Isolated digital input chips offer simplified, flexible configuration in industrial applications

Novosense Microelectronics has introduced two new isolated digital input (DI) chips suitable for 24V digital signal input in industrial control applications such as PLCs, servos and inverters.

The four-channel NSI8604 and the eight-channel NSI8608 provide input/output isolation when converting voltages in the range of -60V to 60V to logic signals. Both devices support bi-directional digital input functionality, allowing flexible configuration of system I/O. Unlike digital isolators, the input stage of the chips integrates current-mode input with a function that limits currents to 2.1mA (typical), reducing power consumption and temperature rises in the target system.

Based on Novosense’s capacitive isolation technology, the ICs use OOK modulation technology to modulate input signals and then transmit them through the SiO2 barrier to the secondary side, where they are demodulated and output via a buffer stage. While fully compatible with the current input form of optocouplers, the chips provide for simplified system design thanks to a higher degree of system integration and the elimination of a need for a field-side power supply.

Key features of Novosense’s latest chips include an isolation withstand voltage of 3kVrms, common-mode transient immunity (CMTI) of 35kV/μs, a data transmission rate of DC to 2Mbps and a data transmission delay figure of 380ns. The devices operate from a power supply voltage of 2.5V to 5.5V and are stable over a wide temperature range from -40°C to 125°C. Each IC meets the performance criteria for switch types 1, 2 and 3 in IEC 61131-2 and is compatible with the I/O level of most microcontrollers.

Available in industry standard SSOP16 and SSOP20 packages respectively, the NSI8604 and NSI8608 are pin-compatible with alternative technologies, allowing users to replace existing parts without modifying the system design.