Application information

L6599AT

24/31

Doc ID 15534 Rev 3

Figure 13.

Line sensing function: internal block diagram and timing diagram

With reference to Figure 11, the following relationships can be established for the ON

Equation 11

Equation 12

While the line undervoltage is active the start-up generator continues working but there is no

between the start-up and the UVLO thresholds, as shown in the timing diagram of

Figure 13

.

As an additional measure of safety (e.g. in cases where the low-side resistor is open or

missing, or in non-power factor corrected systems in cases of abnormally high input voltage)

if the voltage on the pin exceeds 7 V, the L6599AT is shut down. If its supply voltage is

always above the UVLO threshold, the IC restarts as the voltage falls below 7 V.

The LINE pin, while the device is operating, is a high impedance input connected to high

value resistors, thus it is prone to pick up noise, which might alter the OFF threshold or give

origin to undesired switch-off of the IC 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

L

H

OFF

L

6

H

ON

R

24

.

1

R

24

.

1

Vin

R

24

.

1

10

13

R

24

.

1

Vin

=

−

+

⋅

=

−

−

24

.

1

Vin

24

.

1

R

R

;

10

13

Vin

Vin

R

OFF

H

L

6

OFF

ON

H

−

=

⋅

−

=

−