SLLSFM0A March 2022 – June 2022 SN6507
SN6507 has an internal oscillator to set the switching frequency of the power stage. As the two power switches are out of phase, the oscillator frequency is twice of the actual switching frequency of each power switch. The duty cycle is fixed with 70 ns deadtime to avoid shoot-through. The duty cycle is changeable if duty cycle feature is enabled. Please refer to Section 8.3.3.
SN6507 has a wide switching frequency range from 100 kHz up to 2 MHz, which is pin-programmable through a resistor (RCLK) to GND. Below table lists the value of RCLK to achieve certain operating frequencies (fSW). The choice of switching frequency is a trade-off between power efficiency and size of capacitive and inductive components. For example, when operating at higher switching frequency, the size of the transformer and inductor is reduced, resulting in a smaller design footprint and lower cost. However, higher frequency increases switching losses and consequently degrades the overall power supply efficiency.
|0 kΩ (Short to GND)||Default (1 MHz)|
Figure 8-6 can also be used to estimate the programmable switching frequency, fSW, using an external resistor value, RCLK, where RCLK is in kΩ and fSW is in kHz:
If CLK pin is shorted to GND, the part switches at its default frequency, FSW. CLK pin floating is not a valid state of operation and will cause the part to stop switching until an external clock signal is present.