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Discussion Groups | MSP430 | XCAPx setting for 12.5pF watch crystal
The purpose of this group is to foster exchange of information on the Texas Instruments MSP430 family of microcontrollers and related tools. Everyone welcome, all levels of familiarity/expertise.
XCAPx setting for 12.5pF watch crystal - abufadel - Aug 8 9:25:48 2009
Hello,
I am trying to understand how to set the load capacitance for the LFXT1. The datasheet states that the load capacitance should match the specs of the used crystal. The crystal that I am using (ST3215SB) is rated 12.5 pF. Available CLeff from the data sheet are: 1, 5.5, 8.5 and 11 pF. Which one can I use?
Thank you for your help.
Amer
------------------------------------
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I am trying to understand how to set the load capacitance for the LFXT1. The datasheet states that the load capacitance should match the specs of the used crystal. The crystal that I am using (ST3215SB) is rated 12.5 pF. Available CLeff from the data sheet are: 1, 5.5, 8.5 and 11 pF. Which one can I use?
Thank you for your help.
Amer
------------------------------------
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Re: XCAPx setting for 12.5pF watch crystal - Howard Hansen - Aug 8 11:02:43 2009
Are you using a TI starter kit or building your own PCB? The 2 TI
starter kits I have seen come with two installed 12 pf capacitors and
need to be included in the calculation. So if you are using a TI
starter kit check the target board first to see if some capacitors for a
watch crystal have already been installed. If your PCB has no external
watch crystal,capacitors and the PCB tracks are very short try the 11 pf
values first. Because a crystal oscillator is susceptible to noise its
PCB tracks should be as short as possible. If your crystal oscillator
PCB tracks are not short you may need to use the 8.5 pf value.
Howard
abufadel wrote:
>
>
> Hello,
> I am trying to understand how to set the load capacitance for the
> LFXT1. The datasheet states that the load capacitance should match the
> specs of the used crystal. The crystal that I am using (ST3215SB) is
> rated 12.5 pF. Available CLeff from the data sheet are: 1, 5.5, 8.5
> and 11 pF. Which one can I use?
>
> Thank you for your help.
>
> Amer
------------------------------------
(You need to be a member of msp430 -- send a blank email to msp430-subscribe@yahoogroups.com )
starter kits I have seen come with two installed 12 pf capacitors and
need to be included in the calculation. So if you are using a TI
starter kit check the target board first to see if some capacitors for a
watch crystal have already been installed. If your PCB has no external
watch crystal,capacitors and the PCB tracks are very short try the 11 pf
values first. Because a crystal oscillator is susceptible to noise its
PCB tracks should be as short as possible. If your crystal oscillator
PCB tracks are not short you may need to use the 8.5 pf value.
Howard
abufadel wrote:
>
>
> Hello,
> I am trying to understand how to set the load capacitance for the
> LFXT1. The datasheet states that the load capacitance should match the
> specs of the used crystal. The crystal that I am using (ST3215SB) is
> rated 12.5 pF. Available CLeff from the data sheet are: 1, 5.5, 8.5
> and 11 pF. Which one can I use?
>
> Thank you for your help.
>
> Amer
------------------------------------
(You need to be a member of msp430 -- send a blank email to msp430-subscribe@yahoogroups.com )