LSI/CSI
UL
®
LS7362
(631) 271-0400 FAX (631) 271-0405
September 1999
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
A3800
BRUSHLESS DC MOTOR COMMUTATOR/CONTROLLER
FEATURES:
• Speed Control by Pulse Width Modulation (PWM)
of low-side drivers only.
•
Open or closed loop motor speed control.
• +5 to +28 Volt operation (Vss - V
DD
).
• Externally selectable input to output code for 60°,
120°, 240°, or 300° electrical sensor spacing.
• Three or four phase operation.
• Analog Speed control.
• Forward/Reverse control.
• Output Enable control.
• Positive Static Braking.
• Overcurrent Sensing.
• Six outputs drive switching bridge directly.
• LS7362 (DIP); LS7362-S (SOIC);
LS7362-TS (TSSOP) - See Connection Diagram
CONNECTION DIAGRAM
- TOP VIEW
STANDARD 20 PIN PLASTIC DIP
CS1
OUT 1
OUT 2
OUT 3
COMMON
OUT 4
1
2
3
20
19
18
CS2
FORWARD/REVERSE
V
DD
(-V)
LSI
4
17
S3
S2
S1
OSCILLATOR
LS7362
5
6
16
15
14
OUT 5
OUT 6
BRAKE
7
8
9
13
12
11
V TRIP
OVERCURRENT SENSE
V
SS
(+V)
DESCRIPTION:
The LS7362 is a monolithic, ion implanted MOS circuit de-
signed to generate the signals necessary to control a three
phase or four phase brushless DC motor. It is the basic
building block of a brushless DC motor controller. The cir-
cuit responds to changes at the SENSE inputs, originating
at the motor position sensors, to provide electronic com-
mutation of the motor windings. Pulse width modulation
(PWM) of low-side drivers for motor speed control is ac-
complished through either the ENABLE input or through
the V TRIP input (Analog Speed control) in conjunction with
the OSCILLATOR input. Overcurrent circuitry is provided
to protect the windings, associated drivers and power sup-
ply. The LS7362 circuitry causes the external output driv-
ers to switch off immediately upon sensing the overcurrent
condition, and on again only when the overcurrent condi-
tion disappears and the positive edge of either the EN-
ABLE input or the sawtooth OSCILLATOR occurs. This lim-
its 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 deceleration. The
LS7362 is designed for driving Bipolar and Field Effect
Transistors. Because only low-side drivers are pulse width
modulated, the LS7362 is ideally suited in situations where
the integrated circuit interfaces with level converters to
drive high voltage brushless DC motors. By pulse width
modulating the low-side drivers only, the switch losses in
the level conversion circuitry for the high-side drivers is
minimized. Figure 1 indicates how the level conversion is
accomplished.
7362-041100-1
ENABLE
10
The COMMON, Pin 5, is tied to the positive supply rail
and LS7362 Outputs 1, 2, and 3 are used to drive level
converters Q101, Q102 and Q103 respectively. Only the
motor top side drivers consisting of Q107, Q108 and
Q109 which are connected to the motor power supply,
V
M
, will be subject to the high speed switching currents
that flow through the motor. The level converters are
turned on and off at the slower commutation rate.
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. With both inputs low (logic zero), the
sequence is adjusted for 60° electrical separation, with
CS2 high and CS1 low 120° separation sequence is se-
lected, with CS1 high and CS2 low 240° separation se-
quence is selected and with CS1 and CS2 high the 300°
separation sequence is selected. Note that in all cases
the external output drivers are disabled for invalid
SENSE input codes. Internal pull down resistors are pro-
vided at Pins 1 and 20 causing a logic zero when these
pins are left open.
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