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TAS2555 THDN much lower than what datasheet says

Susan Xue
Prodigy 140 points
Other Parts Discussed in Thread: TAS2555

hello team,

    Due to customer's need, I have been testing the electricity characteristic of TAS2555 recently. Test conditions are according to datasheet(ROM Mode 2, VDD= IOVDD = 1.8 V, RESETZ = IOVDD, RL = 8 Ω + 33 μH, I2S digital input), VBAT=5V. I use TAS2555 EVM that's applied online.

    i found that when input frequency is 1KHz, Pout is 1W, it turns out THD+N=0.06%, much larger than the datasheet(0.005%). it seems harmonic is very high. the output resistor and inductor are as below pictures.i use APx555 for generating digital signal and testing output.

    Can you help me with finding out what's wrong with my test?


 


  • 0
    TI__Guru** 102475 points
    Hi Susan,

    Thank you for your question. Jorge Arbona will be responding soon with further detail.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0
    TI__Genius 17290 points

    Figure 18 in the datasheet shows the test circuit that is used for this spec.  We have found that there is mismatch in the Aux Filter that limits the measurable performance of this spec.  By using the configuration shown in the datasheet you should be able to see the true performance of the device.

  • 0 in reply to Scott Bryson
    TI__Prodigy 140 points

    Scott,

       I saw this figure. so you mean the AUX filter leads to higher mismatch between differential outputs of speaker? so we need to build a circuit mannually to ensure symmatrical load in two outputs? if so, I'm not sure about this because I dont use AP SYS-2722. I just use APx555 which should integrate filter inside. I'm not sure if it's same as you said.

       also if i need to add this compensation circuit, should I apply for another test board online? or i have to make the PCB by myself?

        looking forward to your reply, thanks a lot !