iC-MQF: Speedy sine evaluation at x1000 interpolation factor - Embedded.com

iC-MQF: Speedy sine evaluation at x1000 interpolation factor

For optical and magnetic length gauges featuring decimal gratings, iC-MQF from iC-Haus offers a sine resolution of up to 4000 edges. The circuit incorporates a signal conditioning analog front end, a vector-tracking converter for real-time conversion without latency, as well as fault-tolerant RS422 driver stages which output the incremental signals. Reverse polarity protection is also embedded and covers all cable connections.

Differential or referenced input signals from a few millivolts upwards can be connected up, such as those coming from MR bridge sensors or photo sensors, for which alternatively also a low impedance can be selected. Excellent interpolation accuracy is obtained from analog signal corrections: offsets, amplitude mismatches and phase errors can be compensated. After initial adjustment, a controlled current source output maintains the measurement accuracy during operation by tracking the sensor’s excitation. For example, the LED current of an optical encoder or the supply of a magnetic sensor bridge is regulated, so that temperature and aging effects are automatically compensated for.

The encoder signals are supplemented by a generated index signal whose position, width and logic can be set as required. At the same time a patented signal conditioning unit provides glitch-free quadrature signals with hysteresis which always maintain a preset minimum transition distance. This enables counting errors to be avoided and enhances the circuit’s EMI tolerance with sensor applications.

iC-MQF is pin-compatible to the iC-MSB/iC-MQ device family and also available as a 20-pin TSSOP, taking a board space of just approx. 6.4 x 6.4 mm. It is configured using the integrated I2C multi-master interface, either by a microcontroller or a serial EEPROM.

White Paper on Sine/Cosine Interpolation

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