TDK Claims World’s Smallest Point-of-Load DC-DC Converter

µPOL DC-DC converters in compact size, with highest power density point-of-load, lend themselves to a wide variety of applications like big data, AI, and 5G cells.

AAC's Mark Hughes interviewed TDK’s Rich Fry at APEC about their new µPOL series of DC-DC converters, which can handle up to six amperes of current and deliver up to one watt for each cubic millimeter of size. The company claims that the members of this series, with their minuscule 3.3 mm x 3.3 mm x 1.5 mm package size, are the smallest devices in the business.

Better Packaging Technologies, Smaller Components

These new µPOL devices were developed by TDK’s group company, Faraday Semi (FS). They eschew the typical solution of incorporating a side-by-side discrete integrated circuit (IC) and a discrete inductor. Instead, the new FS series integrates the IC and inductor in a compact configuration that offers a high-density solution for space-constrained applications requiring a low-profile power source.

A member of TDK’s µPOL family of 3.3mm x 3.3mm Point-of-Load DC-DC converters, with dime for scale. Image source: TDK

This is achieved by incorporating advanced packaging technologies such as a semiconductor embedded in substrate (SESUB).

Fry notes, "We take the silicon and build a substrate around it with LTCC (low-temperature co-fired ceramic) technology. Once it's built up, we add MOSFETs and the controller inside, put the power inductor on top and two capacitors, and you have a complete point-of-load solution."
The employment of 3D integration allows the units to take up far less board real-estate than comparable devices.

What Are Point-Of-Load DC-DC Converters?

Today’s electronic devices and subassemblies such as PC boards often demand more than one voltage. Point-of-load (POL) DC-DC converters change the available voltage, provided by either the system DC bus or a locally available source, into precisely the voltage needed locally by devices such as ASICs or FPGAs.

The value proposition is as follows: If a specific voltage is needed in only a few places on the PC board, why have a centrally located power supply to generate it? That incurs all the costs involved in building a bus to convey that voltage across the length and breadth of the assembly. POL converters avoid these additional headaches. In addition, the converters help avoid the inductance, capacitance, and resistance inherent to such busses and the filtering that they mandate.

Two Main Types of Point-of-Load DC-DC Converters

POLs can be divided into two classes: isolated and non-isolated. In an isolated POL, the converter’s output is isolated from the system ground. Of course, that requires an isolation transformer, which adds size, weight, and cost to the device. Obviously, designers will avoid those disadvantages whenever they aren’t necessary.

Depending on designation and purpose, POLs can operate from varied input voltages and produce a variety of output voltages, usually 3.3 volts and lower. In all cases, they are designed to produce voltages for components located close by physically. They are not purposed to provide any sort of system-wide power.

Members of the New µPOL series

• The FS1406 is rated at 6 Amps
• The FS1404 is rated at 4 Amps
• The FS1403 is rated at 3 Amps

Fry notes that these devices save design time and increase efficiency because point-of-load designers usually have to use components from different manufacturers.
"[They] have to do the whole design, and each component isn't necessarily optimized for the other because you're getting them from various states," Fry states. "So what we're able to do, since we're controlling the whole design, is optimize each point so that we can get a very efficient design and a very clean design."
These devices all operate over a temperature range of -40°C to 125°C. The company sees their main applications in:

• Network storage: Enterprise SSD/storage area network
• Servers: Mainstream server, rack and blade server, microserver
• Netcoms and telecoms: Ethernet switch and router and 5G small cells and 5G base stations
• Automotive: Future

The Competition

This is a highly competitive marketplace, with many devices available to serve as the basis of point-of-load converters.

The MAX20073 from Maxim Integrated delivers up to 3A load current from 0.5V to 3.8V. The devices operate from an input voltage range of 2.7V to 5.5V. It comes in a 3 mm × 3 mm × 0.85 mm 10-Pin TDFN package.

The TPSM82480 from Texas Instruments is a synchronous step-down DC-DC converter module for low profile point-of-load power supplies. Device size is 7.9 mm x 3.6 mm x 1.5 mm. This device provides 6 A of output current, with an input range over 2.4 to 5.5 V and an output range of 0.6V to 5.5 V.

The IR3883 from Infineon is a 3A device that comes in a 3 mm by 3 mm QFN package. The input range is 2.5 V to 14 V, and out range is from 0.5V to 5V.

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Have you designed a DC-DC converter or used one in an application? Share your experience in the comments.

Featured image used courtesy of TDK.