5-CH MOTOR DRIVER

9

2. Thermal Shutdown

The TSD circuit turns activated when the junction temperature becomes

over 175

°C.

It cuts off the bias current on the output driver and keeps all the output

drivers off. Meanwhile, the junction temperature begins to decrease.

The TSD circuit can be deactivated when the unction temperature falls

under 150

°C, so the output driver begins operating in normal condition

The TSD circuit has the hysteresis temperature of 25

°C.

3. Power Save Function

When the pin22 is high, the TR Q3 is turned on and Q4 is off, so the bias

circuit is enabled. On the other hand, when the pin22 is Low (GND) ,

the TR Q3 is turned off and Q4 is on, so the bias circuit is disabled.

that is, it will make all the circuit blocks except for variable regulator off,

so low power quiescent state can be established.

Truth table is as follows.

4. Variable Regulator

A 33uF capacitor is used as a ripple eliminator in the external cir-

cuit. Therefore, output voltage, Vout can be calculated as follows.

In order to reduce the heating problem on regulator output

Pin#22

FAN8039BD3

High

Power Save Off

Low

Power Save On

VCC

R2

R3

Q0

Output driver

bias

Hysteresis

R1

Ihys

I

REF

22

Q3

Main Bias

(except for

variable reg.)

VCC

Q4

REGVCC

R1

R2

33uF

2.5V

5

6

4

R3

Q1

V

OUT

V

REF

1

R

1

R

2

-------

+





•

2.5

2

×

5V R1

R2

=

()

=

=

=

R3

REGVCC

Vout

1.5

+

()

–

()

I

MAX

-----------------------------------------------------------------------

=