MSP430fr5739 crystal

Sebastian Gerlich said:

For the 32.768 KHz Crystal we work together with Micro Crystal www.microcrystal.com . Here we put in our MSP430 Kits normaly the MS1V-T1K or the MS3V-T1R.

Quality Crystal For MSP430, CC430 and CC1101

A quick search on the TI.com homepage will give you the answer you seek. The MSP-EXP430FR5739 is documented on this page: http://www.ti.com/tool/msp-exp430fr5739

The Hardware User's Guide (down the page) link is: http://www.ti.com/lit/ug/slau343b/slau343b.pdf

In that document, page 15 has the schematic and shows a 12 MHz crystal on XT2 pins. Same document, page 21, has a BOM for the board.

Almost any parallel-resonant crystal can be used if you calculate and install the proper load capacitors and set the appropriate drive strength in the oscillator control registers. Those settings are going to be application specific (depending on the xtal and MSP), thus you will need to read the datasheets for both parts.

Jason,

That information you provided, while good in the general case, is no good for the board that he specifically asks about. The XT1 pins are not wired out on the MSP-EXP430FR5739 board. Only XT2 is wired out, and comes pre-populated with a 12 MHz crystal.

I am little weak on crystal design, so looking at:

http://www.microcrystal.com/getdoc/6308e2c5-0ff9-4730-bf9a-95a1c96c3329/TI_MSP430x5xx_12-5pF.aspx

Does this apply to FR series controllers, so the F5XXX and FR5XXX have the same crystal interface?

 Also, they show that there are no external caps, should I not include external caps as well?

This is the first time I am dealing with crystal.  Thanks for your help.

They are providing those guidelines for using *their* crystal with the MSP430F5xx series. That may not hold true with someone else's crystal.

In general, if you have space on your board, I recommend putting the capacitor land pads there (and don't populate the actual parts) that way you can add capacitors later if needed with just a change to your BOM.

I am not familiar enough with the "F" vs "FR" parts. Look at your User's Guide document for the FR series and the datasheet for your specific device to see what the structure of the UCS peripheral is. They are most likely the same, but do your engineering homework to be sure.

Brian Boorman said:

That information you provided, while good in the general case, is no good for the board that he specifically asks about. The XT1 pins are not wired out on the MSP-EXP430FR5739 board. Only XT2 is wired out, and comes pre-populated with a 12 MHz crystal.

Silver Diamond said:

 Also, they show that there are no external caps, should I not include external caps as well?

In the MSP430FR5739 data sheet find, "Crystal Oscillator, XT1"  That will give you your requirements.

You can then do the design work to figure out your capacitance values based on the configuration you choose.  Here is a template of how to calculate that.

• TI MSP430 device
  • XCAP_? (?? pF internal capacitors)
  • XT1DRIVE_?
• ? pF external capacitors for Cd and Cg
• External crystal
  • CL (load capacitance) = ?? pF
    • CL=((C1 x C2) / (C1 + C2)) + Cstray
      • C1 = XCAP_? + Cd = ?? pF + ? pF = ?? pF
      • C2 = XCAP_? + Cg = ?? pF + ? pF = ?? pF
      • Cstray = ? pF (approximately)
    • CL = ?? pF

Jason Work said:

MSP430FR5739 supports 2 crystal?

See now... making me look stupid. You are indeed correct, as I looked at the wrong device on the board schematics. XT1 it is.