UCC23525 is a single channel, isolated gate driver with opto-compatible input for power semiconductor devices, such as MOSFETs, IGBTs, or SiC MOSFETs. It is intended for use in applications such as motor control, industrial inverters, and switched-mode power supplies. It differs from standard opto isolated gate drivers as it does not have an LED input stage. Instead of an LED, it has an emulated diode (e-diode). To turn the e-diode "ON", a forward current in the range of 5mA to 20mA should be driven into the Anode. This will drive the gate driver output high and turn on the power FET. Typically, MCU's are not capable of providing the required forward current. In this case, a buffer should be used between the MCU and the input stage of UCC23525. Typical buffer power supplies are either 5V or 3.3V. A resistor is needed between the buffer and the input stage of the UCC23525 to limit the current. It is simple, but important to choose the right value of resistance. The resistor tolerance, buffer supply voltage tolerance and output impedance of the buffer, have to be considered in the resistor selection. This will ensure that the e-diode forward current stays within the recommended range of 5mA to 20mA. Detailed design recommendations are given in the Section 8.1. The current driven input stage offers excellent noise immunity that is need in high power motor drive systems, especially in cases where the MCU cannot be located close to the isolated gate driver. UCC23525 offers best in class CMTI performance of >200kV/us at 1000V common mode voltages.

The e-diode is capable of 25mA continuous in the forward direction. The forward voltage drop of the e-diode has a very tight part to part variation (1.4V min to 2V max). The temperature coefficient of the forward drop is <0.9mV/°C. The dynamic impedance of the e-diode in the forward biased region is ~1Ω. All of these factors contribute in excellent stability of the e-diode forward current. To turn the e-diode "OFF", the Anode - Cathode voltage should be <0.8V, or I_F should be <I_FLH. The e-diode can also be reverse biased up to 5V (6V abs max) in order to turn it off and bring the gate driver output low. The large reverse breakdown voltage of the input stage provides system designers the flexibility to drive the input stage with 5V PWM signals in interlock structure without the need for an additional clamping circuit on the Anode and Cathode pin.

The output power supply for UCC23525 can be as high as 30V (36V abs max). The output power supply can be configured externally as a single isolated supply up to 30V or isolated bipolar supply such that V_DD-V_SS does not exceed 30V, or it can be bootstrapped (with external diode & capacitor) if the system uses a single power supply with respect to the power ground. Maximum quiescent power supply current from V_DD is 2.2mA.