topic LPC54xx The maximum frequency for the SCTimer/PWM clock is 100 MHz ?? in LPC Microcontrollers

LPC54xx The maximum frequency for the SCTimer/PWM clock is 100 MHz ??

ZhaiYF — Fri, 24 Dec 2021 03:09:23 GMT

Question 1、
In the figure "The maximum frequency for the SCTimer/PWM clock is 100 MHz."
Is it only applicable for clock after SCTCLKSEL ?

Question 2、
If set CLKMODE=0 in SCTimer/PWM configuration register。Is there maximum frequency
limit for system clock ?

Re: LPC54xx The maximum frequency for the SCTimer/PWM clock is 100 MHz ??

ZhangJennie — Mon, 27 Dec 2021 05:46:15 GMT

HI ZhaiYF

The Maximum freq for SCT is 100Mhz. any input freq. beyond this value is an invalided input and will have un-guaranteed behavior. also , the 100Mhz limit is mainly com from pad limitation. not the SCT module itself

Have a nice day,

Jun Zhang

Re: LPC54xx The maximum frequency for the SCTimer/PWM clock is 100 MHz ??

ZhaiYF — Mon, 27 Dec 2021 07:27:36 GMT

HI Jun Zhang

Thanks.

Maybe I confused the SCTimer clock source and clock input.

Now, SCTimer does not need any external clock input except the system clock. I want to Confirm whether the SCTimer module can work stably if the system clock is greater than 100MHz, such as 180MHz.

The MCU used is lpc54618.

Re: LPC54xx The maximum frequency for the SCTimer/PWM clock is 100 MHz ??

ZhangJennie — Mon, 27 Dec 2021 13:15:22 GMT

Hi ZhaiYF

There are two type of input for SCT, the the 100MHz clock limitation is only valid for the clock source inputted from external pads (SCT_IN7), if you use system clock as the SCTimer/PWM clock source, the system clock frequency can be greater than 100MHz.

You can also see this "Remarks " immediately below "Select a function clock using SCTCLKSEL (Section 7.5.41)."

Hope this helps,

Jun Zhang