What should be the crystal requirements for a USB application using the LM4F131E5QR?
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Frequency: 5, 6, 8, 10, 12, 16, 18, 20, 24, or 25 MHz
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Frequency Stability (over temperature): ±??ppm
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Frequency Tolerance: ±??ppm
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Frequency Drift (over time): ±??ppm/year
Is there an absolute deviation allowed from an ideal frequency in which case it would be up to the designer to fit within that depending on his/her evaluation of the product use case (environment, lifetime, component tolerance selection)?
References:
"The main oscillator must be connected to one of the following crystal values in order to correctly generate the USB clock: 5, 6, 8, 10, 12, 16, 18, 20, 24, or 25 MHz. Only these crystals provide the necessary USB PLL VCO frequency to conform with the USB timing specifications."
Stellaris LM4F131E5QR Microcontroller Data Sheet (Rev. C) PDF 6242 27 Apr 2012
Page 220 of 1251
LM4F232 USB+CAN Evaluation Kits (EK-LM4F232) use these crystals:
Abracon ABM3-16.000MHZB2-T
NDK NX5032GA-16.000000MHZ
Stellaris LM4F232 Evaluation Board User's Manual PDF 537 21 Sep 2011
Page 32 of 34
