Datasheet

VCC

VDVS

5 V

SYNC

RTN

BULK

SYNC_IN

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CCM Applications

5 CCM Applications

For CCM applications, it is important to feed forward a SYNC signal from the primary side to turn-off the

SR-MOSFET to prevent cross-conduction with the primary-side MOSFET. Attach SYNC “pad” to a

synchronization signal derived on the system board. The UCC24610 controller requires a negative-going

SYNC signal referenced to VCC to trigger turn-off of the SR-MOSFET. This can be achieved with a

low-value capacitor connected from the primary-side MOSFET drain to the SR controller SYNC input. A

series resistor helps to reduce peak currents in the SYNC path. The current return path can be through

existing primary-to-secondary stray capacitance, EMI-suppression capacitance, or a dedicated return

capacitance. See Figure 5 below showing CCM-Flyback application. LLC applications are similar.

Figure 5. Connection Diagram for CCM-Flyback Application

SLUU450–September 2010 UCC24610EVM-693 Secondary-Side Synchronous Rectifier Controller Diode

Replacement Demonstration Board

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