LS7260 Datasheet PDF - LSI Computer Systems

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LS7260
LSI Computer Systems

Part Number LS7260
Description BRUSHLESS DC MOTOR COMMUTATOR/CONTROLLER
Page 7 Pages


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LSI/CSI
LS7260
LS7262
U® L LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631) 271-0400 FAX (631) 271-0405
A3800
BRUSHLESS DC MOTOR COMMUTATOR/CONTROLLER
FEATURES:
November 1997
Direct drive of P-Channel and N-Channel FETs (LS7260)
Direct drive of PNP and NPN transistors (LS7262)
CONNECTION DIAGRAM - TOP VIEW
Six outputs drive power switching bridge directly
Open or closed loop motor speed control.
CS1 1
20 CS2
+5V to +28V operation (Vss - VDD).
OUT 1 2
19 FWD/REV
Externally selectable input to output code for 60°,
OUT 2 3
18 V DD (-V)
120°, 240°, or 300° electrical sensor spacing.
Three or four phase operation
Analog Speed control
Direction control
OUT 3 4
COMMON 5
OUT 4 6
17 S3
16 S2
15 S1
Output Enable control
OUT 5 7
14 OSCILLATOR
Positive Static Braking
OUT 6 8
13 V TRIP
Overcurrent Sensing
LS7260, LS7262 (DIP); LS7260-S, LS7262-S (SOIC)
LS7260-TS, LS7262-TS (TSSOP) - See Connection Diag.
BRAKE 9
ENABLE 10
12 O V E R C U R R E N T S E N S E
11 V SS (+V)
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.
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.
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BRAKE (Pin 9) (Cont’d)
An internal pull-down resistor holds the input low when left
open. (Center- tapped motor configuration requires a power
supply disconnect transistor controlled by the BRAKE signal
- See Figure 2A).
ENABLE (Pin 10)
A high level at this input permits the output to sequence as
in Table 3, while a low disables all external output drivers.
An internal pull-up resistor holds the input high when left
open. Positive edges at this input will reset the overcurrent
flip-flop.
OVERCURRENT SENSE (Pin 12)
This input provides the user a way of protecting the motor
winding, drivers and power supply from an overload condi-
tion. The user provides a fractional-ohm resistor between
the negative supply and the common emitters of the NPN
drivers or common sources of N-Channel FET drivers. This
point is connected to one end of a potentiometer (e.g. 100K
ohms), the other end of which is connected to the positive
supply. The wiper pickoff is adjusted so that all outputs are
disabled for currents greater than the limit. The action of the
input is to disable all external output drivers. When BRAKE
exists, OVERCURRENT SENSE will be overridden. The
overcurrent circuitry latches the overcurrent condition. The
latch may be reset by the positive edge of either the saw-
tooth OSCILLATOR or the ENABLE input. When using the
ENABLE input as a chopped input, the OSC input should be
held at VSS. When the ENABLE input is held high, the OSC-
must be used to reset the overcurrent latch.
VTRIP (Pin 13)
This input is used in conjunction with the sawtooth OSC in-
put. When the voltage level applied to VTRIP is more neg-
ative than the waveform at the OSC input, the Outputs will
be enabled as shown in Table 3. When VTRIP is more pos-
itive than the sawtooth OSCILLATOR waveform the external
output drivers are disabled.
The sawtooth waveform at the OSC input typically varies
from .4 Vss to Vss-2V. The purpose of the VTRIP input in
conjunction with the OSCILLATOR is to provide variable
speed adjustment for the motor by means of PWM.
OSCILLATOR (Pin 14)
An R and C connected to this input (See Figure 6) provide
the timing components for a sawtooth OSCILLATOR. The
signal generated is used in conjunction with VTRIP to pro-
vide PWM for variable speed applications and to reset the
overcurrent condition.
OUTPUTS 1, 2, 3 (Pins 2, 3, 4)
For the LS7262, these open drain Outputs are enabled as
shown in Table 2 and provide base current to PNP tran-
sistors or gate drive to P-Channel FET drivers when COM-
MON is floating. If COMMON is held at Vss, these Outputs
can provide drive to NPN transistors or N-Channel FET
drivers. For the LS7260, these Outputs provide drive to
P-Channel FET drivers if COMMON is held at VSS.
OUTPUTS 4, 5, 6 (Pins 6, 7, 8)
These open drain Outputs are enabled as in Table 2 and
provide base current to NPN transistors or gate drive to
N-Channel FET drivers.
COMMON (Pin 5)
The COMMON may be connected to Vss when using a
center-tapped motor configuration or when using all NPN
or N-Channel drivers. For the LS7260, the COMMON is
tied to VSS.
Vss (Pin 11)
Supply voltage positive terminal.
VDD (Pin 18)
Supply voltage negative terminal (ground).
MAXIMUM RATINGS:
PARAMETER
Storage Temperature
Operating Temperature
Voltage (any pin to Vss)
SYMBOL
TSTG
TA
TA (1)
VMAX
(1) Available on special order. Contact factory for details.
VALUE
-65 to +150
-25 to +85
-40 to +125
-30 to +.5
UNIT
°C
°C
°C
V
DC ELECTRICAL CHARACTERISTICS:
(All Voltages Referenced to VDD, TA = 25°C unless otherwise specified)
SYMBOL
MIN
Supply Voltage
VSS 5
Supply Current (Outputs not loaded)
IDD -
Input Specifications:
BRAKE, ENABLE, CS1, CS2
S1, S2, S3, FWD/REV
Voltage (Logic "1")
(Logic "0")
OVERCURRENT SENSE (See Note)
Threshold Voltage
RIN -
VIH VSS-1.5
VIL 0
VTH (VSS/2)-.25
TYP
-
4.5
150
-
-
-
MAX
28
6
UNIT
V
mA
- K
VSS
VSS-4.0
V
V
(VSS/2)+.25 V
7260-111297-2



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Oscillator:
Frequency Range
External Resistor Range
Fosc
0
1/RC
100 kHz
Rosc
22
-
1000
k
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.
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.
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
Q101 and Q105. Since Pin 5 is tied to VSS, the gate of P-
channel Driver Q101 is brought to ground by R1 and the
Gate of N-Channel driver Q105 is brought to VSS by Q4.
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.
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)
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
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
*causes excessive power dissipation
**exceeds max current possible for this voltage
TABLE 3. OUTPUT COMMUTATION SEQUENCE FOR THREE PHASE OPERATION
SEQUENCE SELECT CS1 CS2
00
ELECTRICAL SEPARATION (-60°-)
SENSE INPUTS
S1 S2 S3
000
100
110
* See Figures 1 and 2.
For the LS7260,
Outputs O1,O2,O3 are
111
011
001
the logical inversions of
the corresponding Out-
puts of the LS7262.
010
101
CS1 CS2
01
(-120°-)
S1 S2 S3
001
101
100
110
010
011
000
111
CS1 CS2 CS1 CS2
1 011
(-240°-) (-300°-)
S1 S2 S3 S1 S2 S3
010 011
110 111
100 110
101 100
001 000
011 001
FWD/REV=1
OUTPUTS * DRIVERS *
ENABLED A B C
O1, O5 + - Off
O3, O5 Off - +
O3, O4
- Off +
O2, O4 - + Off
O2, O6 Off + -
O1, O6
+ Off -
FWD/REV=0
OUTPUTS * DRIVERS *
ENABLED A B C
O2, O4
- + Off
O2, O6
Off + -
O1, O6
+ Off -
O1, O5
+ - Off
O3, O5
Off - +
O3, O4
- Off +
000
111
010
101
ALL DISABLED
ALL DISABLED
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
when more positive than the OSC input. The VTRIP input may be disabled by connecting it to VDD and the OSC input to VSS.
(See description under VTRIP)
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Vss
Output
Encoder
12
O1
2
O2
3
O3
4
Q8 Q7 Q6
5
Q5 Q4 Q3
8 O6
O5
7
Vss O4
6
P PP
Q101
Q102
Q103
R1
R2 R3
L1
A
L3
L2
B
M
O
T
CO
R
N
Q104
N
Q105
N
Q106
R4 R5
R6
TO
OVERCURRENT
ADJUSTMENT
Fractional
Ohm
Resistor
FIGURE 1. LS7260 THREE PHASE OUTPUT DRIVER CIRCUITRY
BRAKE
Output
Encoder
12
11
Vss
Vss
Direction of Current Flow
2 O1
O2
3
4 O3
R1
Q8 Q7 Q6
5
Q5 Q4 Q3
R6
8 O6
O5 R5
7
O4
6
R4
Q101
R2
Q102
R3
Q103
L1
A
L3
L2
B
M
O
T
CO
R
Q104
Q105
Q106
TO OVERCURRENT
ADJUSTMENT
R7
R8 R9
Fractional
Ohm
Resistor
FIGURE 2. LS7262 THREE PHASE OUTPUT DRIVER CIRCUITRY
7260-100897-4



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