7314 데이터 시트보기 (PDF) - Analog Devices
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7314 Datasheet PDF : 8 Pages
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AD7314
CE
SCLK
SDO
SDI
1
2
3
4
t4
LEADING
ZERO
DB9
DB8
t6
DON'T
CARE
DON'T
CARE
POWER-
DOWN
DATA-IN IS LOADED INTO
CONTROL REGISTER
ON THIS EDGE
11
12
DB0
Figure 3. Serial Interface Diagram
15
16
Write Operation
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 15th rising SCLK edge.
The data takes effect at this time, i.e., if the part is programmed
to go into shutdown, it does so at this point. If the CE is brought
low before this 15th SCLK edge, the control register will not be
loaded and the power-down status of the part will not change.
MICROCONTROLLER INTERFACING
The AD7314 serial interface allows for easy interface to most
microcontrollers and microprocessors. A typical interface circuit
is shown in Figure 4.
AD7314*
SCLK
SDI
SDO
CE
CONTROLLER*
SCLK
DOUT
DIN
CE
*ADDITIONAL PINS OMITTED FOR CLARITY
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 kW internal pull-down
resistor. If a pull-up resistor is used on Pin 7 to aid in identify-
ing a device, then a pull-up value of 100 kW with VDD at 2.9 V
nominal is recommended. 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 tem-
perature sensor measurements.
2.9V
AD7314*
ID
100k⍀
CONTROLLER*
1k⍀
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 5. Typical ID Pin Interface
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 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 tempera-
ture 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 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 that
provide a safe environment for the device.
–6–
REV. A
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