DAC43401-Q1: Can not initial DAC chip

Part Number: DAC43401-Q1

We are using VDD 5v for the ref vdd and we want to produce square wave (0 ~ 1.8v)

Now I'm initialzing 

0x25, 0x0170

0x26, 0x0000

0xD1, 0xC000

0xD3, 0x0108

0xD3, 0x0118

But, it's not working.

Please check for initializing.