WINSEMI MICROELECTRONICS

WINSEMI MICROELECTRONICS

WINSEMI MICROELECTRONICS

WINSEMI MICROELECTRONICS

WINSEMI MICROELECTRONICS

And then the Rovp resistor value can be calculated by

the equation:

6

10

*

*

67

.

7

120

Tovp

Rovp





（

KΩ）

It is suggested that the open circuit protection voltage is

set at or above 1.5 times maximum load voltage.

Protection Function

The WS9441P offers rich protection functions to

improve the system reliability, including LED open/short

protection, CS resistor short protection, VCC under voltage

protection, thermal regulation. When the LED is open circuit,

the system will trigger the over voltage protection and stop

switching. When the LED short circuit is detected, the system

works at low frequency and the CS pin turnoff threshold is

reduced. So the system power consumption is very low. At

some abnormal fault condition, such as CS resistor shorted

or inductor saturation, the internal fast fault detection circuit

will be triggered, the system stops switching immediately.

After the system enters into faulty condition, the VCC

voltage will decrease until it reaches the UVLO threshold,

then the system will restart again. If the fault condition is

removed, the system will recover to normal operation.

Line Voltage Compensation

The WS9441P integrates line voltage compensation

function, which makes LED current remain unchanged in the

range of full voltage with good line regulation and current

accuracy.

PCB Layout

The following rules should be followed in WS9441P PCB

layout:

VCC Capacitor: The VCC capacitor should be as close

as possible to the VCC Pin and GND pin.

Ground Path: The power ground path for current sense

resistor should be short, and the power ground path should be

separated from small signal ground path before connecting to

the negative node of the bulk capacitor.

The Area of Power Loop: The area of main current loop

should be as small as possible to reduce EMI radiation. And it

should be away from diodes and other heating components.

ROVP PIN: The ROVP resistor should be as close as

possible to the ROVP Pin to increase its resistance to prevent

from the interference.

DRAIN PIN: The copper area of DRAIN pin can be

increased for better thermal dissipation. And it should be away

from CS/VCC and ROVP Pin.