Hello,
I have a customer using the UCC284-EP and he would like to know that what to do with the SD/CT pin if he does not want the output to pulse at a 2.5% duty cycle. In this mode is the CT capacitor still required and the fixed voltage being applied to the SD/CT pin or can the SD/CT pin be left open (since the nominal voltage of this pin per the datasheet is -1.5V) and the CT capacitor not installed?
Forcing the SD/CT pin to any fixed voltage between –0.7 V and –1.6 V with respect to GND enables the output. However, in an overcurrent condition, the output does not pulse at a 2.5% duty cycle, but the output current is still limited to the peak current limit. This circuit may be used where a fixed current limit is needed, where a 2.5% duty cycle is undesirable. The UCC284 supplies a maximum current in this configuration as long as the temperature of the device does not exceed the overtemperature shutdown. This is determined by the peak current being supplied, the input and output voltages, and the type of heat sink being used. Thermal design is discussed later on in this data sheet.
Thanks,
Ali Kozak
Avnet FAE