Encoder device iC-MN is a 3-channel, simultaneous sampling sine-to-digital converter which interpolates sine/cosine sensor signals using a high precision SAR converter with a selectable resolution of up to 13 bits. Each input has a separate sample-and-hold stage which halts the track signal for the subsequent sequential digitization. Various 2- and 3-track Vernier scale computations (after Nonius) can be configured for the calculation of high resolution angle positions; these computations permit angle resolutions of up to 25 bits.
The absolute angle position is output via the serial Interface with clock rates of up to 4 Mbit/s (SSI compatible; up to 10 Mbit/s with BiSS C protocol). The RS422 transceiver required to this end is integrated on the chip and has both a differential clock input and a differential line driver for data output.
Programmable instrumentation amplifiers with a selectable gain and offset and phase correction can be adjusted separately for each channel; these allow differential or single-ended 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.
For the purpose of input signal stabilization the conditioned signals are fed into signal level controllers featuring current source outputs of up to 50mA (master channel) and of up to 10mA (for the nonius and segment channels each). These ACOx source pins either power the LEDs of an optical encoder or the magneto resistor bridges of a magnetic encoder. If the control thresholds are reached this event can be released for alarm messaging using the serial interface or the NERR output.
Both major chip functions and sensor errors are also monitored and can be enabled for alarm indication. In this manner typical sensor errors, such as signal loss due to wire breakage, short circuiting, dirt or aging, for example, can be signaled by alarms.
The device features further digital encoder functions covering the correction of phase errors between the tracks, for example, or the zeroing or presetting of a specific position offset for data output. Using the SSI master also integrated on the chip position data from multiturn sensors, provided by a second iC-MN, for example, can be read in and synchronized. iC-MN is protected against a reversed power supply voltage; the integrated supply switch for loads of up to 20mA extends this protection to cover the overall system. The device is configured via an external