OSD335x Schematic Checklist – AM335x System in Package

Published On: May, 30, 2019 By: Eshtaartha Basu

OSD335x Schematic Checklist - AM335x System in Package

This document provides a generic OSD335x schematic checklist to help users review designs built around the OSD335x, the AM335x System in Package, Family of Devices.  Going through this checklist before or during the schematic design phase will help avoid some common pitfalls. This OSD335x schematic checklist targets a generic embedded system and is not exhaustive. Each design is unique and your custom design may require additional in-depth verification to validate its overall functionality.

The first section of the OSD335x schematic checklist document consists of various sub system checklists to help you validate your design. The second section (i.e., Appendix) consists of supplemental information which will be referenced from the first section to further aid your design validation.

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Table of Contents

1.Introduction
2.OSD335x Schematic Checklists
2.1Essential Connections and Power Design
2.2Reset and Clock
2.3Boot Configuration
2.4USB
2.5eMMC
2.6Other Interfaces
3.Appendix
3.1Use Cases
3.1.1Power Input
3.1.2Reset Circuit
3.2Reference Figures
3.2.1Minimal Connections
3.2.2Crystal Circuit Example
3.2.3Boot Configuration Example
3.2.4eMMC Pinout
3.3Useful App Notes and Links
3.3.1Power Design
3.3.2Reset and Clock
3.3.3Boot Configuration
3.3.4USB
3.3.5eMMC
3.3.6GPIO and Other Interfaces
3.4References
4.Revision History of this Document

A PDF version of this App Note can be found here.

Notice
The information provided within this document is for informational use only. Octavo Systems provides no guarantees or warranty to the information contained.

 

2.      OSD335x Schematic Checklists

2.1       Essential Connections and Power Design

Table 1 Essential Connections and Power Design Checklist - Mandatory

(1) In OSD335x-BAS, all VDDSHVx signals are internally connected to SYS_VDD3_3P3V. Therefore, level shifters are required for any I/O voltage other than 3.3V.
(2) If necessary, can power eMMC using external 3.3V supply instead of SYS_VDD1_3P3V.

Table 2 Essential Connections and Power Design Checklist - Recommended

(1) Not available on OSD335x-BAS.
(2) Only available on OSD335x C-SiP.

2.2       Reset and Clock

Table 3 Reset and Clock Checklist - Mandatory

Table 4 Reset and Clock Checklist - Recommended

(1) In OSD335x C-SiP, 24MHz MEMS Oscillator is internally connected to OSC0 of AM335x. The MEMS Oscillator is enabled by an internal pull-up. Hence, add a test point to OSC0_CTL to have the flexibility of external control.

2.3       Boot Configuration

Table 5 Boot Configuration Checklist - Mandatory

(1) In OSD335x C-SiP, SYSBOOT [15:14] = 0b01 to match the 24 MHz MEMS oscillator frequency within the device.

Table 6 Boot Configuration Checklist - Recommended

2.4      USB

Table 7 USB Checklist - Mandatory

Table 8 USB Checklist - Recommended

2.5      eMMC

Table 9 eMMC Checklist - Mandatory

Table 10 eMMC Checklist - Recommended

(1) OSD335x C-SiP comes with an integrated eMMC. Adding an external eMMC is not necessary.

2.6      Other Interfaces

Table 11 Other Interfaces Checklist - Mandatory

(1) I2C0 pins have internal 4.7K pull up resistors. However, we recommend adding external pull up resistor footprints for I2C0 if more than two (2) external devices use I2C0 to allow for stronger pull ups.
(2) The internal pull-ups on EMU0 and EMU1 are typically weak and therefore external pullup resistors (~4.75K) are recommended. See EMU Considerations section of XDS Target Connection Guide.

Table 12 Other Interfaces Checklist - Recommended

(1) VREFN is not externally accessible on OSD335x-BAS.
(2) Exceptions: Topic IO13.

3.       OSD335x Schematic Checklist Appendix

3.1      Use Cases

3.1.1      Power Input

Table 13 Power Input Use Cases

(1) See Figure 62 of TPS65217C datasheet.
(2) Increasing USB input-current limit may be necessary. See section 8.6.3 of TPS65217C datasheet.
(3) See Figure 61 of TPS65217C datasheet.
(4) DC Power supply can be used in lieu of a battery if no OVP is required
(5) 10K resistor to ground may be substituted if battery pack has no NTC thermistor (i.e. temperature monitoring)

3.1.2      Reset Circuit

The different Reset Configurations supported by the OSD335x Family of Devices are described below. Use the Reset Circuit Selection Guide (Figure 1) to choose a Reset Circuit Use-Case that best suits your design requirement. (Please note that in the AM335x Technical Reference Manual, Section 8.1.7, the WARMRSTN signal may also be called nRESETIN_OUT):

Reset Circuit Selection Guide - OSD335x Schematic Checklist - AM335x System in Package
Figure 1 Reset Circuit Selection Guide
  • Use-Case 1: In this Use-Case:
    • WARMRSTN is used as input.
    • WARMRSTN is controlled by PWRONRSTN.
    • No external components are controlled by WARMRSTN
    • No manual control of WARMRSTN is available.
Reset Circuit Use-Case 1
Figure 2 Reset Circuit Use-Case 1

 

  • Use-Case 2: In this Use-Case:
    • WARMRSTN is used as both input and output.
    • WARMRSTN is controlled by PWRONRSTN.
    • The reset lines of external components are tied to WARMRSTN.
    • Manual control of WARMRSTN is made available.

(NOTE: OSD335x C-SiP integrates an open drain buffer internally connected to PWRONRSTN. See OSD335x C-SiP Reset Circuitry section of OSD335x C-SiP Design Tutorial).

Reset Circuit Use-Case 2
Figure 3 Reset Circuit Use-Case 2
  • Use-Case 3: In this Use-Case:
    • A dedicated Reset Supervisor circuit is used to manage reset circuitry.
    • WARMRSTN is used as both input and output.
    • WARMRSTN is controlled by PWRONRSTN.
    • The reset lines of external components are tied to WARMRSTN.
    • Manual control of WARMRSTN (and debouncing of push button) is made available through reset supervisor.

(NOTE: OSD335x C-SiP integrates an open drain buffer internally connected to    PWRONRSTN. See OSD335x C-SiP Reset Circuitry section of OSD335x C-SiP Design Tutorial).

Caveat
If you intend to use VIN_BAT (battery) input below 4V, make sure the reset threshold of the supervisor circuit does not conflict with the operating range of the battery and reset the processor prematurely as the battery voltage drops during operation. Choose a supervisor circuit with a suitable threshold that can support the required operating range of your battery.
OSD3358-SM-RED reset mechanism Reset Circuit Use-Case 3
Figure 4 OSD3358-SM-RED reset mechanism (Reset Circuit Use-Case 3)
Perk
For more information on Reset Circuit, see Reset Circuitry article of OSD335x Tutorial Series.

3.2      Reference Figures

3.2.1      Minimal Connections

Minimum set of connections when RTC subsystem is enabled
Figure 5 Minimum set of connections when RTC subsystem is enabled

 

Minimum set of connections when RTC Subsystem is disabled
Figure 6 Minimum set of connections when RTC Subsystem is disabled

 

VDDS_RTC and VDDS Power Connections_RTC-only Power Mode Disabled
Figure 7 VDDS_RTC and VDDS Power Connections (RTC-only Power Mode Disabled)

 

3.2.2      Crystal Circuit Example

Example crystal circuit
Figure 8 Example crystal circuit

3.2.3      Boot Configuration Example

Boot configuration example_OSD3358-SM-RED
Figure 9 Boot configuration example_OSD3358-SM-RED

3.2.4      eMMC Pinout

eMMC v5.x pinout
Figure 10 eMMC v5.x pinout

3.3      OSD335x Schematic Checklist Useful App Notes and Links

3.3.1      Power Design

3.3.2      Reset and Clock

3.3.3      Boot Configuration

3.3.4      USB

3.3.5      eMMC

3.3.6      GPIO and Other Interfaces

3.4    OSD335x Schematic Checklist References

3.5      Contact Us

Please contact us on the forums for assistance with any checklist items or to tell us more things you’d like to see on this list. Our team is ready with more than a good-luck charm to help you with your designs. https://octavosystems.com/forums/

4.      Revision History

 
Revision Number Revision Date Changes Author
3 5/30/2019 Restructured document for readability with charts, added C-SiP info and USBx-VBUS   E. Basu