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CD54HC4066: Max Load Current Drive Capability

Murugavelu Thangavelu2
Prodigy 40 points
Part Number: CD54HC4066

Hi,

In regards with the CD54HC4066, we would like to know what is the max load current can the switch drive when the input voltage is 10VDC and VCC is 10VDC. We are using the IC as a buffer / switch between the DAC TLC7226IDW and external interface, the DAC is capable of driving max current of 5mA. As per FIGURE 5. FREQUENCY RESPONSE TEST CIRCUIT, the RL is 50ohms and input is VCC/2, which is 50mA. There is no direct reference to the output current drive on the datasheet.

Kindly let us know what is the max output drive the switch can source / sink.

With Regards,

Muruga

  • 0
    Guru 285390 points

    An analog switch creates a passive connection between two pins; there is no output drive.

    The absolute maximum rating is 25 mA. (The test signal in figure 5 is not digital and has a lower amplitude.)

    Note 1 on page 3 says that there are situations where the voltage drop over the switch must stay below 0.6 V, but 5 mA × 105 Ω = 0.525 V is safe. (And it's likely that the external interface does not actually draw 5 mA.)

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    Hi Clemens,

    Thank you for your response.

    Kindly suggest a analog switch with internal buffer which can drive update up 25mA

    Regards,

    Muruga

  • 0 in reply to Murugavelu Thangavelu2
    Guru 285390 points

    All analog switches are passive. To buffer an analog signal, you need an opamp.

    10 V rail-to-rail opamps with shutdown and strong outputs would be something like the OPAx991 or TLV91xx. How many channels do you need, and what is the highest signal frequency?

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    Clemens,

    We are perfectly fine with the DAC only power driving capabilities,we wanted to address the worst case scenario when the requirement of current drive is about 10mA.  The DAC output is connected to 0-10V driver circuit, when the device is OFF the voltage pulled low on the 0-10v to 1.6V hence we wanted to put a switch to isolate the DAC from the driver circuit. If we use an op-amp it would behave the same when the device is power down.

    We could put a buffer circuit on the input of the Analog Switch to improve on the current drive if the switch can handle the current on each channel. We would also use individual analog switch per output.

    We are using 12 channel of the DAC (3 Devices) on the board.

    In regards with the shutdown option of the opamp, when VCC is not present the shutdown pin cannot be driven hence we are not sure about the op-amp state. If you could shed some light on the state of the op-amp when the VCC is not present and shutdown is floating what would be the output impedance.

    We would like to avoid use of the relay.

    With Regards,

    Muruga

  • 0 in reply to Murugavelu Thangavelu2
    Guru 285390 points

    Opamp control inputs, inputs, or outputs cannot be driven when powered off.

    Can't you always power the opamps (like the switch)?

  • 0 in reply to Murugavelu Thangavelu2
    TI__Expert 5660 points

    Hi Muruga,

    Thank you for posting to E2E. 

    As Clemens stated above, all of TI's analog switches & multiplexers are passive and are not capable of driving current. The Absolute Maximum Ratings table of the switch will specify how much input continuous current the device can tolerate.

    If you are looking for a recommendation for an op amp or other device for your system, I encourage you to post a new thread on E2E so that your question will be answered by the corresponding team at TI.

    If you have any questions about choosing a specific analog switch/mux for your system, feel free to reach out. Otherwise I will close this thread.

    Best regards,
    Kate