Isolated systems can communicate digitally among themselves without conducting ground loops or presenting hazardous voltages—simply by using digital isolators. A capacitive isolation barrier exists between the isolated systems. The transmitter side modulates its digital data with a high-frequency signal that allows it to transmit across the capacitive isolation. Receivers on the other side detect the signal, demodulate it to extract the digital data, and use it.

Digital isolators offer thick insulation distances of greater than 0.5 mm, with reliable high-voltage insulation. ON Semiconductor has patented an off-chip galvanic capacitor isolation technology and offer a full-duplex, high-speed, bi-directional, dual-channel digital isolator—the NCID9211.

NCID9211 supports isolated communications. Therefore, isolated systems do not need conducting ground loops to communicate with digital signals, and it is possible for them to avoid hazardous voltages. The optimized IC design and the off-chip galvanic capacitor isolation technology that ON Semiconductors has developed ensures high noise immunity and high insulation. The power supply rejection and common-mode rejection ratio specifications of the NCID9211 support this. Compared to coreless transformers and thin-film on-chip capacitors, the thick film substrates offer capacitors with 25 times the dielectric thickness.

The digital isolator offers a unique combination of an insulating barrier and an electrical performance along with safety and reliability that only optocouplers had offered so far. NCID9211 comes in a 16-pin small outline package with a wide body. The device has features with several advantages.

NCID9211 is the only digital isolator in the market today that includes insulation reliability matching that offered by optocouplers while offering the same level of safety. The device has a distance through insulation or DTI or over 0.5 mm and uses off-chip capacitive isolation for achieving maximum high-voltage insulation reaching 2000 Vpeak.

The off-chip capacitive isolation offers better long-term reliability and safety compared to other digital isolation methodologies available in the market. ON Semiconductors guarantees the specifications of the NCID9211 over a supply voltage range of 2.5-5.5 DVC and an extended temperature range of -40 °C to +125 °C. The device does not require overdesign as the device performance remains stable over voltage and temperature.

NCID9211 offers a high-speed communication of NRZ or non-return to zero data at rates of 50 Mbits per second. The maximum propagation delay is only 25 ns, while the maximum distortion of the pulse width is only 10 ns.

ON Semiconductor claims NCID9211 has better performance over optocouplers. Compared to optocouplers, NCID9211 does not exhibit insulation material wear out over time up to 1500 V, there is no LED to degrade over time, and the performance across devices is more consistent. Compared to optocouplers, NCID9211 has a longer lifetime expectancy.

With a minimum common-mode rejection of 100 KV/µs, the NCID9211 has a superior noise immunity and it meets stringent performance requirements of EMI/EMC. However, for meeting reliable high-voltage insulation requirements, there must be a minimum creepage and clearance distance of 8 mm between the input and the output.

With full-duplex and bi-directional communication, the NCID9211 has several applications such as isolated PWM control, SPI and I2C type micro-controller interfaces, voltage level translators, isolated data acquisition systems, and many more.