Step-Up Switching Regulator

Maxim Integrated Products have re- cently introduced a series of integrated step-up switching regulators designed 3V LAB =1.31(R i/R2+1) [V] Rz is typically 100 k52. In the application circuit shown here, LED Di at the LBO output lights when the input voltage drops below 2.62 V. It is possible to make the output voltage adjustable by connecting input VFB to a potential divider R3-R4 instead of ground. This option is shown inset in the circuit diagram. The output voltage, Uo, then becomes Uo = 1.31(R3/R4+1) [V] R4 is, again, typically 100 k4. Cx is 100 pF. Remember to observe the voltage rating of C3. Maximum output current of the circuit is 1 A. The input voltage should remain below 5 V. Maximum conversion ef- ficiency is about 80%. As to components: the minimum value for Li, Lmin, is expressed by Lmin = Uiri/(2foimax) Imax depends on the current rating of the inductor and external power transis- tor. Factor fo is the converter oscillation frequency, 45 kHz. The available output p...