• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 478 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

Original question:

LM5035C: How do I connect the 'RAMP' pin?

LM5035C: How do I connect the 'RAMP' pin?

kwnag woon Lee
Prodigy 170 points
Part Number: LM5035C
Other Parts Discussed in Thread: LM5035,

I am trying to design an input voltage 200V and a oscillator frequency of 200kHz.

At this time, When Rff is connected to the input, the Rff value is about 7M ohm.

What is the range of avaliable Rff value?

And how many watts will Rff consume?

Best regards.

  • 0
    TI__Mastermind 27095 points
    Hi Hwnag woon Lee,

    Thanks for your interest in LM5035C. 7MΩ seems quite high for Rff. Could you tell me what values you used in equation 1 in the LM5035 datasheet? Rff is typically in the kΩ range. It is also acceptable to tie Rff to the Ref pin instead of connecting to Vin.

    The RAMP pin voltage is a sawtooth waveform which can go up to 2.5V max. If Rff is connected to Vin, the average power dissipation is equal to ((Vin-Vramp_avg)^2)/Rff.

    Best Regards,
    Ben Lough