DC Voltage Requirements for Electronic Devices on High-Speed PCBs

August 20, 2019 Cadence PCB Solutions

High-speed PCB component

 

When I was first introduced to computers, we had a term to describe the small, but heavy monitors that we used. Affectionately, we referred to them as “dumb terminals.” This was accurate in that the terminals were only displays for a mainframe computer usually located in another laboratory that had all of the “brains.” Well, times have certainly changed! Today, computers and displays are sometimes housed in single units of all sizes and they certainly are not dumb.

Today, not only are computers smart but virtually any product can be obtained that is capable of making decisions. Whether these devices and machines are standalone or a part of an extensive internet of things (IoT) system, they typically utilize high-speed PCBs to acquire, process, store and transmit data. In order to perform these signal and data processing tasks, one or more microprocessors are required. In addition to the requirements for most circuit boards, high-speed design usually means a power supply or power distribution to satisfy varying DC voltage requirements. 

Let’s first explore what makes a board high-speed, the DC voltage requirements, and define a method of ensuring these requirements are met.  

What is a High-Speed PCB?

Circuit boards are classified in a number of ways. For example, they may be categorized according to the number of layers or stackup, the size of the board or complexity of the PCB layout. High-speed; however, is a special classification and requires special consideration. These boards may be multilayer, small and complex, but what sets them apart is they typically require the propagation of varying types of signals; which includes high-speed or frequency digital, analog and DC. 

In order to successfully process these signals requires a design that maximizes signal integrity (SI) and power integrity (PI). For SI, this means making PCB layout and materials choices that minimize signal degradations; such as EMI and crosstalk. Designing for maximum PI is satisfying the DC voltage requirements for all electronic devices on the board.

DC Voltage Requirements for High-Speed Boards

A number of common PCB components are powered by DC. These include transistors, amplifiers, processors and systems on a chip (SoCs). Typical DC voltage levels for these and other components and devices are:

 

TYPICAL DC VOLTAGE REQUIREMENTS FOR ELECTRONIC DEVICES ON PCBS

Voltage (DCV)

Device(s)

Usage

1.2

SoCs, processors

Supply voltage

1.8

ICs, LEDs, memory modules

Supply voltage

2.4

ICs, LEDs, memory modules

Supply voltage

3.3

ICs, LEDs

Supply voltage

5

ICs, SoCs

Supply voltage

12

Operational amplifiers, transistors

Bias voltage, supply voltage

15

Operational amplifiers, transistors

Bias voltage, supply voltage

 

The voltage levels in the table above are not exhaustive. Some PCBs utilize higher DC voltages. For example, power supplies and controllers for motors or industrial equipment.  However, these levels are common for the types of devices that are used in high-speed circuits. Irrespective of the specific DC voltage requirement for the electronic device, the common requirement is that it be constant or regulated to remove any ripples or variations to ensure device operation. 

Using Simulations to Ensure PCB DC Voltage Requirements are Satisfied

The best way to ensure that your board’s DC voltage requirements are satisfied is to analyze the power distribution network. With the proper tool, this evaluation will provide you with the DC electrical parameters of your circuit board necessary to verify whether your requirements are met or where design changes must be made. Errors can then be isolated and discrete devices can be tested and corrected. 

Unfortunately, this type of analysis is not available with most PCB design software packages. Instead, a third party circuit analysis program is required, which may also necessitate design file conversions that introduce the possibility of error. Moreover, if your design has multiple instances where the DC voltage requirements are not met, repeated back and forth between your design software and circuit analysis program may have to be performed. This process is time-consuming and wasteful in terms of development resources. 

The best solution for ensuring your DC voltage requirements for electronic devices is Cadence’s integrated PCB design and analysis solution, which includes the capability to perform DC, analog and mixed-signal simulations using PSpice. 

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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