E981.07 Datasheet, PDF (44/46 Pages) ELMOS Semiconductor AG – Two independent operating channels

E981.07
Two Channel Sensor Interface PSI5
ADVANCE PRODUCT INFORMATION JUL 26, 2011
The ECU-circuitry should be optimised for the connected wiring harness. The proposed circuits work well in
case of point-to-point connection and parallel bus lines.
For serial bus connections (and daisy-chain operation) the wiring harness, together with the sensor capacitors,
form coupled LC-resonant circuits which can only hardly be damped by the resistor on the ECU-board.
ECU
Wire
Sensors
Figure 6.1-3: serial bus connection
The oscillations which can occur in case of wiring harness shown in figure 6.3 can be damped by including
additional series resistors in the wiring harness.
ECU
Wire
Sensors
Resistors for decoupling
Resistors for decoupling
Figure 6.1-4: serial bus connection with damping resistors
The decoupling resistors damp the LC-resonant circuits (wire inductance + sensor capacitance). In the figure
6.4 a pair of resistors is shown. It is also possible to use only one resistor in the supply-line. The value of the
resistor is about 2-4Ohms.
Without damping the data current show oscillations at the rising and falling edge of the data current. This can
lead to a disturbed communication and has to be avoided.
ELMOS Semiconductor AG
Data Sheet 44 / 45
QM-No.: 25DS0050E.00
This document contains information on a new product. ELMOS Semiconductor AG reserves the right to change specifications and information herein without notice.