These Industrial Communications ICs are Oldies but Goodies for Good Reason

March 19, 2019

Andrew Smith  By: Andrew Smith
 Product Manager, Industrial Communications, Maxim Integrated 


Innovation is often associated with the latest and greatest, but this isn’t always the case. There’s a reason for the (old) saying, “oldies but goodies.” Sometimes, a product that was considered ahead of its time remains so for many years. Being innovative isn’t only about creating something new and unique for a particular moment; it’s also about creating something lasting by anticipating and addressing future requirements. Let’s take a look at a few interface and signal routing ICs that can help you simplify designs, cut costs, and miniaturize end products. These ICs have been around for a while, but are still helping users working on a variety of end applications meet their design targets.

Consolidate Interfaces and Signals with “Beyond-the-Rails” Multiplexers
“Beyond-the-rails” multiplexers, or muxes, have amassed a devoted following among a wide user base. With beyond-the-rails muxes, engineers can simplify designs by consolidating up to four signals onto one shared connector. By consolidating interfaces and signals, users are able to cut costs on wiring the additional channels while shrinking the end product. Beyond-the-rails technology allows the mux to switch interfaces and signals with high common-mode voltage while needing only a 3V-to-5V supply rail. Traditional solutions, on the other hand, can only handle interfaces and signals when powered by the same supply voltage as the interface or signal. Beyond-the-rails multiplexers can eliminate the need for extra power supply components, simplifying the design while reducing system cost. Engineers have been integrating these ICs into a variety of end products, such as logistics optimization equipment, home and building automation systems, smart agriculture devices, point-of-sales (POS) terminals, and automotive diagnostic equipment. In logistics optimization equipment, real-time data such as inventory levels, fuel supply, vibration experienced in transit, and dispatch instructions is gathered to optimize supply-chain networks. These muxes are also commonly designed into automotive on-board diagnostic equipment because they allow these systems to receive and transmit a variety of interfaces and signals on a shared connector while only requiring a single supply rail.

Inventory managementBeyond-the-rails muxes can support logistics optimization equipment that enhances supply-chain networks via inputs including real-time inventory data.

One of our popular beyond-the-rails muxes is the MAX14778 dual ±25V above- and below-the-rails 4:1 analog multiplexer. Its 3V to 5V supply supports analog signals (such as RS-485, RS-232, and USB 1.1) up to ±25V. Each multiplexer in the device has separate control inputs, which allows independent switching. You can then use the same connector pins to multiplex different communications signals. Since the IC provides extended electrostatic discharge (ESD) protection of ±6kV (human body model), you can directly interface to cables and connectors. The device’s low 1.5Ω (maximum) on-resistance and 3mΩ (typical) flatness maximize signal integrity over the entire voltage range. The MAX14778 evaluation kit is available for testing the part under a wide range of applications, including audio/data multiplexing, communication systems, connector sharing, gaming machines, handheld industrial devices, POS peripherals, and RS-485/RS-232/USB 1.1 multiplexing.

Switch It Up with Beyond-the-Rails Switches
Maxim also has a variety of beyond-the-rails switches. With these switches, you can take signals of high-voltage interfaces and switch them. Based on the number of channels you’ve got, you can also just simply use a multiplexer. But if you have at least six channels, you would need the multiplexer and the switch. And if you have eight channels, you would need to use two multiplexers to consolidate the input signals, while using the switches to turn the signals on and off. These switches are suitable for applications including audio signal routing and switching, programmable logic controllers (PLCs), instrumentation systems, medical equipment, and industrial measurement systems.

A notable family of switches consists of the MAX14759/MAX14761/MAX14763 above- and below-the-rails analog switches. These switches can pass bipolar signals that are beyond their supply rails. With their low on-resistance, which minimizes power dissipation, as well as high bandwidth, they can be used in both digital- and analog-signal switching applications. They operate from a single +3.0V to +5.5V supply and support signals in the -25V to +25V range, simplifying power supply requirements. Here are a few highlights of each:

  • MAX14759 is a single-pole/single-throw (SPST) analog switch with 1Ω (maximum) on-resistance
  • MAX14761 is a dual-SPST analog switch with 2Ω (maximum) on-resistance
  • MAX14763 is a single-pole/double-throw (SPDT) analog switch with 2Ω (maximum) on-resistance

Also worth noting here are the MAX14760/MAX14762/MAX14764 above- and below-the-rails analog switches. Like the family previously discussed, these switches are also ideal for simplifying power supply requirements for similar targets, like automated test equipment, opto-relay replacement equipment, and other industrial applications. They have higher on-resistance of 20Ω (maximum) but feature lower leakage currents. Here are some details on each:

  • MAX14760 is an SPST analog switch
  • MAX14762 is a dual-SPST analog switch
  • MAX14764 is an SPDT analog switch

Their low leakage currents of 10nA/30nA (maximum) make them suitable for sensitive analog signal switching applications. The MAX147xx evaluation kit is available for assessment of the MAX14759 and MAX14760 family, as well as the MAX14760-MAX14764 devices. The kit consists of a fully assembled and tested circuit board with footprints for 8-pin and 10-pin TDFN surface-mount packages to evaluate any part in this family.

So there you have it, a few oldies but goodies from the analog IC world. Check them out for your next industrial application!