Signal-Conditioning 13 Bit ADC – for magneto/optical angle encoders

The iC-NQ is a high-resolution Sine-to-Digital converter with a signal-conditioning front end to evaluate analog sine/cosine sensor signals, which are, for example, supplied by optical or magnetic position encoders. Adjustable features include decimal as well as binary angle resolutions with up to 13 bit (8192 steps/period), which can be output as incremental A/B quadrature encoder signal or as absolute position data via the embedded BiSS Interface at clock rates of up to 10 Mbit/s.

The Sine/D converter is suitable for various angle sensors, e.g. magnetic Hall devices used in angular position encoders, magneto-resistive bridges featured in linear position sensors, and optical Sin/Cos encoders. Drift-free instrumentation amplifiers allow to directly connect sensor bridges to the inputs without requiring further components.

To meet different signal levels, input gain can be selected between 20 mVpp and 1.5 Vpp. An adaptation for photocurrents can be performed via a few external resistors. As a result of the fully integrated signal conditioning typical signal errors can be immediately corrected within the analog signal path.

Matched D/A converters, which are adjustable via the open-source BiSS interface, are available for the calibration regarding offset, amplitude difference and phase error. Later, the calibration parameters, as well as all other device settings, are supplied by an external serial EEPROM, which was optionally reconfigured via BiSS. The output of special test signals supports the calibration process.

The sine-to-digital conversion with guaranteed no missing codes operates at 70 MSPS typically, virtually in real time, with an output response time of 250 ns, at maximum. Depending on the selected resolution and the output mode input frequencies of up to 250 kHz can be traced. The sensor function is fully monitored: an alarm message is output for an excessive input frequency, an out-of-range input signal level, for instance caused by a wire breakage, short-circuit, loss of magnet etc, and also on invalid configuration data read in after powering up.

IC-Haus GmbH , 55294 Bodenheim, Germany.

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