TPS543B20: Max duty cycle vs frequency chart

Igor,

TPS543B20 has a relatively long minimum off time.  For  typical value, max duty cycle is given by:

Dmax = 1 - (Toffmin * Fsw) where Toffmin = 250 nsec typical

So for Fsw = 300 kHz, Dmax = 92.5%, for Fsw = 2 MHz, Dmax = 50%