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LM27313-Q1: LM27313-Q1

Mehmet Sait
Prodigy 20 points
Part Number: LM27313-Q1

Tool/software:

Hello,

Is it possible to use shutdown pin of LM27313-Q1 to enable and disable the IC?  I used a enable signal from a controller and connected it to the shutdown pin of the IC. Instead of 1k resistor I used a higher one. But it is not working. 

  • 0
    TI__Genius 14480 points

    Hi Mehmet,

    Please shown the whole schematic, at least the block of LM27313-Q1 and where the SHDN signal comes from.

    Regards

    Lei

  • 0 in reply to Lei Zhong
    Prodigy 20 points

    Thanks for the reply. 
    I have not completed the schematic yet. In the datasheet, SHDN pin is connected to Vin. I want to use it as enable-disable pin. 

  • 0 in reply to Mehmet Sait
    TI__Genius 14480 points

    Hi Mehmet,

    The SHDN can be disconnected to Vin and used as a independent enable-disable pin. 

    What's the voltage of the control signal? What's the resistor you used between the controller and SHDN pin? You may try smaller resistor, such as 51kΩ, 1kΩ or even no resistor.

    Regards

    Lei

  • 0 in reply to Lei Zhong
    Prodigy 20 points

    I connected 3.3V to SHDN pin via 51k and I used a 10k pulldown resistor. 

  • +1 in reply to Mehmet Sait
    TI__Genius 14480 points

    Hi Mehmet,

    With the 51kΩ and 10kΩ you used, when the control signal is 3.3V, the voltage at SHDN pin is 0.54V only!

    The SHDN should be at least higher than 1.5V.

    Please remove the 51kΩ, or just use a smaller resistor such as 4.9kΩ and try again.

    Regards

    Lei

  • 0
    Prodigy 20 points

    Thanks for your help. What I missed is that Output cannot be zero with 0V SHDN voltage. Because input is connected to output via inductor and diode. 

  • 0 in reply to Mehmet Sait
    TI__Genius 14480 points

    Hi Mehmet,

    Yes, for LM27313-Q1 even the device is disabled when SHDN = 0, the Vout will equal to Vin (a little lower).

    Regards

    Lei