OMAP-L137 Hardware Design Guide

Hardware Design Timeline →

Constructing the Block Diagram

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Selecting the Boot Mode

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Confirming Pin Multiplexing Compatibility

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Confirming Electrical and Timing Compatibility

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Designing the Power Subsystem

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Designing the Clocking Subsystem

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Floorplanning the PCB

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Creating the Schematics

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Laying out the PCB

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Testing / Debugging

 

Introduction

Welcome to the OMAP-L137/C6747/AM1707 Hardware Design Guide.  The purpose of this guide is to walk hardware designers through the various stages of designing a board around OMAP-L137/C6747/AM1707.  The guide follows the structure shown in the Hardware Design Timeline above.  Each design stage in the Timeline links to a collection of useful documentation, application notes, and design recommendations pertaining to that stage.  Using this Guide, hardware designers can efficiently locate the resources they need at every step in the board design flow.

Constructing the Block Diagram

The first step in designing the hardware platform is to create a detailed block diagram.  The block diagram should contain all major system ICs and illustrate which I/O ports are used for device interconnection.  Below is a collection of resources to aid in the Block Diagram creation process.

• Select from a list of complementary devices to attach to OMAP-L137/C6747/AM1707 in your system
  • OMAP-L137/C6747/AM1707 Complementary IC Wiki

Selecting the Boot Mode

The block diagram should also indicate which interface will be used for booting the processor.  Upon coming out of reset, the processor must boot up by loading its application code from external storage. The application code can be loaded from a ROM or can be downloaded from another processor in the system.  The processor contains a primary bootloader burned into its internal ROM which is run by the processor after coming out of reset. This primary bootloader performs some critical initial tasks and then loads application code from the external interface specified by the processor boot configuration pins. See the below information for selecting an implementing the right boot mode for your system.

• Read the following document to learn about the possible boot options for the processor
  • OMAP-L137 Bootloader Application Report
  • C6747 Bootloader Application Report
  • AM1707 Bootloader Application Report

• Understand the details of the boot process
  • OMAP-L137/C6747/AM1707 Bootloader
• The following Wiki provides example code and walk through the process of creating, flashing, and booting ARM or DSP programs on the EVM:
  • Boot Images for OMAP-L137/C6747/AM1707
• See the following articles on selecting the right boot mode for your application:
  
  • Comparison of various boot media
  • List of NANDs devices supported by TI ROM Bootloaders (RBLs)
  • Comparison of managed NAND vs raw NAND
  • NAND Boot FAQ
• Key Boot Considerations:
  • It is recommended to include population options for other boot modes to aid in development
    
  • Boot pins have other functions after reset. Make sure your board design takes this into account when choosing pullup/down resistors for the boot pins.

Confirming Pin Multiplexing Compatibility

The processor uses internal pin multiplexing to allow for maximum functionality in the smallest and lowest cost package.  Due to this pin multiplexing, not all processor interfaces are always available simultaneously.See the Terminal Functions section of the datasheet for complete details on the pin multiplexing.  Also see the below information for tools and tips related to pin multiplexing.

• Use the following tool to verify that the processor pin multiplexing is compatible with you system block diagram
  • OMAP-L137/C6747 Pin Multiplexing Tool
  • AM1707 Pin Multiplexing Tool

Confirming Electrical and Timing Compatibility

A key step in the hardware design before beginning schematic capture is to confirm both DC and AC electrical compatibility between processor and the other ICs connected to it.  See the below collection of information to aid in confirming the system's electrical compatibility

• Checking I/O voltage compatibility between ICs
• Checking I/O timing compatibility between ICs
• Using IBIS Models for Timing Analysis

• Note: TI provides PCB layout specifications for the following interfaces, eliminating the need to perform electrical analysis:
  • USB

Designing the Power Subsystem

Once the block diagram has been validated for pin multiplexing, electrical, and timing compatibility, the power sub-system can be designed. See the below resources on estimating processor power consumption and designing a matching power subsystem.

• Use the Power Spreadsheet to estimate processor power in a custom application:
  • OMAP-L137 Power Consumption Summary (Power Spreadsheet)
  • C6747 Power Consumption Summary (Power Spreadsheet)
  • AM1707 Power Consumption Summary (Power Spreadsheet)

• Reuse or modify one of the existing processor power supply reference designs
  • OMAP-L137 Power Reference Designs
  • C6747 Power Reference Designs
  • AM1707 Power Reference Designs

• Key Considerations for designing the Power Subsystem:
  • Make sure to follow the supply sequencing requirements listed in the datasheet
  • Make sure to properly filter the PLL power supply according to the recommendations listed in the datasheet

Designing the Clocking Subsystem

In addition to the power subsystem, the clocking subsystem needs to be designed to provide appropriate clocks to all ICs in the system. These clocks can be created by pairing crystals with internal oscillators within the system ICs, or they can be created by a separate clock generator. See the below information on designing the clocking subsystem for your design.

Download the the new PLL, System and Peripheral Clock Calculation spreadsheet for OMAP-L137, C6747/5/3 and AM17x devices

Floorplanning the PCB

Before beginning schematic capture, it is recommended to floor plan the system PCB to determine the interconnect distances between the various system ICs. See the below information on floor planning your PCB.

• TBD: Why and How to floor plan your PCB before starting schematic capture

Creating the Schematics

At this point in the design, it is time to start capturing the schematics. See the below collection of information to aid you in creating the schematics for your design.

• It is often helpful to refer to example schematics throughout the schematic capture process:
  • OMAP-L137/C6747 EVM Schematics
  • AM1707 EVM Schematics
• Below is a collection of articles showing example connections of various components to the processor
  • Using SPI Chip Select Pin on OMAP-L138/C6747/AM1707
  • Connecting NAND Flash to OMAP-L137/C6747/AM1707
• During and after schematic capture, check your design against the schematic checklist:
  • OMAP-L13x / C674x / AM1x Schematic Review Checklist
  • TMS320C674x/OMAP-L1x USB Compliance Checklist
• Below is a link to the IBIS Simulation Models to aid in the design of the device interconnects:
  • OMAP-L137 IBIS Models.
  • C6747 IBIS Models
  • AM1707 IBIS Models
• Below is a link for selecting and placing decoupling capacitors in a BGA design
  • Decoupling Capacitor Selection and Placement for BGAs

• Key Considerations for creating the Schematics:
  • SDRAM (and other) output clocks are internally looped back
  • Don’t forget to install a JTAG connection
  • JTAG: Make sure to use the RTCK pin

Laying out the PCB

After completing schematic capture, see the below information on laying out the PCB for your system:

• It is often helpful to refer to an example layout when designing a custom PCB:
  • OMAP-L137/C6747 EVM Layout
  • AM1707 EVM Layout
• Make sure to follow the Layout Specifications for the following Critical Interfaces:
  • USB 2.0 Board Design and Layout Guidelines

• General Information Articles:
  • BGA/PCB Design for BGAs
  • Decoupling Capacitor Selection and Placement for BGAs

Testing/Debugging

Once your custom PCB has been produced and assembled, refer to the below information on bringing-up and debugging the system.

• See the below information on using GEL Files to aid in configuring your design during debug/development
  • OMAP-L137/C6747/AM1707 Debug GEL File: This can be used with CCS to print out useful debug information such as silicon revision, bootloader error messages, current PC and PSC states, and more.

• See the below information on using the debugging Tools to debug your OMAP-L137 processor
  • OMAP-L137/C6747/AM1707 JTAG

• Below is a collection of information on using the TI provided Booting Tools for OMAP-L137
  • Serial UART Boot and Flash Loading Utility for OMAP-L137/C6747/AM1707
    • You need to change the code to according to your own board configure (SDRAM and flash driver) and recompile the executable program.
  • CCS flash writer can be found in the PSP release (eg. DaVinci-PSP-SDK-03.20.00.14\src\utils\)
    • Contains flash writers for NOR/NAND/SPI-FLASH/MMCSD. These writers can be run from withing CCS to write programs to flash for boot.

• Below is a link to the OMAP-L137 BSDL Files for verifying PCB connectivity
  • OMAP-L137 BSDL File.
  • C6747 BSDL Models
  • AM1707 BSDL Models