UC3845BD1 datasheet by STMicroelectronics

UC3845BD1 Frequently Asked Questions (FAQs)

• What is the recommended operating voltage range for UC3845BD1?
  The recommended operating voltage range for UC3845BD1 is 12V to 28V, with a maximum rating of 30V.
• How do I choose the right resistor values for the oscillator circuit?
  The oscillator circuit requires two resistors, R1 and R2. Choose R1 to be around 1kΩ to 10kΩ, and R2 to be around 10kΩ to 100kΩ. The ratio of R1 to R2 determines the oscillator frequency.
• 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. Connect a capacitor (typically 10nF to 100nF) from the SS pin to ground, and a resistor (typically 1kΩ to 10kΩ) from the SS pin to the output voltage.
• How do I set the maximum duty cycle of the UC3845BD1?
  The maximum duty cycle is set by the ratio of the resistors R3 and R4 in the feedback circuit. A higher ratio of R3 to R4 increases the maximum duty cycle.
• What is the purpose of the undervoltage lockout (UVLO) and how does it work?
  The undervoltage lockout (UVLO) is a feature that prevents the IC from operating below a certain voltage threshold (typically around 8.5V). This is to prevent the IC from malfunctioning or drawing excessive current during startup or brownout conditions.