The UCC27524 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 turn-on transition (when the power switch drain or collector voltage experiences dV/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 turn-on. The on-resistance of this N-channel MOSFET (R_NMOS) is approximately 1.04 Ω when activated.

Figure 7-1 UCC27524 Gate Driver Output Structure

The R_OH parameter 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 the UCC27524 pull-up stage during the turn-on instance is much lower than what is represented by R_OH parameter.

The pull-down structure in the UCC27524 device is simply comprised of a N-Channel MOSFET. The R_OL parameter, which is also a DC measurement, is representative of the impedance of the pull-down stage in the device.

Each output stage in the UCC27524device is capable of supplying 5-A peak source and 5-A peak sink current pulses. The output voltage swings between VDD and GND providing rail-to-rail operation, thanks to the MOS-output stage which delivers very low dropout. The presence of the MOSFET-body diodes also offers low impedance to transient overshoots and undershoots. The outputs of these drivers are designed to withstand 5A of peak reverse current transients without damage to the device.

The UCC27524 device is 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 is possible because of the extremely low dropout 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 these allow alleviate concerns regarding transformer demagnetization and flux imbalance. The low propagation delays also ensure proper reset for high-frequency applications.

For applications that have zero voltage switching during power MOSFET turn-on or turn-off 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.