Datasheet

L6563 - L6563A Application information
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An important advantage of this technique is that the overvoltage level can be set
independently of the regulated output voltage: the latter depends on the ratio of R1 to R2,
the former on the individual value of R1. Another advantage is the precision: the tolerance of
the detection current is 15%, which means 15% tolerance on the ∆V
O
. Since it is usually
much smaller than Vo, the tolerance on the absolute value will be proportionally reduced.
Example: V
O
= 400V, ∆V
O
= 40V.
Then: R1 = 40V/20µA = 2MΩ ; R2 = 2.5·2MΩ·/(400-2.5) = 12.58kΩ.
The tolerance on the OVP level due to the L6563/A will be 40·0.15 = 6 V, that is ± 1.36%.
When either OVP is activated the quiescent consumption is reduced to minimize the
discharge of the Vcc capacitor.
Figure 34. Output voltage setting, OVP and FFP functions: internal block diagram
-
+
2.5V
L6563
L6563A
1
2
INV
COMP
E/A
+
-
Frequency
Compensation
+
-
R2
7
PFC_OK
I
TBO
2.25V
Static OVP
Dynamic OVP
20 µA
Vout
{
R1a
R1b
R1
9.5V
FAULT (latched)
TBO
FUNCTION
R4
{
R3a
R3b
R3
+
-
FAULT (not latched)
0.26V
9.5V