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LMZM33606: About reaction speed of external synchronization function

Part Number: LMZM33606
Other Parts Discussed in Thread: LMZM33603, , , LMZM33603EVM

Hi,

Customers are considering LMZM33606 and LMZM33603.
Customers want to know the specifications described below.

1.The time that LMZM33606/3 follows when synchronized from resistor setting.

2.The time to follow when changing external synchronous frequency.
      And output voltage fluctuation when synchronous frequency is changed.

Could you give me your advice?

Best Regards,
Yusuke

  • Hi Yusuke,

    Is there a specific application condition you want to test for (VIN/VOUT/IOUT/FSW)?

    For the LMZM33606 the device starts out first in RT mode based on the resistor setting. After presenting a valid external clock to SYNC, the device transitions to SYNC mode and with the appropriate switching frequency within 1ms (typical). Once in SYNC mode I'd expect the device to change instantly as the switching frequency is changed. As for the output voltage fluctuation, I don't expect much but I would have to test your condition to provide a value.

    I'd expect the LMZM33603 to react in a similar fashion with regards to external synchronization.

    Regards,

    Jimmy

  • Hi Yusuke,

    I got some additional information for the LMZM33603.

    Here are the following synchronization response:

    • ~100us response to SYNC pulse
    • ~20mV overshoot with a 50uF response time

    Regards,

    Jimmy

  • Jimmy-san,

    Thank you for your kind support.
    I summarized your advice below.
    Is my understanding correct? 
    If there are corrections or any additional information that is necessary please modify it. 

    -------
    ◇LMZM33603
    1.The time that LMZM33603 follows when synchronized from resistor setting.
          And output voltage fluctuation when synchronous frequency is changed.

    →100us response to SYNC pulse. 
    → 20mV overshoot with a 50uF response time

    2.The time to follow when changing external synchronous frequency.
          And output voltage fluctuation when synchronous frequency is changed.

    →100us response to SYNC pulse. 
    → 20mV overshoot with a 50uF response time

    ◇LMZM33606
    1.The time that LMZM33606 follows when synchronized from resistor setting.
          And output voltage fluctuation when synchronous frequency is changed.

    →"1ms (typical)." 
    →No answer
     "As for the output voltage fluctuation, I don't expect much but I would have to test your condition to provide a value."

    2.The time to follow when changing external synchronous frequency.
          And output voltage fluctuation when synchronous frequency is changed.

    →"1ms (typical)."
    →No answer
     "As for the output voltage fluctuation, I don't expect much but I would have to test your condition to provide a value."
    -------

    Best Regards,
    Yusuke

  • Jimmy-san,

    Thank you for your support.
    Do you have any update ?
    Sorry for rushing you.

    Best Regards,
    Yusuke

  • Hi Yusuke-san,

    My hope is to spend some time today in the lab to bench test the synchronization on the LMZM33606EVM and provide you information today or by latest tomorrow similar to the data I got for LMZM33603. Sorry for the delayed response and I hope to answer your question soon.

    Regards,

    Jimmy

  • Hi Yusuke-san,

    I was able go to the lab and get better scopeshots to illustrate the results.

    First is the LMZM33606EVM. The time it takes for the device to change switching frequency after a SYNC is asserted comes out to roughly 1ms. This can be measured from the time SYNC was high to the time the SW node changes switching frequency. The overshoot during the transition between two different frequency is roughly 6mV. The recovery time is about ~60us.

    Also attached is the test on the LMZM33603EVM. The time it takes to transition between switching frequency is 110us. The overshoot is around 10mV with a recovery time of ~60us.

    I hope these two scope shots provide a better understanding of the synchronization feature for both LMZM33606 and LMZM33603 power modules.

    Regards,

    Jimmy

  • Jimmy-san,

    Thank you for your strong support.
    I understood about the output voltage fluctuation and time accompanying the frequency change.
    I will report your test results to the customer.

    There is one more thing I would like to ask you.
    Is the time to shift from the resistor setting to SYNC mode the same?

    ”The time that LMZM33606 and LMZM33603 follows when synchronized from resistor setting.
    And output voltage fluctuation when synchronous frequency is changed.”

    Could you give me your advice?

    Best Regards,
    Yusuke

  • Yusuke-san,

    The EVM data I've collected and what you see in the two images describes the transition between resistor setting (RT mode) and SYNC. The device first starts switching based on the RT value that is on the EVM. Afterwards, I asserted a higher frequency clock signal from an external function generator to switch the device to SYNC mode such that the switching frequency now mirrors the SYNC frequency. The scope shot was triggered off the SYNC rising edge to show how long it takes for the SYNC to get recognized by the device when in RT mode. The two images shown should answer question 1 and the second half of question 2.

    To answer the first half of question 2. "The time to follow when changing external synchronous frequency." The answer is the maximum delay when changing external synchronous frequency is the switching cycle. The PLL should respond within one switching cycle between new asserted switching frequencies. I expect this to the be the general answer to this question for most regulators.

    Here is a reference to that question:

    Regards,

    Jimmy