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VSS_OSC and VSS_RTC connection to PCB ground

Peng Liu50174
Expert 1510 points

Hi,

I saw in the AM335X erreta SPRZ360F Revised November 2013, there is one Advisory 1.0.30 OSC0 and OSC1: Noise Immunity Improved When Crystal Circuit is Connected Directly to PCB Digital Ground.

It is said that "The higher impedance connection through the AM335x device to the PCB digital ground
makes it easier for electrical noise to couple into the crystal circuit. If the noise is large
enough, it is possible that the oscillator output may produce clock glitches to various
internal logic circuits. These clock glitches may cause unexpected behavior."

My question is what what kind of noise is large enough to cause the clock glitches? is this kind of noise availabel in our typical enviroment?

And what are the unexpected behaviors TI is ever reported? lockup or reset?

On our product, we don't connect the VSS_OSC and VSS_RTC directly to PCB ground, we did our design according to the rev.F datasheet. So we want to know the risk level when not connecting VSS_OSC and VSS_RTC directly to PCB ground.

Regards,

Peng

 

  • 0
    TI__Guru**** 393215 points

    Hi Peng,

    The behavior reported by different customers on this forum has been mostly unexpected changes in various clock frequencies, e.g. UART. If your product runs without problems you should not need to apply this Errata. However it's recommended to apply it to all new designs.