FAN7311B Datasheet, PDF (8/14 Pages) Fairchild Semiconductor – LCD Backlight Inverter Drive IC

Figure 5. Burst Oscillator Waveform
Figure 7. OLR Voltage During Striking Mode
Output Drives: The four output drives are designed so
that switches A and B, C and D never turn on simulta-
neously. The OUTA-OUTB pair is intended to drive one
half-bridge in the external power stage. The OUTC-
OUTD pair drives the other half-bridge.
Figure 6. Burst Dimming
Open Lamp Regulation and Open-Lamp Protection: It
is necessary to suspend power stage operation if an
open lamp occurs because the power stage has high
gain. When a voltage higher than 2V is applied to the
OLR pin, the part enters regulation mode and controls the
EA_OUT voltage. This limits the lamp voltage by sum-
ming 105µA into the feedback node. At the same time,
the OLP capacitor, connected to the OLP pin, is charged
by the 1.4µA internal current source. Once it reaches
2.5V, the IC enters shutdown where all output is high.
VIN
8.5V
8.5V
VIN
8.5V
8.5V
Figure 8. Phase-Shift Control Waveforms
© 2007 Fairchild Semiconductor Corporation
FAN7311B Rev. 1.0.0
8
www.fairchildsemi.com