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TL594: About frequency variation (Δf)

Tao_2199
Genius 5670 points
Part Number: TL594

Hello,

 

Regarding to frequency variation on TL594, my customer is asking a question.

(Question)

In case of TA constant, according to datasheet page 5, standard deviation of frequency is 100Hz/kHz (typ)

In case of the full temperature range., how will we estimate the frequency variation (Δf) ?

I couldn’t understand the frequency variation (Δf) (dot line) in datasheet Figure 1.

For example, in case of Oscillator Frequency=10kHz (CT = 0.01uF/RT = 12k ohm,

how will we estimate that by Figure 1?

 

Regards,

Tao2199

  • 0
    TI__Mastermind 26235 points
    Hi Tao_2199,

    For a given Rt and Ct, the closest dotted line provides an estimation of the frequency variation over the full temperature range. For example with Ct = 0.01uF and Rt = 12kΩ, you should see fairly close to 0% frequency variation

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Genius 5670 points

    Hello Ben,

     

    Thank you for reply.

    For example,

    ･CT = 0.01uF,RT = 120k ohm -> Fairly close to 1% frequency variation.

    ･CT = 0.001uF,RT = 25k ohm -> Fairly close to -1% frequency variation.

    ･CT = 0.1uF,RT = 1.8k ohm -> Fairly close to -2% frequency variation.

    My understanding is correct?

     

    Additional question,

    For example, in case of CT = 0.01uF/RT = 12k ohm,

    According to datasheet page 10, oscillator frequency is about 8.3kHz by Equation 2.

    But according to Figure 1.(datasheet page 6), oscillator frequency is 10kHz.

    What is reason for this difference?

    (Frequency variation or standard deviation ,or error of components(Ct/Rt)?) Tao2199

     

    Regards,

    Tao2199

  • 0 in reply to Tao_2199
    TI__Mastermind 26235 points
    Hi Tao_2199,

    Yes, your understanding is correct. I will need to look into your second question and get back to you.

    Best Regards,
    Ben Lough