Circuit Operation
Speed Sensor Input
Short
Circuit
SENSOR is a PNP comparator input which accepts either a sine
wave or a square wave input. This input is protected from excur-
sions above VCC as well as any below ground as long as the cur-
rent is limited to 1.5mA. It has an active clamp set to zero volts to
prevent negative input voltages from disrupting normal opera-
tion. The sensor input can withstand 150VDC as long as the input
current is limited to 1.5mA max. using a series resistor of 100k½.
VCC
Sense
Resistor
Q1
Q2
Q3
Q4
Overvoltage
and
Short
Circuit
Protection
Coil
Short
Circuit
Gnd
Sense
Resistor
Coil Driver Outputs
Simultaneously energizing the source and sink on either leg is
not permitted, i.e. Q1 & Q2 or Q3 & Q4 cannot be energized
simultaneously.
Figure 1: Coil Driver Output
Circuit function is not affected by inductive transients due to coil
loads as specified in the Transition States section.
The transition states occur as indicated in Table 1 without any
intermediate states permitted.
Table 1: Transition States
Output State Table
State
Coil A
+
OFF
Coil B
0
1
2
3
4
5
6
7
+
+
+
OFF
-
-
-
-
-
-
OFF
+
+
Figure 2: Divide by 1 SELECT Mode
OFF
DIVIDE BY TWO MODE SELECT = Gnd
The polarity definition for the coil driver outputs is as follows:
Connect
Coil +
Connect
Coil -
Polarity
Positive (+)
Negative (-)
VCC
Gnd
Gnd
VCC
Divider Select Input
The speed sensor input frequency is either divided by one or divid-
ed by two depending on the state of the SELECT input as follows:
Logic 0 = divide by 2
Logic 1 = divide by 1
Figure 3: Divide by 2 SELECT Mode
Odometer Application Diagram
COIL A
COIL B
C1 - 10µF
C2 - 0.1µF
C3 - 0.01µF
COILA+ COILAÐ
COILB+ COILBÐ
R1 - 3.9½, 500mW
R2 - 100k½
R3 - 15k½
D1 - 1A, 600PIV
Z1 - 50V, 500mW
COIL A - 210 ±12½, 80mH
COIL B - 210 ±12½, 80mH
CS4161
SENSOR
Gnd
V
CC
SELECT
D1
R1
IGN
C2
C1
Z1
R3
Buffered Speed Signal
(Open Collector Drive)
R2
C3
3
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
