High-Efficiency Triple-Output for Notebook Computers
Created: Sep 04, 2014
No description available.
The circuit is configured to provide output voltages of 3.3-V, 5-V, and 12-V. The current capability of both the 3.3-V and 5-V outputs is 2 A (2.5 A peak). The logic controlled 12-V output can provide 150 mA (200 mA peak), which is ideal for flash memory applications. The operating efficiency shown in the figure exceeds 90% for both the 3.3-V and 5-V sections.
The 3.3-V section for the circuit in the figure is comprised of the main switch Q4, synchronous switch Q5, inductor L1, and current shunt Rsense. Current-sense resistor Rsense monitors the inductor current and is used to set the output current according to the formula OUT = 100mV/Rsense. Advantages of current controlled include excellent line and load transient rejection, inherent short-circuit protection, and controlled start-up currents. Peak inductor currents for L1 and T1 for the circuit in the figure are limited to 150mV/Rsense or 3.0 A and 3.75 A, respectively.