High-Resolution Brightness LED Drivers for Enhanced LCD Backlight Control

The CAT3647 and CAT3648 give designers finer control of LED current and brightness with the ability to program in step increments as small as three percent, to produce a richer user experience. This is achieved via Catalyst’s 1-wire EZDim™ programming interface, which supports 32 linear steps from full-scale brightness down to zero current.

The new LED drivers are four-mode fractional charge pumps (1x, 1.33x, 1.5x, 2x), providing 10 percent higher efficiency and no added cost, compared to three-mode charge pumps. The CAT3647 drives three LEDs at 30mA each and the CAT3648 drives four LEDs at 25mA each, both with power efficiency as high as 92 percent. Both devices save significant board space and costs since they come in a low profile, 3mm x 3mm, 16-pad TQFN package and do not require additional capacitors, as do existing four-mode LED drivers.

“The portable LED market is very large, with diverse approaches to driving the LEDs,” stated Scott Brown, vice president of marketing for Catalyst Semiconductor. “Based on our strategy to be a ‘one-stop’ supplier of drivers to meet these varying requirements, we responded to market demand with these two higher-resolution versions of our existing three- and four-channel Quad-Mode LED drivers.”

The CAT3647 and CAT3648 join the following devices in Catalyst’s Quad-Mode family of LED drivers:
the CAT3604V four-channel LED driver with PWM dimming interface; the CAT3636 six-channel (1-wire EZDim interface with 32 dimming levels); the CAT3644 four-channel and CAT3643 three-channel devices (1-wire EZDim interface with six dimming levels); and the CAT3637 six-channel (1-wire EZDim interface with 16 dimming levels).

Pricing for the CAT3647 LED driver is $0.64 each, in 10.000 piece quantities. The CAT3648 is priced at $0.68 each in 10,000 piece quantities. Samples and evaluation kits are available now. Projected lead-time for production quantities is currently 6 to 8 weeks ARO.

Catalyst’s patented Quad-Mode adaptive fractional charge pumps take LED driver performance to a new level by offering a 10 percent efficiency improvement, without the need for an additional capacitor, and with no price premium. The Quad-Mode switching architecture delivers efficiency levels as high as 92 percent, with a lifetime average efficiency of 84 percent, yet saves significant board space and costs.

Catalyst’s innovative, patented Quad-Mode charge pump architecture delivers the high efficiency levels normally associated with inductor-based LED drivers, while eliminating the associated high-profile inductors and unwanted EMI. Most charge pump LED drivers today offer three modes of operation corresponding to the ratio of the output voltage to the input voltage: 1x, 1.5x and 2x. The Quad-Mode architecture adds a fourth mode of operation, 1.33x, without the need for the additional capacitor required by all existing four-mode charge pumps. The 1.33x fractional operating mode also reduces the input switching currents seen at the battery, minimizing the overall supply noise – a critical parameter in portable devices.