VIPER17

Operation descriptions

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7.12

Brown-out protection

Brown-out protection is a not-latched shutdown function activated when a condition of mains

under voltage is detected.

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 Brown out condition is present, the VDD

the timing diagram of Figure 31 on page 25. 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

before said voltage hysteresis. See Figure 31.

choosing the resistors of the divider connect to the BR pin.

Equation 9

Figure 31. Brown-out protection: BR external setting and timing diagram

Rh

Rl

AC_OK Disable

BR

0.1V

VinOK

Vcc

+

-

0.45V

10u

HV Input bus

HV Input bus

VinOK

Vcc

(pin 3)

VDS

Vout

BR

0.45V

15 µA

t

t

t

t

t

t

t

HV Input bus

VinOK

Vcc

(pin 3)

VDS

Vout

0.45V

15 µA

t

t

t

t

t

t

t

BRhyst

BRth

BRth

INoff

BRhyst

INoff

INon

BRhyst

BRhyst

L

I

V

V

V

V

V

V

I

V

R

×

−

−

−

+

−

=