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.

[FAQ] What are the different output types of TI Opto-emulators?

Other Parts Discussed in Thread: ISO8710

FAQ: Isolation >> Opto-Emulators >> Current FAQ

What are the different output types of TI Opto-emulators?

  • What are the different output types of TI Opto-emulators?

    Device

    Output Type

    ISO8710

    CMOS

    ISO8711

    Digital Open-Collector

    ISO811x

    Analog Open-Collector


    CMOS (Push-Pull) Output Type:

    A CMOS (push-pull) output can source current in the high state or sink current in the low state. The digital push-pull configuration of opto-emulators is shown below:

    Input State

    Output State

    Positive Driver (pFET )

    Negative Driver (nFET )

    LOW

    HIGH

    ON

    OFF

    HIGH

    LOW

    OFF

    ON

    When the output is in the high state:

    • The p-channel MOSFET is on and sources current from VCC to the output.
    • The n-channel MOSFET is off and does not allow current to flow to GND.

    When the output is in the low state:

    • The p-channel MOSFET is off and does not allow current to flow from VCC.
    • The n-channel MOSFET is on and sinks current from the output to GND.


    Digital Open-Collector Output Type:

    A digital open-collector output can only sink current in the low state. The digital open-collector configuration of opto-emulators is shown below:

    Input State

    Output State

    Negative Driver ( nFET )

    LOW

    Hi-Z

    OFF

    HIGH

    LOW

    ON

    When the output is in the high-impedance state, the n-channel MOSFET is off and does not allow any current to flow.

    When the output is in the low state, the n-channel MOSFET is on and sinks current from the output to GND.

    Analog Open-Collector Output Type:

    An open-collector output for an analog opto-emulator device works differently than a traditional open-collector device. The analog open-collector configuration of opto-emulators is shown below:

    In an analog opto-coupler, the open-collector output acts similarly to a “gain” of the input forward current. The CTR of the opto-emulator is a major factor in calculating the output current.

    The table below shows how the CTR value for a given input forward current affects the output current when CTR is greater than 100% and also when CTR is less than 100%:

    Input Forward Current (IF)

    Current Transfer Ratio (CTR)

    (CTR÷100) × IF = IC

    Output Current (IC)

    5 mA

    50 %

    2.5 mA

    5 mA

    100 %

    5 mA

    5 mA

    200 %

    10 mA

    5 mA

    400 %

    20 mA

    More information on CTR of an analog opto-emulator can be found here:
    [FAQ] What is Current Transfer Ratio (CTR)? - TI E2E support forums