• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 129 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.

UC2843A-Q1: <50% duty cycle

Shinji Tsuji
Genius 14089 points
Part Number: UC2843A-Q1

Tool/software:

Hi team,

I would like to use UC2843A-Q1  a <50% duty cycle limit.

Could you advise if i can use Rt=1kohm, Ct=12nF? 

I found below recommendation in the datasheet which seems to restrict the range of Rt to >5kohm and 

Ct <4.7nF.

Is there any problem if I use outside of this range?

Does all the performance/features are guaranteed under my use case?

regards,

  • 0
    TI__Guru 72845 points

    Hi,

    No guarantee that you will get same performance such as part to part tolerance linearity or some strange behavior if you use RT and CT with your mentioned numbers.

    We suggest you use the device with its recommended and normal range to get the datasheet specified performance.

  • 0 in reply to Hong Huang
    TI__Genius 14089 points

    Hi Huang-san,

    maximum duty cycle limit feature is to force the device to work below its maximum duty cycle, correct?

    Is there any concern if I select the operating condition(input and output) and transformer specification to meet <50% duty cycle

    with maximum duty cycle is set at 90%(timing resister = 5kohm)? I mean can I limit the maximum duty cycle externally?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Guru 72845 points

    Hi,

    If you use a device with Dmax = 100%, while you design external try to work < 50%, it depends on how your external circuit is designed. If there is no 50% duty cycle clamp, during transient > 50% duty cycle can still be there which can cause unstable operation. There is no good way for this device to make external 50% duty cycle clamp. If your design wants to clamp duty cycle < 50%, you need to use a device with Dmax = 50%. If you use a device with Dmax > 50%, then you need to design in other circuit correspondingly, such as adding current slope compensation.