Catalyst Semiconductor, Inc. a supplier of analog, mixed-signal and non-volatile memory semiconductors, announced its innovative buck converter in a TSOT-23 package optimized for driving high-brightness, 350mA LEDs at up 94 percent efficiency. The first device in a new family of buck converters, the CAT4201 incorporates Catalyst’s patent-pending switching control algorithm. This new architecture reduces system complexity, improves efficiency and allows an external RSET control resistor to preset a regulated LED current up to 350mA from supplies as high as 24 volts, to provide better inductor control and eliminate the need for a dedicated heat sink.

 

The CAT4201 buck converter offers a simpler and significantly smaller alternative to linear regulators for driving high-brightness LEDs in step-down applications, eliminating the need for heatsinks. Additionally, built-in load dump protection allows transients of 40 volts to be safely handled, fully optimizing the CAT4201 for automotive indicator and illumination lighting applications, including turn signal, brake and map reading lights.

 

Traditionally, LEDs from 12V or 24V buses have been driven by linear regulators, which generate a significant amount of heat, resulting in the need for a dedicated heat sink and, therefore, a very large TO263 package. The patent-pending switching architecture of the CAT4201 lets designers easily control the average current with a single external resistor. This results in extremely low internal power dissipation allowing the CAT4201 to be housed in a tiny, 5-lead TSOT-23 package without the need for a dedicated heat sink. Additionally, the device is compatible with switching frequencies up to 1MHz, making it ideal for applications requiring small-footprint, low-cost external inductors.

 

EZM Lighting, a leading manufacturer of safety lighting for traffic environments has designed the CAT4201 into its latest tunnel lighting products. According to Fabiano Paoletto, R&D Manager for EZM Lighting, “Until now, linear regulators provided an adequate solution for our existing, medium-power lighting products. However, as we expanded our product line to include the latest high-power LEDs, driver efficiency and package thermal dissipation issues became critical. The CAT4201 provides a simple yet effective solution, allowing our products to double their lighting power capability without the need for dedicated heatsinking.”

 

 

 

With the whole automotive market poised for LED lighting at the front end of vehicles, intsead of just tail lights -- as with present generation vehicles -- using high-current LEDs, the need to power them effectively has become a big deal. There are plenty of buck LED drivers around but their applications have focused on provided accurate color dimming systems and the like. They are, generally, in 16 and 20 pin TSSOP and QFN.

 

Using linear regulators, going forward in time, is just not a good engineering solution.

 

The CAT4201 is a switching buck converter with good efficiencies, depending on how close the input voltage is to the output voltage, what the load is, switching frequency, and temperature. Numbers for the CAT4201 are typically in the 85% to 90% range.

 

The incoming, probably always battery, voltage can be in the range of 6.5 V to 28 V (with transients to 40 V, making it compatible for both 12 V and 24 V systems) with a switch voltage from zero to 28 V, driving LED strings with up to 20 V total forward voltages and bias currents up to 350 mA. The switching frequency can be between 50 kHz and 1 MHz. Like all switching devices an external switching inductor and Schottky diode are required. A single external resistor sets the LED current and ensures that the device ia always operating at the crossover point between continuous conduction and discontinuous conduction modes; this gives an average LED current that is half of the peak switching current.

 

The CAT4201 can drive a single 1 W LED from 6 V, or up to seven LEDs in a string from 24 V. Dimming can be provided on a control pin. LED short-circuit and open-circuit protection are provided together with thermal protection.

 

The CAT4201 is in a great package, with no need for a heatsink. The product is extremely well timed and the pricing will be scary for potential competition. It will do extremely well in the market. All-in-all, a great move by Catalyst.

 

The CAT4201 is in production in TSOT-23-5 with pricing at $0.72 in 10-k piece lots.

 

Data Sheet