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參數(shù)資料
| 型號： | AD5228 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 數(shù)字電位計 |
| 英文描述： | 32-Position Manual Up/Down Control Potentiometer |
| 中文描述： | 32工位手冊上/下控制電位器 |
| 文件頁數(shù)： | 15/20頁 |
| 文件大?。?/td> | 341K |
| 代理商： | AD5228 |
AD5228
APPLICATIONS
MANUAL ADJUSTABLE LED DRIVER
The AD5228 can be used in many electronics-level adjustments
such as LED drivers for LCD panel backlight controls. Figure 41
shows a manually adjustable LED driver. The AD5228 sets the
voltage across the white LED D1 for the brightness control.
Since U2 handles up to 250 mA, a typical white LED with V
F
of
3.5 V requires a resistor, R1, to limit U2 current. This circuit is
simple but not power efficient. The U2 shutdown pin can be
toggled with a PWM signal to conserve power.
Rev. 0 | Page 15 of 20
0
BUTTON
PBUTTON
A
W
B
GND
10k
V
DD
PRE
PU
PD
AD5228
C1
1
μ
F
C2
μ
F
5V
AD8591
+
–
V+
V–
SD
5V
C3
0.1
μ
F
R1
6
WHITE
D1
PWM
Figure 41. Low Cost Adjustable LED Driver
ADJUSTABLE CURRENT SOURCE FOR LED DRIVER
Because LED brightness is a function of current rather than of
forward voltage, an adjustable current source is preferred as
shown in Figure 42. The load current can be found as the V
WB
of
the AD5228 divided by R
SET
.
V
I
=
SET
WB
D1
R
(7)
The U1 ADP3333ARM-1.5 is a 1.5 V LDO that is lifted above or
lowered below 0 V. When V
WB
of the AD5228 is at its minimum,
there is no current through D1, so the GND pin of U1 is at –1.5 V
if U3 is biased with the dual supplies. As a result, some of the U2
low resistance steps have no effect on the output until the U1
GND pin is lifted above 0 V. When V
WB
of the AD5228 is at its
maximum, V
OUT
becomes VL + V
AB
, so the U1 supply voltage
must be biased with adequate headroom. Similarly, PWM signal
can be applied at the U1 shutdown pin for power efficiency.
0
BUTTON
PBUTTON
A
W
B
10k
R1
V
DD
PRE
GND
PU
PD
AD5228
5V
5V
U3
AD8591
+
–
V+
V–
5V
PWM
V
IN
V
OUT
GND
ADP3333
SD
R
SET
0.1
VL
ID
D1
Figure 42. Adjustable Current Source for LED Driver
ADJUSTABLE HIGH POWER LED DRIVER
The previous circuit works well for a single LED. Figure 43
shows a circuit that can drive three to four high power LEDs.
The ADP1610 is an adjustable boost regulator that provides the
voltage headroom and current for the LEDs. The AD5228 and
the op amp form an average gain of 12 feedback network that
servos the R
SET
voltage and the ADP1610 FB pin 1.2 V band gap
reference voltage. As the loop is set, the voltage across R
SET
is
regulated around 0.1 V and adjusted by the digital
potentiometer.
V
I
=
SET
R
LED
R
SET
(8)
R
SET
should be small enough to conserve power but large enough
to limit maximum LED current. R3 should also be used in par-
allel with AD5228 to limit the LED current within an achievable
range. A wider current adjustment range is possible by lowering
the R2 to R1 ratio as well as changing R3 accordingly.
0
SS
RT GND
IN
ADP1610
SD
SW
FB
COMP
PWM
1.2V
C
10nF
C
C
390pF
R
C
100k
L1
10
μ
F
D1
C3
10
μ
F
R4
13.5k
D2
D3
D4
V
OUT
C2
10
μ
F
5V
+
–
AD8541
U1
L1–SLF6025-100M1R0
D1–MBR0520LT1
U3
V+
V–
5V
C8
0.1
μ
F
U1
AD5228
B
A
10k
R3
200
W
R1
100
R2
1.1k
R
SET
0.25
Figure 43. Adjustable Current Source for LEDs in Series
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| AD5228BUJZ100-R2 | 功能描述:IC DGTL POT 100K UP/DN TSOT23-8 RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)字電位器 系列:- 標(biāo)準(zhǔn)包裝:3,000 系列:DPP 接片:32 電阻（歐姆）:10k 電路數(shù):1 溫度系數(shù):標(biāo)準(zhǔn)值 300 ppm/°C 存儲器類型:非易失 接口:3 線串行（芯片選擇，遞增，增/減） 電源電壓:2.5 V ~ 6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:8-TDFN（2x3） 包裝:帶卷 (TR) |
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