topic Re: KV4x : PWMA : Resolution in Kinetis Microcontrollers

KV4x : PWMA : Resolution

EmbedALM — Wed, 06 Nov 2024 08:34:57 GMT

I have found(on NXP site) and referd document Nano-edge placement of eFlexPWM on KV4x family .

As per the document it helps to increse duty cycle resolution by using fractional unit, so we can have duty cycle like 50.03125,
50.0625, 50.09325,50.125,…….50.96875.

my quary is regarding frequency resolution

in my application i have to use fix 50% duty cyle and have to change frquency as per the need.

Example : e PWM driving clock for KV4x is 100MHz

Total Timer Ticks : 1000 will generate frq 100000 Hz (100KHz)

Total Timer Ticks : 999 will generate frq 100100.1001001001 Hz

so 1 tick will produce 100Hz diffrance...and this diffrance increase as we go higher in frquency.

Is it possible to increase frquency resolution using fractional unit.??

orr it is just helps with duty cycle..??

in my application i need to vary frquency in range from 45KHz to 100KHz. I have no idea right now how much resolution i required but if it is possible to increase resolution like in duty cycle..,,,would like to go for it for precise performance.

Re: KV4x : PWMA : Resolution

xiangjun_rong — Thu, 07 Nov 2024 07:02:32 GMT

Hi,

Of course, you can get fractional frequency.

For eFlexPWM module, the VALUE1 register controls the PWM frequency, for example

Example : eFlexPWM driving clock for KV4x is 100MHz in edge-alignment mode, the tick cycle time is 10nS.

The VALUE1 reg is 1000, the PWM cycle time is 1000*10nS=10uS, in other words, the PWM frequency will be 100Khz.

Assume that the fractional feature is enabled, set the PWM_SM0FRACVAL1 as 16 with

PWMA_SMnFRACVAL1=16<<11;

The PWM cycle time will be 10nS*(1000+16/32)=10005nS, the PWM frequency will be 99.95khz

Hope it can help you

XiangJun Rong

Re: KV4x : PWMA : Resolution

EmbedALM — Wed, 27 Nov 2024 05:18:17 GMT

can we use nano edge fractional unit in signed center alignment with complimentary pairs (with deadtime of 1.5 micro-second) ?

Re: KV4x : PWMA : Resolution

xiangjun_rong — Wed, 27 Nov 2024 06:50:53 GMT

Hi,

The nano-edge fractional unit can be used the signed center alignment mode with complimentary pairs (with deadtime of 1.5 micro-second), but your code should make sure that the dead time is enough to avoid the shorting event between DC power supply and GND.

Hope it can help you

Xiangjun Rong