HI,
1> KL15 ADC VREFH voltage could up to 3.6V, same with VDDA voltage level. VREFL is same with VSSA. There is no ADC VREF pins current data.
2> In general, we recommend to use VREFH = VDDA, VREFL = VSSA.
Customer could check below link about how to design KL15 ADC module hardware and software to get more accuracy performance:
http://cache.freescale.com/files/microcontrollers/doc/app_note/AN4373.pdf
Wish it helps.
best regards
Ma Hui
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