AD5247BKS5-R2 查看數據表（PDF） - Analog Devices
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AD5247BKS5-R2 Datasheet PDF : 20 Pages
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AD5247
LAYOUT AND POWER SUPPLY BYPASSING
It is a good practice to employ a compact, minimum lead-length
layout design. The leads to the inputs should be as direct as
possible with a minimum conductor length. Ground paths
should have low resistance and low inductance.
Similarly, it is a good practice to bypass the power supplies with
quality capacitors for optimum stability. Supply leads to the
device should be bypassed with 0.01 µF to 0.1 µF disc or chip
ceramic capacitors. Low ESR 1 µF to 10 µF tantalum or electro-
lytic capacitors should also be applied at the supplies to
minimize any transient disturbance and low frequency ripple
(see Figure 40). Note that the digital ground should also be
joined remotely to the analog ground at one point to minimize
the ground bounce.
VDD
C3 + C1
10µF 0.1µF
VDD
AD5247
GND
Figure 40. Power Supply Bypassing
CONSTANT BIAS TO RETAIN RESISTANCE SETTING
For users who desire nonvolatility but cannot justify the
additional cost for the EEMEM, the AD5247 may be considered
as a low cost alternative by maintaining a constant bias to retain
the wiper setting. The AD5247 was designed specifically with
low power in mind, which allows low power consumption even
in battery-operated systems. The graph in Figure 41
demonstrates the power consumption from a 3.4 V 450 mAhr
Li-ion cell phone battery, which is connected to the AD5247.
The measurement over time shows that the device draws
approximately 1.3 µA and consumes negligible power. Over a
course of 30 days, the battery was depleted by less than 2%, the
majority of which is due to the intrinsic leakage current of the
battery itself.
110%
108%
106%
104%
102%
100%
98%
96%
94%
92%
90%
0
TA = 25°C
5
10
15
20
25
30
DAYS
Figure 41. Battery Operating Life Depletion
This demonstrates that constantly biasing the pot is not an
impractical approach. Most portable devices do not require the
removal of batteries for the purpose of charging. Although the
resistance setting of the AD5247 will be lost when the battery
needs replacement, such events occur rather infrequently such
that this inconvenience is justified by the lower cost and smaller
size offered by the AD5247. If and when total power is lost, the
user should be provided with a means to adjust the setting
accordingly.
EVALUATION BOARD
An evaluation board, along with all necessary software, is
available to program the AD5247 from any PC running
Windows® 98, Windows 2000®, or Windows XP®. The graphical
user interface, as shown in Figure 42, is straightforward and
easy to use. More detailed information is available in the user
manual, which comes with the board.
Figure 42. AD5247 Evaluation Board Software
Rev. 0 | Page 16 of 20
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