Designing FPGA-Dependent Medical Devices Just Got More Streamlined With New PMIC Reference Designs

March 27, 2020 by Gary Elinoff

Renesas' new reference designs for Xilinx's FPGAs and SoCs solve the issues of multiphase regulators. But how might they also speed up the design process for in-demand medical devices?

FPGAs are becoming more mainstream—and accessible—for evermore applications. And while their value is indisputable, these devices present multiple power rails and can tolerate only very limited voltage variation. Designing capable power supplies for these devices can be tricky, but Renesas’ three reference designs, also available as finished boards, may give designers a quick and easy way out of the morass. 

The Renesas solution is based on two of the company’s four-phase power management ICs (PMIC), the three output ISL91211AIK and the four output ISL91211BIK. Both ICs can deliver up to 20 A of total output. They feature a 2 MHz switching frequency and are available in 4.7 mm x 6.3 mm, 35-ball BGA packages.

The three finished boards, or reference boards as Renesas describes them, along with a representative member of the ISL91211 family, are illustrated below.


Reference boards and ISL91211

Reference boards and ISL91211Image used courtesy of Renesas


The three individual reference boards are designed to power the multiple supply rails of the Xilinx’s Artix-7 FPGAs and Spartan-7 FPGAs as well as Xilinx’s Zynq-7000 SoCs. The latter device incorporates a single-core Arm Cortex-A9 processor along with FPGA technology.


What Is a Multiphase Regulator? 

A multiphase regulator is a set of power stages wired in parallel. Each set includes its own inductor and power MOSFETs, which is called a phase; collectively, they share input and output capacitors. Each phase is active during its own portion of the 360° power cycle.


Representation of a three-phase regulator

Representation of a three-phase regulator. Image used courtesy of Texas Instruments


This arrangement offers the immediate advantage of smaller input and output capacitances. In addition, each phase needs to supply only its own portion of the total power, so both efficiency and heat dissipation are improved. 

And critically, phases can be turned on and off as needed to respond to load transients, keeping the voltage supplied to FPGAs to with the required tight specifications.

As the reader can well imagine, managing the phases requires some deft engineering, and the BOM is larger and more costly than that of a typical switcher. That’s where Renesas’ reference designs come in.


New Reference Designs and Reference Boards

In all three cases, Renesas offers not only a reference design but also a complete board, ready for use and built to the reference design’s specification. They are, respectively:

“Our PMIC reference designs significantly accelerate customer development schedules by providing tested and complete solutions ready to connect to and power Xilinx’s Artix-7, Spartan-7, and Zynq-7000 devices,” said Andrew Cowell, Renesas' VP of mobility, infrastructure, and IoT power business.

“Both multiphase PMICs employ Renesas’ industry-leading R5 modulation technology for blazingly fast transient response, while allowing designers to dynamically scale power to improve overall system performance.”


Speeding Up Development for Devices Like Ventilators

These reference designs and the completed boards speed the design for the specialized power supplies required by FPGAs. These programmable devices are becoming mainstay components in many computing and industrial applications, which may include machine vision, PLCs, motor control, and appliances.

Most importantly, FPGAs also figure in the design in medical equipment such as Nuvation Engineering's low-cost portable ventilator, an important development considering the present health emergency.


A low-cost portable ventilator

A low-cost portable ventilator. Image used courtesy of Nuvation Engineering

Among other applications, Renesas explicitly states that they see these reference designs speeding "the development of power supplies for a variety of industrial and computing applications. . . including portable medical and wireless medical equipment." 



Considering the difficulty involved in designing even an ordinary switching power supply, would you consider “going it alone?” Or, would you prefer a reference design from a trusted source like Renesas? If so, at what size of a production run would you consider simply buying a finished reference board as opposed to going to the trouble of purchasing components and building with the reference design as your guide?

Share your thoughts in the comments below.