TABLE 1

OUTPUT CURRENT LIMITING RESISTOR SELECTION TABLE

POWER

OUTPUT CURRENT

SUPPLY

(VOLTS)

20

15

10

7.5

5

2.5

mA

6

**

**

**

**

**

.24

9

**

**

**

.43 .86

2.2

12

.20 .33 .62 .91 1.5

3.3

15

.36 .56 .91 1.3 2.2

4.3 Resistance

18

*

.75 1.2 1.6 2.7

5.1

(k

Ω)

21

*

*

1.5 2.0 3.3

6.2

24

*

*

1.8 2.3 3.6

7.5

28

*

*

*

2.7 4.3

9.1

*causes excessive power dissipation

**exceeds max current possible for this voltage

TABLE 2

For Power Supply 5V-28V

R1 (k ohms)

Output Voltage

10

Vss -0.5

4.0

Vss -1.0

1.5

Vss -2.0

TYPICAL CIRCUIT OPERATION:

The oscillator is used for motor speed control as explained

under VTRIP. Both upper and lower motor drive transistors are

pulse width modulated (See Fig. 1 or 2) during speed control.

For the LS7262, the outputs turn on in pairs (See Table 3). For

example (See dotted line, Fig. 2): Q8 and Q4 are on, thus ena-

bling a path from the positive supply through the emitter-base

junction of Q101, Q8, Q4, R5, the base emitter junction of

Q105 and the fractional-ohm resistor to ground. The current in

the above described path is determined by the power supply

voltage, the voltage drops across the base-emitter junctions of

Q101 and Q105 (1.4V for single transistor or 2.8V for Darling-

ton pairs), the impedance of Q8 and Q4 and the value of R5.

Table 1 provides the recommended value for R5. R4 and R6

are the same value.

7260-111397-3

Oscillator:

Frequency Range

0

1/RC

100

kHz

External Resistor Range

22

-

1000

k

Ω

NOTE: Theoretical switching point of the OVERCURRENT SENSE input is one half of the power supply determined by an internal bias

network in manufacturing. Tolerances cause the switching point to vary plus or minus .25V. After manufacture, the switching point

remains fixed within 10mV over time and temperature. The input switching sensivity is a maximum of 50mV. There is no hysteresis on

the OVERCURRENT SENSE input.

TABLE 3. OUTPUT COMMUTATION SEQUENCE FOR THREE PHASE OPERATION

SEQUENCE SELECT

CS1 CS2

CS1 CS2

CS1 CS2 CS1 CS2

FWD/REV=1

FWD/REV=0

0

0

0

1

1

0

1

1

ELECTRICAL SEPARATION

(-60°-)

(-120°-)

(-240°-)

(-300°-)

OUTPUTS

DRIVERS

OUTPUTS

DRIVERS

SENSE INPUTS

S1 S2 S3

S1 S2 S3

S1 S2 S3

S1 S2 S3

ENABLED A

B

C

ENABLED

A

B

C

0 0 0

0 0 1

0 1 0

0 1 1

O1, O5

+

-

Off

O2, O4

-

+

Off

1 0 0

1 0 1

1 1 0

1 1 1

O3, O5

Off

-

+

O2, O6

Off

+

-

1 1 0

1 0 0

1 0 0

1 1 0

O3, O4

-

Off

+

O1, O6

+

Off

-

1 1 1

1 1 0

1 0 1

1 0 0

O2, O4

-

+

Off

O1, O5

+

-

Off

0 1 1

0 1 0

0 0 1

0 0 0

O2, O6

Off

+

-

O3, O5

Off

-

+

0 0 1

0 1 1

0 1 1

0 0 1

O1, O6

+

Off

-

O3, O4

-

Off

+

0 1 0

0 0 0

0 0 0

0 1 0

ALL DISABLED

ALL DISABLED

1 0 1

1 1 1

1 1 1

1 0 1

ALL DISABLED

ALL DISABLED

The OVERCURRENT input (BRAKE low) enables external output drivers in normal sequence when more negative than Vss/2 and disables

all external output drivers when more positive than Vss/2. The OVERCURRENT is sensed continuously, and sets a flip flop which is reset

by the rising edge of the ENABLE input or the sawtooth OSCILLATOR. (See description under OVERCURRENT SENSE.)

The VTRIP Input (BRAKE low) enables the outputs in normal sequence when more negative than the OSC input and disables all outputs

(See description under VTRIP)

For the LS7260, (See Fig. 1) the external drivers also

turn on in pairs. Internal operation is somewhat different

than the LS7262. For example, external transistors Q101

and Q105 will turn on when internal transistor Q8 turns

off and Q4 turns on enabling full power supply drive on

channel Driver Q101 is brought to ground by R1 and the

Other external output pairs turn on similarly and the com-

mutation sequence is identical to that of the LS7262 (Ta-

ble 3). Table 2 indicates the minimum value of R1

(=R2=R3=R4=R5=R6) needed as a function of output

drive voltage for Fig. 1.

*

*

*

*

*

See Figures 1 and 2.

For the LS7260,

Outputs O1,O2,O3 are

the logical inversions of

the corresponding Out-

puts of the LS7262.