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ISO7140CC: Carrier frequency of Internal oscillator

Takeshi Sasaki
Expert 4480 points
Part Number: ISO7140CC

Hi team,

The customer wants to know the carrier frequency of the internal oscillator to see what frequency range can be generated. Could you give me comments on this question? They're asking because they want to consider what kind of noise suppression technique can be applied in their application based on that frequency range. Thank you for your support.

Best regards,

Takeshi Sasaki

  • 0
    TI__Guru 53685 points

    Hi Takeshi,

    ISO7140CC employs an edge-based architecture for data transmission across the isolation barrier unlike ISO77xx which uses on-off keying architecture. Edge-based architecture doesn't require any carrier clock frequency to transmit the data, it instead transmits the input data edge information without any modulation. Please do have a look at the below application note for a brief description of edge-based and on-off keying architectures.

    Since ISO7140CC doesn't involve any high frequency carrier, this device doesn't effect other devices and customer need not have to do anything.

    ISO7140CC is one of our older device families, we would recommend customer to use the latest family of digital isolators ISO77xx. It offers various significant amount of performance improvement and is also very competitive in the markert. Thank you.

    Regards,

    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Expert 4480 points

    Hi Koteshwar,

    Thank you for your comments. I have one more question. The customer mentioned the carrier frequency is described in the apps note as follows, "Because low-frequency input signals require the internal capacitors to assume prohibitively large values, these signals are pulse-width modulated (PWM) with the carrier frequency of an internal oscillator, thus creating a sufficiently high frequency, capable of passing the capacitive barrier".

    Could you give me comments on above carrier frequency at low frequency input signal?

    Best regards,

    Takeshi Sasaki

  • 0 in reply to Takeshi Sasaki
    TI__Guru 53685 points

    Hi Takeshi,

    Sorry for the delayed response as I was on travel for last several days.

    Thanks for your inputs, yes there is going to be PWM modulation for low datarate inputs as also described in the application note I have referred earlier and also described in respective datasheets. The frequency of this carrier is about 100kHz. Please do note that this being a very low frequency carrier unlike OOK architecture, we typically do not consider this of any concern for any applications.

    Let me know if you have any other questions, thank you.

    Regards,

    Koteshwar Rao