AN2626

MOSFET body diode recovery

9/13

In normal condition the source and body regions (that is the emitter and the base of the

parasitic bipolar) are shorted via upper source metallization, but by flowing a significant

current into the body region below the source region (see Figure 7), the intrinsic resistance

of this region (shown as Rb) could divert a sufficient current portion able to trigger on the

parasitic bipolar; it means creating a short circuit between drain and source pins thus,

destroying the device.

Figure 7.

Current flow due to the reverse recovery of the body diode

Hence, in order to overcome the previous problems, a MOSFET should have some

characteristics:

●

The intrinsic body diode with low Trr and low Qrr;

●

Ruggedness to the stress due to the trigger on of the parasitic bipolar.

To meet the need related to the body diode a new technology has been developed. The new

FD (fast diode) MOSFET has straightforward advantages in terms of Trr, Qrr, Irm and

ruggedness in dv/dt.