LPC1768 QEI max. frequency

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by yilmazkircicek on Fri May 02 00:15:30 MST 2014
Hi All,

We are testing encoder with LPC1768 QEI module and experienced that we miss some of the pulses with inceasing rpm and encoder resolution.

For example:

Encoder with 40.000 pulse is turns  @3000 rpm. This yields 40.000 * 3000 / 60 = 2 Mhz.

When we turn it 10 times @3000 rpm with a precision servo system, we count 399.9xx instead of 400.000.
It is ok when we slow down the servo to 1500rpm.

I know that the driver IC used in encoder has 2Mhz band witdh and it is mostly related with it.

But I could not able to find max. speed of QEI module in documents. (while digital filter sampling delay = 0)
We are running the LPC1768 and QEI peripheral  @100 Mhz.

Could anyone tell me that what is the limiting speed for QUI module of LPC1768 please ?

Best Regards.