Image Credit: TriQuint | ROHM Semiconductor, USA LLC | Texas Instruments High-Performance Analog 

IC analog switches are integrated circuits (ICs) that allow electric current to flow when closed and prevent current from flowing when open. They are often used to interface analog signals to digital controllers. IC analog switches differ in terms of the number of poles or contacts, and the number of positions or throws. Common pole and throw configurations are single-pole, single-throw (SPST); single-pole, double-throw (SPDT); double-pole, single-throw (DPST), and double-pole, double throw (DPDT).

How Analog Switches Work

SPST switches make or break the connection of a single conductor in a single branch circuit. They typically have two terminals. SPDT switches also make or break the connection of a single conductor, but with either of two other conductors. These switches, which often have three terminals, are commonly used in pairs as three-way switches. DPST switches, another type of double-pole device, make or break the connections of two circuit conductors in a single branch circuit. Normally, DPST switches have four terminals. Finally, DPDT switches make or break the connections of two conductors to two separate circuits. These switches usually have six terminals.

Performance Specifications

Performance specifications for IC analog switches include maximum resistance, propagation delay, minimum operating current, power dissipation, and operating ambient temperature. Some devices include a bilateral feature that allows signals to be transmitted in either direction. Others are radiation tolerant or provide protection against overcurrent and electrostatic discharge (ESD). IC analog switches that meet military specifications (MIL-SPEC) and military standards (MIL-STD) are also available. Supply voltages range from -5 V to 5 V. 

Packaging Options

IC analog switches is available in a variety of IC package types. Examples include ball grid array (BGA), quad flat package (QFP), dual in-line package (DIP), and small outline package (SOP). BGA places output pins in a solder ball matrix and offers reduced package size and improved heat dissipation. Variants include plastic-ball grid array (PBGA), tape-ball grid array (TBGA), and fine-pitch land grid array (FLGA). QFP devices contain a large number of fine, flexible, gull winged shaped leads. Low-profile quad flat package (LFQP) and thin quad flat package (TQFP) are common QFP variants. DIPs can be installed in sockets or soldered into holes that extend into the surface of printed circuit boards (PCBs). They are often made from plastic (PDIP) or ceramic (CDIP). SOP variants include small outline IC (SOIC), shrink small outline package (SSOP), thin small outline package (TSOP), thin very small outline package (TVSOP), and small outline flat-leaded package with heat sink (HSOF). Small outline J-lead (SOJ) is a common form of surface-mount packaging. Plastic leaded chip carrier (PLCC) and leadless ceramic chip carrier (LCCC) are other package types for IC analog switches.

Selection Considerations

Selecting IC analog switches requires an analysis of logic families. Transistor-transistor logic (TTL) and related technologies such as Fairchild advanced Schottky TTL (FAST) use transistors as digital switches. By contrast, emitter coupled logic (ECL) uses transistors to steer current through gates that compute logical functions. Another logic family, complementary metal-oxide semiconductor (CMOS) uses a combination of p-type and n-type metal-oxide-semiconductor field effect transistors (MOSFET) to implement logic gates and other digital circuits. Logic families for IC analog switches include cross-bar switch technology (CBT), gallium arsenide (GaAs), integrated injection logic (I²L) and silicon on sapphire (SOS). Gunning with transceiver logic (GTL) and gunning with transceiver logic plus (GTLP) are also available.

Related Standards

• SMD 5962-81006 - MICROCIRCUIT, LINEAR, CMOS, HIGH LEVEL ANALOG SWITCHES WITH DRIVERS, MONOLITHIC SILICON
• SMD 5962-95812 - MICROCIRCUIT, LINEAR RADIATION HARDENED CMOS, DUAL, DPST ANALOG SWITCHES, MONOLITHIC SILICON
• SMD 5962-95813 - MICROCIRCUIT, LINEAR RADIATION HARDENED CMOS, DUAL SPDT ANALOG SWITCHES MONOLITHIC SILICON