• Resolved

TPS43336-Q1: External clock frequency

Part Number: TPS43336-Q1

 Hi team,

   Please let me ask you a question about TPS43336Q1.

   When an external clock outside specification frequency range is input to the SYNC pin,
   how does the TPS43336Q work?

   For example, the external clock frequency of 400 kHz is input to the Sync pin usually.
   If the external clock frequency change to 40kHz or4MHz,
   how will the TPS43336Q work?

 Best regards.
 Tsuyoshi Tokumoto

  • Hi Tsuyoshi Tokumoto,

    We test our parts to operate within the given parameters in the datasheet. Hence, we cannot guarantee the performance and reliability of the part, when operating outside of those parameters. We do not recommend that you operate the part outside of specifications. If the part does not meet your performance needs maybe we can provide you with an alternative solution.

    http://www.ti.com/product/tps43336-q1/description

    -Ray

  • In reply to Raymundo Hernandez-Toscano:

    Hi Raimundo_san,

    Thank you very much for your prompt reply.
    I understand your opinion and suggestion.

    However, please let me ask for you advice again.

    As a background,my customer designs automotive products.
    He decides to use the TPS43336Q to next product.

    From the viewpoint of FMEA,he wants to understand the behavior of
    TPS43336Q in the case of abnormal state.

    Therefore, he wants to understand how it will work,
    if an external clock outside specification frequency range is input to the SYNC pin.
    (It is not a request that he wants us to guarantee it.)

    From the above, could you please answer the following inquiry?

      ①Is there a possibility that the operation clock of the TPS43336Q switches between internal and external,
                even though a same frequency(for example,40kHz or 4MHz) external clock is input to the SYNC pin?
      ②Is there a possibility that the output voltage of the TPS43336Q goes to above and below from the range
                that the customer designed?
      ③Is there a tendency of behavior for low frequency(40kHz) and high frequency(4MHz)?

    Based on the above answers, he intends to design the system.


    Best regards.
    Tsuyoshi Tokumoto

  • In reply to tsuyoshi tokumoto:

    Tokumoto-san,
    As Raymundo correctly pointed out, the part is not specified below 150kHz and above 600kHz external clock frequency, so applying a clock outside this range is entirely at customers own risk.
    My ASSUMPTION (!) is:
    The PLL will likely still be able to lock to a frequency slightly above or below the given range and thus operate at that clock
    At such extreme values as 40kHz or 4MHz, it will most likely not be able to lock to such a frequency and interpret this as "loss of clock" and switch at the fall-back-frequency (note: there will be limited regulation-capabilities during the change of clocks). The default clock would be 400kHz typical. We do recommend to use a RT-resistor that sets a frequency close to the (desired!) external clock.
    To your questions:
      ①Is there a possibility that the operation clock of the TPS43336Q switches between internal and external,
    even though a same frequency(for example,40kHz or 4MHz) external clock is input to the SYNC pin?
    --> unlikely that it switches between internal and such extreme external frequencies. However, it the SYNC-pin is toggling, it will likely attempt to synchronize to "something" and during the "transition" customer has to expect limited regulation capabilities (variance on Vout, in particular in case of line- or load-transients)
      ②Is there a possibility that the output voltage of the TPS43336Q goes to above and below from the range
    that the customer designed?
    --> yes, per above.
      ③Is there a tendency of behavior for low frequency(40kHz) and high frequency(4MHz)?
    --> the part will not be able to switch at such frequencies.
    Bottom line: the customer should design the system in a way that either the correct clock (between 150kHz and 600kHz) is applied, or NO clock is applied.

    Best regards,
    Frank
  • In reply to Frank Dehmelt:

    Frank_san,

      I apologize for the delay in my response.

      Thank you very much for your prompt reply and detailed explanations.

      I am always helped by your advice!


    Best regards.
    Tsuyoshi Tokumoto