Other Parts Discussed in Thread: TPS92200
I have to design a circuit to drive three CREE XPEBRD-L1-0000-00901 LEDs independently. These red LEDs are rated to 1A with a Vf at about 2.4V. The power source will be a single cell 3.7V LiPo or Li-Ion battery. I can supply three independent PWM's from an MCU. Low cost is important, but so is efficiency. Else I would have used PWM, a MOSFET and a resistor, but too much power would be wasted in the resistor (1.3W each).
It appears the TPS61169 will suit as a possible solution - low cost and efficient, except I am unsure whether it will drive just one solitary LED from varying brightnesses. The value of RSET would be 0.2 ohms only; and the current through the LED will peak at 1A.
A possible good alternative is I just use a single 3A or 4A DC-DC converter, set to near 2.4V (say, 2.7V) and have a MOSFET turn on and off with PWM with a current limiting resistor (say 300 millohms). Therefore only about 300mW is wasted through each resistor. However, the issue here might be variance between the Vf's on the LEDs causing variances in brightness between products. Harmonics switching high currents with a square wave is not ideal, however I can use ferrites,capacitors and short tracks.
So two questions, if I may:
1. Will the TPS61169 drive only one red LED up to 1A?
2. If (1) is not good, is my DC-DC converter alternative a viable solution?
Any help much appreciated. By the way, I love TI's products.... great company and it often vendor of choice.