Reinforced isolator maxes power transfer efficiency, with lowest noise
The device is packaged in a 16-pin wide (W-) SOIC, that provides sufficient creepage/clearance distances between input and output to achieve its rated isolation. Mounted on FR4 with no copper under the device’s body, there is no need for additional measures such as PCB slots. It offers ratings that enable it to operate across the substantial shifts in ground potential that can occur in industrial environments.
The part has a power path comprising a DC/DC converter that runs at around 65 MHz, with dithering applied to the switching to spread the spectrum of emitted RFI. This enables the part to meet established EMI limits without additional measures, or screening. A planar transformer uses dual windings in antiphase to cancel external fields. Synchronous rectification on the secondary side generates the DC output. Primary switching transistors and secondary synchronous rectifiers are integrated on the CMOS chip(s). A TI spokesman comments, “The key points of this device are that it is the coolest [lowest temperature rise] and quietest [low noise] part on the market.” The high efficiency, he adds, fits it for high-ambient-temperature industrial applications where additional temperature rise would take other devices out of their safe operating region. TI claims the isolator’s integrated power path offers 80% higher efficiency than existing integrated devices, representing a device temperature lower by up to 40C. Input voltage range is 3 to 5.5V.
TI also specifies more than 10-dB lower radiated emissions, rating the ISOW7841 to provide electromagnetic compatibility to meet International Electrotechnical Commission (IEC) 61000-4-x standards for electrostatic discharge and electrical fast transient events. The device comes “pre-certified”, minimising the certification work to be done on end-products.
The device also contains a capacitively-coupled data path, transferring data at up to 100 Mbps. The ISOW7841 reinforced isolator with a three forward/one backward channel configuration is the first device in the ISOW78xx family, with multiple devices expected later in 2017.
An evaluation module (ISOW7841EVM) costs $49, and there are reference designs for isolated RS-485 and RS-232. Additionally, another reference design is available to help integrate reinforced isolation and power in an industrial grid design.
The ISOW7841 will cost $5.50 (1,000). Application areas are the expected industrial scenarios of factory automation, grid infrastructure, motor control, isolated power supplies; and also test and measurement equipment, where there is a requirement to safely instrument (for example) high-voltage circuitry.
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