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CT pin of TL7700

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: TL7700

We have questions about TL7700.

Can we use this IC without capacitor of CT pin?

Please tell us the terminal processing of CT pin if we can use this IC without capacitor of CT pin.(Open or Connected to GND and so on)

Please tell us the reason if we can't use this IC without capacitor of CT pin.

Best regards,

Takahiro Nishizawa

  • 0
    TI__Mastermind 19550 points
    Hi Takahiro-san,

    If CT is open, the device can be used as an adjustable-threshold noninverting comparator. So it will function the same but the timing, Tpo, will be short.
    If Ct = 0, tpo is not 0, but approximately 5 μs to 10 μs.

    -Marcoo
  • 0 in reply to Marcoo Z
    Genius 5575 points
    Thank you for your answer!

    Are there any problem that CT pin is open?

    Please tell us more detail about used adjustable-threshold noninverting comparator.
    How does this affect operation of TL7700?

    We can't understand difference of CT pin tarminal processing.
    How does difference of CT pin tarminal processing affect operation of TL7700?
    Please tell us more detail.

    1. If CT is open, the device can be used as an adjustable-threshold noninverting comparator.
    2. If CT is low, the internal output-stage comparator is active, and the RESET output transistor is on.

    Best regards,

    Takahiro Nishizawa
  • 0 in reply to Takahiro Nishizawa
    TI__Mastermind 19550 points
    Hi Nishizawa-san,

    Sorry for the delay response. Data on this device is very limited.

    There is no problems if CT is open.

    1. The term "adjustable-threshold noninverting comparator" just means voltage reset IC with no delay. In TI if a reset IC has delay we call it a supervisor. If it has no delay it is just a reset IC or voltage monitor.

    CT only affects how fast the reset signal recovers after a fault. Some customers like using CT pin to add delay to make sure the Under voltage event is finished.

    2. yes. until CT is finished charging. Section 8.3.3. has more detail. In summary, if there is a capacitor, it needs to charge above Vth to let RESETb go back to high.

    -Marcoo