To help system designers and operators overcome electrically harsh environmental conditions found in many industrial settings, Maxim Integrated has released three new Isolated CAN (or Controller Area Network) transceivers, all of which share the same datasheet:
Protect Against Industrial Communication Hazards
Electrically noisy environments, electrical shorts, ESD strikes, and hefty ground shifts can all be characterized as communication hazards in the world of industrial communications. By using one of Maxim's newly released isolated CAN transceivers, you are offered a single IC solution (i.e., an integrated solution) that withstands up to 5kV of voltage differential between the CAN bus and the IC’s circuit-side ground potential. It also provides ±54V of fault protection and ±15kV of HBM (human body model) ESD protection. Seems impressive.
To be more specific regarding the withstand isolation voltage, the MAX14879 is rated for 2750 VRMS for 60 seconds, whereas the MAX14878 and MAX14880 are rated for 5000VRMS for 60 seconds.
However, one wonders why there are two different ratings. Would the 5kV option be better suited for a more harsh environment, or does the difference between the two simply come down to cost? Furthermore, do one or both of these isolation protection levels exceed—or perhaps far exceed—some automotive or industrial standard put forth by IEEE, UL, VDE, ISO, or the government? These questions aren't meant to beat up on Maxim, but rather to put their products' specifications in context to ensure that a design team or an end-user facility is getting the most bang for the buck. Regardless, the table below shows the isolation protection levels along with other associated insulation characteristics.
Figure 1. Specs for the MAX14878-80, from the datasheet (PDF).
Low-Power Standby Mode
As can be seen in the simplified block diagram below, one difference between the MAX14878 and the MAX14879/80 is a low-power standby mode pin. As described in the datasheet, this active-high input pin disables the CAN bus driver and places the transceiver into a low-power mode. What's not described, unfortunately, is how much power is saved, or what the typical current draw should be, when the IC enters this mode of operation. Strange.
Figure 2. The MAX14879 and MAX14880 have a low-power standby pin; the MAX14878 does not. Image courtesy of Maxim Integrated.
The industrial environments that create large differences in ground potential are also likely places for major changes in ambient temperature. Thus, it’s important to be aware of how an IC’s performance might be affected by temperature. Maxim has provided quite a few plots indicating the effect of temperature on various operational characteristics, which is helpful, and in general the part seems quite robust in this respect.
Figure 3. Plots indicating that performance tends to be stable despite large variations in ambient temperature, from the datasheet (PDF).
Industry-Compatible Pinouts in a 16-pin SOIC Package
According to the MAX14878/79/80 News Release, these ICs are available in industry-compatible pinouts in 16-pin SOIC packages. This statement suggests that these ICs are capable of being dropped into existing designs that use similar 16-pin SOIC isolated (or even non-isolated) CAN transceivers. By doing this IC drop-in method, one could quickly test, analyze, and compare Maxim's isolated CAN transceivers, in a current design, with those from other manufacturers. Nice.
An Evaluation Kit Is Available
If you're interested in testing these isolated CAN transceivers, Maxim offers their MAX14880EVKIT for evaluating any of the three ICs in this family. Additionally, Maxim has generously provided, within the datasheet, the schematics, the BOM, and PCB layout images for this evaluation kit.
Have you had a chance to use any of these three isolated CAN transceivers, or their evaluation kit, from Maxim? If so, leave a comment and tell us about your experiences.