Application Note: SLAS626-March 2011 pg 42; Crystal Oscillator, LFXT1, low-frequency mode mentions that the f_LFTXT1,LF (test condition XTS = 0) the suggested crystal to use is a 32768 Hz.
Question1 : What is the range that this IC allows for operation? Example +/- 100Hz or +/-50ppm, etc..... We plan to use a +/- 20ppm 32768Hz crystal and calculated its possible temperature variance, but there is nowhere in the document that shows the Min/Max range that I can guarantee for this micro-controller MSP430F47197 to operate properly. is there a range or suggested range allowed?
Question 2: if there is a shift in crystal oscillation, when it uses for MCLK, ACLK, etc. does it have internal PLL circuit or such to correct itself to get more accuracy?Reason I am asking is is oscillation crystal is off, the frequency calculation timing becomes shifted also (effects a lot of internal sampling calculation). I would like to determine if I need a even better ppm part to use.
Regards,
Daichi Tanaka
Hello,
@Question 1:
The accuracy of your XTAL also determines the accuracy of your system. I do not think that there is any suggested or allowed range for 32768 XTAL. If there is a 42122Hz +/- 2 kHz XTAL available, it will work too.
@ Question 2:
The FLL+ module of your chip has an FLL. This control loop allows one to set the clock to a multiple of the XTAL clock (max. frequency is limited by DCO). It also produces a clock with a jitter, as the frequency of the DCO has to be controled to a multible of XTAL clock. But you need at least one trusted accurate clock source (XTAL).
Regards
Marco
Daichi TanakaReason I am asking is is oscillation crystal is off, the frequency calculation timing becomes shifted also (effects a lot of internal sampling calculation). I would like to determine if I need a even better ppm part to use.
In addition to the good information which Marco already gave, please check the two Application Notes below which might be helpful for you:
1) MSP430 32-kHz Crystal Oscillators (Rev. B)
2) MSP430 LFXT1 Oscillator Accuracy
BR,
Mo.
Daichi TanakaWhat is the range that this IC allows for operation? Example +/- 100Hz or +/-50ppm, etc.....
Daichi Tanaka if there is a shift in crystal oscillation, when it uses for MCLK, ACLK, etc. does it have internal PLL circuit or such to correct itself to get more accuracy?
Daichi Tanaka is oscillation crystal is off, the frequency calculation timing becomes shifted also
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