CA3165 Intersil, CA3165 Datasheet - Page 6

• Manufacturer Part Number: CA3165
• Description: Electronic Switching Circuit
• Manufacturer: Intersil

Application Information
Figure 5 and Figure 6 show the application of the CA3165 in
a typical ignition system. The oscillator on the chip operates
at about 400kHz as determined by the tuned circuit L1, C2.
The amplitude of the oscillation is detected on the chip and
applied to a Schmitt trigger which sets the terminal voltage
as shown in the chart in Figure 1 and Figure 2 for the
unloaded condition of the oscillator. As a metallic tooth in the
rotor passes the coil L1, eddy-current losses occur which
reduce the Q of the resonant circuit and decrease the ampli-
tude of the oscillations to a level below that of a reference in
the detector circuit. The output terminals are then switched
to states as shown in the chart in Figure 1 and Figure 2 for
the loaded condition of the oscillator. The oscillation is main-
tained at this lower amplitude by switching in additional feed-
back in the oscillator circuit. The fact that the oscillator
continues to operate at some minimum level during this
dwell period eliminates timing variations which would occur if
the oscillator had to be restarted by random noise.
Spark occurs as terminal 4 is switched from high to low. The
output amplifier clamps terminal 4 low through the regulator
during the duration of the spark.
The Dwell period represents the time that terminal 10
(CA3165E1) or terminal 6 (CA3165E) is high, terminal 4 is
low, and the coil is charged.
The value of the oscillator feedback, resistor, R
to set the dwell period. With a sintered-iron 8 f-tooth rotor, a
typical value of R
a 45 degree cycle. For a star-type rotor and a particular coil
in a typical distributor, the feedback resistor would be larger
(typically 8800 ) depending on clearances, coil geometry
and tooth shape.
L1 SENSOR COIL,
INDUCTANCE
UNLOADED Q
F
is 6500
100 H,
0.01 F
53
C6
for 28.5 degrees of dwell out of
FIGURE 6. TYPICAL IGNITION SYSTEM USING THE CA3165E
R1
220
0.01 F
C3
6
7
8
F
6490
, is selected
CA3165E
VIEW
TOP
METALLIC TRIGGER WHEEL,
ONE TOOTH PER CYLINDER
R6
0.15%
CA3165
L1
10-30
2
1
5
4
3
For typical F-Tooth Rotor with Rod Sensor and 113 H of coil
inductance, the Q and frequency with respect to rotor posi-
tion was measured for the following positions
(Free air Q = 55.7 at 375kHz.)
DETECTOR
CENTER 46 at 377kHz
SLOT
FIRE
TERM 10
220
SPARK
820
1W
5%
TERM 4
C2
1500pF
SILVER
MICA
HIGH
HIGH
LOW
LOW
LOADED
OSC
15 at 381kHz
6 at 390kHz
OSCILLATOR
FIGURE 7. TIMING SEQUENCE
CHARGE
V
200
1W
OUT
DWELL
5%
COIL
ALL RESISTORS 1/2 W 5%
UNLESS OTHERWISE SPECIFIED
RESISTOR VALUES IN OHMS
+13V
DWELL
PERIOD
DWELL
OSC
UN-
LOADED