DAC output voltages
The datasheet tels us, that 4.5V is nominell, max at 4.8V...
Check pls figs 9...11 & pp6 (Uout Analog full-scale output voltage, RL,10 kΩ typ. 3.5V, but, you must eventuelly buffer it (Rload>=50KOhm).. .
As sum; I think it is to use as hobby circuit w. your wishes, but as product... Find some other solution.
K.
The datasheet isnt enough detailed to tell exat yes- in relation your problem ..
You wish to take Vcc as reference? Vorget it, then it has lot of changes, isnt referencebar:-(... You need min. a Zener , normally an "referenc source/circuit-IC"!