Can two LM2621 boost circuits use the same frequency-setting resistor so that their switching frequencies are synchronized?
Using the same resistor (tied to the FREQ pins of two LM2621s) to set matching or synchronized frequencies will not work. Both ICs will have a slightly different tolerance on the oscillator so using the exact same resistor may not produce the same results. If you could guarantee the same oscillator frequency for a given resistor, you would still have differences since the the LM2621 runs hysteretically at lower load currents. You could never guarantee that they would have a switching burst at the same time or for the same duration.
