ZHCSK44G December 2009 – November 2022 UCC28C40-Q1 , UCC28C41-Q1 , UCC28C42-Q1 , UCC28C43-Q1 , UCC28C44-Q1 , UCC28C45-Q1
PRODUCTION DATA
Synchronization is best achieved by forcing the timing capacitor voltage above the oscillator's internal upper threshold. A small resistor is placed in series with CCT to GND. This resistor serves as the input for the sync pulse which raises the CCT voltage above the oscillator’s internal upper threshold. The PWM is allowed to run at the frequency set by RRT and CCT until the sync pulse appears. This scheme offers several advantages including having the local ramp available for slope compensation. The UCC28C4x-Q1 oscillator must be set to a lower frequency than the sync pulse stream, typically 20 percent with a 0.5-V pulse applied across the resistor.