How to select the FREQ risistor when the output voltage of the 2 channel are different?

Hi 

In the LTM4622 datasheet, there is a statement that  To reduce switching current ripple, 1.5MHz to 2.5MHz operating frequency is required for 2.5V to 5.5V output with Rfset to GND. as below screen snapshot shown.

In my application, the output volatage of these two channel are quitt different, one is 1.0V, the other is 5.0V, but there is only one FREQ pin to set the frequency, so in this case, how do I select the best value of Rfset to make these two channel work in the best switching current ripple?

Regards

  • +1
    •  Analog Employees 
    on Mar 8, 2021 12:06 AM

    Hello patsburg, 

    For this, when output voltages have different recommended operating frequencies, please set the frequency to the frequency being recommended for the higher output voltage. This is to prevent choosing too low of an operating frequency for the output rail, which if too low could make the inductor current ripple for the rail too large and potentially lead to inductor valley current hitting fixed negative current threshold which would cause the output to potentially rise above the regulation setpoint (if the load current is sufficiently low).

    Thanks!