Several services can be unified in this fashion, including Internet access, cable TV and even phone services. The multiplicity and complexity of all these blocks impose significant challenges on designers at both the component and board levels. In addition, compatibility with analog TV calls for clean analog signal processing from the wall TV cable outlet to the TV set. Therefore, selecting a proper partition for integrated functions becomes a key requirement for combining high quality TV reception and high data rates in a cable modem at low cost. Inside a typical digital set-top box.
Low cost is of vital importance, so selecting a proper technology is key to a successful design.
ASICs that include significant digital and analog content are often difficult to schedule due to the time needed to handle the inherent design challenges and the frequent need for customer feedback. Figure 3 is a block diagram of the AD9873 Analog Front End Converter for Set-Top Boxes and Cable Modems. A pair of 8-bit ADC's is used to convert quadrature inputs from the demodulated OOB channel. A tighter specification is required from the 10-bit ADC, due to its major role in digitizing cable modem data. The outputs of all these converters are multiplexed to reduce the number of package pins.