SLUSFI2 December 2024 UCC33020-Q1
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
The UCC33020-Q1 uses hysteretic control to regulate the output voltage between upper and lower bands as shown in Figure 7-4. The regulation block on the secondary side senses the regulated output voltage and sends a feedback signal to the primary side through the inductive communication channel to turn the primary power stage On or Off to maintain the regulated output whithin the hysteresis bands. During steady-state regulation, the burst frequency will change according to the output capacitors and loading conditions. The burst frequency will be highest at higher loading conditions and lowest at light loading conditions by which light load efficiency improvments can be achieved.
The Burst-On duration (tON) will increase with heavy loading conditions or higher output capacitor. The UCC33020-Q1 will enter an overpower protection mode if the Burst-on duration exceeds tON-MAX typical value of 13μs as shown in Figure 7-5. In this condition, as the VCC hasn't reached the upper hysteresis threshold, the device will turn-on the power stage again after minimum Burst-off duration of tOFF-MIN typical value of 1.5μs. This will repeat as the heavy load condition remains resulting in higher peak-to-peak VCC steady state ripple or lower VCC regulation voltage. The UCC3302x_CALC can help the system designer appropriately select the output capacitor for the targeted maximum load and input voltage range conditions to avoid triggering this condition.
The UCC33020-Q1 can program the VCC_REG voltage accoring to the SEL pin connection. The SEL pin voltage is monitored during soft-start sequence when VCC < VVCC_UVLO threshold. The output voltage is then programmed to 5.0V with SEL = VCC or to 5.5V with SEL = GNDS. Note that after this initial monitoring, the SEL pin no longer affects the VCC output level. In order to change the output mode selection, either the EN/FLT pin must be toggled or the VINP power supply must be cycled off and back on.