33_V_FROM_5_V_LOGIC_SUPPLIES

Published:2009/6/23 4:36:00 Author:Jessie | From:SeekIC

Microprocessor chip sets and logic families that operate from 3.3-V supplies are gaining acceptance in both desktop and portable computers. Computing rates, and in most cases, the energy consumed by these circuits, show a strong improvement over 5-V technology. The main power supply in most systems is still5 V, necessitating a local 5-V to 3.3-V regulator. Linear regulators are viable solutions at lower (IO≤1 A) currents, but they must have a low dropout voltage in order to maintain regulation with a worst-case input of only 4.5 V. The ftgure shows a circuit that converts a 4.5-V minimum input to 3.3Vwith an output tolerance of only 3% (100 mV). The LT1129-3.3 can handle up to 700 mA in surface-mount conftgurations, including both 16-μA shutdown and 50-μA standby currents for system sleep modes. Unlike other Iinear regulators, the LT1129-3.3 combines both low-dropout and Iow-voltage operation. Small input and output capacitors facilitate compact, surface-mount designs.



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