MP6900- FAST TURN-OFF INTELLIGENT CONTROLLER

MP6900 Rev. 1.12

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9/19/2012 MPS Proprietary Information. Patent Protected. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2012 MPS. All Rights Reserved.

BLOCK DIAGRAM

Figure 1—Functional Block Diagram

OPERATION

The MP6900 supports operation in CCM, DCM

and Quasi-Resonant topologies. Operating in

either a DCM or Quasi-Resonant topology, the

control circuitry controls the gate in forward mode

and will turn the gate off when the MOSFET

current is fairly low. In CCM operation, the control

circuitry turns off the gate when very fast

transients occur.

Blanking

The control circuitry contains a blanking function.

When it pulls the MOSFET on/off, it makes sure

that the on/off state at least lasts for some time.

The turn on blanking time is ~1.6us, which

determines the minimum on-time. During the turn

on blanking period, the turn off threshold is not

totally blanked, but changes the threshold

voltage to ~+50mV (instead of -30mV). This

assures that the part can always be turned off

even during the turn on blanking period. (Albeit

slower, so it is not recommended to set the

synchronous period less than 1.6us at CCM

condition in flyback converter, otherwise shoot

through may occur)

VD Clamp

Voltage JFET is used at the input. To avoid

excessive currents when Vg goes below -0.7V, a

the drain of the external MOSFET.

Under-Voltage Lockout (UVLO)

When the VDD is below UVLO threshold, the part

is in sleep mode and the Vg pin is pulled low by a

10k

Ω resistor.

Enable pin

The Enable function is only available on the

SOIC-8 package. If EN is pulled low, the part is in

sleep mode.