hi,
For TTL logic inputs, connect VLC to 0v.
Set the Iref input to 1mA, with a +4v source use a 4K resistor to the Vref input pin and connect -Vref pin to 0v via a 4K resistor .
Look at page 4 of the datasheet at the Ifs/Iref graph.
On the I out pins connect a 1K resistor to 0v on each pin, this should give a +/-1V swing on the output voltage for a binary input code of 00h to FFh.
I would connect an OPA on the I outputs in order to buffer the DAC.
The Vref is misnamed IMO, its really a stable external voltage source which is used to drive the Iref current into the Vref pin. A series resistor from this external source sets the input Iref current and the OUTPUT currents..
Any external stable +V voltage source can be used to drive the +Iref input providing the current is limited to the specification in the d/sheet.
The lower the power supply to the DAC the lower the possible output current that be given at the Iouts, See the graph Page 4.
Yes I could use a +4V Vref, but I still don't understand what Vref- is used for.
The +Vref and -Vref are the inputs to a 'long tail pair' transistor amplifier.
This type of transistor amplifier can accept bipolar inputs, also it can be used with a signal input on only one input, the other input is then connected to 0V or common via a resistor.
So in the DAC circuit +Vref is the pin with the signal input ie: 1mA ,,, the other pin -Vref is connected to 0V.
In order to give the optimum operation of the long tailed pair amplifier, the unused pin ie: -Vref is connected to 0V thru the same value resistor as the +Vref