FAN7311_07 Datasheet, PDF (8/16 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
summing 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 shut down where all output is
high.
VIN
8.5V
8.5V
VIN
8.5V
8.5V
Figure 8. Phase-Shift Control Waveforms
© 2006 Fairchild Semiconductor Corporation
FAN7311 Rev. 1.0.6
8
www.fairchildsemi.com