There are many factors to take into consideration when trying to find a replacement part for an RS-485 or RS-422 transceiver IC. Electrical and mechanical specifications, market availability, and price must all be accounted for. The process of finding and validating a cross-reference between two parts is a time consuming task for an engineer, which is an expensive task for an organization. Whether cross-references are being assembled for a pre-production risk minimization or for an emergency replacement, automation of this task can save thousands of dollars in engineering resources. In this article, the requirements of an RS-485 or RS-422 transceiver IC cross-reference will be shown and a tool for automating this process will be introduced.
Requirements of RS-485 and RS-422 Cross-References
RS-485 and RS-422 are similar hardware standards, but not equivalent. Both standards use differential signaling, but RS-422 offers only one-way communication per bus, while RS-485 can communicate in both directions on a single bus. This means that while RS-485 transceivers can be used for RS-422, the opposite is not possible. This is just one difficulty in finding proper cross-references for these applications.
In order to build a cross-reference list for a bill of materials, an engineer must first consider the PCB footprint. The termination style (through hole or surface mount), number of pins, and package must be equal to the original part. This is complicated by the fact that many manufacturers use proprietary package names for common packages. In addition to the mechanical specifications, the engineer must also verify that the functional pinout is the same. After that has been verified, the electrical specifications must be compared. These include supply voltage range, data rate, receiver hysteresis, operating temperature range, and duplex style (full- or half-duplex). Only after comparing all of these characteristics can an engineer have the confidence to add the target part to the cross-reference list.
Using the SourcingBot Cross-Reference Tool to Automate the RS-485 and RS-422 Transceiver IC Cross-Referencing Process
Performing the above cross-referencing process is time consuming, but luckily much of it can be automated using the SourcingBot cross-referencing tool. For example, pin-to-pin replacement parts for the Analog Devices ADM1485ANZ can be found by searching the part number at sourcingbot.com. This leads to the part page at. Here, the datasheet specifications of the part can be found, and below that a list of recommended replacements.
The important datasheet parameters can be compared easily, and a transparent similarity score is shown which demonstrates the difference between the datasheet values from the original part. Here we find replacements from Texas Instruments, Maxilinear, and Maxim Integrated, while further down the list more replacements from Analog Devices and Linear Technology can be found. This table eliminates the manual searching and comparing, which is much of the work in creating a cross-reference list. From this point, only the functional pinout must be verified.
In addition to cross-referencing single parts, SourcingBot can find replacement parts for an entire bill of materials. At sourcingbot.com/xref-tool, a bill of materials and cross-reference options can be submitted, and a cross-reference list is generated automatically. The cross-reference tool can be configured to find replacements from all manufacturers or a list of manufacturers specified by the user. The datasheet data, pricing, availability, and cross-referencing information from SourcingBot is also available via API, including lab-measured data for over 100k components. On top of transceiver ICs and other semiconductor products, SourcingBot can calculate cross references in many passive component categories, including resistors, capacitors, and inductors, as well as many connector categories, including circular connectors, terminal blocks, FFC and FPC connectors, and more.
