Power Management ICs with Integrated Passive Components

Since TechInsights launched its power management integrated circuit (PMIC) process analysis channel in late 2021, a variety of devices have been analyzed. Topics range from high-voltage gate drivers and automotive-grade power conversion ICs to mobile power management ICs. It has been observed that more and more manufacturers are attempting to integrate passive components into power management IC products in a co-package configuration or "fully integrated" with the silicon IC itself.

As with all power electronics, size, weight and power (SWaP) are key performance metrics. To increase system efficiency, we need smaller, lighter systems with higher power density. In the case of power management ICs operating at relatively low power levels, integration is ideal and theoretically feasible.

One type of "integrated voltage regulator" (IVR) has received particular attention. Since relatively small changes can damage delicate transistors in precision components such as CPUs, a voltage regulator circuit is used to provide a stable constant voltage.

Many consumer electronics have an input voltage of 12 V (48 V for the latest server architectures). The final "point-of-load" (PoL) step-down conversion process inside the product supplies the CPU, GPU, and other internal components with their required voltage (typically <2 V). As architectures become more complex and require different input voltages, multiple regulator circuits are required to provide different voltages, which take up valuable board space. There are clear benefits to integrating this functionality.

Early Attempts at "Fully Integrated" Regulators

Perhaps Intel's most high-profile attempt at the technology so far. Intel experimented with a so-called "fully integrated voltage regulator" (FIVR) solution on 4th and 5th generation core microprocessors (Haswell and Broadwell). A paper presented at the 2014 APEC meeting demonstrated this approach - integrating a non-magnetic inductor into a land grid array (LGA) package. A research paper submitted in 2016 shows more details on the different inductors under discussion, including uncoupled solenoids, interleaved solenoids, shielded plated through-hole (PTH) rings, and 3DL. The paper concludes that magnetic materials may have to be used in the future to meet current density requirements. An early demonstration in 2011 showed the study of on-chip inductance, including a magnetic CoZrTa envelope.

Starting with the 6th generation, Intel dropped the fully integrated voltage regulator approach, and one of the reasons seems to be that this approach would generate extra heat near the CPU. The technology is rumored to be reintroduced, and as evidenced by a demonstration at VLSI 2022, Intel is still working on the concept in some form.

Apple APL1028 Integrated Voltage Regulator

Our teardown channel provides detailed coverage of the most important consumer electronics ever released. According to the analysis of the 2021 MacBook Pro (16 inches) with the M1 processor, we found that the Apple APL1028 chip is placed on the back of the PCB inside the cooling case of the M1 processor area. We have since written a Power Management IC Process Analysis report on this device and highlighted integrated inductor technology in a recent Power Management IC Briefing.

As shown in Figure 1, the APL1028 is available in a flip-chip ball grid array (FCBGA) package.

Apple APL1028 Integrated Voltage Regulator

Our teardown channel provides detailed coverage of the most important consumer electronics ever released. According to the analysis of the 2021 MacBook Pro (16 inches) with the M1 processor, we found that the Apple APL1028 chip is placed on the back of the PCB inside the cooling case of the M1 processor area. We have since written a Power Management IC Process Analysis report on this device and highlighted integrated inductor technology in a recent Power Management IC Briefing.

As shown in Figure 1, the APL1028 is available in a flip-chip ball grid array (FCBGA) package.

This product has some similarities to the Apple APL1028 integrated voltage regulator discussed earlier in this blog. Similar to the APL1028, we believe that the "TRIO-C" chip in the picture is likely to be based on TSMC's 12 FF process. However, its integration method is different, and the on-chip inductor is not used in the figure. In contrast, Ampwall provides two solutions:

For customized services, AMPWORD will assist in the design of the dedicated inductance traces to be integrated on the PCB.

AMPWORD also offers the EP7037B, which contains an inductor wrapped in a flip-chip BGA package.

Using four additional silicon deep-trench capacitor chips is another way to reduce additional passive components and shrink board space. Figure 5 shows a SEM cross-section of one such chip. A bimetallic aluminum process with tungsten silicide contacts connects to the deep trenches that fill the polysilicon and form the capacitors.

Summarize

Integrating passive components into a power chip has clear advantages. This increases power density, minimizes board space, and shortens the bill of materials (BoM), all of which are very attractive. But this came with its own set of drawbacks, and previous attempts at the technology were quickly discontinued.

We'll see if Apple carries over this philosophy to the M2 Pro and Max MacBooks, and how they make trade-offs in terms of thermal management.

Integrated voltage regulators (IVRs) are by no means the only power management IC technology that could benefit from this approach. System-level performance is important when discussing any power conversion product, and even more so at higher powers where even a small increase in efficiency becomes very important. This is important when discussing new wide bandgap products such as silicon carbide (SiC) and gallium nitride (GaN) transistors. Discrete transistors themselves may be more expensive than silicon transistors, but not only do they improve transistor performance, they also undoubtedly provide cost savings for larger system designs. They do this through higher switching frequencies, allowing for reduced capacitance and a cheaper, lighter, and more power-dense solution. When looking at high power modules, we have come to appreciate the importance of modular layout and short interconnects to reduce inductance.

For the low power end of the spectrum and power management ICs, we can go further and integrate the passives into discrete packages, and in the case of the Apple APL1028, actually into the semiconductor die. We look forward to seeing breakthroughs in this area in the coming years.