Can anyone tell me how this circuit works? is it equal to use a standard transimpedance amplifier at the Iout pin?
The AD5543/53 is a Multiplying DAC. With DC Vref, a 16-bit/14-bit current can be set on IOUT. For normal DAC operations, a generic op-amp can be used as the output I-to-V converter. The transfer function for this setup is given equations (1) and (2) on the datasheet. R2 can be set for higher gain output voltage, the internal RFB is set up so that the full-scale output is -1*VREF.
This type of DAC could also accept an AC Vref for 2-quadrant or 4-quadrant multiplication. For more info here, see the Applications Information section on the datasheet.
Let me know if you have more questions.