The TPS62150 can be used as a power supply for power LEDs. The FB pin can be easily set down to lower values than nominal by using the SS/TR pin. With that, the voltage drop on the sense resistor is low to avoid excessive power loss. Because this pin provides 2.5 µA, the feedback pin voltage can be adjusted by an external resistor per Equation 15. This drop, proportional to the LED current, is used to regulate the output voltage (anode voltage) to a proper level to drive the LED. Both analog and PWM dimming are supported with the TPS62150. Figure 9-38 shows an application circuit, tested with analog dimming:

Figure 9-38 Single Power-LED Supply

The resistor at SS/TR sets the FB voltage to a level of about 300 mV, with a value calculated from Equation 15.

Equation 15.

The device now supplies a constant current, set by the resistor at the FB pin, by regulating the output voltage accordingly. The forward voltage requirement of the LED determines the minimum input voltage rating. More information is available in the Using the TPS62150 as Step-Down LED Driver With Dimming Application Report.