The MAX17220, MAX17222,and MAX17224 have the Enable Transient Protection feature and will require a high impedance pull up (application dependent, typically 33 Meg) on the EN pin which adds around 61nA ​to the quiescent current with VIN=1.5V, VOUT=3.3V and efficiency=85%. The MAX17221, MAX17223, and MAX17225 do not have the Enable Transient Protection and the EN pin can be tied to the input voltage without any extra current draw.