

I'm testing a testing board using LT3021 as power to digital 1.8V and 3.3V, analog 1.8V and 3.3V.The testing board is connecting to Xilinx's ZC702 board to be controlled.Without connecting to ZC702.The voltage of digital 3.3V is 3.291V.The voltage of digital 1.8V is 1.799V.The voltage of analog 3.3V is 3.282V.The voltage of analog 1.8V is 1.799V.The voltage of ADJ to digital's LT3021 is 0.198V.After connencting KC702 and burning logic,The voltage of digital 3.3V is 3.202V.The voltage of digital 1.8V is 1.754V.The voltage of analog 3.3V is 3.283V.The voltage of analog 1.8V is 1.799V.The voltage of ADJ to digital's LT3021 is 0.192V.Why the voltage drops?