UC3845D datasheet by Texas Instruments

UC3845D Frequently Asked Questions (FAQs)

• What is the maximum voltage rating of the UC3845D?
  The maximum voltage rating of the UC3845D is 30V, but it's recommended to operate it at a maximum voltage of 25V to ensure reliable operation.
• How do I choose the right resistor values for the oscillator circuit?
  The oscillator circuit resistor values (Rt and Ct) depend on the desired switching frequency. A good starting point is to use the values recommended in the datasheet, and then adjust them based on the specific application requirements.
• What is the purpose of the soft-start pin (SS) and how do I use it?
  The soft-start pin (SS) is used to gradually increase the output voltage during startup, reducing inrush currents and electromagnetic interference (EMI). Connect a capacitor from the SS pin to ground, and the IC will slowly ramp up the output voltage during startup.
• How do I ensure the UC3845D operates within the recommended operating temperature range?
  Ensure good thermal design and heat dissipation by providing adequate heat sinking, using a thermally conductive material, and keeping the IC away from heat sources. Monitor the junction temperature (TJ) and ensure it stays within the recommended range of -40°C to 125°C.
• What are the key considerations for layout and PCB design when using the UC3845D?
  Keep the power stage components (e.g., FETs, diodes, and inductors) close together to minimize parasitic inductance and capacitance. Use a solid ground plane, and ensure the feedback traces are short and shielded to minimize noise coupling.