VIPER27 STMicroelectronics, VIPER27 Datasheet - Page 24

• Manufacturer Part Number: VIPER27
• Description: VIPerPlus family: fixed frequency high performance off line high voltage converter
• Manufacturer: STMicroelectronics

Operation descriptions
24/31
Figure 31. Brown-out protection: BR external setting and timing diagram
Rh
Rl
V IN
BR
Fixed the V
can be established for the calculation of the resistors R
Equation 9
Equation 10
For a proper operation of this function, V
minimum mains and V
minimum mains and maximum load.
The BR pin is a high impedance input connected to high value resistors, thus it is prone to
pick up noise, which might alter the OFF threshold when the converter operates or gives
origin to undesired switch-off of the device during ESD tests.
It is possible to bypass the pin to ground with a small film capacitor (e.g. 1-10 nF) to prevent
any malfunctioning of this kind.
If the brown-out function is not used the BR pin has to be connected to GND, ensuring that
the voltage is lower than the minimum of V
enable the brown-out function the BR pin voltage has to be higher than the maximum of
V
DIS
I BRhyst
threshold (150 mV, see
INon
V BRth
V DIS
and the V
Vcc
+
-
+
-
R
V
DD
R
L
IN off
=
H
=
−
INoff
AC_OK Disable
V
less than the minimum voltage on the input bulk capacitor at
V
I
BRhyst
BRhyst
INon
Table 8
levels, with reference to
Doc ID 15133 Rev 5
V in_OK
−
V
+
I
).
BRhyst
INoff
V
INon
IN on
−
V
DIS
V
−
INoff
BRhyst
V DRAIN
V
V INon
V INoff
must be less than the peak voltage at
V in_OK
I BRhyst
V DDon
V DDoff
V OUT
threshold (50 mV, see
V BRth
INoff
V BR
V
V IN
I
BR
−
DD
V
×
−
BRth
R
V
Figure 31
BRhyst
H
L
+
and R
R
V
I
BRhyst
BRhyst
L
×
L
I
V
BRhyst
, the following relationships
:
BRth
Table 8
). In order to
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