Datasheet

Over-Current Protection
PCL
+
V
PCL
1.08V
ISENSE
Soft Over Current (SOC)
R
ISENSE
R
ISENSEfilter
+–
C
ISENSEfilter
(Optional)
LINE
INPUT
V
OUT
V
SOC
0.73V
Peak Current Limit (PCL)
SOC
+
-1x
300 ns
Leading Edge
Blanking
+
V
ISOP
0.1V
ISOP
+
I
ISOP
1.5µA
ISENSE Open-Pin
Protection (ISOP)
Soft Over Current (SOC)
Peak Current Limit (PCL)
UCC28019A
SLUS828B – DECEMBER 2008 – REVISED APRIL 2009 .................................................................................................................................................. www.ti.com
Inductor current is sensed by R
ISENSE
, a low value resistor in the return path of input rectifier. The other side of
the resistor is tied to the system ground. The voltage is sensed on the rectifier side of the sense resistor and is
always negative. The voltage at ISENSE is buffered by a fixed gain of -1.0 to provide a positive internal signal to
the current functions. There are two over-current protection features; Soft Over-Current (SOC) protects against
an overload on the output and Peak Current Limit (PCL) protects against inductor saturation.
Figure 24. Soft Over Current/ Peak Current Limit
Soft Over-Current (SOC) limits the input current. SOC is activated when the current sense voltage on ISENSE
reaches -0.73 V, affecting the internal VCOMP level, and the control loop is adjusted to reduce the PWM duty
cycle.
Peak Current Limit (PCL) operates on a cycle-by-cycle basis. When the current sense voltage on ISENSE
reaches -1.08 V, PCL is activated, immediately terminating the active switch cycle. PCL is leading-edge blanked
to improve noise immunity against false triggering.
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