Parallel-to-Serial Converter (PISO)

A Parallel-to-Serial Converter (PISO) is a fundamental component within a Serializer/Deserializer (SerDes) system. Its primary role is to take multiple bits of data presented simultaneously on parallel input lines and sequentially output them one bit at a time on a single serial line. This conversion is essential for high-speed data transmission over channels with limited physical connections, enabling efficient communication between digital systems. The PISO converter typically operates using a shift register. Parallel data is loaded into the register in one clock cycle. On subsequent clock cycles, the register shifts its contents, outputting the least significant bit (or most significant bit, depending on design) at each cycle until all parallel bits have been transmitted serially. Control logic manages the loading and shifting phases. This directory entry provides reference parameters for typical PISO components used in industrial applications. The number of input bits ranges from 8 to 16, determining the width of the parallel data bus. Maximum clock frequency ranges from 100 to 500 MHz, with higher frequencies enabling faster serial data rates. Supply voltage is compatible with standard logic levels, typically 3.3 to 5.0 V. Output data rate, a product of clock frequency and input bits, ranges from 0.8 to 8 Gbps. Propagation delay from parallel input to serial output is 1 to 5 ns. Operating temperature range is -40 to 85 °C, industrial grade, with reference to IEC 60068-2-1 and IEC 60068-2-2. Input logic levels are TTL/CMOS, and output logic levels are selectable between LVCMOS and LVDS to match receiver requirements. Power consumption depends on clock frequency and output load, ranging from 50 to 500 mW. Package types include SOIC-16 and QFN-24, surface mount, RoHS compliant, with reference to JEDEC MS-012. ESD protection is ±2 to ±8 kV (HBM) per IEC 61000-4-2. Weight varies with package type, from 0.1 to 0.5 g. These values are directory reference ranges and must be confirmed for the specific model and application with the legal manufacturer or supplier. Standards listed are procurement references, not certifications of compliance.

The PISO converter uses a shift register to convert parallel data to serial. In a load phase, parallel bits are captured into the register on a clock edge. Then, in shift mode, each subsequent clock edge shifts the register contents, outputting one bit per cycle. The order (LSB or MSB first) depends on design. Control logic toggles between load and shift states, ensuring proper timing. This allows multiple parallel lines to be multiplexed onto a single serial line for transmission.