The maximum operating frequency of UC3843AD is 500 kHz. However, it's recommended to operate it at a frequency between 100 kHz to 400 kHz for optimal performance.
The minimum input voltage is typically 8.5V, and the maximum input voltage is 35V. However, it's recommended to operate it within 12V to 25V for optimal performance. You can use the formula: Vin(min) = 8.5V + (Vout / Rfb) and Vin(max) = 35V - (Vout / Rfb) to calculate the minimum and maximum input voltage, where Rfb is the feedback resistor value.
The soft-start pin (SS) is used to slowly ramp up the output voltage during startup, preventing inrush currents and reducing electromagnetic interference (EMI). It's recommended to connect a capacitor (typically 10nF to 100nF) between the SS pin and ground to set the soft-start time.
The feedback resistors (Rfb) and (Rin) are used to set the output voltage. A good starting point is to use Rfb = 2.2kΩ and Rin = 1kΩ. You can adjust these values based on your specific application requirements. A higher Rfb value will result in a higher output voltage, while a higher Rin value will result in a lower output voltage.
The undervoltage lockout (UVLO) is a feature that prevents the IC from operating when the input voltage is below a certain threshold (typically 8.5V). This ensures that the IC operates within its specified voltage range and prevents damage or malfunction.
UC3843AD datasheet
by Texas Instruments
Findchips
Findchips