• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 64 subscribers
  • Views 582 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.

LM3481: Variation of soft start

na na78
Guru 16770 points
Part Number: LM3481

Hi

We have question of soft-start delay.

We got the followong wave form.

FA/SYNC/SD is controlled externally like figure 27 of datasheet.

When SD is controlled, 12Vin is applied in advance.
The softstart delay seems to be 2msec.

Is it normal operation of LM3481?
Is there such variation of soft-start delay?

BestRegards

  • 0
    TI__Guru* 76785 points
    Yes it is normal. There are few factors that causes such delay, including the VCC under voltage (not mentioned in datasheet but VCC must establish to a certain level to start switching), PWM comparator input offset (the COMP voltage must be higher than that level shift of the current sense signal), etc. Refer to our ref design tests, and you can see that such delay always exists.