External Clock Frequency range LPC55Sxx

Watarat — Tue, 12 Jan 2021 00:06:35 GMT

I am unclear as to the range of frequencies that can be applied as an external clock.
I wish to use an external TCVCXO at 10.0000MHz as the system clock.

UM11126 Section 1.2 under clock generation says
" Crystal oscillator with an operating frequency of 12 MHz to 32 MHz. Option for
external clock input (bypass mode) for clock frequencies of up to 24 MHz"

LPC55S6x Data sheet (7.22.1) says
Crystal oscillator with an operating frequency of 1 MHz to 32 MHz. Option for external
clock input (bypass mode) for clock frequencies of up to 24 MHz

Also
In bypass mode, an external clock (maximum frequency of up to 24 MHz) can also be
connected to XTAL32M_P if XTAL32M_N is left open. External [0 – VH] square signal can
be applied on the XTAL32M_P pin from 0 V to 850 mV.

Playing with the clock configuration tool, I cannot set a crystal value of < 12MHz in "Normal crystal oscillation mode.", however by selecting "External clock input (bypass mode)." mode - I can set it to 10MHz.
I am presuming that external clock source can be 1MHz to 24MHz, and the Crystal can be 12MHz to 32MHz

Is this correct??

Re: External Clock Frequency range LPC55Sxx

ZhangJennie — Tue, 12 Jan 2021 06:40:52 GMT

You are right. external clock source can be 1MHz to 24MHz, and the Crystal can be 12MHz to 32MHz.

Have a nice day,

Jun Zhang

topic Re: External Clock Frequency range LPC55Sxx in LPC Microcontrollers

External Clock Frequency range LPC55Sxx

Re: External Clock Frequency range LPC55Sxx