AD5162 datasheet(15/20 Pages) AD

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AD5162

Rev. A | Page 15 of 20

LAYOUT AND POWER SUPPLY BYPASSING

It is good practice to employ 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 also good practice to bypass the power supplies

with quality capacitors for optimum stability. Supply leads to the

device should be bypassed with disc or chip ceramic capacitors

of 0.01 µF to 0.1 µF. 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 39). Note that the digital ground should also be

joined remotely to the analog ground at one point to minimize

the ground bounce.

VDD

GND

VDD

µF

0.1

µF

AD5162

Figure 39. 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 AD5162 may be considered as a

low cost alternative by maintaining a constant bias to retain the

wiper setting. The AD5162 is designed specifically with low

power in mind, which allows low power consumption even in

battery-operated systems. The graph in Figure 40 demonstrates

the power consumption from a 3.4 V 450 mAhr Li-Ion cell

phone battery, which is connected to the AD5162. The measure-

ment over time shows that the device draws approximately

1.3 µA and consumes negligible power. Over a course of

30 days, the battery is depleted by less than 2%, the majority of

which is due to the intrinsic leakage current of the battery itself.

This demonstrates that constantly biasing the potentiometer 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 AD5162 is lost when the

battery needs replacement, such events occur rather infre-

quently such that this inconvenience is justified by the lower

cost and smaller size offered by the AD5162. If and when total

power is lost, the user should be provided with a means to

adjust the setting accordingly.

DAYS

90%

92%

94%

96%

510

98%

100%

102%

104%

106%

108%

110%

TA = 25°C

Figure 40. Battery Operating Life Depletion

EVALUATION BOARD

An evaluation board, along with all necessary software, is

available to program the AD5162 from any PC running

Windows 98/2000/XP. The graphical user interface, as shown in

Figure 41, is straightforward and easy to use. More detailed

information is available in the user manual, which comes with

the board.

Figure 41. AD5162 Evaluation Board Software

The AD5162 starts at midscale upon power-up. To increment or

decrement the resistance, the user may simply move the scroll-

bars on the left. To write any specific value, the user should use

the bit pattern in the upper screen and press the Run button.

The format of writing data to the device is shown in Table 8.

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