SLYY200A April 2021 – December 2023 LM25149 , LM25149-Q1 , LM5156-Q1 , LM5157-Q1 , LM53635-Q1 , LM60440-Q1 , LM61460-Q1 , LM61495-Q1 , LMQ62440-Q1 , LMR33630-Q1 , LMS3655-Q1 , TPS55165-Q1 , UCC12040 , UCC12050
One of the main approaches to reducing high-frequency emissions is to minimize the power-loop inductance. Step-down converters from TI such as the LM53635-Q1, LMS3655-Q1, LM61495-Q1, LMR33630-Q1 and LM61460-Q1 move away from bond-wire packages to leadframe-based flip-chip (HotRod) packages that help lower the power-loop inductance and in turn reduce switch-node ringing.
HotRod packages flip the silicon die and place it directly on a lead frame in order to minimize the parasitic inductance caused by bond-wires on pins running switching currents. Figure 17 shows the construction and benefit of HotRod packages. Along with an improvement in power-loop inductance, HotRod-style packages also help lower resistance in the power path, leading to higher efficiency while making a smaller solution size possible.
An additional benefit of devices in the HotRod package is that they facilitate parallel input path pinouts — the layout arrangement of a DC/DC converter’s input capacitors. By optimizing the pinout of the DC/DC converter so that there is symmetry in the input capacitors’ layout, the opposing magnetic fields generated by the input power loops are within the symmetric loops, thereby minimizing emissions to nearby systems. A parallel input path further minimizes high-frequency EMI, particularly in the most stringent FM band, as shown in Figure 18.