FROM EDN EUROPE: Converter extends battery life
By Graham Prophet, Editor -- EDN, May 11, 2006
Texas Instruments designed its TPS63000 buck-boost converter to power all portable products that use a single-cell lithium-ion battery, or a two- or three-cell alkaline, nickel-cadmium or NiMH battery.
TI asserts that this converter will enable you to get 15 to 25% longer operating time from a single charge or a set of batteries compared to chips that use only a 3.3V buck design. The gain comes from the fact that the IC maintains conversion efficiency across the range of input voltages as the battery declines—other products, TI says, have an efficiency curve that declines sharply as the battery voltage falls: as the battery reaches the end of its charge cycle, the application draws disproportionately more current, hastening the end of operation.
TI claims that the 63000 achieves 94% efficiency or better from an input ranging from just over 2.5 to 5.0V. It will supply up to 1.2A output current at 3.3V output in step-down mode (3.6 to 5.5V input) and 800 mA in step-up mode (down to 2.4V input)—and the transition between modes is, TI says, glitch-free. Quiescent current is under 50 mA. Efficiency gains come, in part, because TI has devised a circuit topology in which fewer transistors are switching in a given mode of operation than in other layouts, cutting switching losses. The chip operates at a fixed 1.5 MHz frequency, comes in a 333-mm 10-pin package and costs $2.75 (1000).
