MP174A – NON-ISOLATED OFF-LINE REGULATOR

MP174A Rev. 1.0

www.MonolithicPower.com

14

2/27/2019

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Open-Loop Detection

If VFB is less than 0.5V, the IC will stop switching

and a re-start cycle will begin. During soft start

and the following 512 switching cycles, the open-

loop detection is blanked, in order to guarantee

successful start-up with a large output capacitor.

Leading-Edge Blanking

An internal leading-edge blanking (LEB) unit

avoids premature switching pulse termination

due to a turn-on spike. A turn-on spike is caused

by parasitic capacitance and reverse recovery of

the freewheeling diode. During the blanking time,

the current comparator is disabled and cannot

turn off the external MOSFET. Figure 5 shows

the leading-edge blanking.

ILIMIT

350ns

IDS

t

Figure 5: Leading-Edge Blanking