KEA128 48MHz with external resonator

[hanisamara]

Hello, 

i would like to get 48MHz core frequency and 24MHz Bus frequency in FEE Mode. But if i am using an 8 MHz crystal i just get 40 MHz and 20 MHz. Which crystal and which RDIV i need to get 48 MHz and 24 MHz? i do not think that i could find something like 9,6/9,9MHz Crystal on the market?

the OSC frequency must be in the range 31.25 kHz to 39.0625 kHz. So if i have 39.0625KHz then after FLL (x1280) i will get 50MHz on the ICS output!! But KEA128 can max. 48MHZ!! 

how to solve this?

thanks in advance,

Hani

[mjbcswitzerland]

Hello Hani

For 48MHz you need 37.5kHz at the FEE input and there are various crystals that can be used, although 2.4MHz, 4.8MHz, 9.6MHz are not standard frequencies. You can however contact most crystal manufacturers and specify the frequency that you need any they will cut them to it.

In case you are doing a hobby project where you don't want to order a small quantity to specification, or you don't need the accuracy and stability of the crystal, you can also use the 37.5kHz IRC as source and possibly additionally trim again it to get the most accurate frequency possible at the operating temperature.

regards

Mark

Complete KEA solutions, training and support:http://www.utasker.com/kinetis.html
Kinetis KEA128:
- http://www.utasker.com/kinetis/TRK-KEA128.html
- http://www.utasker.com/kinetis/FRDM-KEAZ128Q80.html

[hanisamara]

Hello Mark, 

thank you for your reply. 

i need this for a real project in the automotive area. I need the external crystal cause i have also Lin Stack on the Controller, therefor i need the accuracy. We are talking about 1-2 million controllers :smileywink:. 

I have many interrupts in the system (Lin, I2c, ADC, Timer, PWM) so i need 24 MHz.

**the crystal should also be automotive certified. 

regards, 

Hani

[mjbcswitzerland]

Hi Hani

That means that you are looking for 1..2 million crystals and you are experienced in manufacturing in the automotive sector and high volumes. So you will also know that that you can go to any crystal manufacturer for your requirements and they will be pleased to supply you with the exact frequency that you need - just point out that it needs to be automotive certified and chose the best offer that ensures this.

Regards

Mark