Operation descriptions

VIPER27

24/31

Doc ID 15133 Rev 5

Equation 9

Equation 10

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

enable the brown-out function the BR pin voltage has to be higher than the maximum of

Figure 31.

Brown-out protection: BR external setting and timing diagram

Rh

Rl

AC_OK Disable

BR

VDIS

Vin_OK

Vcc

+

-

VBRth

IBRhyst

VIN

VIN

VDRAIN

VOUT

VBR

VBRth

Vin_OK

t

t

t

t

t

t

t

VINon

VINoff

IBRhyst

t

t

t

t

t

t

t

VDDon

VDDoff

BRhyst

BRth

BRth

INoff

BRhyst

INoff

INon

BRhyst

BRhyst

L

I

V

V

V

V

V

V

I

V

R

×

−

−

−

+

−

=

BRhyst

BRhyst

L

L

BRhyst

BRhyst

INoff

INon

H

I

V

R

R

I

V

V

V

R

+

×

−

−

=