Multi-Board Circuit Analysis

 

Introduction

Advanced electronics products often include several PCBs with many interconnections. While each board can function as expected on its own, the complete unit may fail to operate due to design errors related to board integration. Boards may come from a single source or from different sources (manufacturer, OEM, ODM, etc.). In either case you need to perform integration testing for error detection. Fixing such errors requires time consuming root cause analysis and additional design cycles. Early identification of these errors can save a lot of time and money.

Standard Multi-Board Verification

The standard method for interfacing several boards correctly is by using ICD (Interface Control Document) where all inputs and outputs of each board are defined. Ideally the ICD should be well defined, and each board should comply with its own ICD. Unfortunately, this is often not the case. Following are some typical examples of issues that BQR engineers encountered while analyzing customer multi-board designs:

 

  • ICD may not be well defined, this causes confusion between the different groups that design the separate boards.
    Until recently there was no standard for ICDs. BQR’s CTO Yizhak Bot led the effort to formulate such a standard for the aerospace industry [1].
  • A main power supply provides power to several boards. While the power is sufficient for each separate board, the power may be insufficient for all boards together.
  • I2C communication requires a pull-up resistor, but each board designer believes that the other board includes the pull-up resistor, and eventually no resistor is implemented in the system design.

 

Simulation based Multi-Board Verification

BQR’s fiXtress software has the unique capability to conduct circuit stress simulation over large multi-board designs. Rather than depending on ICDs, the simulation verifies the actual integrated detailed design. In this way many design errors are found at an early stage, saving time and money.

 

References

[1] IEC-63238-1 Process management for avionics – Electronics design – Part 1: Electrical signal properties, naming conventions and interface control document (ICD)