Data Sheet

AD5246

Rev. C | Page 15 of 16

LAYOUT AND POWER SUPPLY BYPASSING

It is a good practice to use 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 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

electrolytic capacitors should also be applied at the supplies to

minimize any transient disturbance and low frequency ripple

(see Figure 34). Note that the digital ground should also be

joined remotely to the analog ground at one point to minimize

the ground bounce.

AD5246

C1

C3

GND

10

µF

0.1

µF

+

Figure 34. Power Supply Bypassing

CONSTANT BIAS TO RETAIN RESISTANCE SETTING

For users who desire nonvolatility but cannot justify the addi-

tional cost for the EEMEM, the AD5246 may be considered as

a low cost alternative by maintaining a constant bias to retain

the wiper setting. The AD5246 was designed specifically with

low power in mind, which allows low power consumption

even in battery-operated systems. The graph in Figure 35

demonstrates the power consumption from a 3.4 V 450 mA/hr

Li-ion cell phone battery, which is connected to the AD5246.

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.

DAYS

0

90%

92%

94%

96%

5

10

15

98%

100%

102%

104%

106%

108%

110%

20

25

30

Figure 35. 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 AD5246 will be lost when the battery

needs replacement, such events occur rather infrequently, so

that this inconvenience is justified by the lower cost and smaller

size offered by the AD5246. If and when total power is lost,

the user should be provided with a means to adjust the setting

accordingly.