The circuit diagram shown here is of a 10V switching regulator based on the LM5007 from National Semiconductors. The LM5007 is an integrated step down switching regulator which has all necessary systems required for making a cost effective and reliable switching regulator circuit. The IC is available in MSOP-8, LLp-8 packages and has a lot of built in features like thermal shut down, under voltage lock out, duty cycle limiting, current limiting etc.
The output voltage of this regulator can be adjusted using the resistor R3 and R4. For the given values of R3 and R4 in the circuit diagram, the output voltage will be 10V. The equation governing the output voltage is Vout = 2.5 x (R3+R4)/R4. Resistor R1 sets the switch on time and C4 is the boost boot strap capacitor. Resistor R2 determines the variation of OFF time and C3 is a decoupling capacitor.
- The supply voltage can be anything between 12 to 72V DC.
- Output voltage can be adjusted using R3 and R4.
- C1 and C5 are polyester capacitors.
- C1 and C2 must be rated at least 100V.
- R5 and C5 forms a filter network.
- The output current limit of LM5007 is 700mA.