AD5227

Rev. B | Page 12 of 1

6

APPLICATIONS

MANUAL CONTROL WITH TOGGLE AND

PUSHBUTTON SWITCHES

The AD5227’s simple interface allows it to be used with

mechanical switches for simple manual operation. The states of

the CS and U/D can be selected by toggle switches and the CLK

input can be controlled by a pushbutton switch. Because of the

numerous bounces due to contact closure, the pushbutton

switch should be debounced by flip-flops or by the ADM812 as

shown in

.

Figure 31

UP/DOWN

MR

RESET

GND

ADM812

CLK

AD5227

CS

U/D

5V

INCREMENT

Figure 31. Manual Push Button Up/Down Control

MANUAL CONTROL WITH ROTARY ENCODER

Figure 32 shows another way of using AD5227 to emulate

mechanical potentiometer in a rotary knob operation. The

rotary encoder U1 has a C ground terminal and two out-of-

phase signals, A and B. When U1 is turned clockwise, a pulse

generated from the B terminal leads a pulse generated from the

A terminal and vice versa. Signals A and B of U1 pass through a

quadrature decoder U2 that translates the phase difference

between A and B of U1 into compatible inputs for U3 AD5227.

Therefore, when B leads A (clockwise), U2 provides the AD5227

with a logic high U/D signal, and vice versa. U2 also filters

noise, jitter, and other transients as well as debouncing the

contact bounces generated by U1.

U3

AD5227

DIGITAL

POTENTIOMETER

CLK

1

8

U/D

2

CS

7

A1

3

B1 6

GND

4

W1 5

B1

A1

W1

U2

LS7084

QUADRATURE

DECODER

RBIAS

1

CLK

8

2

U/D

7

VSS

3

X4/X1

6

A

4

B

5

B

C

A

U1

ROTARY

ENCODER

RE11CT-V1Y12-EF2CS

R3

10k

Ω

R1

10k

Ω

R2

10k

Ω

5V

Figure 32. Manual Rotary Control

ADJUSTABLE LED DRIVER

The AD5227 can be used in many electronics-level adjustments

such as LED drivers for LCD panel backlight control. Figure 33

shows an adjustable LED driver. The AD5227 sets the voltage

across the white LED D1 for the brightness control. Since U2

requires a resistor, R1, to limit the U2 current. This circuit is

simple but not power-efficient, therefore the U2 shutdown pin

can be toggled with a PWM signal to conserve power.

A

W

B

10k

Ω

GND

CS

CLK

U/D

U1

AD5227

C1

1

μF

C2

0.1

μF

5V

U2

AD8591

+

–

V+

V–

SD

5V

C3

0.1

μF

R1

6

Ω

WHITE

LED

D1

PWM

Figure 33. Low Cost Adjustable LED Driver

ADJUSTABLE CURRENT SOURCE FOR LED DRIVER

Since LED brightness is a function of current rather than

forward voltage, an adjustable current source is preferred over a

voltage source as shown in Figure 34.

A

W

B

10k

Ω

R1

418k

Ω

GND

U2

AD5227

5V

CS

CLK

U/D

5V

U3

AD8591

+

–

V+

V–

5V

PWM

GND

U1

ADP3333

ARM-1.5

SD

0.1

Ω

VL

ID

D1

Figure 34. Adjustable Current Source for LED Driver

SET

WB

D

R

V

I

=

(5)