39.8.2 Reference Control

Name: REFCTRL
Offset: 0x01
Reset: 0x00
Property: PAC Write-Protection, Enable-Protected

Bit 76543210 
 ONREFBUF     REFSEL[1:0] 
Access R/WR/WR/W 
Reset 000 

Bit 7 – ONREFBUF Reference Buffer On

Turning on the buffer increases the impedance seen on the external reference, so that the current load reduces from 5μA to 0.10μA. This needs to be matched with whatever type of reference circuit is used.

ValueDescription
0 Reference Buffer Off
1 Reference Buffer On

Bits 1:0 – REFSEL[1:0] Reference Selection

These bits select the reference for the ADC.

Note: The reference buffer should be enabled (ONREFBUF=1) when using the internal INTREF or DAC output as reference.
ValueNameDescription
0x0 INTREF Internal voltage reference, supplied by the bandgap (refer to SUPC.VREF.SEL for voltage level information)
0x1 VREFB pin External 1-5.5V
0x2 DAC output Internal 1-5.5V
0x3 VDDANA Supply 2.7-5.5V