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Best way to generate 200KHz clock ?

Alessandro Giacometti
Prodigy 145 points
Other Parts Discussed in Thread: SE555, TLC555, CDCE913

Hi all,

I need to generate a 200KHz clock. I'm looking the SE555 IC but I'm worried about the accuracy.

Can anyone suggest me other solutions to get the best 200KHz clock?

Thanks in advance. Best Regards

  • 0
    TI__Guru*** 140136 points

    Alessandro,

    You are correct to worry about accuracy with the SE555 at 200kHz. Propagation delay become a very significant factor at that frequency. TLC555 is faster, it is not "best" 200kHz clock.

  • 0 in reply to Ron Michallick
    Prodigy 145 points

    Hi Ronald,

    there's any other IC which generates a 200KHz clock with the period as stable as possible ?

  • 0 in reply to Alessandro Giacometti
    TI__Guru*** 140136 points

    Alessandro,

    Yes, there are devices. However, I only support the 555 timers in this forum.  
    There are others monitoring this forum who will provide a solution.

    Can we assume best stability at any cost?

  • 0 in reply to Alessandro Giacometti
    TI__Expert 5325 points

    Hello Alessandro,

    how stable does the clock need to be? Can you share your requirements?

    How many outputs of the 200kHz do you need and which signaling standard do you have in mind?


    We have some general purpose clock generators which can achieve these low frequencies.

    You could use a CDCE913. It has one internal PLL. In this case we would bypass it and just use the output divider (up to 127).

    For example you put a 20MHz crystal and you can generate three LVCMOS 200kHz by setting all output dividers to 100.

    The CDCE913 comes with an EEPROM and I2C. So you have various options how to program it. This comes from a whole family of devices with up to four internal PLLs and up to nine outputs.

    So if this is good enough for you can generate 9x 200kHz. If that is still not enough clocks, you can check out our buffers.

    Best regards,

    Patrick

  • 0 in reply to Patrick Kammermayer
    Prodigy 145 points

    Hello Patrick

    thanks for your reply.

    Your suggestion i ìs good. I need only one output and I don't have avaible the I2C line.

    However I see that the CDCE913 can be configured by the S0,S1,S2 pin replacing the I2C.

    Can I configure the CDCE913 to have 200KHz only by S0,S1 and S2?

    My requirements are:

    f = 200KHz

    Frequency tolerance Δf/f = +- 100ppm

    output rise time = 30 ns

    output fall time = 30 ns

    Vo = 5 V

    Best regards.

  • 0 in reply to Alessandro Giacometti
    TI__Expert 5325 points

    Hello Alessandro,

    there is no pure pin-programmable mode to set the dividers directly. 100ppm of 200kHz can be achieved using the CDCE913.

    Depending on your volume you could either program the EEPROM before the assembly or you buy them pre-programmed (TI or distributor).

    Unfortunately we do not have any devices which support 5V directly. I am pretty sure there are some nice op amps from other colleagues to take care of that amplification.

    Best regards,

    Patrick