UC3846
LINEAR INTEGRATED CIRCUIT
OPERATION DESCRIPTION(Cont.)
Protection Controls
The IC takes on more protection functions such as OVP and OTP etc. In case of those failure modes for continual
blanking time, the driver is shut down. Driver is reset after failure is eliminated.
OVP
The OVP will shut down the switching of the power MOSFET whenever VDD>VOVP. The OVP case as followed
FIG.3. The test circuit as followed FIG.4.
FIG.4OVP test circuit
FIG.3 OVP case
OTP
OTP will shut down driver when junction temperature TJ>T (THR) for continual a blanking time.
PCB Layout Note
Noise from the current sense or the control signal can cause significant pulse width jitter in continuous-conduction
mode. While slope compensation helps alleviate these problems. Good placement and layout practices should be
followed. Avoiding long PCB traces and component leads, locating compensation and filter components near the
UTC UC3846, and increasing the power MOS gate resistance is advised.
UNISONIC TECHNOLOGIES CO., LTD
7 of 10
QW-R103-053.B
www.unisonic.com.tw
UTC [ Unisonic Technologies ]
