The operation of the references used by the MAX1343 depend on the clock mode, type of conversion, and whether the ADC or DAC are in use. Regardless of clock mode, temperature conversions are performed using the internal reference. For all clock modes, the reference source of the MAX1343 can be selected by writing a command byte to the Setup Register. A single byte with the first two bits set to 01 will automatically write the remaining six bits to the Setup Register. The REFSEL[1:0] bits in the Setup Register control the type of reference selected.
REFSEL[1:0] = 00 selects the internal reference for both the DAC and ADC.
REFSEL[1:0] = 01 selects external single-ended references. REF1 is used for the DAC and REF2 is used for the ADC.
REFSEL[1:0] = 10 selects the external reference REF1 for the DAC and the internal reference for the ADC.
REFSEL[1:0] = 11 selects the external reference REF1 for the DAC and the external differential reference (REF1 - REF2) for the ADC.
To configure both the ADC and the DAC of the MAX1343 for an external reference, send the following command:
01XX01XX