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10ch 120 WLED driver IC highlights efficiency

Posted: 06 Aug 2010 ?? ?Print Version ?Bookmark and Share

Keywords:boost driver IC? white LED driver? LCD displays?


The SC442 from Semtech is 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 make it the 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 percent. 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 minimized across the operating range; yielding greater than 90 percent 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 tradeoffs across the input/output voltage range. Alternatively, the SYNC pin allows the designer to synchronize 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 percent current matching; integrated 3A switch; low current sink voltage; up to 91 percent enery 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 channnel, over-temperature protection; MLPQ-28 lead-free package (WEEE and RoHS compliant).

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