Can MAX3390 talk to itself ?

No, MAX3373E–MAX3376E/MAX3378E/MAX3379E and MAX3390E–MAX3393E, these parts cannot talk to itself. When two parts are planned to interface each other, one cannot talk to another one. Similarly, for a "loop back" connection on the same side of the level shifter, the logic levels would not be adequate to meet the min/max specifications. The VOH minimum is lower than the VIH maximum specification. The input threshold values (VIH & VIL)are not compliant to receive the output threshold levels(VOH & VOL), even both of them shares the same power levels. A sample calculation is given below for both logic-side and VCC side power supply rails of 3.3V. VL VCC 3.3 3.3 VIH 3.1 2.9 VIL 0.15 0.15 VOH 2.211 2.211 VOL 0.4 1.4