Switching Regulator IC Drives up to Eight LEDs

Jan 28, 2009 10:35 AM

Texas Instrument's TPS61500 is a monolithic switching regulator with integrated 3-A, 40-V power switch. It is an ideal driver for high brightness 1-W or 3-W LED. The device has a wide input voltage range to support application with input voltage from multi-cell batteries or regulated 5-V, 12-V power rails. An external resistor sets the switching frequency between 200-kHz and 2.2-MHz.

The IC operates from a 2.9-V to 18-V input range. Its internal power switch can drive four 3-W LEDs from a 5-V input and eight LEDs from a 12-V input. Power conversion efficiency is up to 93%.

The LED current is set with an external sensor resistor R3, and the feedback voltage that is regulated to 200-mV by current mode PWM (pulse width modulation) control loop. The device supports analog and pure PWM dimming methods for LED brightness control.

Connecting a capacitor to the DIMC pin configures the device to be used for analog dimming, and the LED current varies proportional to the duty cycle of an external PWM signal. Floating the DIMC pin configures the IC for pure PWM dimming with the average LED current being the PWM signal's duty cycle times a set LED current.

The device features a programmable soft-start function to limit inrush current during start-up, and has built-in other protection features, such as pulse-by-pulse over current limit, programmable over voltage protection and thermal shutdown.

The TPS61500 is available in 14-pin HTSSOP package with PowerPad.

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