U3848B-S08-R datasheet(9/13 Pages) UTC

9 / 13 page

U3848/A/B/C

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

9 of 13

www.unisonic.com.tw

QW-R103-033,B

FUNCTIONAL DESCRIPTION(Cont.)

(3) Protection section

U3848/A/B/C takes on more protection functions such as OLP, OVP and OTP etc. In case of those failure

modes for continual 7.2µs (blanking time), the driver is shut down. At the same time, IC enters auto-restart, VCC

power on and driver is reset after VCC power on again.

OLP

After soft-start phase end (VSS>5.1V), IC will shutdown driver if over load state occurs (corresponding to

VFB>4.6V) for continual 7.2µs. OLP function will not inactive during soft-start phase. OLP case as followed FIG.6.

The test circuit as followed FIG.8 for U3848/A/B/C.

VCC

VOUT

VFB

VSS

5.1V

4.6V

8.1V

12.6V

7.2µs Blanking

SS Phase

VCC

Driver

ON/OFF

VFB

VSS

5.1V

4.6V

8.1V

12.6V

7.2µs Blanking

SS Phase

Trestart

16V

3.9V

OVP Phase

FIG.6 OLP case

FIG.7 OVP case

OVP

Power supply VCC’s OVP function are enabled only when VSS<3.9V & VFB>4.6V during soft-start phase. During

above condition, driver will be shutdown if over voltage state occurs (VCC>16V) for continual 7.2µs. OVP function will

not inactive after soft-start phase. OLP case as followed FIG.7. The test circuit as followed FIG.9 for U3848/A/B/C.

OTP

OTP will shut down driver when junction temperature TJ of internal circuits is more than threshold 135°C for

continual 7.2µs.

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