Specifications

EMC-CS-2009.1
© Copyright Ford Motor Company – All Rights Reserved Page 100 of 121
February 11, 2010
Annex D (Normative): CI 220 Transient Waveform Descriptions
CI220 transient immunity testing consists of both standard pulses as delineated in ISO 7637-2 in addition to non-standard
pulses including those produced by electromechanical switching of an inductive load. These non-standard transient pulses
have been included to produce transient waveforms that are absent in ISO 7637-2, but are prevalent in the vehicle’s electrical
power distribution system. Non-standard transients created from this approach are highly affected by a number of factors
including but not limited to resistive/capacitive loads sharing the same circuit as the inductive load. Although consecutive
transients events produced in this manner are often not repeatable as compared to standard ISO test pulses, experience has
shown that this random behavior can produce anomalies that are frequently missed when using only the standard repetitive
ISO pulses.
This annex provides information about the characteristics of the CI 220 transient pulses delineated in this specification. This
information shall also be considered during initial design of the component or subsystem.
D.1 Test Pulses A1, A2, C, E
Figure E-1 illustrates a simplified automotive circuit consisting of an ignition switch used to activate or deactivate the
inductive load (e.g. power door lock). L
W
represents the series wiring inductance between the battery, and ignition switch.
The load inductance "L" is significantly greater than the series inductance of the wiring (typically 1 uH/meter).
Figure D-1: Simplified Automotive Circuit for Transient Immunity
SW
L
W
+
_
BATT
+
_
BATT
L
W
<< L
R
L
Inductive
Load
R
L
Inductive
Load
C
DUTDUT
ZZ
DUTDUT
A1
A2
Z = 220 
Test Pulse A1 represents the voltage transient produced during switching of higher current (1 – 5 ampere) inductive loads
that share the same circuit with the DUT. "Z" represents the impedance of the other electrical loads sharing the same circuit
with the DUT and the inductive load. The value of "Z", which is set to 220 , simulates minimally loaded circuits. Figure
D-2 illustrates Pulse A1. The peak pulse voltage levels will vary between –250 to –300 volts.
Test Pulse A2 represents the voltage transient produced during switching of a lower current (< 1 ampere) inductive loads that
shares the same circuit with the DUT. The characteristics of Pulse A2 can vary significantly depending on the impedance of
the other loads sharing the same circuit as the DUT. Given this dependency, two separated conditions exist for Pulse A2.
They are:
Pulse A2-1
Occurs when the circuit consists only of the DUT and the switched inductive load.
Pulse A2-2
Occurs when the circuit includes other electrical loads that share the same circuit as the DUT and the switched
inductive load.. The other electrical loads are predominately capacitive (e.g. wiper motor filter capacitor)
Figures D-3 and D-4 illustrate waveforms that typify Pulses A2-1 and A2-2. When external circuits effects are not
considered, the transient (Pulse A2-1) is largely the result of contact arcing. The characteristics of this transient consist of a
high frequency repetitive pulse with peak positive voltages levels between +100 to +300 volts and peak negative voltage
levels are between –280 to –500 volts. Duration of individual pulses (see Figure D-3b) may vary between 100 nsec to 1 usec.
The characteristics illustrated in Figure D-3 were measured when the contacts open, however similar transients can occur
when the switch contact bounce during closure. A2-1 transients are also commonly referred to as "showering arc transients."