RT9271 데이터 시트보기 (PDF) - Richtek Technology
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RT9271 Datasheet PDF : 15 Pages
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RT9271
R3 = VOUT − 3VFb − VDS
(4)
Ib
R4
= R5
=
R6
=
VOUT − 3VFk
Ik
(5)
VDS = Ib ×RDS(ON)
(6)
C1
VIN 2.2uF
LX
10uH
VCC
EN
LX
OVP
GND FB
RT9271
D1
SS0520
C3
1uF
R2
5.1k
backlight
+
VFb
-
Ib
R1
239k
R3
PWM
VOUT =12V
keypad
+
VFk
-
Ik
Ik
Ik
R4
R5 R6
PWM >22kHz
Figure 10. Constant output voltage for backlight and keypad
C1
VIN 1uF
LX
10uH
D1
SS0520
VCC
LX
C3
1uF
VOUT
keypad
+
D2
VFk
-
D3
Ik
Ik
Ik
EN
OVP
R3
VFB
10k
GND FB
R4
RT9271
23.7k
Rdc
100k
Cdc
0.1uF
D4
VLED R5
R2
12
R6 R7
2.8V
0V
PWM signal
Figure 11. Constant output current for backlight and keypad
www.richtek.com
12
DS9271-13 March 2007
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