High-efficiency white LED driver solution--Semtech SC442

Semtech's SC442 is a 10-channel high-efficiency 120 white LED driver with an input voltage of 4.5V-21V. The high-efficiency boost converter allows output voltages up to 42V, making it ideal for medium to large LCD displays. Programmable current layer, up to 30mA per channel, current between channels is +/-1%, integrated with 3A switch, efficiency up to 91%, flexible LED configuration, up to 50kHz dimming frequency, greater than 500:1 dimming Range, switching frequency 500kHz - 1MHz, mainly used in automotive LCD backlights, desktop monitors, notebook computers and portable TV. The main features of the SC442 and typical application circuits are described below.

SC442: It is a 10-channel, integrated, high efficiency white LED driver .

The SC442 is a 10-channel, high-efficiency, integrated step-up (boost) driver IC with a power supply capability of up to 120 WLEDs. The device has an internal voltage regulator or a wide input voltage of 4.5 V to 21 V without the necessary bypass capacitors. The wide input range, output voltage up to 42 V and flexible implementation make it an ideal LED backlight drive solution for medium to large LCDs. The current between the channel and the external resistor programmed to 30mA is matched to +/- 1%. The device increases the lifetime of the LCD panel by disabling the enabled LEDs that are only open or shorted on the LED channels. The LED voltage of the channel mismatch channel is placed by the resistor adjustment SCPSET. Current parallel operation of the sink channel may increase the LED current. Unused channels are disabled by the voltage connected to the input pins.

The SC442 minimizes losses in switching devices and current sources achieve greater than 90% efficiency over the entire operating range. It also increases the life of portable systems such as batteries.

The device accepts PWM dimming up to 50kHz. The maximum darkening range is greater than 350 bar operation, and the PWM dimming characteristics are good linearity 500:1. High-frequency dimming capability (> 20kHz) eliminates audio emissions and allows the output of small ceramic capacitors. The programmable switching frequency ranges from 200kHz to 1MHz, allowing efficiency to be traded off the output voltage range. In addition, the SYNC pin allows the designer to synchronize the switching frequency with the external system clock and, if required, the SC442 unit, which eliminates potential system and intermodulation interference issues.

Moreover, the SC442 also has an over-temperature shutdown protection circuit that activates the protection circuit to cut off the power supply under abnormal conditions of overheating. The device package is available in the MLPQ-28 package, which is available in a small 4mm x 4mm maximum height of 0.6mm. The SC442 is fully compliant with the WEEE and RoHS directives.

Main features of SC442:

Wide input voltage range from 4.5 V to 21 V; maximum operating output voltage up to 42 V.

The current layer is programmable, each LED current is up to 30mA, and the current between the channels is matched at +/-1%

Integrated 3A switch

Up to 91% efficiency

Flexible LED configuration

Disable single mismatched LED channels

Parallel channel LED current

PWM dimming function

Dimming frequency up to 50kHz

Dimming range > 500:1

Switching frequency: 500kHz - at 1MHz

Synchronous pin parallel device operation

Protection function: Adjustable overvoltage protection, cycle-by-cycle current limit, LED disable/open channnel short channel, over temperature protection.

MLPQ-28 lead-free package (WEEE and RoHS standards), 4 Ã— 4 mm Ã— 0.6 mm

SC442 main application areas:

Car LCD backlight

Desktop monitor

laptop

Portable TV

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