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EVM Capable of driving 2x 4-8 ohms and 1x2 ohms (not simultaneously)

Other Parts Discussed in Thread: TPA3123D2, TPA3118D2, TPA3116D2

Hi,

I am looking for an audio amplifier capable powering a variety of voice coil motors. The main requirements are to be able to:

Drive two 4 ohm impedances simultaneously, with a power of up to 50 [W] per voice coil.

Drive a single 8.5 ohm impedance, at up to approx 20 [W].

Drive a single 2 ohm impedance, at 5-15 [W].

Ideally, the amplifier will be available as an EVM to reduce design and manufacturing time for the small quantities we need.

Right now I am driving all of these impedances from a TPA3123D2, in an EVM. However, the 2 ohm impedance is actually below the 3.2 ohm absolute minimum impedance.

Is there some way I can drive all of these loads (not at the same time) with a single amplifier? It seems like it would be easy to do with the TPA3118D2, but would require some switching to switch between a single PBTL of 2 ohms and two outputs of 4-8. However, it would be nice to not have to use switches.

At low power (<15W, likely <10W), is driving the 2 ohms with the TPA3123D2 going to destroy the amp? What would be a better solution?

Thanks,

Tom.

  • Hi Tom,

    My recommendation would be the TPA3116D2. This would be able to hit your 2x 50W 4ohm target and your 2 ohm 15W target as well. If you can get by with 2X 30W 4ohms, than the TPA3118D2 would work.

    In order to achieve your 2ohm target, running the TPA3116D2 and TPA3118D2 in PBTL is recommended since this is a very heavy load. The EVMs support PBTL mode by simply inserting a pair of 100mil jumpers on the headers already soldered onto the EVMs. Then the outputs can be bridged. If you insure the power level will not exceed 10-15W with a 2ohm load, than a single channel of BTL may work but this is not recommended.

    For the TPA3123D2 a 2ohm load is quite a heavy load. As long as it isn’t pushed harder than 10W it should be ok. The amplifier efficiency will also be reduced due to the increased current draw and the RDSon of the output FETs. For continued use some heatsinking on the back side of the PCB may be required.

    Regards,
    Matt
  • Hi Matt,

    Thank you for your quick reply. This is very helpful. I will see what sort of current I really do need on the 2x4 ohm load and then choose between the 3 amplifier EVMs discussed.

    -Tom.

  • Hi,

    I have a follow up question related to low frequency performance of these amps, at e2e.ti.com/.../465927

    It would be awesome if you could again provide a suggestion.

    Many thanks,
    Tom.
  • Tom,

    I think both Matt and I have suggested good parts for you to use to meet your power needs.  As I said in the linked post, the functionality below 20Hz is not specified and you will need to test this for your needs.  We do not guarantee our specifications outside of the datasheet specifications.  Please order the EVM of your choice and make the measurements to see if it meets your needs.