Hello friends,

Studying AD9859, I noticed some discrepancies I like to clear:

At pag. 16, on Amplitude Scale Factor description, datasheet says .... 10-bit amplitude scale factor used in the output shaped

keying (OSK) operation..... but on register map description (Table 5), ASF register has 14 bits for amplitude scale factor.

Also in figure 1, the bus for ASF is 10 bit wide.

So which one is it? 10 or 14 bits for amplitude scale factor ? If 10 bits is correct, then ASF[13:10] bits should be n/u.

Can somebody clarify, thanks very much.

Hi Zuzu,

The AD9859 is a derivative of the AD9954 DDS. Same die but bonded differently. The AD9954 has a 14 bit DAC and 14 bits of amplitude scale factor. The AD9859 data sheet was modified from the AD9954 data sheet for efficiency. However, the AD9859 is bonded to have a 10 bit DAC, so there's only 10 bits of amplitude scale factor enough though the register map has 14 bits. Note, the MSB is bit is 13. So, the 10 bits are <13:4>.