DATA SHEET
AAT2822/2823/2824/2825
TFT-LCD DC/DC Converter with WLED Driver and VCOM Buffer
The output capacitor size can be estimated using the
equation:
LCD VCOM Buffer
The VCOM buffer is designed to drive the voltage on the
backplane of an LCD display. The buffer must be capable
of sinking and sourcing capacitive pulse current at low
frequency. A 10nF ceramic output capacitor in series
with a 100Ω resistor is sufficient for buffer stability at
high frequencies.
IOUT · DMAX
FS · ∆VOUT
COUT
=
To maintain stable operation at full load, the output
capacitor should be sized to maintain ΔVOUT between
100mV and 200mV.
The VCOM output voltage is typically set to half of the
main boost output voltage VADD. The maximum input bias
voltage for the VCOM buffer (VOPIN) cannot exceed 13V. In
applications where the main boost output voltage VVADD is
greater than 13V, VOPIN should be connected to an exter-
nal supply to prevent damage to the device; the jumper
The WLED boost converter input current flows during
both ON and OFF switching intervals. The input ripple
current is lower than the output ripple and, as a result,
a lower input capacitance is required.
J7 should be left open to disconnect VAVDD from VOPIN
.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
20
202081B
• Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 2, 2012
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
