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About LM27403

Kissn Liu
Expert 1245 points
Other Parts Discussed in Thread: LM27403, LM10011

those days i am look into LM27403,and here is my question:

1、what is SYNC pin used for ? did the SYNC frequency influence the value of the inductor?

2、in my design,the input voltage is  6-20v, output current is 5A MAX

     if i want to dynamicly control the output voltage  from 3.0 - 4.5V with 10mv step by mcu,do this application can be realized?

can this be reached by adjust electronical  potentiometer of the feedback resistor,and i have seen that when the feedback resistor changes,the error amp component will change.

  • 0
    TI__Guru 73072 points

    Hello Kisn,

    Please consider the LM10011 to dynamically adjust the output voltage. The SYNC pin is used when an external synchronization signal is available at the required switching frequency. The free-running switching frequency is set an external resistor at the FADJ pin.

    Tim

  • 0 in reply to Timothy Hegarty
    Expert 1245 points
    Hi,Tim
    1. that is to say if i attached the sync pin to 1MHz PWM signals,the switch frequency of the BUCK will be 1MHz?
    2.did the duty cycle of the PWM influence the output voltage of the circuit?
    3.did you confirm the LM10011 can dynamically control the output of the voltage by step of 10mV with the output range from 3.0V to 4.5V?
  • 0 in reply to Kissn Liu
    TI__Guru 73072 points

    Kissn,

    1. Yes, that's correct, the switching frequency locks in frequency and phase to the applied SYNC frequency. For more details, see the LM27403 datasheet.

    2. The duty cycle corresponds to D = Vout / Vin.

    3. The LM10011 provides 6 bits of resolution or 64 steps. This corresponds to 23.4mV step size for a 1.5V window.

    Regards,

    Tim