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How to connect differents VDD together | Cypress Semiconductor

How to connect differents VDD together

Summary: 5 Replies, Latest post by Anjana Muralidharan on 07 Sep 2016 01:21 AM PDT
Verified Answers: 3
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alex934's picture
User
37 posts

I'm designing a board with a PSoC4247BLE and I didn't find any info how to connect all the differents VDD (see my schematic in attachement).

I mean, in my schématic I separated VDDR, VDDA, VDDIO and VDDD but how should I connect them together?

I understand that each VDD have its purpose (digital, analog, IO and RF) but in my case they all will be at  3.3v.

I looked at the schematic of the PSoC4BLE kit and they use 3 inductors but there is no value, what is the purpose? And why VDDD is connected to VCCD with a 0ohm resistor?

Thank you very much

tonyp12's picture
User
17 posts

If you don't have 3 power rails, name one VDD33 and connect all them to that.
​They are EMI Filter Beads (a close cousin to the inductor), this one is a good one to use:
http://www.mouser.com/Search/ProductDetail.aspx?R=BLM18KG331SN1Dvirtualk...

0 Ohm is just a soldered-jumper, with really thick traces they could act a fuse as hopefully them blow before traces burn off.

And traces past the beads you could start naming them VDDA, VDDD etc.

alex934's picture
User
37 posts

Thank you for the answer,

Is that any probleme is everything is powered by USB like in my attachment?

"And traces past the beads you could start naming them VDDA, VDDD etc." what do you mean by "the beads"?

Thank you

 

tonyp12's picture
User
17 posts

single usb vbus rail is OK

1.9-V to 5.5-V radio supply
1.71-V to 5.5-V digital supply

though the ferrite is a 0603 package, they're still called beads.

 

 

alex934's picture
User
37 posts

Cool
Ok so I will use 3 inductors to connect them all
I forgot the attachment,  let me know if you see any mistake 

Thank you

Attachments: 
Anjana Muralidharan's picture
Cypress Employee
160 posts

Hi Alex,

The connections of supply pins seems to be ok.

When you will design the PCB layout, Please make sure you will place the capacitors of supply pins as below:

Capacitor recommendation for VDD pins:

For VDDD - If you are shorting all VDDD pins, you can have one 1uF cap in parallel. And place each .1uF near to each pin separately (close to each VDDD pin).

For VDDA -  If you are shorting all VDDA pins, you can have one 1uF cap in parallel. And place each .1uF near to each pin separately (close to each VDDA pin).

For VDDR - If you are shorting all VDDR pins, you can have one 1uF cap in parallel. And place each .1uF near to each pin separately (close to each VDDR pin).

Thanks,

Anjana

 

 

 

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