ADAU1452 IOVDD and PVDD Sequence

TomY Question

Apr 6, 2017 00:00

Hello, ADI Support Team

I could find the description of Power Up Sequence in ADAU1452 Datasheet as follow.

<Page 24>
All power pins can be supplied simultaneously.

<Page 25 & Page 26>
If possible, apply the required voltage to all four power supply domains (IOVDD, AVDD, PVDD, and DVDD) simultaneously

Therefore, I could understand all power can be supplied at the same timing.

However, I am concerned about the following description.

<Page 24>
When a crystal is in use, the crystal oscillator circuit must provide a stable master clock to the XTALIN/MCLK pin by the time the PVDD supply reaches its nominal level.

Does this mean that PVDD should supply after XTALIN stable?

In other word, does this mean that IOVDD and PVDD can not be supplied at the same timing, when a crystal is in use?

If so, I think the explanation contradicts.

Best Regards, TomY

Audio Signal Processors

adau1452

SigmaDSP Audio Processors

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TomY Reply

Apr 11, 2017 00:00

Hello, ADI Support Team

Do you have any reply?

Thanks in advance.

TomY

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DaveThib Reply

Apr 12, 2017 00:00

Hello TomY,

Sorry for the delay.

Look at the details on Figure 14. You will find this note:

IF POWER SUPPLIES ARE SEPARATE, APPLY VOLTAGETO IOVDD FIRST. APPLY MASTER CLOCK SIGNAL TO XTALIN/MCLK, UNLESS MASTER CLOCK IS AUTOMATICALLY GENERATED USING A CRYSTAL OSCILLATOR CIRCUIT.

So here it says that the master clock has to be applied when IOVDD is applied but if it is a crystal it does not have to be applied first.

What the quote on page 24 that you noted is saying is that the crystal has to come up and be stable by the time PVDD has reached nominal. This is pointing out the quality of the crystal to come up smoothly. It is not saying that PVDD has to be delayed.

The quote I gave above is a detail on what to do if the power supplies are not applied at the same time. If all the power supplies are applied at the same time then it will all come up fine so long as the crystal comes up in a stable manner.