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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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ITEMSECTIONSCHEMATIC CHECKLIST TOPIC
12.1Prepared to Check your Power Design?
2
2.2Adding an Oscillator?
32.2Ready to Reset?
42.3Best Boot Configuration Settings?
Make sure your design can boot properly.
52.4 & 2.6Planning for Peripheral Success?
Check your USB, I2C, UART, SPI and more in this section.
62.6Prepping for Peripheral Success?
Leaving off some peripherals? Let's check your IO in this section.
72.5Enabling eMMC?
Need non-volatile storage? Are meeting the requirements?
82.6Ready to Juggle JTAG?
Check for a properly connected JTAG to be a great debug resource.
92.6Excited about EEPROM?
Let's check your EEPROM WP pin.
103.5 Have you used your good-luck charm?
(Having ten things on a list made marketing happy.)

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

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Mandatory
PD1??????Input Power Connections: Choose a power input use case from Table 13 based on design requirements and implement mandatory connections
PD2??????In-Rush Current: The power source connected to a power input must be able to supply the necessary in-rush current: VIN_AC - ~1.2A; VIN_USB - ~0.5A; VIN_BAT - ~0.35A
PD4??????External Capacitance: ~50uF of external capacitance required on SYS_VOUT
PD5?????IO Voltage: Connect each of the six VDDSHVx pins to either SYS_VDD3_3P3V (for 3.3V I/O) or SYS_VDD_1P8V (for 1.8V I/O)(1) (See Pin Attributes section of AM335x datasheet to find the VDDSHVx domain of a pin)
PD6??????Processor – PMIC Connections: See Figure 5 and Figure 6 for mandatory connections between TPS65217C (PMIC) and AM335x processor based on required RTC mode
PD7????RTC Power Connections: See Figure 7 for VDDS and VDDS_RTC power connections
PD8????eMMC Power Connections: Connect EMMC_VCC and EMMC_VCCQ (2) to SYS_VDD1_3P3V

(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

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Recommended
PD9
??????Power Budget: Power Budget: Create a Power Budget for your design using the power app notes:
Power Application Note for OSD335x-BAS/IND
Power Application Note for OSD335x-BSM/ISM
PD10??????Clamping Circuit: Review OSD335x Clamping Circuit app note to determine if your application needs the clamping circuit
PD11??????Test Points: Add a test point on each signal if possible:
Boot Signals: PMIC_POWER_EN, RTC_PWRONRSTN, EXT_WAKEUP, EXTINTN
Reset/Control Signals: PWRONRSTN, WARMRSTN, PMIC_NRESET (1), SYS_VDD1_CTL (2)
Output Power Rails: SYS_VOUT, SYS_VDD1_3P3V, SYS_VDD2_3P3V, SYS_VDD3_3P3V (1), SYS_RTC_1P8V, SYS_VDD_1P8V
PD12??????App Notes: Understand if any app notes listed under section 3.3.1 applies to your design

(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

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Mandatory
RC1
??????Reset Connections: Choose a reset circuit use case from section 3.1.2 based on design requirements and implement mandatory connections
RC2??????OSC1 Unconnected: If the AM335x Real-Time Clock (RTC) is not used, leave pins OSC1_IN, OSC1_OUT, and OSC1_GND floating

Table 4 Reset and Clock Checklist - Recommended

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Recommended
RC3
??????Oscillator Connections: Use the oscillator circuit shown in Figure 8 for OSC0 and OSC1 clock design (1). This will allow tuning of the crystal oscillator if needed
RC4??????App Notes: Understand if any app notes listed under section 3.3.2 applies to your design

(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

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Mandatory
BC1?????Oscillator Frequency: Set SYSBOOT [15:14] to OSC0 crystal / oscillator frequency (1)
0b00     19.2 MHz
0b01     24 MHz
0b10     25 MHz
0b11     26 MHz
BC2??????CLKOUT1 Default Setting: Set SYSBOOT [5] high only if CLKOUT1 (pin XDMA_EVENT_INTR0) is used during boot for OSC0 frequency output
BC3??????Boot Mode:Set SYSBOOT [4:0] to the appropriate value from Table 26-7 of the AM335x TRM to support the required boot peripherals for the design. For example, some common boot modes include:
Value          Peripheral Boot Sequence
0b11000     SPI0 ? MMC0 ? USB0 ? UART0
0b11100     MMC1 ? MMC0 ? UART0 ? USB0
BC4??????Other Pins:Pull other SYSBOOT pins low unless they are needed for the Boot Mode
BC5??????SYSBOOT Conflicts: Check that there are no pull ups, pull downs or drivers on the SYSBOOT pins that could incorrectly modify the value of SYSBOOT before the SYSBOOT pins are sampled (i.e. reset is de-asserted)

(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

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Recommended
BC6??????Resistors: Use ~100K resistors to set SYSTBOOT pins high/low to reduce static power dissipation. Use stronger resistors only if needed. Boot configuration example shown in Figure 9
BC7??????App Notes:Understand if any app notes listed under section 3.3.3 applies to your design

2.4      USB

Table 7 USB Checklist - Mandatory

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Mandatory
UB1??????USB VBUS Sense Input: USBx_VBUS is a voltage sense input and NOT a power output pin. Check that a valid voltage (>=4.4V) is present on the pin to enable the USBx peripheral.
UB2??????USB Termination Resistors: There should be no series resistors on USBx_DP and USBx_DM lines. Additionally, do not add any external capacitors to the USB lines
UB3??????USB Routing:USBx_DP and USBx_DM traces must be length matched between the OSD335x and the USB endpoint or connector with minimal stubs
UB4??????USB Host Mode Power:Connect USBx_DRVVBUS to enable pin of external power switch/regulator to external USB devices when port in Host mode
UB5??????USB ID Connection: USBx_ID pin values:
Host Mode     Pulled to Ground
Client Mode     Floating
OTG Mode     Connected to USB client connector

Table 8 USB Checklist - Recommended

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Recommended
UB6??????App Notes: Understand if any app notes listed under section 3.3.4 applies to your design

2.5      eMMC

Table 9 eMMC Checklist - Mandatory

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Mandatory
MC1?????eMMC Pull-up Resistors: Use 10K pull-up resistors on RST#, CMD, and all DAT signals

Table 10 eMMC Checklist - Recommended

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Recommended
MC2?????eMMC Termination Resistors: Include a 22ohm series resistor on MMCx_CLK signals close to the processor to eliminate possible reflections and false clock transitions
MC3?????eMMC Connections:The AM335x supports the MMC v4.3 interface so only those signals must be connected. Any MMC v5.x signals do not need to be connected (1)
MC4?????eMMC Routing:In Figure 10, the “No Connect” (NC) pins can be routed through but “Reserved for Future Use” (RFU) pins should not be routed through to allow larger trace widths when routing the eMMC
MC5?????App Notes:Understand if any app notes listed under section 3.3.5 applies to your design

(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

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Mandatory
IO1??????Pin Mapping: If porting from legacy AM335x design, verify the pin mapping between AM335x and OSD335x using OSD335x Family Pin Assignments app note
IO2??????Pin Muxing:Verify pin mux settings using TI Pin Mux Tool. All chosen pins of a peripheral must belong to the same IO set
IO3??????UART RequirementsImplement Null Modem for all UART devices (i.e. TX -> RX; RX -> TX; CTS -> RTS; RTS -> CTS; DTR -> DSR; DSR -> DTR)
IO4??????SPI Requirements:Each SPI device should have its own Chip Select (CS)
IO5??????I2C requirements:All I2C busses must be pulled up(1)
IO6??????JTAG Requirements:EMU0 and EMU1 pins must be connected to the JTAG debugger. Add 4.75K pullup resistors on both pins (2)
IO7??????EEPROM Write Protect:Connect EEPROM_WP pin to either an external test point or ground jumper or external control logic. EEPROM_WP needs to pulled low in order to write to the EEPROM

(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

Topic No.OSD335xOSD335x-SMOSD335x C-SiPSCHEMATIC CHECKLIST TOPIC - Recommended
IO8??????Unused IO: Leave unused IO peripheral pins floating (2)
IO9??????Advanced JTAG:Connect EMU2, EMU3 and EMU4 to JTAG debug header if advanced JTAG features (HS-RTDX, Core Trace, System Trace, etc.) of high-end debuggers are required
IO10??????MII Termination Resistors: Add termination resistor footprints for TX and RX lines of MII/RMII/RGMII interfaces.
IO11??????Cape Header Compatibility:If BeagleBone® Cape Header compatibility is not required, remove the resistor MUXes between pins GPMC_A0 and GPMC_CSN3; and ECAP0_IN_PWM0_OUT and MCASP0_ACLKR (Seen in OSD335x Reference Designs)
IO12??????Static Signals with ADC:If ADC is used to monitor static voltages (e.g., 3.3V rail), then you do not need any external filter capacitors / resistors between SYS_ADC_1P8V, VSSA_ADC, VREFN and VREFP
IO13??????Unused ADC:If the ADC module is not used, connect VREFP, VREFN(1), AIN [7:0] and VSSA_ADC terminals to system ground
IO14??????App Notes:Understand if any app notes listed under section 3.3.6 applies to your design

(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

Use CasePower Input: VIN_ACPower Input: VIN_USBPower Input: VIN_BATSource ConnectionSink Connection
1????Connect VIN_AC
Connect VIN_USB
Connect VIN_BAT
Connect PMIC_TS
to Ground (1)
to Ground (1)
to PMIC_BAT_SENSE and battery (4)
to NTC thermistor of battery pack (5)
2????Connect VIN_AC
Connect VIN_USB
Connect VIN_BAT
Connect PMIC_TS		to Ground
to VBUS of USB client connector (2)
to PMIC_BAT_SENSE
to nothing (i.e. leave floating)
3?????Connect VIN_AC
Connect VIN_USB
Connect VIN_BAT
Connect PMIC_TS		to Ground
to VBUS of USB client connector (2)<
to PMIC_BAT_SENSE and battery (4)
to NTC thermistor of battery pack (5)
4????Connect VIN_AC
Connect VIN_USB
Connect VIN_BAT
Connect PMIC_TS		to 5V DC Power Supply (3)
to Ground
to PMIC_BAT_SENSE
to nothing (i.e. leave floating)
5?????Connect VIN_AC
Connect VIN_USB
Connect VIN_BAT
Connect PMIC_TS		to 5V DC Power Supply
to Ground
to PMIC_BAT_SENSE and battery (4)
to NTC thermistor of battery pack (5)
6?????Connect VIN_AC
Connect VIN_USB
Connect VIN_BAT
Connect PMIC_TS		to 5V DC Power Supply
to VBUS of USB client connector (2)
to PMIC_BAT_SENSE
to nothing (i.e. leave floating)
7??????Connect VIN_AC
Connect VIN_USB
Connect VIN_BAT
Connect PMIC_TS		to 5V DC Power Supply
to VBUS of USB client connector (2)
to PMIC_BAT_SENSE and battery (4)
to NTC thermistor of battery pack (5)

(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 NumberRevision DateChangesAuthor
35/30/2019Restructured document for readability with charts, added C-SiP info and USBx-VBUS  E. Basu

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