Datasheet

Table Of Contents
VIPER37 Operation description
Doc ID 022218 Rev 1 29/35
Figure 32. Burst mode timing diagram, light load management
8.12 Brownout protection
Brownout protection is a not-latched shutdown function activated when a condition of mains
undervoltage is detected.
The brownout comparator is internally referenced to V
BRth
,
Tabl e 8
, and disables the PWM if
the voltage applied at the BR pin is below this internal reference. Under this condition the
Power MOSFET is turned off. Until the brownout condition is present, the VDD voltage
continuously oscillates between the V
DDon
and the UVLO thresholds, as shown in the timing
diagram of
Figure 33
. A voltage hysteresis is present to improve the noise immunity.
The switching operation is restarted as the voltage on the pin is above the reference plus the
previously mentioned voltage hysteresis, see
Figure 5
.
The brownout comparator is provided also with a current hysteresis, I
BRhyst
. The user must
set the rectified input voltage above which the Power MOSFET starts switching after
brownout event, V
INon
, and the rectified input voltage below which the Power MOSFET is
switched off, V
INoff
. Thanks to the I
BRhyst
, see
Tabl e 8
, these two thresholds can be set
separately.
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