The recommended operating voltage range for UC3843AD1 is 12V to 28V, with a maximum rating of 30V. However, it's essential to ensure that the voltage supply is well-regulated and filtered to prevent noise and oscillations.
The values of Rt and Ct depend on the desired switching frequency. A good starting point is to use the values recommended in the datasheet (Rt = 10kΩ, Ct = 3.3nF) for a 52kHz switching frequency. You can then adjust these values to achieve the desired frequency using the formula: Fs = 1 / (2.86 * Rt * Ct).
The soft-start pin (SS) is used to gradually increase the output voltage during startup, reducing inrush currents and preventing voltage overshoots. 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. This creates a ramp-up time of around 1ms to 10ms.
To ensure stability, follow these guidelines: 1) Use a well-regulated input voltage, 2) Add a low-pass filter (e.g., RC filter) at the output, 3) Use a stable voltage reference (e.g., TL431), 4) Minimize parasitic inductance and capacitance in the layout, 5) Avoid using long wires or traces, and 6) Add a snubber network (e.g., R-C-R) across the switch node.
The UC3843AD1 is a controller IC and does not have an output current capability. It's designed to drive an external power switch (e.g., MOSFET or IGBT) that can handle the desired output current. The maximum output current depends on the power switch and the converter design.
UC3843AD1 datasheet
by STMicroelectronics
