Due to the discontinuous input current of a step-down buck converter, a low-pass filter is typically necessary at the IVINP and IVINN pins as shown in Figure 1 and Figure 4. A much smaller filter at the SENSE+ and SENSE– pins may also be useful in filtering high frequency noise, but it is not necessary. Even with these filters, the monitors are fast enough to track reasonably short PWM pulses as shown in Figure 8. Nevertheless, if a designer is more concerned with average current levels than instantaneous current levels, then additional lowpass filters can be easily added to the ISMON and IVINMON pins.
The LT3763 is a versatile step-down buck converter that integrates many complex features essential for not only LED drivers, but solar harvesters and battery chargers as well. A PWM driver and current monitors are included with fault detection, current limiting, input and output voltage regulation. Due to its high voltage rating, all of these features can be utilized to illuminate long strings of LEDs or charge stacks of batteries. Available in a 28-lead TSSOP package, the LT3763 is a compact, complete, and efficient power system.
About the author:
Luke Milner is Design Engineer at Linear Technology Corporation