RAA210040 | what will happen when the device loses synchronization during operation?

Hello Team,

I am promoting The RAA210040 to customer who had serval projects.

The question from the engineer is regarding the external synchronization of this module.

What happens when the device loses synchronization during operation and what is the likelihood that it will occur?

Waiting for your kind feedback, thanks a lot.

KR,

Shai

  • Hi Shai, 

    As per recommendation external  SYNC frequency should be within ±25% of the switching frequency set by the FS . So It will work properly/ not loses the synchronization.  

    Thanks 

    AB

  • Hello ,

    Thanks a lot for your input, but the question that the customer has asked is, what would happen when for any reason the device loses the synchronization?

    Thanks in advance

    KR,

    Shai

  • ,

    I trust this message finds you well. The customer has inquired about the potential consequences in the event of a loss of synchronization with the device for any reason.

    Could you kindly provide clarification regarding the resultant effects or outcomes? Thank you very much for your assistance.

    KR,

    Shai

  • Hi, 

    I will check & come back to you

    Thanks

    AB 

  • Hi, 

    If customer use SYNC pin, it should be notes that using an external SYNC frequency within ±25% of the switching frequency set by the FS pin.

    To avoid big change of operational frequency in the event of a loss of synchronization. We have instructions on DS as below.

     

    And our die has an internal 1MΩ pull-down resistor to prevent an undefined logic state in case of SYNC pin float.

    This means that if the SYNC signal is lost, the module will switch to PFM mode and the frequency will change to the switching frequency set by the FS pin at higher load.

    The attachment are some waveforms under steady state, with different SYNC frequency and FS resistors. SYNC has higher priority but should avoid the situation that SYNC is pull down and fs resistor is floating.

     

    And we have some compare test for SYNC switching process and find two issues:

    1. iout=4A, Vin=5V, Vout=2.5V, SYNC 1Mhz change to pull-down, FS floating.

    Cause to hiccup mode after SYNC pull-down, Vout is not stable. So, FS cannot float.

    1. Iout=0.5A, Vin=5V, Vout=2.5V, SYNC 2Mhz change to pull-down, FS resistor to 200kohm(1Mhz).

    Vout ripple is big if frequency change obviously at the time of SYNC ON and SYNC OFF.  Recommend the external SYNC frequency within ±25% of the switching frequency set by the FS pin.

    Thanks 

    AB