Some content here goes back to the 2003-2002 timeframe, see updates at end (last update, April 2007).
Original Question by glire
What about the TPS63000 ?
Not a bad choice for lower currents, like 350mA, but efficiency suffers a bit due to the buck-boost mode (especially as the current level goes up, might be a great choice for a Lithium Ion rechargable battery though- higher voltage than primaries, thus lower input currents): http://www.ti.com/corp/docs/landing...ble+PA+tps63000
Though it might not be that bad for Li-Ion use. (if one would like to purchase a decent converter that uses this chip, dat2zip now carries his design at The Sandwich Shoppe)
The TPS63000 starts to tank a while before the 61030, especially at 1A output off of primaries. But the 63000 is a good fit for Li-Ion.
Every day I see more and more chips hitting the market, for things like this.
There is a short list of devices, which happens to be lines that Future Electronics carries (thus leaves out quite a number of other possibilities), which most folks know about, but not all...
LT3476 2.0A LED Driver Buck, Boost, Sepic, Up to 1000:1 Dimming Ratio
Each channel of the LT3476 can drive up to eight 1A LEDs in series, enabling the LT3476 to drive up to 32 1A LEDs while delivering efficiencies up to 96%. Each of the four channels is operated by an independent True Color PWM signal, enabling each channel to be dimmed independently to ratios as high as 1000:1. http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1094,P24013
TI has some app notes where they also discuss the technique.
Here are some Buck-Boost chips that could be adopted for flashlight converters.
On the first one, notice on page three, a no sense resistor technique which helps increase the efficiency considerably, by using the current mirror. This buys you another 3% efficiency (which transposes into another 3% runtime and less heat generated by the resistor), over a solution that would use a 0.1 ohm resistor in the same scenario at 1A to the LED. The first example is a tiny DFN-12 surface mount package with no pins sticking out, 4mm by 3mm, six pins on a side with a thermal pad underneath: