TAS5508C oscillator fails to startup

Hi, Vladimir,

Try changing out your crystal. Another customer had a similar problem, and it turned out his crystal was bad.

-d2

Hi! 

I've tried a different crystal. After the device was powered up, for a half a minute there was no frequency. Then frequency appeared on XCL_IN with 250mV amplitude. Current consumption was about 20mA.

After 3 or so minutes frequency dissappered, and device power consumption became about 110mA and began to rise. Investigation showed, that 1,8V power pins are shorted to gnd, as well as XCL. 

During normal operation period nothing was made to pcb, not even touched, so a don't see any reason, why that could happen.

Edit: Top side marking 11AYNCTG4.

Also, a can provide pcb files and schematics, if it heps.

Hello Vladimir:

Please check the crystal manufacturer for correct load capacitance.

Best regards,

Tuan

Hi! 

Thanks for the fast reply. Is it possible, that wrong load capacitance can cause internal voltage regulator failure?

Hi Vladimir:
No, it shouldn't damage the internal vreg.  Do pins 17 and 33 have 1.8V present?

Best regards,

Tuan

Hi!

Yes, the voltage was present while device worked normal. When consumption rised, voltage began to drop.

Hello Vladimir:
Will you please clarify on "when the consumption rised"?  Does this mean when the crystal is present, or when PWM starts switching?

I forget to ask ... the crystal is 13.5 MHz, correct?  Can you please try add a 10uF on VR_DIG pin 33?

Best,

Tuan

Hi!

Excuse me for my english, its not my native language.

That happened when crystal was present. Without stable frequency I2C communication cannot be established, so no PWM was avaliable.

The crystal is 13.5 MHz. I'll try to add additional capacitance, will write about results later.

Thanks.

Hi!

The results of adding extra capacitor are almost the same. 

Hi!

Are there any avaliable PCB layout reference designs for TAS5508C?

Thanks in advance.

The TAS5508C pin-out is exactly the same as TAS5518.  The evaluation board information is here:

http://www.ti.com/lit/ug/slau244/slau244.pdf

Best regards,

Tuan