iC-GI22 - Dual Channel Inductive Signal Demodulator - iC-Haus GmbH

Compact 2-Channel Inductive Position Sensor

The new iC-GI22 from iC-Haus is a space-saving front-end chip for evaluating inductive position sensors and contains two independent channels with cable drivers that output conditioned 1V sine/cosine signals. A sine-to-digital converter is also built-in for further evaluation, which considerably simplifies the angular measurement for absolute encoders.

The iC-GI22 inductive front-end integrates the complete circuitry for coil excitation, two independent channels for demodulation, signal processing and error correction as well as cable drivers for industry-standard 1V signals on an area of only 5×5 mm. A new feature is the chip-internal interpolator with SSI output, which can transfer a start angle to the external MCU or interpolation circuit. When the iC-TW29 encoder processor is connected, absolute angles with more than 16 bits can be resolved with an accuracy comparable to optical encoders thanks to automatic error correction.

iC-GI22 operates at 2 to 5 MHz and can compensate for large level differences on the receiver side. Programmable amplifiers that accept and process small to large receiver coil signals are used to drive the external interpolation circuit – or the A/D converter on an MCU. Level differences and signal offsets are adjustable via I2C, and automatic gain control allows full scale operation of the external electronics even when the motor axis shows axial play. The output level and the common-mode voltage can be selected; the use of a reference input for the center voltage is optional.

Integrated diagnostics monitor start-up and operation, including RAM configuration. All status flags can be masked to indicate alarms at the error output or via SSI. iC-GI22 operates from 3.3 V to 5 V and configures itself from an external EEPROM in stand-alone operation or receives its setup from the microcontroller via I2C. Reference designs are available with evaluation boards; a GUI for PC simplifies setting up operation.

The user is free to design and apply any scale dimension and is not restricted to specific coil layouts. The chip design allows signal frequencies of up to 50 kHz, which enables speeds of at least 90,000 rpm with up to 64 signal periods at the input, for example.

Inductive sensors are not a new invention; classic resolvers have been known for decades as robust rotary transformers and provide good signals, but require extensive cabling and complex signal evaluation. As a modern integrated solution with high-frequency excitation, iC-GI22 offers comparable application advantages, improves resolution and linearity, and saves costs thanks to inexpensive board-based coils. These are easily scalable, so that any motor can become a measuring device without additional ball bearings or encapsulation.