Maximum ETPU channel frequency

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Maximum ETPU channel frequency

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vrushalitaklika
Contributor III

Hi,

Can someone please highlight, what is the maximum limit of etpu channel frequency?

In the application notes, it states 

freq (uint32_t): The frequency of the PWM output in Hz. The range of this parameter is determined by the complete system but normally should be between 1 Hz and 100 kHz.

However I have to generate PWM of 300Khz, and When I generate, I get a square wave in which the vertical edges are not vertical.The rise and fall in voltage should be instantaneous but here there is a distinct lengthening of the rise and fall times plus a certain amount of rounding of the waveform.

I tried to use different value of slew rate while configuring SIU_PCR register.

Please suggest.

Waveform generated by my code is similar to one attached.

Thanks

Vrushali

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davidtosenovjan
NXP TechSupport
NXP TechSupport

Hi, which device is this question related to?

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vrushalitaklika
Contributor III

This is for MPC5777C controller

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davidtosenovjan
NXP TechSupport
NXP TechSupport

Hi, timing of output pads with slew rate control you have defined in

MPC5777C Microcontroller Data Sheet Data Sheet, Rev. 11, 04/2017,

Figure 5 and Table 9.

 

AN2849 (document describing eTPU PWM function) speaks about 100kHz.

If we take into account that the PWM function was written for MPC5554, its eTPU max frequency is 66MHz and max eTPU frequency for MPC5777C is 100MHz (in eTPU or normal clock mode), we could simply estimate maximum frequency around 150kHz, but it is given by eTPU code execution time, not by pad performance.