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LM5145: SYNCOUT Specification

hideyuki sakai
Mastermind 6250 points
Part Number: LM5145
Other Parts Discussed in Thread: LM5175-Q1

Dear, Sir.

My customer is utilizing SYNCOUT function on LM5145. They are asking the

specification of it at this time.

1. SYNCOUT Output Volatge.

a)The datasheet is defined min. 3V, but real voltage  is not clear.

   Please let me know how to calculate maximum SYNCOUT volatge.

b)If above voltage is depended on the source/sink current, Please clarify the

  correlation chart SYNCOUT volatge & Source/sink current.

2. SYNCOUT Duty.

a)Please clarify the min. & max duty of SYNCOUT signal.

Please give your advice.

Best Regards,

H. Sakai

  

  • 0
    TI__Mastermind 35210 points

    Sakai-san,

    It sounds like the customer is interested in getting very specific information in regards to the clock and clock timing of the device.

    I will need to consult with the design team on this. 

  • 0 in reply to Marshall_Beck
    TI__Guru 72782 points

    Hi Sakai-san,

    SYNCOUT can only pull up to approximately the internal VDD voltage, which is loosely regulated to 5V.

    With no SYNCIN applied, the SYNCOUT duty cycle is always 50%.  It’s just shifted in time by ~140ns. With SYNCIN applied, the SYNCOUT duty cycle will be lower depending on the SYNCIN frequency.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    Mastermind 6250 points

    Dear, Tim-san. 

    Thank you so much for all of your advice. 

    My customer is using LM5145 with external Sync(SYNCIN) = 425 ~ 500kHz, around 50% duty. 

    And LM5145's SYNCOUT is provided to following LM5175-Q1. 

    Now, they are checking the validness of their design. So, I would like to make sure more deeply.

    Please give your advice, again. 

    1. You mentioned that "SYNCOUT can only pull up to approximately the internal VDD voltage, which is loosely regulated to 5V.". 

        Following LM5175-Q1 has the peak signal limit as 3.3V. Is it possible to clarify the range of SYNCOUT voltage? 

    2. They are using SYNCIN = 425 ~ 500kHz, around 50% duty. 

        Is it possible to clarify CYNCOUT duty accuracy under this condition? 

    Best Regards, 

    H. Sakai

  • 0 in reply to hideyuki sakai
    Mastermind 6250 points

    Dear, Tim-san. 

    Sorry to disturb your job again & again. 

    I am expecting your advice one more time. 

    Best Regards, 

    H. Sakai

  • 0 in reply to hideyuki sakai
    TI__Guru 72782 points

    Hi Sakai-san,

    The value of the RT resistor for the LM5145 is important. If the SYNCIN frequency is close to the free-running oscillator frequency, then the SYNCOUT signal will be 50% duty cycle. Also, the SYNCOUT signal amplitude will be 5V, so this should be considered when interfacing to the LM5175-Q1 buck-boost controller.

    Regards,

    Tim