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PSoC™ 5, 3 & 1 Forum Discussions

jjc7809
Level 1
Level 1
First reply posted First question asked First like given

Hello All,

 

I'm working with a team of students and we are developing a prototype using a PSoC 5LP. A question I have is, when applying power to the PSoC 5LP, is it required to  to have separate supplies (We are using LDO's) for VDDA, and VDDD? Also, we are not planning on using an of the analog peripherals.  Any help would be appreciated.

 

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BragadeeshV
Moderator
Moderator
Moderator
First question asked 1000 replies posted 750 replies posted

Hi @jjc7809 ,

In general, it is  good to have separate voltage regulators for VDDA and VDDD. This ensures that the high speed switching signals do not interfere into the sensitive analog section of the design. However, if for cost reasons or if your digital section of your design does not contain high-speed or high-current switching signals or if you do not have sensitive analog circuits in the design,  you can use a single voltage regulator. You need to power VDDA whether or not you use the analog components of the device.

However, you need to wire the power supply as though you have separate voltage regulators. Separate both power and ground signals for the analog (VDDA, VSSA) and digital supplies (VDDD, VSSD). Make the connection between these two supplies (analog and digital) as close to the power supply source as possible (preferably using a zero ohm resistor or a ferrite bead). Usually the output impedance of the power supply is low, and with such a connection, the digital supply has less of an effect on the analog supply.

BragadeeshV_0-1615394410571.png

 

We recommend you to go through the app note PSoC®
3, PSoC 4, and PSoC 5LP Mixed-Signal Circuit Board Layout Considerations for better understanding!

https://www.cypress.com/documentation/application-notes/an57821-psocr-3-psoc-4-and-psoc-5lp-mixed-si...

Also please check the PSoC 5 LP Developement Kit layout for reference.

https://www.cypress.com/documentation/development-kitsboards/cy8ckit-050-psoc-5lp-development-kit

Hope this helps!

Regards,
Bragadeesh

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4 Replies
BragadeeshV
Moderator
Moderator
Moderator
First question asked 1000 replies posted 750 replies posted

Hi @jjc7809 ,

In general, it is  good to have separate voltage regulators for VDDA and VDDD. This ensures that the high speed switching signals do not interfere into the sensitive analog section of the design. However, if for cost reasons or if your digital section of your design does not contain high-speed or high-current switching signals or if you do not have sensitive analog circuits in the design,  you can use a single voltage regulator. You need to power VDDA whether or not you use the analog components of the device.

However, you need to wire the power supply as though you have separate voltage regulators. Separate both power and ground signals for the analog (VDDA, VSSA) and digital supplies (VDDD, VSSD). Make the connection between these two supplies (analog and digital) as close to the power supply source as possible (preferably using a zero ohm resistor or a ferrite bead). Usually the output impedance of the power supply is low, and with such a connection, the digital supply has less of an effect on the analog supply.

BragadeeshV_0-1615394410571.png

 

We recommend you to go through the app note PSoC®
3, PSoC 4, and PSoC 5LP Mixed-Signal Circuit Board Layout Considerations for better understanding!

https://www.cypress.com/documentation/application-notes/an57821-psocr-3-psoc-4-and-psoc-5lp-mixed-si...

Also please check the PSoC 5 LP Developement Kit layout for reference.

https://www.cypress.com/documentation/development-kitsboards/cy8ckit-050-psoc-5lp-development-kit

Hope this helps!

Regards,
Bragadeesh

Hello.

An excellent description by Bragadeesh!

Something that many developers overlook, it's in the datasheet as a Note:
The power supplies can be brought up in any sequence. However, once stable, VDDA must be greater than or equal to all other supplies.

And,
The VDDIO supply voltage must be greater than the maximum voltage on the associated GPIO pins. Maximum voltage on GPIO pin =< VDDIO =< VDDA.

Pay close attention to the datasheet description in the Power System section.  Again, Vccd pins are very important to connect properly.

AN61290 application note has great details on powering and other aspects.

Good luck with your project.

Thank you for your help! Much appreciated.

Regards,

Joe

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Len_CONSULTRON
Level 9
Level 9
500 solutions authored 1000 replies posted 750 replies posted

jjc,

Bragadeesh and BiBi are correct.

Simply put: It is possible to use one supply from a single LDO.  In general, take care when PCB routing VDDD and VDDA.  It is best to connect the two trace routes for VDDD and VDDA right at the bulk cap off the LDO output.  This provides some isolation for the VDDA supply.   

Also, there should be bypass caps off at least 1uF at the PSoC5 pins to minimize current surges during switching events.

Len
"Engineering is an Art. The Art of Compromise."