• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 98 subscribers
  • Views 265 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Questions about AM3358 -unused signal and Ferrite bead

shin sang.gil
Prodigy 40 points

1.     About how to take care of the unused signal

 In the AM335x Schematic Checklist, it is recommended that unused ADC signal should be dealt with as shown below.

Among the terminals stated above, VDDA_ADC is a power terminal. Please confirm that it is okay to connect the VDDA_ADC terminal to GROUND.

 1)     If it is okay to connect the VDDA_ADC terminal to ground, is that power terminal completely separated from the other power rails? Moreover, does the GROUND stated above indicate the DGND which is the normal board ground?

 2)     What if I connect VDDA_ADC to 1.8V instead of ground when not using the ADC signal?

  

2.     About the use of Ferrite Bead for the PLL and Analog supplies

In the AM335x Schematic Checklist, I have read the Decoupling Capacitors section as shown below.

 

1)     Do the PLL supplies above mean DPLL Power Supply? To be more specific, do they mean VDDA1P8V_USB0, VDDS_PLL_MPU, VDDS_PLL_CORE_LCD, VDDS_PLL_DDR?

2)     If I use ferrite beads to keep the noise, should I use separate beads for each power supply or use just one bead for all power supplies?

3)     Do you have any recommendations for the DCR value and impedance value for Ferrite Bead?

 

Your prompt response regarding this request would be greatly appreciated.

If you have any questions regarding this request, please contact me through email.

I look forward to hearing from you soon. Thank you for your help in advance.

  

Yours sincerely,

SangGil Shin

 

  • 0
    TI__Guru* 86550 points

    SangGil,

    1.  Yes it is ok to connect VDDA_ADC ground if you are not using any of the ADC signals.  Connect it to the same ground as VSSA_ADC, which can be DGND if ADC is not being used.  The main reason to do this is to avoid any power leakage to help reduce power consumption.  Connecting it to 1.8V is also fine, but you may see a slight increase in power.

    2.  Yes, the comment on the PLLs refers to the PLL supplies.  Note that the beads are probably not necessary for power sources that only supply one rail or are otherwise isolated from the rest of the system.  If you check our EVM schematic this is the case for the VDDS_PLL supplies which only come from one source and are not sourcing other non-PLL rails.  On the Beaglebone design, there is a bead on the PLL_MPU which is being supplied by a generic 1.8V supply to the rest of the system. 

    Regards,

    James