SLUU182A January 2004 – March 2022 TPS5124
Many factors influence frequency selection. Higher switching frequency leads to smaller output inductor and capacitors, reducing the size of the converter. However, higher switching frequencies increase switching losses, and lower the efficiency of the converter. A frequency of 300 kHz is chosen for this design for reasonable efficiency and size.
Capacitor C16, which is connected from CT (pin 5) to ground, programs the oscillator frequency. A C16 value of 47 pF yields a switching frequency of 300 kHz at 25°C.