Jump to content
Sign in to follow this  
cde

Best target voltage for the MSP430? 3.3v vs 3.6v?

Recommended Posts

Does anyone know what the best target voltage for a msp430? 3.3V is a pretty standard voltage level, yet the launchpad runs everything at 3.6V (and it's regulator only shows 0.2v drop at near full load ~250mA).

 

If someone was making a general purpose board, what voltage would you suggest they target? I've been lucky enough that all parts I've used have a wide voltage range, but trying to interface with 5v parts, which often have a 5v * 0.7 = 3.5v minimum for a logic level high, might be an issue at 3.3v. Yet most regulators with preset outputs have 3.3v as the option.

 

Thoughts?

Share this post


Link to post
Share on other sites

I think you nailed it, 3.6V is better for interfacing with 5V parts.  I've had issues with the WS2811 LEDs driving them with a 3.3V fixed-output LDO that cleared up when injecting 3.6V from the LaunchPad into the Vcc circuit.

 

I'm guessing ~3.0-3.3V is a nominal voltage for "3V" parts, 3.3V keeps it high but offers some margin since many 3V parts list 3.6V as the outlying "maximum".  Example, the MAX31855 thermocouple chip--it specifies Vcc of 2.7-3.6V as its required operating voltage.  So I think for general purpose boards, finding a 3.6V regulator is a good investment.

Share this post


Link to post
Share on other sites

i usually go for 3.3v to keep things standard, but often i will use 3.0v without regulation because thats what alot of coin cell batteries come in such are the cr2032 and cr1225

3.3v regulators could possibly be cheaper then a 3.6v regulator, although there are plenty of cheap adjustable ones, at least then if you target 3.6 with it somebody can resolder the resistor to get a lower output if needed

Share this post


Link to post
Share on other sites

Yea, that's what I'm seeing. 3.6 is non-standard. One I'm about to sample from microchip has 3.6 but it's not sample-able and can only be bought directly through them, instead of regular distributors. And the adjustable ones, while mostly priced the same, does bring up the part count and board size some. Though, I did find a neat trick for offering selectable voltage on a adjustable regulator. 

 

post-44-0-18572200-1366508438_thumb.png

 

The switch could be a switch, a header/jumper or a solder jumper, or like what the regulator had internally a mosfet or transistor.

 

Share this post


Link to post
Share on other sites

I think you nailed it, 3.6V is better for interfacing with 5V parts.  I've had issues with the WS2811 LEDs driving them with a 3.3V fixed-output LDO that cleared up when injecting 3.6V from the LaunchPad into the Vcc circuit.

 

I'm guessing ~3.0-3.3V is a nominal voltage for "3V" parts, 3.3V keeps it high but offers some margin since many 3V parts list 3.6V as the outlying "maximum".  Example, the MAX31855 thermocouple chip--it specifies Vcc of 2.7-3.6V as its required operating voltage.  So I think for general purpose boards, finding a 3.6V regulator is a good investment.

 

On the other hand, I had issues with several W5200 chips when powered from 3.6V instead of 3.3V.

 

Thanks for mentioning WS2811 spirilis, I have a 3.3V WS2811 driver board and I am experiencing a lot of random issues, I will see if raising Vcc will clear them up.

Share this post


Link to post
Share on other sites

My half cent would be to stick with 3.3V. 3.3V chips make up a large majority of the market. Luckily, the MSP430 can still maintain 16MHz at 3.3V. Its not necessarily reliable long-term to push 3.3V chips to 3.6Vs or to trust intermediate voltage levels when attempting to interface 3.6V with 5V logic. Level shifters cost a couple cents and guarantee functionality. Best to play it safe rather than the potential for random failures. TI's 3.6V micros are just TI being.... TI.. :?

Share this post


Link to post
Share on other sites

I once powered from 2*AA cell, depending on use of alkaline or NiMH the voltage would become 3.0 our 2.4 volts.

I used this because 3*AA would exceed the 3.6 max with 3 alkaline summing up to 4.5 volts.

Share this post


Link to post
Share on other sites

Fwiw, alternately, if you use the MSP430F5172 you can power the MSP430 via 3.3V but select DVIO to anything between 1.8 and 5.5V... and certain ports (P2.*, P1.6-P1.7, some P3.x) will be driven at that voltage allowing you native 5V I/O.

 

This is exactly what I am doing here and it's working great.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...