Sensors & Transducers e-Digest, Vol. 70, Issue 8, August 2007: Product News
(ISSN 1726- 5479)
Reverse Polarity-Protected Quadrature Encoder
with Fast Interpolation
The new encoder device iC-MG is a fast sine-to-digital converter which translates optical or magnetic sine/cosine sensor signals into encoder quadrature signals. Programmable up to a factor of 50, this real-time interpolator supplements signal conditioning at both the input and output ends of the component, making it a world premiere in this respect. A sensor regulator stabilizes the input signals to be interpolated; integrated, differential RS422 output drivers make the chip line compatible and error tolerant. Short circuits or a falsely connected supply voltage do not destroy the device.
Programmable instrumentation amplifiers with a selectable resolution and offset and phase correction can be adjusted separately for each channel; these allow differential or referenced input signals. At the same time the inputs can either be set to high impedance for voltage signals from magneto resistor sensor bridges, for example, or to low impedance for adaptation and use with photosensors which provide current signals, for instance. This enables the device to be directly connected up to a number of different optical and magnetic sensors.
Input signal levels are stabilized by an integrated regulator circuit via a 50 mA source output, which can directly supply either optical encoder transmitter LEDs or magnetic encoder MR sensors with power. It is thus possible to automatically compensation for the effects of temperature and aging or for varying operating distances.
All the major chip functions are monitored and can be configured for alarm indication, allowing typical sensor errors, such as signal loss due to wire breakage, short circuiting, dirt or aging, for instance, to be recognized. Two selections are possible here; either an alarm can be displayed at the error output or the output drivers can be switched to high impedance, the latter option providing useful protection against a possible thermal overload of the drivers, for example.
Only those A/B quadrature signals which can safely count with and process the ensuing system are output. A patented signal processing unit ensures glitch-free digital signals with hysteresis which always maintain a preselectable minimum transition distance. Set to comply with the application and possible environmental interferences, input errors are filtered without causing an increase in the signal transit time.
The incremental encoder signals are supplemented by an internally generated zero signal when the ZERO input is enabled. The position, width and logic of this zero signal can be set as required.
iC-MG is available as a 20-pin TSSOP which takes up just ca. 6.4 x 6.4 mm board space. It configures itself using the integrated I2C interface from a serial EEPROM.
The device is immune to a reversed supply voltage or one connected up to the wrong pins. A supply switch of up to 20 mA is also provided for the system’s peripheral electronics, such as the configuration EEPROM or the sensor, for example, ensuring that these components are also protected against reverse polarity.
Typical applications include: Optical rotary encoders; Automotive applications; Magnetic rotary encoders; Electronic power-assisted steering; Linear displacement measurement; Wheel sensor technology; Motor commutation (electromechanical brakes); Built-in sensors for DC motors; Pedal evaluation (brake by wire).
With a single supply of +5V the device functions within an industrial operating temperature range of -25 to +100 °C. A more capacious temperature environment is also possible, as the converter chip has been designed to cope with operating temperatures of -40 to +125 °C.
iC-Haus GmbH, Am Kuemmerling 18,
Tel: +49 - (0)6135 - 9292-300, fax: +49 - (0)6135 - 9292-192
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