A Study of High Speed implementation for System on Chip on 2 layers Printed Circuit Board

Abstract

In today fast pace complexity of silicon design environment, silicon is not longer a standalone device that you could provide to customers. Customers are now looking at a full solution with the whole PCB bill of materials besides the standard software package that should come along. With a rapidly closing market window, constantly cost saving and design challenges, traditional design methodologies can no longer met the requirement. For example, to lower the cost, 2 layers PCB design which is never come into consideration for high speed system design, it is going to come to place. That has inevitably posed great challenges to the PCB design. However, following the theoretical analysis of signaling, it is almost impossible to implement a high speed signals for System on Chip (SOC) on a 2 layers printed circuit board (PCB). This is due to the fact that high speed signals require a very strong complete ground plane and good power plane which 2 layers PCB board is unable to fulfill such requirement. To improve the signal integrity, it requires at least a 4 layers PCB board design for all the high speed PCB design. Some design even goes up to 20 layers of PCB board to ensure signal integrity. If following the simulation tools, it will require a signal to ground plane distance in order to calculate the signal integrity. A series termination resistor could help to reduce the overshoots or ringing of the signals. In the past decade, single layer or double layers PCB are only suitable for low speed application such as analogy TV for consumer's products. In the continuously of price pressure, SOC chip does not have the luxury to sit on a multi layers PCB board anymore but need to implement on a 2 layers PCB board in order to survive on the consumer price sensitive market. This prompt the need to re-study and re-thinking in order to use SOC chip on a 2 layers PCB board. This paper study the SOC design implementation changes to support 2 layers PCB design and the signals analysis and EMI test results for 2 layers PCB board..