperature Error @ 2.65 V
REV. 0
–7–
AD7314
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Mini/Micro SOIC
(RM-8)
0.122 (3.10)
0.114 (2.90)
8
5
4
0.122 (3.10)
0.114 (2.90)
0.199 (5.05)
0.187 (4.75)
1
PIN 1
0.0256 (0.65) BSC
0.120 (3.05)
0.112 (2.84)
0.120 (3.05)
0.112 (2.84)
0.043 (1.09)
0.037 (0.94)
0.006 (0.15)
0.002 (0.05)
33؇
0.018 (0.46)
0.008 (0.20)
27؇
0.028 (0.71)
0.016 (0.41)
0.011 (0.28)
0.003 (0.08)
SEATING
PLANE
–8–
REV. 0
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