6 Channel RS-422 Driver with Encoder Link

Each push-pull driver stage is capable of driving up to 65 mA maximum at 5 V and operating at an output frequency of up to 10 MHz with RS-422 termination. The driver stages are current limited, short circuit proof, and over-temperature protected. The current limitation also reduces EMC.

As well as being pin configurable, the iC-HF also contains reverse polarity protection for a safe sensor-side supply of up to 60 mA. A safe external signal sequence at two complementary line driver outputs activates the Encoder Link state. In the Encoder Link state, 9 pins are connected from the sensor side to the field side. With this low impedance bypassing, internal analog sensor signals and digital communication signals (BiSS, SPI, I²C, etc.) can be accessed at the line driver output pins.

Conventional sensors can be calibrated or programmed through usual RS-422 outputs, due to the Encoder Link function, and no extra contacts, pins, control lines or signals are required. Even in the field, such systems can be accessed without opening the housing. Common parts, reduced pin counts, smaller connectors, and fewer lines in the cable result in significant potential cost reduction.

The device provides under-voltage detection and on-chip temperature monitoring to switch the driver stages to high impedance on demand. A sensor error signal is combined with the iC-HF error states. On a fault, the open-drain error output NERR is activated. All inputs are CMOS and TTL compatible and ESD protected.

Besides the 3 x RS-422 line drivers (for differential quadrature signals or commutation signals, for example), an additional 2 x RS-422 receivers and one RS-422 driver are available for the BiSS interface. For BiSS bus applications, the iC-HF receivers and drivers can be reconfigured to comply with BiSS bus structures. Therefore 3 x RS-422 line drivers and 3 x RS-422 receivers are available for the BiSS bus communication. In BiSS bus applications with broken or open bus structures, the communication signals can be redirected to recover communication. iC-HF redirects the BiSS communication (“loopback”) by pin control.

iC-HF works at supply voltages of 3 V to 5.5 V. Operating temperatures range from -40°C to +125°C. The device is housed in a 32-pin QFN package measuring 5 x 5 mm. The design-in process is supported by ready-to-operate demo boards including the Encoder Link signal sequence generator.