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WINSEMI MICROELECTRONICS

WINSEMI MICROELECTRONICS

WINSEMI MICROELECTRONICS

WINSEMI MICROELECTRONICS

WINSEMI MICROELECTRONICS

And then the Rovp resistor value can be calculated by

the equation:

6

3.3*

*10

Rovp

Tovp



（

kohm）

Protection Function

The WS3441 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 (5kHz), and the CS pin turn off

threshold is reduced to 200mV. So the system power

consumption is very low. At some catastrophic fault

condition, such as CS resistor shorted or inductor saturated,

the internal fast fault detection circuit will be triggered, the

system stops switching immediately.

After the system enters into fault condition, the VCC

voltage will decrease until it reaches the UVLO threshold,

then the system will re-start again. If the fault condition is

removed, the system will recover to normal operation.

Thermal Regulation

The WS3441 integrates thermal regulation function.

When the system is over temperature, the output current is

gradually reduced; the output power and thermal dissipation

are also reduced. The system temperature is regulated and

the system reliability is improved. The thermal regulation

temperature is set to 150℃ internally.

PCB Layouts

The following rules should be followed in WS3441 PCB

layout:

Vcc Capacitor

The bypass capacitor on VCC pin should be as close as

possible to the VCC Pin and GND pin.

ROVP Pin

The ROVP resistor should be as close as possible to

the ROVP Pin.

Ground Path

The power ground path for current sense 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, such as the inductor, the

power MOSFET, the output diode and the bus capacitor

loop.

NC pin

The NC pin should be connected to GND (pin1).

Drain Pin

To increase the copper area of DRAIN pin for better

thermal dissipation. However too large copper area may

compromise EMI performance.

The material of PCB

Avoid choosing the material that is easy to absorb the

moisture, just like paper copper-clad laminates.