Switching frequency affects the power dissipation through switching losses, hence low frequency is desired for better efficiency and thermal performance (smaller package). The user wants higher frequencies to decrease the output voltage ripple, to improve the response to line and load transients, and to reduce size of the external inductor and capacitors. This slide shows a few typical cases and the representative part numbers in the STMicroelectronics portfolio. At 100 kHz the priority is efficiency, for example an SPV1040 solar battery charger with MPPT algorithm. 250-500 kHz is used in high voltage converters, because the switching losses are proportional to the frequency and to the Vin, so it is not necessary to push the switching frequency too high. The sweet spot for size efficiency and cost of external components is 600 kHz-1 Mhz, with devices such as the value line ST1S40 converter or L6738 controller. In the 1-3 MHz range the balance of priorities shifts toward board space, either because it is a portable application or because the board has to fit into a small space like a small form factor STB, a small hard disk drive, or other. Finally, the 3-6 MHz devices are for extreme space constraints such as mobile devices, portable fitness equipment, thin smart phones, and tablets.