In an industrial system, a field-side fault rooted deep inside the equipment can be the difference between, say, continuous uptime in an automated factory or money-draining periods of lost productivity. Signal monitoring is essential, whether you need to detect if the voltage is at the right threshold, a relay contact is present, or some other condition. And power and data isolation between high-voltage field-side circuits and low-voltage logic-side circuits can be advantageous in preventing faults, eliminating noise and ground loops between the two sides, and, overall, ensuring operational safety of the equipment.
Engineers utilize a variety of methods to accomplish diagnostic monitoring, though these approaches have typically been time-consuming and/or costly. For example, many choose to integrate discrete components such as capacitors and diodes to manage voltages and currents. Not only does this method entail designing these discrete circuits, but it also involves a lot of debugging to pinpoint the exact source of the error in your system.
As for power isolation, transformers are traditionally used and, to create the data isolation barrier, optocouplers (or digital isolators) come into play. While these discrete approaches are effective, they utilize a significant amount of board space and the design becomes costly. For example, consider a typical data and power isolation scheme in a high-voltage monitoring system. Here, you could have an analog-to-digital converter (ADC) sampling the high field-side voltage and generating a digital output in the form of a four-wire serial peripheral interface (SPI). Digital isolator circuitry located between the ADC and the microcontroller unit (MCU) transmits the field-side digital signal to the logic-side MCU. On the other hand, the ADC, the isolator, and the MCU would require separate power supply circuitry on both the field side and logic side and would occupy valuable board space.
What if diagnostic monitoring of your system along with data and power isolation capabilities were already integrated into your industrial communications circuitry?
A new system architecture called MAXSafe from Maxim Integrated helps simplify diagnostic monitoring while also providing isolated power. MAXSafe is the industry's first integrated isolated micropower architecture, providing up to 250µA—enough to power up internal chips and a simple field-side circuit in a design. Developed with proprietary isolation technology, the field-side power of this architecture is supplied by the logic side using an integrated isolated DC-DC converter. This approach eliminates the bulky, expensive external isolated power supply when the power demand on the field side is small. Self-diagnostics and monitoring is on the isolated field side. Functionality and status can be communicated over isolated circuitry to the design's microcontroller. Isolated diagnostics ensure robust communications.
The MAXSafe architecture delivers:
- 4x space savings as compared to using traditional isolated power supplies
- Greater than 2x increased channel density
The diagram in Figure 2 illustrates the MAXSafe architecture. On the control side is a 3.3V to 5.5V power supply. The isolated DC-DC converter that's a part of the MAXSafe architecture delivers up to 250µA to the field-side circuitry, which is enough to power internal and external circuits.
You can find the MAXSafe architecture in the MAX14001/MAX14002 isolated, single-channel 10-bit ADCs. These devices have programmable voltage comparators and inrush current control optimized for configurable binary input applications. They have 3.75kVRMS of integrated isolation between the binary input side (field side) and the comparator output/SPI side (logic side). The DC-DC converter integrated into the devices powers field-side circuitry, so you can run field-side diagnostics even without the presence of an input signal. The ADCs continually digitize the input voltage on the field side of an isolation barrier, transmitting the data across the isolation barrier to the logic side of the device, where the magnitude of the input voltage is compared to programmable thresholds. Figure 3 provides a block diagram of the MAX14001/MAX14002.
Learn more about these devices in the design solution, "Isolated ADC with Integrated DC-DC Converter Simplifies Field-Side Circuitry."
Maxim will continue to expand its portfolio of industrial communications ICs with the MAXSafe architecture. Stay tuned for future MAXSafe products to power up your internal circuits while simplifying the diagnostics.