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LTM8063 Sync pin sampling

the operation mode (burst mode, pulse-skipping, spread-spectrum) is selected via the Sync pin. Is the state of this pin only sampled during startup or can one change the operation mode on-the-fly?
To enter enable spread-spectrum mode a voltage of 2.9 - 4.2 V is needed. If the mode can be set continuously, a voltage divider on the LTM8063 output could supply this voltage.

  • Hi engineer42,

    I am not sure if it is advisable to change modes while the regulator is working. You can try simulating a design like this in LTspice or make a prototype design and observe if issues will arise.

  • Thank you very much,

    i did some simulations in LTspice but i am not sure how accurate the model is.
    Under certain conditions the output voltage would not rise to the desired value but stay well below it.
    Today i found the following statement on page 1 of the DC2494 evaluation board datasheet :
    Once JP1 is on SPREAD SPECTRUM position, an external DC source can be applied to the SYNC pin to enable low EMI spread spectrum operation. This DC source can also be generated from Vout with appropriate voltage divider if VOUT is 2.9V or higher.

    This suggests that one can use VOUT to set Sync pin to 2.9 - 4.2 V for spread spectrum mode. However the datasheet of the LTM8063 doesn't mention this option. Is there any further information about it e.g. in case of long ramp up times or low input voltage?

  • Hi engineer42, for LTM8063 operation mode can be adjusted on the fly. LTM8063 has the spread spectrum mode when you tie SYNC pin between 2.9V and 4.2V. The low input voltage or long ramp up time should not impact on the function of SYNC pin.

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