ad5227 Analog Devices, Inc., ad5227 Datasheet - Page 14

• Manufacturer Part Number: ad5227
• Description: 64-position Up/down Control Digital Potentiometer
• Manufacturer: Analog Devices, Inc.

AD5227
CONSTANT BIAS WITH SUPPLY TO
RETAIN RESISTANCE SETTING
Users who consider EEMEM potentiometers but cannot justify
the additional cost and programming for their designs can con-
sider constantly biasing the AD5227 with the supply to retain
the resistance setting as shown in Figure 38. The AD5227 is
designed specifically with low power to allow power conservation
even in battery-operated systems. As shown in Figure 39, a
similar low power digital potentiometer is biased with a 3.4 V
450 mA/hour Li-Ion cell phone battery. The measurement shows
that the device drains negligible power. Constantly biasing the
potentiometer is a practical approach because most portable
devices do not require detachable batteries for charging. Although
the resistance setting of the AD5227 is lost when the battery
needs to be replaced, this event occurs so infrequently that the
inconvenience is minimal for most applications.
SW1
+
–
Figure 38. Constant Bias AD5227 for Resistance Retention
U1
V
DD
AD5227
GND
GND
V
DD
U2
COMPONENT X
GND
V
DD
U3
COMPONENT Y
GND
V
DD
Rev. 0 | Page 14 of 16
3.50
3.49
3.48
3.47
3.46
3.45
3.44
3.43
3.42
3.41
3.40
0
Figure 39. Battery Consumption Measurement
2
4
DAYS
6
8
T
A
10
= 25°C
12