BRUSHLESS DC MOTOR COMMUTATOR/CONTROLLER

FEATURES:

120°, 240°, or 300° electrical sensor spacing.

LS7260-TS, LS7262-TS (TSSOP) - See Connection Diag.

DESCRIPTION:

The LS7260/LS7262 are monolithic, MOS integrated cir-

cuits designed to generate the signals necessary to con-

trol a three phase or four phase brushless DC motor.

They are the basic building blocks of a brushless DC

motor controller. The circuits respond to changes at the

SENSE inputs, originating at the motor position sensors,

to provide electronic commutation of the motor wind-

ings. Pulse Width Modulation of outputs for motor speed

control is accomplished through either the ENABLE in-

put or through the Analog input (VTRIP) in conjunction

with the OSCILLATOR input.

Overcurrent circuitry is

provided to protect the windings, associated drivers and

power supply. The overcurrent circuitry causes the ex-

ternal output drivers to switch off immediately upon

sensing the overcurrent condition and on again only

when the overcurrent condition disappears and the pos-

itive edge of either the ENABLE input or the sawtooth

OSCILLATOR occurs. This limits the overcurrent sense

cycling to the chopping rate of the ENABLE input or the

sawtooth OSCILLATOR.

A positive braking feature is provided to effect rapid de-

celeration. While the LS7262 is designed for driving

NPN and PNP transistors (See Fig. 2), the LS7260 is

designed to drive both NMOS and PMOS Power FETs

and develops a full 12V drive for both the N-Channel

and P-Channel devices (See Fig. 1) when using a 12V

power supply.

CS1

OUT 1

OUT 2

OUT 3

OUT 4

COMMON

OUT 5

OUT 6

BRAKE

ENABLE

CS2

FWD/REV

S3

S2

S1

OSCILLATOR

V TRIP

OVERCURRENT SENSE

CONNECTION DIAGRAM - TOP VIEW

1

2

3

4

5

6

7

8

9

10

20

11

12

13

14

15

16

17

18

19

INPUT/OUTPUT DESCRIPTION:

COMMUTATION SELECTS (Pins 1, 20)

These inputs are used to select the proper sequence of outputs

based on the electrical separation of the motor position sensors.

See Table 3. Note that in all cases the external output drivers

are disabled for invalid SENSE input codes. Internal pull down

resistors are provided at Pins 1 and 20 causing a logic zero

when these pins are left open.

FORWARD/REVERSE (Pin 19)

This input is used to select the proper sequence of Outputs for

the desired direction of rotation for the Motor (See Table 3). An

internal pull-up resistor holds the input high when left open.

SENSE INPUTS (Pins 15, 16, 17)

These inputs provide control of the output commutation

sequence as shown in Table 3. S1, S2, S3 originate in the posi-

tion sensors of the motor and must sequence in cycle code or-

der. Hall Switch pull-up resistors are provided at Pins 15, 16 and

17. The positive supply of the Hall devices should be common

to the chip Vss.

BRAKE (Pin 9)

For the LS7262, a high level at this input unconditionally turns

OFF Outputs 1, 2 and 3 and turns ON Outputs 4, 5 and 6 (See

Fig. 2). For the LS7260, a high level at this input turns ON Out-

puts 1, 2 and 3 and Outputs 4, 5 and 6 (See Fig. 1). In both

cases, transistors Q101, Q102 and Q103 cut off and transistors

Q104, Q105 and Q106 turn on, shorting the windings together,

The BRAKE has priority over all other inputs.

November 1997

7260-041100-1

LSI/CSI

LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747

(631) 271-0400 FAX (631) 271-0405

LS7260

LS7262

UL

®

A3800