TAS6424E-Q1: On the inductors of the four analog output backend, a 2.11MHz PWM wave and a 128KHz sine wave can be measured

Ray Tong

Part Number: TAS6424E-Q1
Other Parts Discussed in Thread: TAS6424, TAS6424E

My customer connected to pcm6340 after TAS6424, and the audio signal of TAS6424 included in pcm6340 has obvious background noise. Currently, they have found that 2.11MHz PWM wave and 128KHz sine wave can be measured on the inductors of the four analog output backend of TAS6424. Is this phenomenon normal?

4 months ago

0 Gregg Scott 4 months ago

TI__Mastermind 36605 points

Hi Ray,

Have you measured the noise in the audio band with an A-weighting filter? This is the true measure of audio noise.

The 2.11MHz PWM must be on the input side of the inductor. The 128kHz wave is most likely the resonance of your LC filter. If not, it could from the PCM6340 not being filtered well enough before the TAS6424E.

Provide the schematic of the PCM6340 and TAS6424E. I do not have enough information from the provided schematic.

Regards,
Gregg Scott

0 Ray Tong 4 months ago in reply to Gregg Scott

TI__Intellectual 1330 points

Hi Gregg

The schematic diagram is placed below

江淮H7201(M116)_PB_V2.0生产BOM_20240130（tas6424e）.pdf

0 Yanming Gong 4 months ago in reply to Ray Tong

TI__Mastermind 19260 points

Hi Ray

As Gregg commented, the 128KHz sine wave may be LC filter resonance.

Could you ask customer provide test condition? Open load or speker load?

What's the test waveform?

Regards,

Derek

Audio

Audio forum

TAS6424E-Q1: On the inductors of the four analog output backend, a 2.11MHz PWM wave and a 128KHz sine wave can be measured