Fig. 1 Functional Block Diagram
The ASNT1124-KMM SiGe IC is a low power and high-speed digital 4 to 1 serializer-multiplexer (MUX) that functions seamlessly over data rates (fbit) ranging from DC to its maximum frequency. The main function of the part shown in Fig. 1 is to multiplex 4 parallel differential CML data signals d0p/d0n, d1p/d1n, d2p/d2n, d3p/d3n running at a bit rate of fbit/4 into a high speed serial bit stream qp/qn running at a bit rate of fbit. Differential or single-ended half-rate clock cep/cen (DDR mode) must be provided by an external source for the part to function properly. The duty cycle of the internal clock can be adjusted through analog ports dccp/dccn.
The serialized data words qp/qn and the clock divided-by-4 signal c4op/c4on are transmitted through CML output interfaces. The clock and data outputs are phase-matched to each other resulting in very little relative skew over the operating temperature range of the device. The amplitude of the clock signal can be adjusted through an analog port ampadj. The part’s I/O’s support the CML logic interface with on chip 50Ohm termination to vcc and may be used differentially, AC/DC coupled, single-ended, or in any combination. In the DC-coupling mode, the input signal’s common mode voltage should comply with the specifications shown within the ELECTRICAL CHARACTERISTICS section of the product data sheet. In the AC-coupling mode, the input termination provides the required common mode voltage automatically. The differential DC signaling mode is recommended for optimal performance.