MP6925A – FAST TURN-OFF, CCM/DCM DUAL LLC SYNCHRONOUS RECTIFIERTurn-Off Phase Light-Load Mode Normal Mode When VDS rises to trigger the turn-off threshold, the gate voltage is pulled to zero after a very VDS tLL + tLL-H short turn-off delay (see Figure 3). VLL_DS Turn-Off Blanking VGS When VDS reaches the turn-off threshold and the gate driver is pulled to zero, turn-off blanking is triggered. This ensures that the gate ISD driver is off for a minimum time (tB_OFF) to prevent any erroneous triggers on VDS.
Secondary Side Current Light-Load Latch-Off FunctionFigure 5: MP6925A Exiting Light-Load Mode To improve efficiency, the MP6925A’s gate Light-load enter timing (t driver latches off to improve efficiency and LL) is configurable by connecting a resistor (R reduce driver loss under light-load conditions. LL) to LL. By monitoring the LL current (the LL voltage is kept at about The MP6925A compares the CH1 SR gate 2V internally), tLL can be calculated with (VG1) driver with the light-load enter pulse- Equation (1): width threshold (VLL-GS) every cycle to 2 determine the gate driver pulse width. If the .3 s t R (k) (1) LL LL CH1 SR gate driver pulse width remains below 100k tLL every cycle for longer than the light-load If the LL pin resistor is disconnected, light-load enter delay (tLL-D), the MP6925A shuts down mode is disabled. In this case, it is both channel gates immediately and enters recommended to place a capacitor (typically light-load mode, which latches off the SR 22pF) on the LL pin to avoid noise.