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WEBENCH of LM2733

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: LM2733

We have questions about LM2733.

We simulate circuit of LM2733 by WEBENCH.

Question 1.

About external resistor of SHDN pin

In datasheet p.11 "7.4.1 Shutdown Pin Operation"

. If the SHDN function will be needed, a pull-up resistor must be used to VIN (approximately 50k-100kΩ recommended). The SHDN pin must not be left unterminated.

In datasheet p.18 "9 Power Supply Recommendations"

  For applications that do not require a shutdown function the shutdown pin may be connected to the VIN pin. In this case a 47-KΩ resistor is recommended to be connected between these pins.

In WEBENCH(attached document)

 External resistor of SHDN pin is 48.7kΩ

⇒Please tell us the reason why 50k-100kΩ, 47-kΩ and 48.7kΩ are different.

   Which value should we use?

   And please tell us about the precautions on terminal processing.

Question 2.

   We will use this inductor.

    LQH32PN100MN0L(MURATA)  10μH、750mA、0.38Ω

   

　Are there any problems?

Question 3.

We will use this diode.

MBRS2040LT3G(Onsemi conductor)   VF=0.43V、VRRM=40V

www.onsemi.com/.../MBRS2040LT3-D.PDF

Are there any problems?

Best regards,

Takahiro NishizawaWEBENCH LM2733.pdf

  • 0
    TI__Mastermind 34201 points
    Hi Takahiro,

    1. Datasheet says approximately 50k-100kohm is recommended(not must between 50k-100kohm). Both 47k and 48.7k ohm works well and you could trust either of these two values.
    2. What's the input voltage range? Is it a constant value 5V? If so, this inductor can meed the demand.
    3. Yes. It has larger current and voltage ratings. But the higher VF may decrease efficiency.