LPFLL clock accuracy issue of MKE14Z256VLL7

qinshengli — Thu, 26 Oct 2017 19:19:57 GMT

MKE14Z256VLL7 is used for our motor control board.

The crystal frequency is 4 MHz and LPFLL clock frequrncy is set to 72MHz.

The LPFLL clock is used for FlexTimer 0 (FTM0). The FTM0 is used for motor PWM control.

By testing we found that there are some LPFLL clock errors.

Three target boards are used for the test. The clock errors from 2 boards are negligible while the clock error from the 3^rd one is about 0.8%.

Then the crystal is changed for the 3rd board but error is still the same.

What could be source of the clock error?

Re: LPFLL clock accuracy issue of MKE14Z256VLL7

jingpan — Mon, 30 Oct 2017 09:12:17 GMT

Hi Qinsheng,

the LPFLL Frequency accuracy in closed loop is 1%. So you'd better do not use FLL as the clock base.

Regards

Jing