LT3798 LINER [Linear Technology], LT3798 Datasheet - Page 16

• Manufacturer Part Number: LT3798
• Description: Isolated No Opto-Coupler Flyback Controller
• Manufacturer: LINER [Linear Technology]

LT3798
OPERATION
Protection from Shorted Output Conditions
During a shorted output condition as shown in Figure 6, the
LT3798 operates at the minimum operating frequency. In
normal operation, the third winding provides power to the
IC, but the third winding voltage is zero during a shorted
condition. This causes the part’s V
switching. The part starts switching again when V
reached its turn-on voltage.
16
Figure 6. Switching Waveforms When Output Short-Circuits
Figure 5. Switching Waveforms When Output
Open-Circuits or at Very Light Load Conditions
V
V
3RD WINDING
3RD WINDING
20V/DIV
10V/DIV
20V/DIV
50V/DIV
1A/DIV
1A/DIV
V
I
OUT
OUT
I
V
PRI
IN
100ms/DIV
1ms/DIV
IN
UVLO to shutdown
3798 F05
3798 F06
IN
has
Usage with DC Input Voltage
The LT3798 is flexible enough to operate well from low
voltage to very high voltage DC input voltage applications.
When the supply voltage is less than 40V, the startup re-
sistor is not needed and the part's V
directly to the supply voltage. The startup sequence for
voltages higher than 40V is the same as what is described
for high voltage offline supply voltages.
The loop compensation component values can be chosen
to provide faster loop response since the LT3798 does
not have to provide PFC for the slow 50Hz/60Hz AC input
voltage. For DC input applications, connect a 25k resistor
from V
IN_SENSE
to INTV
CC
.
IN
can be connected
3798f