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High-voltage driver lights up 72 white LEDs

Posted: 25 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:LED driver? Bipolar-CMOS-DMOS? white LED?

A LED driver capable of driving up to 72 white LEDs has been developed by Power Analog Microelectronics. First in the high-voltage series of LED drivers, the PAM2846 is capable of driving up to 6-strings of LEDs and delivering up to 7W of output power. The circuit is based on the high voltage Bipolar-CMOS-DMOS (BCD) Technology developed at Taiwan Semiconductor Manufacturing Corporation, Hsinchu, Taiwan.

The PAM2846 integrates a 3A power MOSFET with a current mode step-up converter that drives six parallel strings of LEDs connected in multiple series of up to 72 (6 x 12) white LEDs. With built-in string-current-control circuits, the PAM2846 achieves 3 percent regulation accuracy between strings that ensures even brightness for all LEDs. The PAM2846 has a wide +4.5V to +26V input voltage range, and provides a fixed (20mA) or adjustable (5mA to 30mA) full scale LED current.

The PAM2846 includes multiple features to protect the regulator from fault conditions. Separate feedback loops limit the output voltage, if one or more LEDs fail open or short. The regulator features cycle-by-cycle current limit to provide consistent operation and soft start capability. Other features include programmable dimming control through direct PWM or analog dimming, wide (10,000:1) PWM dimming range with no color shift, and thermal shut down protection.

The PAM2846 is housed in a 16pin QFN (4mm x 4mm) package and aimed at slim LED displays with 7- to 15-inch panel sizes. Applications include notebooks, portable-DVD, LCD monitors, avionic and automotive displays.

- Ismini Scouras

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