The block diagram of a typical DOCSIS downstream network is shown in Figure 143. The physical layer (PHY) of the cable modem termination system (or CMTS) must support normal downstream operating range from 54 MHz to 1002 MHz as well as extended operating range up to 1794 MHz. The high input bandwidth (up to 3.33 GHz) of DAC38RF82 and DAC38RF89 makes these devices suitable for DOCSIS CMTS. Also the integrated high performance PLL simplifies system clocking by eliminating the need to generate and distribute high frequency sampling clock to the DAC. In the following sections, the performance of DAC38RF82 (and DAC38RF89) used to generate DOCSIS 3.0, Annex A, 6 MHz 256-QAM carriers will be described.