WS3442 ProductDescription
And then the Rovp resistor value can be calculated by
the equation:
PCB Layouts
The following rules should be followed in WS3442 PCB
layout:
Vcc Capacitor
Rovp 3.3*Tovp*106
（kohm）
The bypass capacitor on VCC pin should be as close as
possible to the VCC Pin and GND pin.
ROVP Pin
Protection Function
The WS3442 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.
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.
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.
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.
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.
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.
Thermal Regulation
The WS3442 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.
The material of PCB
Avoid choosing the material that is easy to absorb the
moisture, just like paper copper-clad laminates.
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
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