Hi dorinc,
As said in the LOAD DAC Input(/LDAC) FUNCTION Section in page 18 of the data sheet, the operation of the /LDAC function is like that of an OR logic gate. If you wish to control the DAC through software, the /LDAC pin should be tied to high and the /LDAC bits set as required. Alternatively, if you wish to control the DAC through hardware, the /LDAC mode bits should set to high (01).
Do you require simultaneous updating of all DAC outputs? If not, you may tie /LDAC pin permanently low. This way, the DAC registers are automatically updated once there is a new data in the corresponding input register.
Regards,
Mark