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PCM5121 load impedance and output voltage

Akio Ito
Genius 3595 points
Other Parts Discussed in Thread: PCM5121

Hi,

A customer will use PCM5121. They have question about PCM5121 datasheet as below.

Their question is about load impedance, in PCM5121 Datasheet, page 9, it say the load impedance is >5KΩ, like below

But in page1, it say the load can down to 1kΩ,and in page 7, also has such data below.


a) Why the data is different in datasheet? When use 1kΩ load, Can PCM5121A output 2.1Vrms? They also hope TI can provide the diagram of Load impedance vs output voltage.
b) What is the tolerance of output voltage( in above table, only typical value:2.1 Vrms, They need the min and max data).

Best regards,
Akio Ito

  • 0
    TI__Mastermind 27850 points
    Hi Akio,

    A) 1 kΩ is the minimum load for the PCM5XXX series. This seems to be a typo in the data sheet.

    B) The gain error of max +/-6% of 2.1 Vrms will gve you the min max of full scale. Which would be 1.974 VRMS and 2.226 VRMS

    Justin
  • 0 in reply to Justin Bohr
    Genius 3595 points

    Hello, Justin-san,

    Our customer measured THD+N by AudioPrecision. THD+N was 0.005% at 2.2 kΩ load. But it increased to 0.75% at 1 kΩ load. He said the output signal seemed to be clipping at minus power side.

    I think that 5 kΩ is not a simple typo, it would be the minimum load to secure 2.1 Vrms output. If we attenuate the output level by the volume via I2C, we might get the output signal without distortion even if load impedance is 1 kΩ.
    Please teach us the meaning of difference between 1 k ohm and 5 k ohm.

    Best regards,
    Akio Ito