• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 64 subscribers
  • Views 388 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.

UC3843: About coefficient of fosc equation

Hide
Guru 21045 points
Part Number: UC3843

We understand that 1.72 of fosc equation is typical values.

If correct, could you please let us know the min and max values?

 

<Background>

We calculated fosc, as a result, 95.3kHz at RRT=8.2kohm and CRT=2200pF.

However, actual fosc is 91kHz (lower than calculation result 95.3kHz).

Therefore, we would like to estimate variation of fosc.

(Of cause, we understand that there is RRT and CRT variation.)


 

Regards,

Hide

  • 0
    TI__Mastermind 31580 points

    Hi Hide,

    TI does not provide a min and max value for the 1.72 in the formula above. But f you look at the datasheet, on page 7 you can see that the range given for the Oscillator frequency is 47kHz to 57Khz for a typical value of 52kHz at 25C, which is a little over +/-10% variation around the setpoint. The RC is 10k and 3.3nF and the component tolerance is not part of this variation.

    So if you calculate a value of 95.3kHz then I would expect to values in the range of 85kHz to 105kHz in practice at 25C, plus the variation due to the RC components themselves.

    Regards

    Peter

  • 0 in reply to Peter Meaney
    Guru 21045 points

    Hi Peter-san,

    Thank you for the information.

    I greatly appreciate your cooperation.

    Regards,

    Hide