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TAS2552: PLL Frequency requirements

Part Number: TAS2552

Hi,

In TAS2552 datasheet the PLL output clock in 44.1 word rate should be 22.5792MHz (see SLAS898B section 7.3.7 PLL and Figure 27. Clock Distribution Tree).

But in PLL and Clocking Configuration for Audio Devices Application Report (SLAA892) Section 3.2  TAS2552 in the registers setting example

(see table in page 8) it is clear that the 22.5792MHz should be after the fix by 8 divider (see Figure 8. TAS2552 Clock Distribution in the Application Report page 7)

This mean that we can't generate the PLL clock from bit clock due the multiplier value (J) should be greater than 96.

For example:

Suppose word rate is 44.1K Wps,

Word bits=2x16=32,

BCLK frequency should be 2.8224MHz.

a. According datasheet the PLL multiplier J = P^0 x 22.5792MHz/(0.5 x 2.8224MHz) = 32, So we can use BCLK as PLL input clock

b. According the Application Report the PLL multiplier J= P^0 x 8 x 22.5792MHz/(0.5 x 2.8224MHz) = 256 which is greater than 96 allowed for J.

The only way to solve this issue is by using MCLK as PLL clock input and MCLK is BCLK x 4 = 11.2896MHz (as example in the Application Report).

So, what is the true??

Thanks

Naftali Tourjeman

• Hello,

Our team is looking into this thread and will respond as soon as possible.

Best Regards,

Justin Beigel

• Hi Justin

We stop our card re-layout for fixed this issue

Thanks

Naftali

• HI Naftali,

Sorry for the delay, I'm checking this out and will provide further comments shortly.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

• HI Naftali,

Both data sheet and app note show the same clock tree diagram, fixed divider by 8 is in both as well.
I'm not clear on what is the difference you're mentioning between these documents, could you clarify?

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

• Hi Ivan,

Simple question,

Are the PLL 22.5792MHz output clock in 44.1KHz word rate should be before the by 8 fixed divider (as appear in PLL Clock tree in the datasheet) or after the by 8 fixed divider as can be understand from the example in the application note??

Thanks

Naftali

• Hi Naftali,