Supplement: Power
Configuring four-switch buck-boost µmodule regulators for versatile applications: step-up, step-down, or inverting output
By Ling Jiang, senior manager; Wesley Ballar, senior engineer; Anjan Panigrahy, product applications engineer; and Henry Zhang, ADI fellow, all with Analog Devices
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any power conversion applications need to support wide input or output voltage ranges. Analog Devices has a high current, high efficiency,
fully integrated four-switch buck-boost power module for such applications. This device integrates the controller, MOSFETs, power inductor, and capacitors within an advanced 3D integrated package, enabling compact design and robust performance. This µModule regulator delivers high power density, impressive efficiency, and excellent thermal performance across a wide range of input and output voltages. This article further highlights the versatility, demonstrating its ability to operate in various topologies, including buck (step-down), boost (step-up), and inverting buck-boost configurations for negative output applications.
Utilise the four-switch buck-boost topology as a buck (step-down) regulator
ADI has introduced multiple 40V step-down µModule regulators. Figure 1 highlights the available regulators capable of supporting a maximum load current exceeding 4A. However, these buck regulators are limited in their voltage and current range. By employing the newly released four-switch buck-boost µModule regulator, the LTM4712, as a step- down converter, the operating range can be significantly extended, simplifying system design for customers.
The four-switch buck-boost converter can be effortlessly configured as a buck converter without requiring any special adjustments. When VIN > VOUT, the internal controller keeps power FET M3 off and M4 continuously on. M1 and M2 regulate the output, operating like a standard buck converter, as illustrated in Figure 2. Compared to the previous step- down regulator, the LTM4613, the new device achieves superior power efficiency, despite the additional conduction loss introduced by M4, as shown in Figure 3. This improvement
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Figure 1. 40VIN (>4A) buck µModule regulators.
Figure 3. Buck mode efficiency and current capability comparison: (a) 5VOUT efficiency and (b) 12VOUT efficiency.
Figure 2. Utilising as a buck regulator.
is made possible by advancements in MOSFET and inductor technologies.
The thermal comparison without forced cooling, shown in Table 1, underscores the efficiency advantage of the buck-boost converter. Despite delivering significantly higher power than the buck regulator, the new device operates at a cooler temperature with a similar footprint area.
Utilise four-switch buck-boost as a boost (step-up) regulator As shown in Figure 4 (on page 34), ADI has previously released one 40V boost µModule
regulator. While the LTM4656 supports a maximum current of 4A, the newly released four-switch buck-boost converter can handle a higher load current when it functions as a step-up regulator. When using the four-switch buck-boost converter in applications where VIN < VOUT, internal switch M1 remains on, while M2 stays off. M3 and M4 naturally regulate the output as a typical boost converter as shown in Figure 5 (on page 34). Unlike standard boost converters, which lack output short-circuit protection, the four-switch buck-boost offers inherent
short-circuit protection. If the output is shorted to ground, M1 and M2 begin switching as a buck converter, limiting the current flowing from input to output. The maximum short circuit current is restricted by either the RSENSE resistor placed in the input or output paths, or the peak inductor current limit, whichever is lower. In addition, during the initial fast VIN ramping up stage, a conventional boost converter usually has uncontrolled, high inrush current through the boost diode to charge up COUT. As the four-switch buck-boost
Continues on page 34 Components in Electronics May 2025 33
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