TPS631000: Duty cycle when VIN=VOUT

Hi Team, 

My customer is considering TPS631000 with following condition. 

・Vin : 4.5V~5.5V(Typ.) and nominal value is 5V 

・Vout：5.0V(within ±5%)

・Iout：1.5A 

How should customer use formula (2) to calculate duty cycle in datasheet in this case? 

If customer uses 5V for both Vin and Vout, duty cycle will be 0. 

https://www.ti.com/jp/lit/ds/symlink/tps631000.pdf#page=11

Thanks.

Regards,

Jo