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INA1650: application problem

Reed
Expert 2280 points

Part Number: INA1650
Other Parts Discussed in Thread: INA1620

Use INA1650 to do differential input, single end output audio circuit, input end added phantom 48V power supply,

help to see the next schematic connection method has a problem,

Thank you!

  • 0
    TI__Mastermind 31255 points

    Hello, 

    I have put your circuit into Tina (attached below). I do not see any issues with the functionality. I checked the gain bandwidth as well as transient analysis. I do not see any spiking if I switch in the phantom power, so this setup looks good functionally. I checked both input current and voltage on the input while switching on and off the phantom power. Is the mic level on the input at line level?

    INA1650 Diff in Single out with Phantom Power.TSC

    Best Regards, 

    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Expert 2280 points

    Chris Featherstone,

    Thank you.

    As shown IN the figure below, 48V phantom is supplied on the differential audio input, and the phantom power microphone is connected to the input. After several times of plugging and unplugging the microphone, the audio output has A great noise. The test finds that the pin voltage of IN+A, in-A, in-B, and IN+B becomes 0V, and the pin voltage is 7.5V when the audio output is normal. Schematic diagram reference data manual Figure 58,VCC voltage of 15V, please ask whether it is correct.

  • 0 in reply to Reed
    TI__Mastermind 31255 points

    Hello Reed, 

    Operating the device at 15V with the configuration shown in Figure 58 is ok to do. Figure 58 assumes the device is being used as a line receiver meaning that there would be a prior pre-amp stage that provides phantom power to the microphone. '

    • Does your microphone have volume control such that it outputs a line level signal?

    Assuming the microphone is outputting a line level signal and the INA1650 will be used as the front end, we generally recommend protection for situations such as the one you described when using phantom power. An example can be found in the INA1620 product datasheet in Figure 60 as shown below:

    • Are you seeing any spikes occurring on the input point below or the supply during the fault condition? 
    • What is the nominal DC voltage seen on the node below during normal operation? 

    Under fault conditions such as the microphone being unplugged and plugged with active phantom power, spiking can occur. For this reason we recommend a protection scheme on the inputs and supply line if spiking is present. 

    Best Regards, 

    Chris Featherstone