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L6235

Slow decay mode

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Slow decay mode

Figure 13 shows the operation of the bridge in the slow decay mode during the off time. At

any time only two legs of the 3-phase bridge are active, therefore only the two active legs of

the bridge are shown in Figure 13 and the third leg will be off. At the start of the off time, the

lower power MOS is switched off and the current recirculates around the upper half of the

bridge. Since the voltage across the coil is low, the current decays slowly. After the deadtime

the upper power MOS is operated in the synchronous rectification mode reducing the

impedance of the freewheeling diode and the related conducting losses. When the

monostable times out, upper MOS that was operating the synchronous mode turns off and

the lower power MOS is turned on again after some delay set by the deadtime to prevent

cross conduction.

Figure 13. Slow decay mode output stage configurations