ADA4922-1: Power dissipation / Howto connect to a short twisted pair cable

Hi,

In our system (industry electronics) we use the ADA4922-1 to convert a single-ended signal to a differential signal (a short twisted pair cable will be connected). The issue is that the ADA 4922 gets quite hot, even in steady state condition (when power dissipation shout be at its minimum), no cable connected. The package heats up to about 60°C with an environment temperature of about 25°C. When calculating the power dissipation from this temperature, you get around 300mW.

In a steady state condition, we have a signal input of 0.5V, nothing is connected to the output. There is a small copper area connected to the exposed pad. Power supply is -12V and +12V, the supply pins are blocked with 100nF ceramic capacitors. Disable pin is at 12V. No cable is connected, which leaves about 1cm of copper trace per output. I guess power dissipation should be around 1mW (input signal, internal resistors).

So the question would be, where in the IC and why is this high amount of power is dissipated? Do you have an idea? Measuring the outputs and power pins with an oscilloscope shows no oscillation.

Do you also have a hint about connecting a a twisted pair cable (length about 1m) to the device? Should it be done directly, or is it better to use a resistor/capacitor network to prevent too high capacitve load? The signal Frequency will be around 10kHz.

Thanks,

Michael

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    •  Analog Employees 
    on Jul 26, 2012 3:47 PM over 8 years ago

    Hi Michael,

    First I would like to ask you about your +/-12V sypply requirement?

    Is that supply voltage a requirement to increase the common mode voltage?

    If not, maybe we can either reduce the supply voltage to lower the power or chose another part that meets your requirement.

    Second, for such cable, you have to have a resitor on the output of the amplifier and terminate the cable on the other side. you might want to increase the gain of the amplifier to make up the 6 dB loss.

    Please feel free to contact me via private message using my community profile for more detailed info.

    Charly

    Message was edited by: Andy Rose - Removed phone number from thread.

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  • 0
    •  Analog Employees 
    on Jul 26, 2012 3:47 PM over 8 years ago

    Hi Michael,

    First I would like to ask you about your +/-12V sypply requirement?

    Is that supply voltage a requirement to increase the common mode voltage?

    If not, maybe we can either reduce the supply voltage to lower the power or chose another part that meets your requirement.

    Second, for such cable, you have to have a resitor on the output of the amplifier and terminate the cable on the other side. you might want to increase the gain of the amplifier to make up the 6 dB loss.

    Please feel free to contact me via private message using my community profile for more detailed info.

    Charly

    Message was edited by: Andy Rose - Removed phone number from thread.

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