UC3863AL-SH2-R datasheet(7/10 Pages) UTC

7 / 10 page

UC3863A

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

7 of 10

www.unisonic.com.tw

QW-R103-148.B



OPERATION DESCRIPTION (Cont.)

Protection Controls

The IC takes on more protection functions such as OVP, OLP 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 event as followed

Fig.3.

VFB

Driver

ON / OFF

VFB(IN)

VOLP

T1<TDelay

T2=TDelay

Fig.3 OVP case

Fig.4 OLP case

OLP

OLP will shut down driver when VFB> VOLP for continual a blanking time. The OLP event as followed Fig.4.

OTP

OTP will shut down driver when junction temperature TJ>T (THR).

PCB Layout Note

Noise from the current sense or the control signal can cause significant pulse width jitter in

continuous-conduction mode, and 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 UC3863A, and increasing the power MOS gate resistance is advised.

UC3863AL-SH2-R Datasheet(PDF) 7 Page - Unisonic Technologies