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Optoelectronics/Displays  

10ch step-up driver IC powers up to 120 LEDs

Posted: 13 Aug 2010     Print Version  Bookmark and Share

Keywords:boost driver IC  white LED driver  LCD displays 

SC442

Semtech reveals the SC442, a 10ch, high efficiency integrated step-up (boost) driver IC capable of powering up to 120 WLEDs. The device accepts a wide input voltage of 4.5V to 21V with no internal regulator or bypass capacitor required. The wide input range, up to 42V output voltage and flexible implementation offer an ideal LED backlight driver solution for medium to large LCD displays. The current sink channels are programmed with an external resistor up to 30mA each.

The device features a channel-channel current matching of �1 per cent. It also disables open or shorted LEDs by disabling only the affected LED channel, thereby increasing LCD panel life. The channel-channel LED mismatch voltage is accommodated by adjusting the SCPSET resistor. Losses in the switching device and current sinks are minimised across the operating range; yielding greater than 90 per cent efficiency and optimum battery life for portable systems.

The driver IC also accepts PWM dimming up to 50kHz. Maximum dimming range is greater than 500:1 with remarkable linearity for optimum PWM dimming characteristics. The high frequency dimming capability (>20kHz) eliminates audio emissions and allows small ceramic output capacitors.

Switching frequency is programmable from 200kHz to 1MHz; allowing efficiency versus L/C sizing trade-offs across the input/output voltage range. Alternatively, the SYNC pin allows the designer to synchronise the switching frequency to an external system clock and, if needed, a parallel SC442 device - eliminating potential system intermodulation and interference problems.

The device has an over-temperature shutdown protecting the IC from over-heating under abnormal conditions. It is available in a small 4mm x 4mm MLPQ-28 pin package with 0.6mm maximum height and is fully WEEE and RoHS compliant

In summary, features of the LED driver include: wide input voltage range from 4.5V to 21V; 42V maximum operating output voltage; programmable LED current up to 30mA per string �1 per cent current matching; integrated 3A switch; low current sink voltage; up to 91 per cent energy efficiency; flexible LED configurations; PWM dimming capability; switching frequency: 500kHz � 1MHz; parallel device operation with sync pin; protection features such as adjustable OVP, LED short channel with disable/open channel, over-temperature protection; MLPQ-28 lead-free package (WEEE and RoHS compliant).





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