Datasheet

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APPLICATION CIRCUITS
C1+
SDAT DS1 DS2 DM5
VIO
NC
GND
GND
NC-G
NC
DM1DM2DM3DM4IS
ENA
GND
C2+
C2-
C1-
VOUT
VIN
MainDisplay
C1
C4
C2
1 Fm
C3
SubDisplay
SCLK
I
2
CInterface
1.8VforI/O
Input
R
1
562kW
1 Fm
4.7 Fm
4.7 Fm
h
Light
+
I
O
V
F
V
in
ǒ
I
O
) I
op
Ǔ
(7)
TPS60251
SLVS767C – APRIL 2007 – REVISED NOVEMBER 2007
Figure 20. The Typical Application Circuit for Sub and Main Display
As shown in Figure 20 , this is a typical application circuit for a clam shell phone with 5 main LEDs and 2 sub
LEDs. Recently, the LCD panel makers have developed a new panel that has improved the transparency rate
which makes system efficiency with a 100- µ A LED current a critical load point. To meet system efficiency
requirements with the light load conditions for the new LCD operating panel, the TPS60251 has a maximum
55- µ A operating current with the 100- µ A output load condition. In this application, the controller always operates
in 1 × mode due to the WLED's low forward voltage drop (about 2.6V
F
with a 100- µ A WLED current). Thus, the
total efficiency at a light load condition is determined using Equation 7 :
Where:
I
O
: Output Load (WLED) Current
V
F
: Forward Voltage Drop of WLED
V
in
: Input Voltage
I
op
: Operating Current of LED Driver
Copyright © 2007, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Link(s): TPS60251