JAJSRJ4 October 2023 UCC44273
PRODUCTION DATA
The UCC44273 has internal Undervoltage Lockout (UVLO) protection feature on the VDD-pin supply-circuit blocks. Whenever the driver is in UVLO condition (for example when VDD voltage is less than VON during power up and when VDD voltage is less than VOFF during power down), this circuit holds all outputs LOW, regardless of the status of the inputs. The UVLO is typically 4.2 V with 300-mV typical hysteresis. This hysteresis helps prevent chatter when low VDD – supply voltages have noise from the power supply and also when there are droops in the VDD-bias voltage when the system commences switching and there is a sudden increase in IDD. The capability to operate at low voltage levels such as below 5 V, along with best-in-class switching characteristics, is especially suited for driving emerging GaN wide-bandgap power-semiconductor devices.
For example, at power up, the UCC44273 driver output remains LOW until the VDD voltage reaches the UVLO threshold. The magnitude of the OUT signal rises with VDD until steady-state VDD is reached. In the non-inverting operation (PWM signal applied to IN pin) shown in Figure 7-1, the output remains LOW until the UVLO threshold is reached, and then the output is in-phase with the input. Note that in these devices the output turns to high-state only if IN pin is high after the UVLO threshold is reached.
Because the driver draws current from the VDD pin to bias all internal circuits, for the best high-speed circuit performance, two VDD bypass capacitors are recommended to prevent noise problems. The use of surface-mount components is highly recommended. A 0.1-μF ceramic capacitor should be located as close as possible to the VDD to GND pins of the gate driver. In addition, a larger capacitor (such as 1 μF) with relatively low ESR should be connected in parallel and close proximity, in order to help deliver the high-current peaks required by the load. The parallel combination of capacitors should present a low impedance characteristic for the expected current levels and switching frequencies in the application.