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TAS5717: Operating with light or no load

Zotin Khuma
Prodigy 120 points
Part Number: TAS5717
Other Parts Discussed in Thread: TAS5806MD

Is it safe to run this chip with a light or no load? Specifically, I have a product in which the TAS5717 is used to drive two small 8-ohm speakers. The output has an LC network which I have not traced in detail. Power supply voltage is unknown at the moment. Rated output is 20W but this is likely to be an inflated figure.

I want to adapt this so that the existing speakers are disconnected and the amp is loaded with a resistive load of 100 ohms or more per channel without modifying the existing coupling circuit. At the moment I am more concerned with safety for the chip rather than with the effect on audio quality.

  • 0
    TI__Expert 6720 points

    Hi Zotin,

    Do you want to check whether TAS5717 support dynamically 8ohm speaker connect/disconnect (100ohm or more resistive load)?

    What's more, our lasted generation closed-loop audio amplifier integrated HP driver is TAS5806MD, which has better audio performance and less BOM cost. You can email me (matthew-miao@ti.com) with system requirements for more detailed discussion.

    Regards,

    Matthew

  • 0 in reply to Matthew Miao
    Prodigy 120 points

    I'm afraid you missed the point. Maybe I didn't explain properly. Let me try again.

    1. I have a device that uses a TAS5717 as the audio amplifier.
    2. Each channel of the amp is internally connected to an 8-ohm speaker.
    3. Each speaker is coupled to the TAS5717 through an LC network.

    4. I want to disconnect the existing speakers and replace them with resistors.
    5. The resistors will be connected through the existing LC network without modification.
    6. Each resistor may be 100 ohms or higher. May even be left open.

    Can this harm the TAS5717 - perhaps due to switching transients or instability due to the
    large change in load impedance?

  • 0 in reply to Zotin Khuma
    TI__Expert 6720 points

    Hi Zotin,

    Now it's clear with your system behavior. The only concern is large dummy load will introduce low impedance point together with LC filter.

    Here are some simulation results:

    10uH + 0.68uF filter, load is 8ohm and 100ohm, the impedance curve from amp perspective.

     ~61kHz, 8ohm load 1.65ohm impedance, 100ohm 0,2ohm impedance.

    Considering the audio BW is limited under 20kHz, so OC trigger risk is small. 

    Regards,
    Matthew