8.1 Introduction

This chapter is intended to communicate, guide and illustrate a PCB design strategy resulting in a PCB that can support TI’s latest Application Processor. This Processor is a high-performance processor designed for automotive Infotainment based on enhanced OMAP™ architecture integrated on a 28-nm CMOS process technology.

These guidelines first focus on designing a robust Power Delivery Network (PDN) which is essential to achieve the desirable high performance processing available on Device. The general principles and step-by-step approach for implementing good power integrity (PI) with specific requirements will be described for the key Device power domains.

TI strongly believes that simulating a PCB’s proposed PDN is required for first pass PCB design success. Key Device processor high-current power domains need to be evaluated for Power Rail IR Drop, Decoupling Capacitor Loop-Inductance and Power Rail Target Impedance. Only then can a PCB’s PDN performance be truly accessed by comparing these model PI parameters vs. TI’s recommended values. Ultimately for any high-volume product, TI recommends conducting a "Processor PDN Validation" test on prototype PCBs across processor "split lots" to verify PDN robustness meets desired performance goals for each customer’s worst-case scenario. Please contact your TI representative to receive guidance on PDN PI modeling and validation testing.

Likewise, the methodology and requirements needed to route Device high-speed, differential interfaces , single-ended interfaces (i.e. DDR3, QSPI) and general purpose interfaces using LVCMOS drivers that meet timing requirements while minimizing signal integrity (SI) distortions on the PCB’s signaling traces. Signal trace lengths and flight times are aligned with FR-4 standard specification for PCBs.

Several different PCB layout stack-up examples have been presented to illustrate a typical number of layers, signal assignments and controlled impedance requirements. Different Device interface signals demand more or less complexity for routing and controlled impedance stack-ups. Optimizing the PCB’s PDN stack-up needs with all of these different types of signal interfaces will ultimately determine the final layer count and layer assignments in each customer’s PCB design.

This guideline must be used as a supplement in complement to TI’s Application Processor, Power Management IC (PMIC) and Audio Companion components along with other TI component technical documentation (i.e. Technical Reference Manual, Data Manual, Data Sheets, Silicon Errata, Pin-Out Spreadsheet, Application Notes, etc.).