The UCC25800-Q1 open-loop LLC transformer driver integrates the switching power stage, the control, and the protection circuits to simplify isolated bias supply designs. The LLC topology allows the design to utilize a transformer with higher leakage inductance, but much smaller parasitic primary-to-secondary capacitance. This low-capacitance transformer design enables an order of magnitude reduction in the common-mode current injection through the bias transformer. This makes the UCC25800-Q1 an ideal solution for the isolated bias supply in various automotive applications to minimize the EMI noise caused by the high speed switching devices. The UCC25800-Q1 operates with soft switching to further reduce the EMI noise.
UCC25800-Q1 has a programmable frequency range of 100 kHz to 1.2 MHz. This high switching frequency reduces the transformer size and footprint, as well as the overall cost of the bias supply. The integrated SYNC function allows the bias supplies in the system to be synchronized with an external clock signal, further reducing the system level noise.
The dead-time of UCC25800-Q1 is adjusted automatically to minimize the conduction loss and simplify the design. The maximum dead-time is programmable to ensure power stage design flexibility.
With the integrated low-resistance switching power stage, the UCC25800-Q1 can achieve a 6-W design with 24-V input. With a fixed input voltage that is above 9 V and below 34 V, the open-loop LLC converter control also helps the output regulation to remain ±5% when the load is above 10%.
The programmable over-current protection (OCP) allows flexibility on the power stage design to minimize the transformer size, further reducing the system cost. The protection features such as adjustable OCP, input OVP, TSD and the protection from pin faults ensure robust operation. A fixed 1.5-ms soft start reduces the inrush current during start-up and fault recovery.
UCC25800-Q1 also provides a dedicated multi-function pin for external disabling, and fault code reporting. The fault code reporting sends the fault code once the bias supply is in the protection mode, allowing the system level controller to make more intelligent decisions during system failure modes.
The UCC25800-Q1 is offered in an 8-pin DGN package with the thermal pad to enhance its thermal handling capability.