• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 177 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM5017: Why the inductor in series with a resistor?

chou weixi
Prodigy 10 points
Part Number: LM5017

Dear TI experts,

The circuit below is from the spec of LM5017,

My question is why the inductor in series with a resistor R8?

When should I put R8 in the design?

thanks!!

  • 0
    TI__Expert 5130 points

    Hi,

    The resistor is placed for the convenience of inductor current test.

    Regards,

    Hongjia

  • 0 in reply to Hongjia-Wu
    Prodigy 10 points

    Hi,

    Thanks for your reply. I have three more questions...

    1. The datasheet shows two ways to calculate Cr for the type3 ripple circuit, witch one should I follow 25 or 50mV? What is the meaning of them?

    2. If there is no 3300pF for C6(Cr), can I use 2200 or 4400Pf to replace it? Which one you recommend?

    3. Does LM5017 include soft start feature? If I want to add the soft start feature, I had to add the external circuit below, using the diode to connect Vfb and Vcc??

    Best regards

  • 0 in reply to chou weixi
    TI__Expert 5130 points

    Hi,

    1. It should be 25mV. You can also refer to datasheet Table 7.1. 

    2. You can use Equation 7 in Table 7.1 for calculation. A smaller Cr will make the ripple larger and therefore benefits stable operation for COT.

    3. Yes please use the external soft start circuit to realize this function.

    Regards,

    Hongjia