When I look at the datasheet, I don't know how precise width control can be performed per 1 clk.
I see the above parameter as the sampling rate.
The datasheet says 1GSPS. However, it is confusing because the output is up to 400 MHz analog.
overview : 1GSPS, 14-Bit, 3.3 V CMOS Direct Digital Synthesizer
FEATURES : 1 GSPS internal clock speed (up to 400 MHz analog output)