DAC38RF83: Is "Toggle RESETB pin low then high" necessary?

Hello,

user6293841 said:

In datasheet 8.1.1 Start-up Sequence, "Toggle RESETB pin low then high." is showed. Is this necessary?

Yes, this step is necessary. The reset circuit reset all of the internal digital logic to ensure good known start-up of the device.

user6293841 said:

To avoid unintended reset, I will not connect RESTB pin to any controller such as CPU or FPGA, and place a pull-up resistor of 1kohm or less on RESETB pin 
Does this circuit have any problem?

I recommend to have a reset signal to reset the DAC at start-up. A pull-up resistor is good practice to ensure after initial reset the RESETB pin is always in logic HI

user6293841 said:

I afraid unintended DAC output before configuring DAC38RF83.

Please take advantage of the TXENABLE signal. The TXENABLE signal ensures the output are in shut-off during initialization. You can then enable the TX through TXENABLE after the complete DAC + JESD204 initialization