TI E2E Community
C2000 32-bit Microcontrollers Forum
Concerto: Xtal frequency and load capacitance
I have a couple of questions please...What is a good common crystal frequency to use for running the 100/150 MHz Concerto?
What is the load capacitance of the Xtal pins (X1 and X2) on the Concerto device?
I guess a good start is to check the design of the Concerto Control Card. Download TIs "controlSUITE" for C2000 microcontrollers. In the folders (F28M35x) you can find the schematic.
Andy ChernockWhat is a good common crystal frequency to use for running the 100/150 MHz Concerto?
Are you trying to run the M3 at 100 and the 28x at 150? If so this combination is not supported. The M3 subsystem is a divider off of the PLLSYSCLK (which is also the 28x frequency). So if you run 28x at 150 the max you can run the M3 is 150/2 = 75. if you want to run the M3 at 100, then you could run the 28x at 100 as well.
For a 150/75Mhz config you would use 30MHz input and for 100Mhz/100MHz config we would use 20MHz.
Andy ChernockWhat is the load capacitance of the Xtal pins (X1 and X2) on the Concerto device?
We do not have this information at this time and cannot make a recommendation. When the information is available it will be added to the data manual. If you like you can subscribe to changes to the documentation using the link on the product folder (“Alert me about changes” http://www.ti.com/product/f28m35h52c upper right corner).
In general, TI recommends that customers have the resonator/crystal vendor characterize the operation of their device with the microcontroller. 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 ensure start-up and stability over the entire operating range.
We are looking at having char done by a manufacturer as well.
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