7.3.5 Output Stage

The output stage of the UCC27611 device is illustrated in Figure 11. OUTH and OUTL are externally connected and pinned out as OUTH and OUTL pins. The UCC27611 device features a unique architecture on the output stage, which delivers the highest peak source current when it is most needed during the Miller plateau region of the power switch turnon transition (when the power switch drain and collector voltage experiences dV and dt). The device output stage features a hybrid pullup structure using a parallel arrangement of N-channel and P-channel MOSFET devices. By turning on the N-channel MOSFET, during a narrow instant when the output changes state from low to high, the gate-driver device is able to deliver a brief boost in the peak-sourcing current, enabling fast turnon.

Figure 11. UCC27611 Device Gate Driver Output Structure

The R_OH parameter (see Electrical Characteristics) is a DC measurement, and it is representative of the on-resistance of the P-channel device only, because the N-channel device is turned on only during output change of state from low to high. Thus, the effective resistance of the hybrid pullup stage is much lower than what is represented by R_OH parameter. The pulldown structure is composed of a N-channel MOSFET only. The R_OL parameter (see Electrical Characteristics), which is also a DC measurement, is representative of true impedance of the pulldown stage in the device.

The driver output voltage swings between VDD and GND, providing rail-to-rail operation thanks to the MOS output stage that delivers very low dropout. The presence of the MOSFET body diodes also offers low impedance to switching overshoots and undershoots. This means that in many cases, external Schottky diode clamps may be eliminated. The outputs of these drivers are designed to withstand 500-mA reverse current without either damage to the device, or logic malfunction.