MP6901- FAST TURN-OFF INTELLIGENT CONTROLLER
BLOCK DIAGRAM
Figure 1—Functional Block Diagram
OPERATION
The MP6901 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.
VD Clamp
Because VD can go as high as 180V, a High-
Voltage JFET is used at the input. To avoid
excessive currents when Vg goes below -0.7V, a
small resistor is recommended between VD and
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
10kΩ resistor.
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)
Enable pin
The Enable function is only available on the
SOIC-8 package. If EN is pulled low, the part is in
sleep mode.
Thermal shutdown
If the junction temperature of the chip exceeds
170oC, the Vg will be pulled low and the part
stops switching. The part will return to normal
MP6901 Rev. 1.05
3/15/2016
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