Over Current Protection.

The driver output pins (M+ and M-) are over cur-

rent protected by 4 separate linear current limit-

ers, one for each of the 4 power output transis-

tors. The output drivers resume normal operation

as soon as the over current is removed.

Motor Over Voltage Protection.

The motor is over voltage protected by switching

off (to Hi-Z) the M+ and M- output drivers, when

Vcc rises above the 19V typ. over voltage shut

down threshold.

Over Temperature Protection.

The chip is over temperature protected by switch-

ing off (to Hi-Z) the M+ and M- output drivers.

Power Supply Transient Protections.

The device provides over voltage suppression for

fast Vcc voltage transients (Fig. 5). The Vcc is

clamped at typ. 70V by turning on all four, bridge

connected, power output transistors. They are

roughly subjected to equal currents and voltages

for even transient energy distribution.

The over voltage suppression is deactivated for

slow Vcc voltage transients (Fig. 4) by raising the

Vcc voltage clamp at typ. 80V.

M

M+

M-

-

-

+

+

OSCILLATOR

U709

R osc

27K

Ω

Cosc

10nF

1nF

1nF

GND

COSC

ROSC

VCOM

VFB

1K

Ω

1K

Ω

EMI

Protection

Networ k

100nF

DC

MOTOR

VCC

Reverse Battery

Protection Diode

GROUND

POWER

100nF

1nF

Figure 6. Recommended Application Diagram for Positive Control

M

M+

M-

-

-

+

+

OSCILLATOR

U709

Rosc

27K

Ω

Cosc

10nF

1nF

1nF

GND

COSC

ROSC

VCOM

VFB

10K

Ω

20K

Ω

EMI

Protection

Capacitors

100nF

DC

MOTOR

VCC

Reverse Battery

Protection Diode

GROUND

POWER

100nF

1nF

DIR

20K

Ω

Protection

Resistor

DIR

Threshold

Voltage

Figure 7. Recommended Application Diagram for Direction Control

L9909

6/9