Abstract
This article introduces a new high performance step-up and step-down buck- boost μModule regulator. It achieves the highest power efficiency and the coolest thermal performance compared to the old generation high current buck- boost μModule regulators. Several other great features, including parallelable configuration for higher power applications, optional constant current regulation, and redundant input configuration, are also introduced.
Introduction
There are many applications with wide input and/or output voltage ranges, such as a battery-powered system. The power supply needs to regulate its output voltage while the input voltage can be lower or higher than the output voltage. A four-switch buck-boost topology can offer the highest efficiency and power density for such an application, as long as ground isolation is not required. Furthermore, a buck-boost power regulator is very flexible and can be used as a buck-only (step-down) or boost- only (step-up with short circuit protection) power supply.
Analog Devices’ μModule group has developed several buck-boost regulators. Figure 1 illustrates the LTM8045, LTM8049, LTM8083, and LTM4693 targeting for lower current applications. High current applications (up to 12 A) are supported by the LTM4607 fam- ily, LTM8055 family, and the newly released LTM4712 buck-boost module. The LTM4607/ LTM4605/LTM4609 family incorporates the controller and MOSFETs internally, requiring an external power inductor and sensing resistor (RSENSE) on the PCB to form a com- plete power solution, as depicted in Figure 2. Alternatively, the LTM8054, LTM8055, and LTM8056 integrate the power inductor and RSENSE into the μModule package, simplifying the design and layout efforts for customers, as highlighted in Figure 3. The LTM8055 family offers a smaller solution size compared to the LTM4607 family, but its output current is constrained by a small-size integrated inductor, therefore limiting thermal and efficient performances.
In 2023, a new high current, four-switch buck-boost regulator, LTM4712, was released. It is a 36 VIN(max), 12 A power module in a high density 16 mm × 16 mm × 8.34 mm BGA package. It integrates a high performance power inductor into the package using advanced ADI proprietary component-on-package technology. Figure 4 shows a pro- prietary current sensing scheme integrated in the module. This not only saves space but also minimizes additional power loss. Leveraging a cutting-edge buck-boost con- troller and the advanced ADI package, this device achieves the highest power level, power density, efficiency, and excellent thermal performance across a wide input and output voltage range.
The LTM4712’s fast, cycle-by-cycle current-mode control enables reliable protection and smooth mode transitions. It facilitates excellent current sharing when parallel con- figurations are employed for higher current applications. Additionally, this new device supports an optional constant output current mode for battery charging applications and allows redundant inputs, enhancing its versatility as a redundant power supply.
Table 1 offers a comprehensive module comparison among the LTM4712, LTM4607 fam- ily, and LTM8055 family. The LTM4712 stands out for its high current, power efficiency, and user-friendly design, making it an ideal choice for applications where its 8.34 mm height is acceptable.
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