TMS320F2800157-Q1: Frequency offset problem of crystal oscillator used with 2800157

Hi Joesph,

I have received your reply, and the background of this question is that the temperature of the external crystal oscillator that our company is currently using with F2800XXX exceeds the calibrated working temperature in the specification. Therefore, we need to select a crystal oscillator with a higher working temperature, and the corresponding frequency difference will also be changed accordingly. However, what we are not sure about is that although the recommended frequency of the external crystal oscillator is marked in the specification book, there is no indication of the frequency difference limit of the crystal oscillator. If the crystal oscillator frequency I am using is 20Mhz, there must be a difference between the total frequency difference of ± 20ppm and ± 50ppm. Can your company provide the corresponding recommended deviation range for our company's reference? Thank you

Hi Z,

The best way to approach this is to check the clock accuracy requirement of your applications if they still function reliably with a frequency deviation of +/-20ppm and +/-50ppm.  For instance, do the CAN peripherals still properly communicate with this clock deviation and are the EPWMs still going to toggle accurately for your control application with this deviation from the external clock? The crystal oscillator circuit in the F2800x family would operate based on the input from the external clock and would produce corresponding SYSCLK and deviation based on the characteristics of the external crystal.

Regards,

Joseph