Data-back up Linear voltage regulator for Hard Disk Drive Application

The data back-up voltage regulator for hard disk drive application was realized by linear voltage regulators. Its output is 5v. It is enabled when either 5 or 12volt external supply is interrupted. The linear voltage regulator used for hard disk drive application have passed different design modifications. The problem with previous version of the data back-up linear voltage regulator was that; it was not designed to handle large input voltage variations, especially when the input voltage is below the nominal output voltage of the regulator. The regulator has very good frequency response above the nominal output voltage. but When the input is at or below the nominal output voltage, the regulator doesn’t have the desired properties. the regulator designed in this thesis showed efficient way to handle the problem of large voltage variation. The new topology followed different approach from conventional linear voltage regulators, where in the latter case the pass device is usually turned off when the input goes below the nominal output voltage. here the external pass element will stay well active when the input voltage is below the nominal output voltage. this improves the frequency response of the circuit when the input voltage goes down. Also the start time of the regulator was much improved in this topology. The details of the transistor level implementation of the circuit was explained in this thesis. Test results were presented comparing the old version with the new one to better clarify the advantage and disadvantage of the two topologies.