UC3844AN datasheet by STMicroelectronics

UC3844AN Frequently Asked Questions (FAQs)

• What is the maximum voltage rating for the UC3844AN?
  The maximum voltage rating for the UC3844AN is 30V, but it's recommended to operate it within 15V to ensure reliable operation and to prevent damage from voltage spikes.
• How do I choose the right value for the timing capacitor (CT) and resistor (RT)?
  The values of CT and RT determine the oscillator frequency. A good starting point is to use the values recommended in the datasheet (CT = 3.3nF, RT = 10kΩ). Then, adjust them based on your specific application requirements and the desired switching 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 current and stress on the power supply. Connect a capacitor (typically 10nF to 100nF) from SS to GND, and a resistor (typically 1kΩ to 10kΩ) from SS to VCC. This will create a soft-start ramp time of around 1-10ms.
• How do I ensure stable operation and prevent oscillations in the UC3844AN?
  To ensure stable operation, make sure to decouple the power supply with a capacitor (typically 10uF to 100uF) close to the IC, and use a low-ESR capacitor for the output filter. Also, keep the layout clean and avoid long traces, especially for the feedback loop.
• What is the maximum output current that the UC3844AN can handle?
  The UC3844AN is a controller IC and does not have an output stage, so it does not have a maximum output current rating. The output current is determined by the external power MOSFET or switch, which should be chosen based on the specific application requirements.