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How is a logic HI MK26FN2M0VMD18 input on an unpowerd MK26FN2M0VMD18 supplying 1.6V to 3.3V logic supply.

Question asked by MARK BRINKMAN on Jan 23, 2019
Latest reply on Jan 23, 2019 by John Suchyta

Active USB device port powers USB-to-UART bridge (CP2102). The logic +3.3V MK26FN2M0VMD18 supply is OFF. CP2102 UART TXD and RXD are connected to MK26FN2M0VMD18 PTE1 and PTE0 respectively. UART TXD logic HI output is partially (1.6V) powering +3.3V supply through MK26FN2M0VMD18 PTE1 (ADC1_SE5a). Data sheet states there are no ESD diodes to VDD on any MK26FN2M0VMD18 digital IO or analog input. Why is +3.3V logic supply 1.6V when it is OFF?