ERROR AMPLIFIER Inputs (Pins 6, 7 ) Output (Pin 8)

For closed loop control, the TACHOMETER Output is applied

through a resistor to the negative input of the Error Amplifier on

Pin 7. A speed control potentiometer is connected to the positive

input of the Error Amplifier on Pin 6. A parallel RC Network is con-

nected between the Output of the Error Amplifier on Pin 8 and Pin

7. The Amplifier, configured this way, enables the variable pulse

width to be converted to a DC voltage which is used to control the

motor speed. The potentiometer is used to set the desired motor

speed. For open loop control, configure the Error Amplifier as a

voltage follower by connecting Pin 7 directly to Pin 8 and do not

connect the TACHOMETER Output signal to the Error Amplifier.

TOP DRIVER POLARITY SELECT Input (Pin 20)

A High on this input selects a High Polarity for the Top Output

Drivers Motor ON condition and a Low selects a Low Polarity.

OUTPUT DRIVERS (Pins 12, 13, 14, 15, 16, 17)

Each Driver Output provides a CMOS compatible signal for driv-

ing Buffers/Power Transistors. The Outputs are capable of sink-

FAULT INDICATOR Output (Pin 3)

Open drain output to provide sinking current for driving an ex-

ternal device such as an LED to indicate a malfunction condition.

The output occurs under any of the following conditions:

1) Overcurrent Sense condition

3) Invalid Sensor code

4) Chip power supply less than 9V

5.5V Reference Voltage Output that can supply 20mA of current

OSCILLATOR (Pin 9)

An external RC network is connected to this input to set the fre-

quency of the Sawtooth Schmitt Trigger Oscillator. The Sawtooth

is applied to the PWM Comparator along with the output of the Er-

ror Amplifier. The output of the PWM Comparator is a Pulse

Width Modulated Signal which is used to vary the effective drive

to the motor and, hence, the motor speed.

OVERCURRENT SENSE (Pins 10, 11)

The input to Pin 10 comes from the high side of a fractional ohm

current sensing resistor. The voltage at this input is compared to

an internal 100mV Reference. When the voltage exceeds the

100mV Reference, an Overcurrent Condition exists and the Out-

put Drivers are switched OFF until the end of the sawtooth os-

cillator ramp-up. When the sawtooth switches low, the Over-

current Condition is sampled, and if it no longer exists, the Output

Drivers are switched ON again. Otherwise, the Output Drivers re-

main OFF until the end of the next sawtooth. The input to Pin 11

comes from the low side (Gnd) of the current sensing resistor and

connects to the low side of the internal 100mV Reference.

PWM CONTROL Input (Pin 21)

A High on this input causes only the Bottom Drivers to be Pulse

Width Modulated. A Low on this input causes both Top and Bot-

tom Drivers to have PWM.

TACHOMETER Output (Pin 5)

The output of the Frequency To Pulse Width Converter is tied to

this pin. The Converter uses the three SENSOR Inputs and ex-

ternal RC Network to generate a variable frequency output with a

fixed positive pulse width.

RC Input (Pin 4)

The external RC network connected to this input programs the

positive pulse width of the Frequency to Pulse Width Converter.

7560-040198-2

MAXIMUM RATINGS (Voltages referenced to Vss)

SYMBOL

VALUE

UNIT

Power Supply Voltage

20

V

Voltage at any input

V

Operating Temperature

-25 to +85

°C

Storage Temperature

-65 to +150

°C

Output Drive Sink/Source Current

Io

75

mA

30

mA

ELECTRICAL CHARACTERISTICS

PARAMETER

SYMBOL

MIN

TYP

MAX

UNIT

Reference Voltage

4.75

5.5

6.25

V

Line Regulation

-

100

200

mV

Temperature Stability

-

+/- 1.0

-

%

-

+/- 1.3

-

%

Error Amplifier:

Input Offset Voltage

-

5

15

mV

Input Current

-

0

10

nA

Input Common Mode Voltage Range

V

Ω)

70

80

-

dB

Common Mode Rejection Ratio

60

-

-

dB

Power Supply Rejection Ratio

60

-

-

dB