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DRV135: Using DRV135 with Line Driver IN

Daniel Fischer
Prodigy 30 points
Part Number: DRV135
Other Parts Discussed in Thread: PGA2500

Hi,

we are considering to use DRV135 as Balanced Output Driver in our Audio System.
Befor the DRV135 will be an Audio Codec that has a Singleended Line Driver Output 2Vrms on 600ohm.
Our System runs on +-5V (PGA2500 PreAmp befor the Codec)

The DRV135 has 10k input impedance. So direct connection should be fine?

Should we consider some protection circuit befor the DRV135?
Otherwise i would layout the designe like shown in: Figure 29. Complete Audio Driver and Receiver Circuit (DRV135 Datasheet)

Thank You for taking a look to...


  • +1
    TI__Mastermind 26055 points

    Hi Daniel, 

    The codec can drive a current of Irms = 2Vrms/600 = 3.3mA. The 10k input impedance of the DRV135 will be easy for it to drive based on the provided information. For the input signal to the DRV135, 2Vrms is 2.83Vpeak. If I apply that to the DRV135 on a +/-5V supply I see the output clip. For this reason the input will need to be lower, or the supply will need to be increased in order to accommodate the input signal.

    The linear output swing with no load is shown below:

    With a load this will decrease, so the load should be accounted for in your simulation to ensure you are operating in the linear range. 

    • I assume that on the split supply your DC voltage on the codec output is 0V? If so I don't see any issue from a DC common mode perspective on the input of the DRV135. 
      • if there is a DC voltage other than 0V being provided from the codec you may consider AC coupling to the DRV. 
    • Will there be any hot plugging going on to the DRV input or output such as cabling etc?
      • If so you may consider adding pads for TVS diodes to protect the inputs of the DRV. Same can be done on the output if there will be any hot plugging to the system. For the input, if there are any transient spikes that could occur from such actions you may want to consider adding a series resistor to the input such that the current is kept to 10mA or less for over current protection. 

    Best Regards, 
    Chris Featherstone

  • +1 in reply to Chris Featherstone
    Prodigy 30 points

    Thank you very much.

    After ruining the output stage of an audio codec, I focused more on the input of the DRV135 and almost forgot that I should also protect the output of the DRV135.


    The 2Vrms on the input side of the DRV135 are the maximum values (0dBFS) of the codec. So I will connect a T-pad with 1dB attenuation (35ohm/5200ohm/35ohm), which will automatically give me a resistor for current limiting and still provide approx. 7dBu output...