IC-PI datasheet(2/49 Pages) ICHAUS

2 / 49 page

preliminary

iC-PI PROGRAMMABLE 12-BIT

Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

Rev B1, Page 2/48

DESCRIPTION

iC-PI is an interpolator with a non-linear A/D converter

which digitizes sine/cosine sensor signals using a

count-safe vector tracking conversion with both se-

lectable resolution and hysteresis. The angle reso-

lution per sine period can be set using SELRES; up

to 4000 decimal angle steps, and up to 4096 binary

angle steps are possible (see page 32).

The angle position is output incrementally by differen-

tial 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 and out-

put when the X1/X2 inputs receive an enable signal.

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 1 T).

A preselectable minimum edge distance ensures

glitch-free output signals and prevents counting er-

rors which in turn boosts the noise immunity of the

position encoder.

Programmable instrumentation amplifiers with se-

lectable gain levels allow differential or single-ended,

referenced input signals; an external reference volt-

age can be connected to input X2 then operated as a

reference input.

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 to the device. The optical scan-

ning of low resolution code discs is also supported 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 ac-

curately and 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 op-

tical 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 measur-

ing 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 interpolation circuit across

the entire operating temperature range.

If control limits are reached, these can be indicated

at the maskable error pin ERR. Faults such as over-

drive, wire breakage, short circuiting, dirt or aging, for

example, can be logged.

iC-PI includes extensive self-test and system diag-

nosis functions which check whether the sensor is

working properly or not. For all error events the user

can select whether the fault is indicated at the pin ERR

or whether the outputs should 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 regis-

tered in the error memory.

iC-PI 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 up to 20 mA). Reverse polarity protection also

covers the short-circuit-proof output drivers so that an

unintentional faulty wiring during initial operation is

tolerated.

On being activated the device configuration is loaded

via the serial I2C interface from an external EEPROM

and verified with a CRC. A microcontroller can also

configure iC-PI; the implemented interface is multi-

master-capable and allows direct RAM access to con-

figuration and position data.

IC-PI Datasheet(PDF) 2 Page - IC-Haus GmbH

IC-PI Datasheet(HTML) 2 Page - IC-Haus GmbH

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