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LM5180: About RSET resistor accuracy

Tsukui Yusuke
Guru 21930 points
Part Number: LM5180

Hi,

Could you tell me about RSET?
Data sheet recommends installing 12.1kΩ.



However, Customers want to use E12 series resistors.

What is the effect of using 12kΩ?
Could you advice on the recommended resistor accuracy and impact for RSET?

Best regards,
Yusuke

  • 0
    TI__Expert 8245 points

    Hi,

    RSET is used to set the reference voltage internally, if you use a E12 resistor which mean there is a ±10% variation, then there's at least 20% variation on the output voltage. It's highly recommended to use E96 resistor here.

  • 0 in reply to Iven Su
    Guru 21930 points

    Hi Iven,

    Thank you for your support.
    Let me ask you one more thing.

    Checking Equation 8,
    Vout is determined by the combination of Rset and Rfb.
    Why recommend 12.1kΩ?
    For example, when Rset is 12 kΩ, accuracy can be maintained by selecting Rfb considering 12 kΩ.
    s this understanding right?



    Best regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Expert 8245 points

    Hi,

    From the datasheet, both I_REST and V_REST are tested under the 12.1kOhm condition, it means changing the resistor may have influence the both specs, so it is recommend to keep a 12.1k resistor.