Datasheet
UCC28710, UCC28711
UCC28712, UCC28713
UCC28714, UCC28715
SLUSB86 –NOVEMBER 2012
www.ti.com
Fault Protection
There is comprehensive fault protection. Protection functions include:
• Output over-voltage fault
• Input under-voltage fault
• Internal over-temperature fault
• Primary over-current fault
• CS pin fault
• VS pin fault
A UVLO reset and restart sequence applies for all fault protection events.
The output over-voltage function is determined by the voltage feedback on the VS pin. If the voltage sample on
VS exceeds 115% of the nominal V
OUT
, the device stops switching and the internal current consumption is I
FAULT
which discharges the VDD capacitor to the UVLO turn-off threshold. After that, the device returns to the start
state and a start-up sequence ensues.
The UCC28710 family always operates with cycle-by-cycle primary peak current control. The normal operating
range of the CS pin is 0.78 V to 0.195 V. There is additional protection if the CS pin reaches 1.5 V. This results
in a UVLO reset and restart sequence.
The line input run and stop thresholds are determined by current information at the VS pin during the MOSFET
on-time. While the VS pin is clamped close to GND during the MOSFET on-time, the current through R
S1
is
monitored to determine a sample of the bulk capacitor voltage. A wide separation of run and stop thresholds
allows clean start-up and shut-down of the power supply with the line voltage. The run current threshold is 225
µA and the stop current threshold is 80 µA.
The internal over-temperature protection threshold is 165°C. If the junction temperature reaches this threshold
the device initiates a UVLO reset cycle. If the temperature is still high at the end of the UVLO cycle, the
protection cycle repeats.
Protection is included in the event of component failures on the VS pin. If complete loss of feedback information
on the VS pin occurs, the controller stops switching and restarts.
18 Submit Documentation Feedback Copyright © 2012, Texas Instruments Incorporated
Product Folder Links: UCC28710, UCC28711 UCC28712, UCC28713 UCC28714, UCC28715