VLED=Vbk2(1.25V)
x
(
R
1
+
R
2
)
/
R
2
VLED=Vbk3(0.5V)x
(
R
1
+
R
2
)
/
R
2
LED BACKLIT application circuit
Note--DC_FBK2 comparator is 1.25V and
DC_FBK3
comparator is 0.5V.
CPT 7" LED Bac
k
l
i
t
u
n
i
t
equivalent
diagram
Output:
programmable
DC_PWM2/3:2
19KHz
SCHEMATIC DIAGRAM
MODEL NO.: PF-2821TFT LED BACKLIT SCH
NOTE: subject to change without notice for improvement!
VLED-
PW
M1
[2]
DCPWM3
[2]
DC_FBK2
[2]
PWM
1
[2]
DCPWM2
[2]
DC_FBK3
[2]
IGND
+Vinv
IGND
IGND
+5VD
+12V
IGND
IGND
VLED
IGND
IGND
+5VD
GNDD
IGND
IGND
IGND
+5VD
R244
220R
L42
22uH/STD0403
R251
NC/4.7K
R243
33K
C175
10u/25V
C176
10u/25V
Q17
NC/BC848B
1
2
3
R250
NC/4.7K
R240
100K
C173
0R/1206
C174
NC
L44
0R/1206
R247
4.7K
C177
47n
R242
0R
L43
NC/22uH/STD0403
R248
NC
R252
NC/100
J18
CON2/2.0mm
1
2
D13
NC/BZT52C3.3B
2
1
Q16
2SD965A/S
O
T
8
9
1
3
2
F2
1.0A 32V (1206)
R245
NC
F1
NC/1.0A 32V (1206)
EC37
22u/16V
R241
NC
D12
SSM14/SMA
2
1
R246
0R
Q18
NC/2N7002
1
2
3
R249
2.2R/1206
