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LM2907-N: Response time (settling)

Matteo Magistra
Prodigy 30 points
Part Number: LM2907-N
Other Parts Discussed in Thread: VFC110, VFC320

Hello,

I found out the LM2907 would be an interesting low-cost solution for my audio application (configured as f to v converter), but I first would like to know if the response time can be as short as I need, before I buy it.

Question: Is it possible to choose values for C1, R1 and C2 in order to reach a response time of max. 1 ms?

I assume that the value of Vripple can be heavily affected by this requirement, but I forsee to filter the signal to "clean it up" a little bit from the Vripple.

Thanks and best regards,

Matteo

  • 0
    TI__Genius 15565 points

    Hey Matteo,

    If you could provide more details of the characteristics you are trying to achieve, that would be very helpful. For example, what is your desired maximum input frequency and what would you like your max output voltage to be at this frequency?

    Best,

    Hasan

  • 0 in reply to Hasan Babiker31
    Prodigy 30 points

    Dear Hasan,

    thank you for your reply.

    We should have a 10V output voltage @ 15 kHz input frequency (maximum values).

    Best regards,

    Matteo

  • 0 in reply to Matteo Magistra
    TI__Genius 15565 points

    Hey Matteo,

    We believe that the 1ms response time is achievable with the above specs, but will run some tests just to make sure. What is the range of frequencies you will be using for your input and at what peak to peak voltage?

    Best,

    Hasan

  • 0 in reply to Matteo Magistra
    TI__Genius 15565 points

    Hello Matteo,

    Based on some benchmark tests, a response time of 1ms is possible. However, these results were inconsistent and varied upon different tests and devices. Because of this, one of the devices on our VFC product line may be more suitable to your application.

    Devices such as the VFC110, VFC121, and VFC320 can be configured as frequency-to-voltage converters. The attached application note provides details into using these devices as FVCs. A technique to set up these devices in a “fast-settling FVC” configuration is also provided and includes an equation to approximate the settling time of your output. 

    Best of luck,

    Hasan

    FVCAppnote.pdf