Datasheet

0 400 800 1200 1600 2000
0
10
20
30
40
50
60
R
DLY
(k)
DELAY TIME (ns)
TPS92311
SNVS811B –MAY 2012–REVISED MAY 2013 www.ti.com
Figure 18. Delay Time Setting
Protection Features
OUTPUT OPEN CIRCUIT PROTECTION
If the LED string is disconnected from the output of the TPS92311, The output voltage (V
LED
) increases and thus
V
ZCD-PEAK
increases. When V
ZCD-PEAK
is greater than V
ZCD-OVP
for 3 continues switching cycles, the Over Voltage
Protection (OVP) feature is triggered. Switching of Q
1
is stopped, and V
CC
decreases until it drops below the
falling threshold of V
CC-UVLO
, the TPS92311 restarts, and re-enter into startup state (Figure 20).
OUTPUT SHORT CIRCUIT PROTECTION
If the LED string is shorted, V
ZCD-PEAK
drops, and as V
ZCD-PEAK
drops below V
ZCD-TRIG
, the TPS92311 will enter
low switching frequency operation. During low switching frequency operation, power supplied from L
AUX
to V
CC
is
not enough to maintain V
CC
. If the short remains V
CC
will drop below the falling threshold of V
CC-UVLO
, the
TPS92311 will attempt to restart at this time (Figure 19). When the short is removed the TPS92311 will restore to
steady state operation.
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