AD5245

Rev. B | Page 15 of 20

CONSTANT BIAS TO RETAIN RESISTANCE SETTING

For users who desire nonvolatility but cannot justify the

additional cost for the EEMEM, the AD5245 can be considered

a low cost alternative by maintaining a constant bias to retain

the wiper setting. The AD5245 is designed specifically with low

power in mind, which allows low power consumption even in

battery-operated systems. Figure 42 demonstrates the power

consumption from a 3.4 V, 450 mA-hr Li-Ion cell phone battery

that is connected to the AD5245. 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 is 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%

510

15

98%

100%

102%

104%

106%

108%

110%

20

25

30

Figure 42. Battery Operating Life Depletion

This demonstrates that constantly biasing the potentiometer

can be a practical approach. Most portable devices do not

require the removal of batteries for charging.

Although the resistance setting of the AD5245 is 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 AD5245. If total power is lost, then

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 AD5245 from any PC running

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

in Figure 43, is straightforward and easy to use. More detailed

information is available in the user manual, which is provided

with the board.

Figure 43. AD5245 Evaluation Board Software

The AD5245 starts at midscale upon power-up. To increment or

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

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

bit pattern in the upper screen and click the Run button. The

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

the data from the device, the user can simply click the Read

button. The format of the read bits is shown in Table 9.