The input pins of the UCC27444 gate driver device are based on a TTL compatible input threshold logic. With a high threshold of 2.2 V and a low threshold of 1.2 V, the logic level thresholds are conveniently driven with PWM control signals derived from 3.3-V and 5-V digital power controller devices.

The UCC27444 device high resistance driver inputs reduces leakage currents in the input pins. The driver input signals are expected to be in a defined high or low state to control the driver outputs. If a controller is used which may have undefined or tri-state conditions on the driver control signals, it is recommended to have an external pull down resistance from the INx pins to ground.

The input pins can handle wide range of slew rate. In most power supply applications, the gate driver is either driven by the output of a digital controller or logic gates. Therefore, in most applications the input signal slew rate is fast and is no concern for the UCC27444 family of devices. If limiting the rise or fall times to the power device is the primary goal, then an external gate resistor is highly recommended between the output of the driver and the gate of the switching power device. This external resistor has the additional benefit of reducing part of the gate-charge related power dissipation in the gate driver device package and transferring it into the external resistor itself. In short, some of the power gets dissipated in the gate resistor rather than inside of the gate driver. Additionally, the input pins of UCC27444 are capable of handling –5 V. This improves the system robustness in noisy (electrical) applications. This also enables the driver to directly connect to the output of a gate drive transformer without the use of rectifying diodes, which saves board space and BOM cost.