Dual decoder/demux for address expansion
This Texas Instruments CD4556BMT is a dual 1-of-4 decoder/demultiplexer from the 4000B CMOS logic family. It contains two independent circuits, each decoding a 2-bit binary input to four mutually exclusive active-low outputs.
Operates from 3V to 18V single or dual supply — the wide range covers battery-powered 3.3V portable gear through industrial 12V rails. Each output sources or sinks 6.8mA typical, enough to drive standard CMOS or TTL loads without external buffers in low-speed address decoding.
Package and board fit
The narrow-body SOIC footprint is common across 4000B logic — a single PCB land pattern serves multiple decoder variants in the family.