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AM2432: A Few Clock-related Questions

Mari Tsunoda
Expert 5726 points

Part Number: AM2432

Hi Team,

My customer has a few questions regarding clock inputs.

1) Related to the datasheet p207, Figure 7-19. 1.8-V LVCMOS-Compatible Clock Input: If Main domain boots first, and subsequently boots the MCU domain, why is the clock source or Xtal is connected to MCU_OSC0_XI terminal on EVM board? (the terminal seems to belongs to MCU domain)

2) Can the system clock be input to EXT_REFCLK1 terminal? According to the TRM p2913, it seems that the clock signal input from this terminal is distributed to limited modules.

3) When Clock oscillator (not Xtal) is used, what is the frequency range? (Datasheet p205, Table7-18 only shows when Crystal Resonator is used)

Best regards,

Mari Tsunoda

  • +1
    TI__Expert 8400 points

    Hi Mari,

    To address your questions:

    1) The terminal does belong to the MCU domain, the PLLCTRL0 inputs in the Main Domain are driven by default from the MCU_HFOSC0. The reason this does not conflict with the boot sequence of our device is because, by default, MCU_HFOSC0 is enabled right after MCU_PORz. This pin is held in reset until all power supplies are stable upon power-on.

    For more information please refer to section 5.3.1 Overview (Reset Overview) and 5.4.4.1.1 Oscillator with External Crystal of the TRM

    2) EXT_REFCLK1 is an optional external clock input to the Main Domain, there is no internal loopback from the MAIN_SYSCLK0 into EXT_REFCLK1. While Figure 5-676 MAIN Domain PLLs Integration does not show it, this input is also used as a reference clock to MAIN_PLL2 (PER1 PLL).

    3) The datasheet requirements also applies to clock oscillators if this is being used instead of a crystal (25MHz requirement to ensure correct operation).

    Hope this helps.

    Best,
    Daniel Bermudez

    Link to TRM: https://www.ti.com/lit/ug/spruim2c/spruim2c.pdf?ts=1646691026744&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FAM2434

  • 0 in reply to Daniel Bermudez
    TI__Expert 5726 points

    Hi Daniel,

    Thank you for your timely response!

    I've relayed this information to my customer and will mark this thread as resolved!

    Best regards,

    Mari