All:
It looks like there is a difference in range for crystals on these two processors. If a 20 MHz crystal with ESR of 60 ohms is used for the F28035, can that same crystal be used for the F28335? It appears not. Can someone confirm that a lower ESR crystal is necessary for proper operation of the F28335?
F28335:
3.6.1.1 External Reference Oscillator Clock Option
The typical specifications for the external quartz crystal for a frequency of 30 MHz are listed below:
• Fundamental mode, parallel resonant
• CL (load capacitance) = 12 pF
• CL1 = CL2 = 24 pF
• Cshunt = 6 pF
• ESR range = 25 to 40Ω
TI recommends that customers have the resonator/crystal vendor characterize the operation of theirdevice with the DSC chip. The resonator/crystal vendor has the equipment and expertise to tune the tank circuit. The vendor can also advise the customer regarding the proper tank component values that will produce proper start up and stability over the entire operating range.
F28035:
3.8.2 Crystal Oscillator Option
The typical specifications for the external quartz crystal (fundamental mode, parallel resonant) are listed in Table 3-17.
Furthermore, ESR range = 30 to 150 Ω.
Regards,
Todd Anderson
From the datasheet ESR spec, it looks like a different crystal may have to be used, but there may be other factors. I have requested the product team to comment on this if there are any additional things to be aware of.What is the load capacitance of the 20 Mhz crystal you have on the F28035?
Load capacitance on 20 MHz crystal used on F28035 is 18 PF.
An additonal item from the Hardware Design Gudelines document (SPRAAS1A):
"It is recommended to select a fundamental mode parallel resonant type crystal having a CLOAD of around 12pF and ESR of 30 to 60 ohms."
Can I get clarification of the requirements for the sm320f28335-ht processor?
.
Answered in http://e2e.ti.com/support/microcontrollers/tms320c2000_32-bit_real-time_mcus/f/171/t/209735.aspx