TAS5558: i get only 192kHz PWM Output

Rene Wagler

Part Number: TAS5558
Other Parts Discussed in Thread: TAS5548

Hi, im currently designing an 7.1 AMP with PSVC inkl. Subwoofer an i have problems with the TAS5558.

I2C Connection works as expected and i get ACK´s. The 3V3 power is stable. On pin 11 MCLK i have an 12,288MHz Oscillator and 10k on pin 12 (18k dont work)

My INIT I2C sequence is:

1. 0x12 = 0x00

2. 0x03 = 0xA0

3. 0xE0 = 0x00 0x00 0x00 0x04

4. 0xD9 = 0x00 0x00 0x00 0x48

5. set /MUTE pin HIGH

after that i VALID HIGH and PWM out, Audio is working fine but only 192kHz PWM?

Is there someting miss configured ?

greatings from germany

over 3 years ago

0 Luis Fernandes de Pina over 3 years ago

TI__Genius 14420 points

Hello Rene,

It seems you are trying to use a crystal oscillator rather than an externally driven mclk, if you are using a crystal oscillator, you should follow the components and configuration shown in the TAS5548 diagram. The 18k resistor for the configuration that you are using an external mclk rather than the external oscillator which is likely why you are seeing issues.

Best Regards,

Luis

0 Rene Wagler over 3 years ago in reply to Luis Fernandes de Pina

Prodigy 90 points

Hey tanks for the quick response. I use a Qantek QX8T50B12.28800B50TT. Ok i will try a normal crystal on monday and will report back if its work.

0 Luis Fernandes de Pina over 3 years ago in reply to Rene Wagler

TI__Genius 14420 points

Hello Rene,

Thanks for the response, look forward to seeing the results of your test.

Best Regards,

Luis

0 Rene Wagler over 3 years ago in reply to Luis Fernandes de Pina

Prodigy 90 points

Hi, crystal and PLL components are connected like in figure 54 now. With C7 and C8 = 33pF i get I2C ACK but no VALID and no PWM. I tried 18pF too but then i get no ACK vom I2C.

My crystal: QCL12.2880F18B23B maybe the problem is that this crystal only allow 18pF load instead of 30pF

Under "6.14 Switching Characteristics" are lisetd: 100nF 200 ohms and 10nF. And under "figure 54" stands 470 ohms 47n and 4,7nF... what are correct values here?

On the Picture is the signal output of the Oscilator from "Qantek QX8T50B12.28800B50TT"

EDIT: ok now i got it to work on 384kHz PWM, but not as shown in the Datasheet...

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TAS5558: i get only 192kHz PWM Output