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LM4674: schematic check

GARETH OU
Guru 11765 points
Part Number: LM4674


Hi

Could you help check the below LM4674 schematic and any need to adjust ,Thanks

audio.pdf 

  • 0
    TI__Guru** 112315 points

    Hi Gareth,

    Thanks for sharing this design for review.

    The schematic shows they're using the same inductor/capacitor filter as the Demo Board schematic. The filter used on the Demo Board is mainly purposed for external measurements, being 300-Ohm the load for the 1mH/0.022uF filter. For actual speaker loads the filter should be re-designed based on the speaker impedance.
    I would suggest following one of the examples from Figure 8-2 or 8-3 depending on the speaker impedance, this is in section 8.9 in the latest data sheet update.

    Other than that, the schematic looks OK.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Guru 11765 points

    Hi Ivan

    5V power supply G0 = H G1 = H SDR = H SDL = H L31/L32/L33/L34 = 15uH
    Does the R1066/R1067 (highlighted in red) = 300ohm require an additional component?
    Currently, an additional component is installed. This is the current setup, but there is still no output. All three components are experiencing this issue.
    Output: No speaker connected; the measured signal initially showed a signal, but after several measurements, the signal disappeared.
    CON-7229 Speaker.pdf
  • 0 in reply to GARETH OU
    TI__Guru** 112315 points

    Hi Gareth,

    One thing you can try is removing the filter at the output, this is L31/32/33/34 and C25/26/27/28 and R1066/1067, then connect the speaker directly at OUTxA/B.

    As mentioned before, I'd recommend replacing the filter with the one in Figure 8-3, you can also try this.

    Best regards,
    -Ivan Salazar
    Applications Engineer