• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 62 subscribers
  • Views 167 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.

Original question:

TPA3106D1: output LC Value of magnetic beads

TPS2491: DELAY TIME

zhang ping
Genius 3195 points
Part Number: TPS2491

In our application, we want to add a delay of more than 100ms in en, so c289 is adjusted to 10uF, 4.7uf, 10uF (170ms) results in tps2491 not starting, MOSFET is not turned on, and c289 can start normally when c289 is 2.2uf. Please help to analyze the reason? How can I start tps2491 with a delay of more than 100ms-200ms

   
  • 0
    TI__Guru* 95801 points

    Hi Zhang,

    Thanks for reaching out!

    Can you please share test waveform of Vin, EN, GATE, input current when c289 is 10uF  to analyze

    Regards, Rakesh

  • 0 in reply to Rakesh
    Genius 3195 points

    The first figure shows 48V input and EN waveform, where yellow is EN. The second figure shows 48V output and gate voltage, where yellow is gate voltage andC289 is 10uF。Why does the delay of EN cause tps2491 start failure?

  • 0 in reply to zhang ping
    TI__Guru* 95801 points

    Hi Zhang,

    In the above, you mentioned that "the second figure shows 48V output and gate voltage, where yellow is gate voltage and C289 is 10uF" 

    So the system is starting up ? Am I missing something.. Let us know the issue.

    By the way, why the EN voltage is so noisy. ?

    Regards, Rakesh

  • 0 in reply to Rakesh
    Genius 3195 points

    The second figure is at C289 = 10uF, and R740 is changed to 7.5K, so as to adjust vprog voltage, realizing Vout = 48V, gate voltage is normal, as shown in the figure. However, when c289 is larger than 10uF, MOSFET cannot be turned on. Please help to analyze the reason why TPS2491 can't be started due to the increase of C289?

  • 0 in reply to zhang ping
    TI__Guru* 95801 points

    Hi Zhang,

    Kindly share the test waveform to analyze when the system is not starting (i.e., with higher value of C289).

    Two scope shots would be helpful, use 4-channel oscilloscope 

    1. Vin, EN, GATE, input current

    2. Vin, EN, GATE, Vout

    Best Regards, Rakesh