Electronmicroscopy Comes To Life

EE 24 October 1987 current so the diodes must be dimensioned accordingly. All of these problems are eliminated by using the L4960 as a post regulator as shown in Fig. 7. Note that for all of the auxiliary outputs only one sec- ondary is needed, simplifying the transformer. Cross regu- lation is no longer a problem and the power dissipated in the stage depends mainly on load current and is almost unaf- fected by dropout. Moreover, the diode on the secondary can be smaller since the input cur- rent of a stepdown switching regulator is always less than the output current. Finally, short circuit protection is provided for all of the auxili- ary outputs by the chip"s internal current limiter and thermal protection circuit. How it works The SGS L4960 is a monolithic stepdown switching regulator providing output voltages from 5.1y to 40V and delivering up to 2.5A output current. At the heart of the device is a regulation loop consisting of a sawtooth oscillator, error amplifier, comparat...