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Positive output step-up and step-down dc-dc converters have a common limitation in that neither can handle input voltages that are both greater than or less than the output. For example, when converting a 12-V sealed lead/acid battery to a regulated +12 V output, the battery voltage might vary from a high of 15 V down to 10 V. By using a MAX641 to drive separate P-and N-cbannel MOSFETs, both ends of the inductor are switched to allow non inverting buck/boost operation. A second advantage of the circuit over most boostonly designs is that the output goes to 0 V when shutdown is activated. Inefficiency is a drawback because two MOSFETs and two diodes increase the losses in the charge and discharge path of the inductor. The circuit delivers +12 V at 100 mA at 70 percent efficiency with an 8-V input. Step up Down DC - DC Converter Circuit Diagram

L4962 is a monolithic step-down  switching regulator. It provides  output voltage of 5.1V to maxi-mum 40V, delivering current up to  1.2A to 1.5A, depending on the type  and package. The theoretical internal  functions are almost the same. The  heart  of  the  device  is  the  regulation  loop  consisting  of  a  saw  tooth  oscillator, error amplifier, comparator and  source-sink output stage. Circuit diagram : Fig. 1: Circuit of switching regulator An error signal is produced by  comparing  the  output  voltage  with  a precise 5.1 volt on chip reference  (which is zener zap trimmed to ±2  per cent). This error signal is then  compared  with  the  saw  tooth  signal  to generate the fixed frequency pulse  width  modulated  pulses  which  drive the output stage. Fig. 1 shows circuit diagram of  the regulator. The gain and frequency  of the loop can be set by RC network  connected to IC pin 11. When the loop  is  closed  directly  by  connecting  the  supply output to the feedback...