AN458 Datasheet, PDF (1/19 Pages) STMicroelectronics – DISCONTINUOUS MODE POWER SWITCHING REGULATOR

AN458
APPLICATION NOTE
DESIGNING WITH THE L4963 MONOLITHIC
DISCONTINUOUS MODE POWER SWITCHING REGULATOR
by M. Roncoroni
The L4963 is a new switching regulator designed to operate in discontinuous mode, reducing the num-
ber of the external components, giving a very cost effective solution. This application note explains how
the device operates and how it can be used. Typical application circuits are also described.
The L4963 is a new monolithic stepdown switching regulator IC operating in discontinuous mode. This device,
able to deliver 1.5A to the load at a voltage of 5.1V and up to 36V with derated current, is designed to satisfy
very low cost applications due to the fact that the number of the external components are dramatically reduced.
Moreover the inductor value is reduced by a factor of three or four in comparison with a corresponding contin-
uous mode solution. Also the plastic package (Powerdip 12+3+3), that needs no heatsink, contributes to de-
creasing the cost of the overall application. Although the L4963 is intended for very low cost applications, it
integrates features like remote inhibit, reset and power-fail outputs for microprocessor. In the following we will
explain in detail its principle of operation and the criteria that regulate the choice of the external components.
CIRCUIT OPERATION
The L4963 operates in discontinuous mode. In principle in this kind of operation the energy stored in the inductor
is fully discharged to the load before to start a new cycle. To operate in this way, the device contains, in its reg-
ulation loop, additional blocks compared to the usual Error/Amplifier, Oscillator and Pulse Width Modulator used
in the continuous mode devices.
Figure 1. L4963 Block Diagram
December 2003
1/19