Some Doubts about Crystal choice in MSP430F1491

[gorkin]

msp430f1491 8mhz 3.3v

Hello!
I am start one application and my system must be supply with +3.3V . I use
the MSP430F1491 and reading more details about the crystal for hight speed
oscilator module (XT2) I found in the datasheet(SLAS272F - page24) one
graphical about frequency x power supply, but not have any mention about
the oscilator type (DCO or XT2) . Can someone explain more about this?
In observation field before the graph, have a note explain this:

NOTES:
1. In LF mode, the LFXT1 oscillator requires a watch crystal. A 5.1M§Ù
resistor from XOUT to VSS is recommended when VCC <
2.5 V. In XT1 mode, the LFXT1 and XT2 oscillators accept a ceramic resonator
or crystal up to 4.15MHz at VCC ¡Ã 2.2 V. In XT1 mode,
the LFXT1 and XT2 oscillators accept a ceramic resonator or crystal up to
8MHz at VCC ¡Ã 2.8 V.

2. In LF mode, the LFXT1 oscillator requires a watch crystal. In XT1 mode,
LFXT1 accepts a ceramic resonator or a crystal.

Then, if my supply voltage is greather then 2.8V I can use 8MHz crystal? If
positive what the purpose of the graphical later?
Thanks a lot, Gorkin.

 

[bobcat1]

Hello Gorkin

Use LF crystal 32.768 KHz connected to lo xtal input LFXT1(if you can place low cap load crystal you need not to use exernal cap - oscilator work well without )


If you want to work in high speed use hi frequency crytal up to 8 MHz on HFXT1

You can also use LFXT1 with 32KHz and Do FLL in software to lock the DCO high frequency to the low frequency for high stability

if you want full speed from the micro you can use 8MHZ crystal on HFXT1,2 but using this method drow more power from the micro

All the best

BObi