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DS110rt410 part Reference Clock

shiva raju
Prodigy 50 points
Other Parts Discussed in Thread: DS110RT410, DS110DF410EVK

Hi

We are using DS110rt410 part re-timer in our design, when i saw reference clock requirement for this part its showing 25MHZ anlog , i observed they specifically says its analog clock for this signal all reaming signals are CMOS.

Can i give CMOS signals clock to this?

why they are specifically saying analog clock, is it mean we need to give sin wave clock only?

Thanks

Shiva

  • 0
    TI__Mastermind 29655 points

    Hi Shiva,

    The 25 MHz clock is provided by an external oscillator, usually a crystal. For example, the DS110DF410EVK features the following 25 MHz crystal with 2.5V tied to VCC :

    http://www.txccrystal.com/images/pdf/7c.pdf

    Therefore, you cannot provide a CMOS signal explicitly, since the Ref_Clk pin specifies a 2.5V LVCMOS clock, not a 5V CMOS clock. The Ref Clk you provide should be 2.5 V, 25 MHz, and should be a sine wave, since this is the waveform that external oscillators naturally generate. We specify analog clock to indicate that an external crystal oscillator is intended for use there.

    Specifications about the signaling for the Ref Clk are shown from the Electrical Characteristics Table below:

    Thanks,

    Michael

  • 0 in reply to Michael Lu (Santa Clara)
    Prodigy 50 points

    Hi

    As per above explanation we should give 2.5V 25MHZ Analog oscillator output but logic level table showing above is for 2.5V LVCMOS.

    I did not understand analog input voltage levels comparison with LVCMOS levels?

    Is there any specific voltage level for analog clock requirement?

    Thanks

    Shiva 

  • 0 in reply to shiva raju
    TI__Mastermind 29655 points

    Hi Shiva,

    The analog reference clock input can be either LVCMOS square wave or simply oscillate as a 25 MHz sine wave with 2.5Vpp if you choose to use a crystal oscillator like the one I mentioned in my previous post. The use of either square wave or sine wave for the Ref Clk input will work as long as there is a 2.5Vpp signal with 25 MHz frequency as specified in the datasheet.

    Thanks,

    Michael