Hello. And welcome to TI's low EMI training series. I'm Sam Jaffe. And in this short video, we'll be discussing the benefits of our Hotrod and enhanced QFN packages.

Hotrod, also called flip-chip on lead frame, is a package technology which eliminates the need for bond wires. The typical wire bond IC will use bond wires to connect the silicon die to the lead frame. From there, lead frame pins solder to the PCB to connect to external components. But bond wires add inductance to this path, which will worsen EMI emissions. Bond wires also add resistance to the path, which reduces efficiency and power density, which can also worsen EMI emissions.

Hotrod flips the silicon die and solders the copper bumps directly to the lead frame, which effectively eliminates the inductance and resistance that this path would have had from the bond wires. This significantly reduces switch node ringing and improves EMI performance. We'll see why on the next slide.

To understand why less inductance leads to less ringing, let's discuss the requirements of a low-EMI layout. EMI comes from input ripple and capacitive or inductive coupling to the car chassis or other circuits. To reduce ripple and coupling, the layout must consider and minimize parasitic inductances and capacitances in the circuit. More generally, the layout should keep quickly changing voltages or high dv/dt nodes shielded or small, as well as keeping quickly changing currents or high di/dt loop areas small.

These red parasitic components show the most critical layout considerations of a buck when it comes to EMI. And these notes explain which rules they apply to and why we want to pay attention to them when creating a layout. For our discussion now, we can focus on note 2.1.

During normal continuous conduction mode operation, the inductor will have current flowing. Inductor current can't change instantaneously. So when the low-side FET turns off on the high-side FET turns on, the inductor immediately pulls current from vin from the input capacitors.

This transient current causes a ringing from the interaction between the parasitic inductance of the input loop and the parasitic capacitance of the low-side FET. By placing this input capacitor as close as possible to the IC, we reduce the loop area, thereby reducing the parasitic inductance, which reduces the energy in this ring, which results in reduced EMI emissions. The Hotrod package removes the bond wire inductance in the path from the vin and ground pins to the mosfets, which further reduces this input loop parasitic inductance, which reduces switch ringing and reduces EMI emissions.

On this slide, you can see the wire bond QFN switch ring compared to the no wire bond QFN or Hotrod switch ring. Newer devices have even more advanced package technology called enhanced QFN, which provides the benefits of both QFN and Hotrod. To understand this, we need to talk about power density.

Power density can have a large impact on EMI performance. Large components are effectively larger antennas and will radiate more. Keeping devices small keeps devices quieter, reducing emissions.

But we run into issues when reducing the size of components. At a certain point, the heat dissipated by the device can't spread away from the device quick enough. And the device starts to overheat.

We can help this by increasing efficiency, which decreases power dissipation, which we did by eliminating the resistor bond wires. We can also help this by spreading the heat from the IC to the board through low thermal resistance paths. QFN devices have a thermal pad or a die attach pad, which connects to the die and is used to transfer heat from the AC to the board.

But Hotrod flipped the chip. So we no longer have a thermal pad. Heat instead flows through the pins to the rest of the board. This isn't an issue since the pins have a much higher thermal conductivity than pins which connect with the bond wire.

Connecting the ground pins to the ground plane typically provides good thermal performance. But this isn't always practiced, since engineers are used to using thermal pads. For this reason, we've introduced our enhanced QFN package, which has all the benefits of Hotrod but with the addition of a thermal pad.

This gives us the best of both worlds. Not only are the bond wires removed and the pins provide heat flow from the die to the board, we're also able to make available a thermal pad for even better thermal performance. This keeps the solution small, which helps you achieve best-in-class EMI performance.

That concludes this video on package optimization talking about Hotrod and enhanced QFN. Thank you for watching. And check out our other videos for more tips on optimizing your EMI performance.