The UCC2752x device output stage features a unique architecture on the pullup structure 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 or collector voltage experiences dV/dt). The output stage pullup structure features a P-channel MOSFET and an additional N-channel MOSFET in parallel. The function of the N-channel MOSFET is to provide a brief boost in the peak sourcing current enabling fast turnon. This is accomplished by briefly turning-on the N-channel MOSFET during a narrow instant when the output is changing state from Low to High.

Figure 7-6 UCC2752x Gate Driver Output Structure

The R_OH parameter (see Section 6.5) is a DC measurement and it is representative of the on-resistance of the P-Channel device only. This is because the N-Channel device is held in the off state in DC condition and is turned-on only for a narrow instant when output changes state from low to high. Note that effective resistance of UCC2752x pullup stage during the turnon instant is much lower than what is represented by R_OH parameter.

The pulldown structure in UCC2752x is simply composed of a N-Channel MOSFET. The R_OL parameter (see Section 6.5), which is also a DC measurement, is representative of the impedance of the pulldown stage in the device. In UCC2752x, the effective resistance of the hybrid pullup structure during turnon is estimated to be approximately 1.5 × R_OL, estimated based on design considerations.

Each output stage in UCC2752x can supply 5-A peak source and 5-A peak sink current pulses. The output voltage swings between V_DD and GND providing rail-to-rail operation, thanks to the MOS-output stage which delivers very low drop-out. The presence of the MOSFET-body diodes also offers low impedance to switching overshoots and undershoots which 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.

The UCC2752x devices are particularly suited for dual-polarity, symmetrical drive-gate transformer applications where the primary winding of transformer driven by OUTA and OUTB, with inputs INA and INB being driven complementary to each other. This situation is due to the extremely low drop-out offered by the MOS output stage of these devices, both during high (V_OH) and low (V_OL) states along with the low impedance of the driver output stage, all of which allow alleviate concerns regarding transformer demagnetization and flux imbalance. The low propagation delays also ensure accurate reset for high-frequency applications.

For applications that have zero voltage switching during power MOSFET turnon or turnoff interval, the driver supplies high-peak current for fast switching even though the miller plateau is not present. This situation often occurs in synchronous rectifier applications because the body diode is generally conducting before power MOSFET is switched on.