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TMS320C5517: USB power connection

user5844389
Prodigy 90 points
Part Number: TMS320C5517
Other Parts Discussed in Thread: TMS320C5505, , TMS320C5515

Our product use the TMS320C5505 and will change the hardware architecture.
However, the TMS320C5505 is "NRND" status. Therefore, we will change from the TMS320C5505 to the TMS320C5517.
We have checked the CLK_SEL information in the datasheet.
The system clock of the TMS320C5505 can use the 32.768kHz(RTC OSC) and the system clock of the TMS320C5517 cannot use the 32.768kHz(RTC OSC).
We will use a 12MHz(USB OSC) for the TMS320C5517.

Our hardware architecture doesn't use the TMS320C5517 USB function.
Therefore, when the TMS320C5517 USB function isn't used,we cannot understood the USB power connection method.
We understood the USB power connection as the following but is this correct?


USB_MXI,USB_MXO:Connect to the crystal connection
USB_VSSOSC:Connect to the crystal load capacitors
USB_VDDOSC:Connect to the 3.3V power
USB_VDDA3P3:Connect to the 3.3V power
USB_VSSA3P3:Connect to the ground
USB_VDDPLL,USB_VSSPLL,USB_VDD1P3,USB_VSS1P3,USB_VDDA1P3,USB_VSSA1P3:Connect to the ground

  • 0
    TI__Mastermind 30140 points
    Hi,

    There are a few hardware differences between C5505/15 and C5517. Refer to the appnote Migrating from TMS320C5515 to 5517 www.ti.com/.../sprabl8

    Plan on using the I2S ports in slave mode (where a codec provides bit clock and word clock to the C5517 I2S ports). McBSP can be used as clock master.

    Regarding the connections to disable USB permanently...

    On C5517, CLK_SEL determines whether the 12MHz USB crystal (CLK_SEL = 0) is fed to the PLL or if an LVCMOS clock signal on the CLKIN pin is used (CLK_SEL = 1). If you only ever use CLKIN (CLK_SEL = 1), then you may ground the USB power supplies and terminate USB signals according to the datasheet (www.ti.com/.../tms320c5517)

    Datasheet Table 4-11. USB2.0 Signal Descriptions includes recommendations for terminating USB power supplies and crystals. Look for "When the USB peripheral is not used,"

    Datasheet Figure 5-12. Connections when USB Oscillator is Permanently Disabled also descripes these signal terminations.

    USB_VDDOSC should be connected to ground (VSS).
    USB_MXI should be connected to ground (VSS).
    USB_MXO is left unconnected (FLOATING)
    USB_VSSOSC signal is connected to board ground (VSS)
    USB_VBUS signal should be connected to ground (VSS).
    USB_DP and USB_DM signals should both be tied to ground (VSS)
    USB_R1 signal should be connected via a 10-kO resistor to USB_VSSREF.
    USB_VSSREF signal should be connected directly to ground (Vss).
    USB_VDDA3P3 signal should be connected to ground (VSS).
    USB_VDDA1P3 signal should be connected to ground (VSS).
    USB_VDD1P3 signal should be connected to ground (VSS).
    USB_VDDPLL signal should be connected to ground (VSS).


    See also this thread, and my response that links to the C5517 PLL Calculator tool. This spreasheet can be used to validate PLL settings on the C5517 device. The PLL is different from C5505/15 to C5517.

    e2e.ti.com/.../677738

    Reagrds,
    Mark
  • 0 in reply to Mark M
    Prodigy 90 points

    Thanks for the speedy response to that question.

    Datasheet Table 4-11. USB2.0 Signal Descriptions includes recommendations for terminating USB power supplies and crystals. Look for "When the USB peripheral is not used,"
    →We use the 12MHz USB crystal(CLK_SEL=0) and don't use the USB peripheral.
    When the USB peripheral is not used, the USB_VDDOSC and the USB_VDDA3P3 should be connected to ground(VSS) in the dataheet Table4-11.
    However,when the 12MHz USB crystal is used, the USB_VDDOSC and the USB_VDDA3P3 connect to the 3.3V in the datasheet Figure5-11.
    The USB_MXI and USB_MXO power domain is the USB_VDDOSC. Therefore,we think that cannot operate the 12MHz USB crystal if the USB_VDDOSC be connected to ground(VSS).
    Which expression is correct? We want to know the USB power connect condition with the 12MHz USB crystal operating state and the USB peripheral non-operating state.
    Should the USB_VDDOSC and the USB_VDDA3P3 connect to 3.3V and the other USB power pin connect to VSS?
    (*The other USB power:USB_VDDA1P3,USB_VDD1P3,USB_VDDPLL)

    Regards.

  • 0 in reply to user5844389
    TI__Mastermind 30140 points
    Hi,

    Sorry I misunderstood your question. You wish to use the USB oscillator as the system clock, but you do not need the USB peripheral. Is that right?

    I am not finding any recommendation for that scenario. But obviously you cannot ground all USB supplies and expect the USB oscillator to function. Customers usually use an off-chip clock oscillator into the CLKIN pin or use USB as a device.

    To play it safe, I would power all of the USB supplies. I'm not certain what would happen if you grounded the supplies that are possibly not required just to use the USB oscillator like USB_VDDPLL or USB_VDDA3P3. It was not tested in that way could cause problems like an internal leakage path to ground.

    Both 3.3V and 1.3V rails are required. If the USB oscillator is chosen as the clock source (CLK_SEL = 0), then the 1.3V USB_LDO is enabled at reset and cannot be disabled by software. The USB LDO is intended to supply the 1.3V rails USB_VDD1P3 and USB_VDDA1P3.

    processors.wiki.ti.com/.../How_to_process_unused_USB_pins_of_DM6446
    I like this example, where the DM6446 is not using the USB but keeps it powered. In this case the oscillator is not used to clock the system and they use digital supplies to replace analog supplies. I would avoid that here with the sensitive USB oscillator responsible for clocking the chip.

    The terminations for DP/DM, VBUS, and USB_R1 seem fine, however.

    In software, the clock to the USB peripheral may be gated to keep the active power of the peripheral down. Power consumption may be estimated and compared (grounded vs idle vs active). Check out the Estimating Power Consumption on the TMS320C5517 appnote and spreadsheet: www.ti.com/.../sprabv3

    Hope this helps,
    Mark
  • 0 in reply to Mark M
    Prodigy 90 points

    Dear Mark Mckeown

    >Sorry I misunderstood your question. You wish to use the USB oscillator as the system clock, but you do not need the USB peripheral. Is that right?

    →Yes. That's right.

    Thank you very much. I have understood your comment and I think that the all power pins should connect to the power lines for safety.

    Regard.