iC-MQ TSSOP20

Description

Inter polator iC-MQ is a non-linear A/D converter which digitizes sine/cosine sensor signals using a count-safe tracking conversion principle with selectable resolution and hysteresis. The angle resolution per sine period can be set using SELRES; up to 400 angle steps are possible (see page 25). The angle position is output incrementally by differential RS422 drivers as an encoder quadrature signal with a zero pulse or, if selected, as a counter signal for devices compatible with 74HC191 or 74HC193. The zero pulse is generated electronically when an enable has been set by the X1/X2 inputs. This pulse can be configured extensively: both in its relative position to the input signal with regard to the logic gating with A and/or B and in its width from 90° to 360° (1/4 to 1T). A preselectable minimum transition distance permits glitch-free output signals and prevents counting errors which in turn boosts the noise immunity of the position encoder. Programmable instrumentation amplifiers with selectable gain levels allow differential or single-ended, referenced input signals; via input X2 the external reference can be used as reference voltage for the offset correction. The modes of operation differentiate between high impedance (V modes) and low impedance (I modes). This adaptation of the iC to voltage or current signals enables MR sensor bridges or photosensors to be directly connected up to the device. The optical scanning of low resolution code discs is also suppor ted by the reference function of input X2; these discs do not evaluate tracks differentially but in comparison with a reference photodiode. The integrated signal conditioning unit allows signal amplitudes and offset voltages to be calibrated accurately and also any phase error between the sine and cosine signals to be corrected. The channel for the zero signal can be configured separately. A control signal is generated from the conditioned signals which can track the transmitting LED of optical encoders via the integrated 50 mA driver stage (output ACO). If MR sensors are connected this driver stage can also track the power supply of the measuring bridges. By tracking the sensor energy supply any temperature and aging effects are compensated for, the input signals stabilized and the exact calibration of the input signals is maintained. This enables a constant accuracy of the inter polation circuit across the entire operating temperature range. When control limits are reached, these can be indicated at the maskable error pin ERR. Faults such as overdrive, wire breakage, shor t circuiting, dir t or aging, for example, are logged. iC-MQ includes extensive self-test and system diagnosis functions which check whether the sensor is working properly or not. For all error events the user can select whether the fault be displayed at error pin ERR or the outputs shutdown. At the same time errors can be stored in the EEPROM to enable failures to be diagnosed at a later stage. For encoder applications the line count of the code disc, the sensor signal regarding signal level and frequency and the operating temperature can be monitored, for example, the latter using an adjustable on-chip sensor. Display error pin ERR is bidirectional; a system fault recognized externally can be recorded and also registered in the error memory. iC-MQ is protected against reverse polarity and offers its monitored supply voltage to the external circuit, thus extending the protection to the system (for load currents to 20 mA). Reverse polarity protection also covers the short-circuit-proof line drivers so that an unintentional faulty wiring during initial operation is tolerated. On being activated the device configuration is loaded via the serial configuration interface from an external EEPROM and verified by a CRC. A micro controller can also configure iC-MQ; the implemented interface is multimaster-competent and enables direct RAM access.

Features