3

SENSOR IN is a PNP comparator input that accepts a sine or

damage the input as long as the input current is limited to

1.5mA. An active clamp at 0V prevents negative input voltages

from disrupting normal operation. The input can withstand 150

VDC as long as the input current does not exceed 1.5mA. This is

possible if a 100k

Ω resistor is placed in series with the SENSOR

IN.

SENSOR OUT is an open collector NPN transistor that produces

a buffered and inverted version of the SENSOR IN signal. It is

capable of driving a 4.7k

Ω load connected to a 5V supply.

The eight step sequencer moves the two H bridge output drivers

through 8 sequential states (Table 1, Figure 1). In State 0, current

flows from COILA+ out through COIL A and back in through

COILA-. The same polarity also holds for COIL B. In State 1,

COIL A outputs turn off while COIL B outputs continue con-

ducting with the same polarity. In State 2, current flows from

COIL A- out through the coil and back in COIL A+. COIL B out-

puts continue with their original polarity. COIL A outputs

maintain this polarity through States 3 and 4 during which

COIL B outputs are first turned off and then reversed. COIL B’s

reversed polarity continues in Stages 5 and 6. COIL A’s outputs

are turned off in Stage 5 and then turned back on (positive

polarity) in Stage 6. In Stage 7, COIL B is off and COILA outputs

continue with a positive polarity.

Table 1: Transition States

The polarity definition for the coil driver outputs is as follows:

Connect

Connect

Polarity

Coil +

Coil -

Positive (+)

Gnd

Negative (-)

Gnd

Each H-bridge output stage consists of 4 power NPN transistors

with fly back diodes (Figure 2). Each half bridge has a composite

The output stage is designed to prevent cross conduction: i.e., at

no time can Q1 and Q2 or Q3 and Q4 conduct. This dead zone

time minimizes fly back energy and helps protect the output

stages from damage.

The CS8442 is protected from short circuit, over voltage and

thermal runaway conditions. When any of these faults is detect-

ed, an internal flip-flop is set and both H bridges are disabled.

When the fault condition is removed, the Flip-Flop is reset after

the first positive going edge from the speed sensor input.

Package Pin Description

Application Information

Speed Sensor

Sequencer

H Bridge Outputs A and B

Protection Circuitry

PACKAGE PIN #

PIN SYMBOL

FUNCTION

8L PDIP

1

Gnd

Ground connection.

2

COILA+

Output stage, when active, supplies current to COIL A.

3

COILA-

Output stage, when active, supplies current to COIL A.

4

SENSOR IN

Input signal from wheel speed or engine rpm.

5

SENSOR OUT

Buffered and inverted output of SENSOR IN signal.

6

COILB-

Output stage, when active, supplies current to COIL B.

7

COILB+

Output stage, when active, supplies current to COIL B.

Supply Voltage.

Short

Circuit

Sense

Resistor

Coil

Short

Circuit

Sense

Resistor

Gnd

Q3

Q4

Q1

Q2

Overvoltage

and

Short

Circuit

Protection

Figure 2: Coil Driver Output

Figure 1: State Diagram for Coil Outputs

0

1

2

3

4

5

6

7

0

COIL A

COIL B

+

–

+

–

STATE #

Output State Table

State

Coil A

Coil B

0+

+

1

OFF

+

2-

+

3

-

OFF

4-

-

5

OFF

-

6+

-

7

+

OFF