This is a continuation of FAQ .
I Understand that we need to tie RUN, TRACK/SS, FB and COMP pin to use the paralleling operation.
But as each control module has its own oscillator, after power-up will all the module be running with the CLKOUT from the first module.
The first module will run with an internal clock and provide the clock for CLKIN of the second module and so on.
One more quick question of how to select from the internal clock or clock from the previous module.
With best regards and wishes
For the LTM4644 the clock signal originates at CH1 clock output which is fed to CH2 clock input, CH2 clock output goes to CH3 clock input and so on, this connection is fixed inside the module. If there is an external clock it will set CH1 clock output frequency. If the clock signal is not present at the channel's controller, the channel will operate at its internally set frequency (1MHz), the clock propagation down the line is still the same. If paralleling multiple modules, it would be recommended to use an external clock to drive the CLKIN of each module, and interleave those clock signals to minimize input & output ripples. This also reduces jitter for the configuration since it does not propagate the clock through more than one module.
Hi Young ,
Thank you for the information.
Is my understanding correct for the following in terms of single LTM4644 module.
With regard to clock propagation, it will still generate a phase difference when propagating without regarding the internal or external clock.
And the default clock for CH2,3,4 is input from CH1 with a phase difference.
If CH2 is disabled then CH3 will run with internal and feed clock to CH4.
With best regards
Could you please let me know if you have any further information on this issue.
The internal phase shifts are according to below (CH1 = 0 deg, CH4 = 90deg, CH2 = 180deg, CH3 = 270deg), phase shifts are the same with and without external clock.
If a previous phase is shut down then there will be no CLKOUT signal to the next phase's CLKIN. When there is no clock input to a phase it will operate based on its internal clock. The following phases down the line will follow the phase shifts listed above / shown below.
Hello, SYoung san
Can I ask additional questions?
Is an internal oscillator prepared for each channel?
Or is one oscillator shared?
I am concerned that a frequency error will occur between the internal oscillators.