OM9373SP International Rectifier Corp., OM9373SP Datasheet - Page 6

• Manufacturer Part Number: OM9373SP
• Description: Full-featured Power Module For Direct Drive Of 3-phase Brushless Dc Motor
• Manufacturer: International Rectifier Corp.

FROM MOTOR HALL SENSORS
OM9373
Fig 2: Implementation of a Voltage -Mode Controller
Modes of Operation
Figures
provides schematic representations of typical voltage-
mode and current -mode applications for the OM9373
controller/driver.
Figure 2 represents the implemenation of a typical
voltage-mode controller for velocity control. A voltage
or speed command is applied to the noninverting
input of the error amplifier which is configured as
voltage follower. The ouput of the error amplifier is
compared to a pulse width modulated ramp,and
since motor speed is nearly proportional to the
average phase output voltage, the average speed is
controlled via duty cycle control. If a speed feedback
loop is required, the tachometer output can be
connected to the inverting input of the error amplifier
via a loop compensation network.
6
+15V
H3
H2
H1
1k
2 and 3, shown on the following pages,
3.24k
1.50k
COMMAND
4700pF
10uF
.1uF
+
232
232
.1uF
10k
.1uF
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
1
2
3
4
5
6
7
8
9
Vcc
EA1-
EA2+
EA1+
VREF
EA2-
EA2_OUT
EA1_OUT
PWM_IN
OSCILLATOR
I_SENSE
ISH
ISL
QUAD_SEL
TACH_OUT
BRAKE
OV_COAST
SOFT_START
GROUND
H3_HALL_INPUT
H2_HALL_INPUT
H1_HALL_INPUT
SPEED_IN
DIRECTION
CSH
CSL
Figure 2 also shows the implementation of the
cycle-by-cycle current limit/overcurrent protection
feature of the OM9373. The load current is monitored
red via the controller’s internal sense resistor. The
current sense signal is filtered and fed into the current
rent sense amplifier where the absolute value of
ISH-ISL is multiplied by two and biased up by 2.5V
The output of the current sensor amplifier is compared to
a fixed reference, thus providing cycle-by-cycle
current limiting and/or overcurrent protection as
necessary. The typical peak current threshold (ISL-ISH)
is 0.2V; the typical over current threshold (ISH-ISL) is
0.3V.
MOTOR_RETURN
MOTOR_RETURN
PHASE_A_OUT
PHASE_A_OUT
PHASE_B_OUT
PHASE_B_OUT
PHASE_C_OUT
PHASE_C_OUT
SOURCE_A
SOURCE_A
SOURCE_B
SOURCE_B
SOURCE_C
V_MOTOR
V_MOTOR
V_MOTOR
N/C
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
C_BUS
+
HALL SENSORS
www.irf.com
C_FILT
V_MOTOR
H1
H2
H3
MOTOR