A3932SEQ Allegro Microsystems Inc, A3932SEQ Datasheet - Page 11

• Manufacturer Part Number: A3932SEQ
• Description: IC CTRLR MOSFET 3PH 32-PLCC
• Manufacturer: Allegro Microsystems Inc

Specifications of A3932SEQ

• Applications: DC Motor Controller, Brushless (BLDC), 3 Phase
• Number Of Outputs: 1
• Voltage - Supply: 18 V ~ 50 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-PLCC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output: -
• Voltage - Load: -

A3932
Current Control. Internal fi xed off-time PWM circuitry is
implemented to limit load current to a desired value. When a
high-side and low-side MOSFET are turned on, current will
increase in the motor winding until it reaches a value given by
enable latch, turning off the high-side driver. Load inductance
causes the current to recirculate (decay) for the fi xed off time.
The current path during recirculation is determined by the
confi guration of the MODE and SR inputs.
in parallel from the RC terminal to AGND, are used to set the
fi xed off-time period (t
of 10 kΩ to 500 kΩ. The t
50 μs. Larger values for t
input voltage as long as the PWM input stays high. If direct
control of the torque/current is desired by PWM input, a voltage
can be applied to the REF input to set an absolute maximum
current limit.
PWM Blank. The capacitor (C
set the blank time duration. At the end of the PWM off cycle, a
high-side gate selected by the commutation logic will turn on.
At this time, large current transients can occur during the reverse
recovery time (t
power MOSFETs. To prevent false tripping of the current-sense
comparator, the blank function disables the comparator for a
time
current-spike duration.
Braking. The A3932 will dynamically brake by forcing all
low-side MOSFETs on and all high-side MOSFETs off. This
will effectively short-circuit the BEMF and brake the motor.
During braking, the load current can be approximated by:
At the trip point, the sense comparator resets the source-
An external resistor (R
Torque control can be implemented by varying the REF
The user must ensure that C
rr
t
) of the intrinsic body diodes of the external
blank
= 1.9 x C
off
I
BRAKE
I
TRIP
= R
off
off
T
) and capacitor (C
can result in audible noise problems.
T
should be in the range of 10 μs to
≈ V
= V
x C
T
T
/(0.001 - [2/R
T
) also serves as the means to
REF
is large enough to cover the
BEMF
T
). R
/R
/R
S
T
.
should be in the range
L
Applications Information (cont’d)
T
T
])
), connected
Three-Phase Power MOSFET Controller
resistor during a dynamic brake, care must be taken to ensure
that the power MOSFET’s maximum ratings are not exceeded.
FETs off, coasting the motor.
Low-Voltage Operation. Although VREG can be connected
to VBB for 12 V systems, the V
must be observed including transients. If transients cannot be
adequately controlled, use VREG in the regulator mode (not
connected to VBB). With V
voltage level specifi cation may not be met. Note that in this
mode the VREG undervoltage threshold may leave the system
with little headroom if V
Driving an H Bridge. The A3932 may be used to drive an
H bridge (e.g., a brush dc motor load) by hard wiring one state
for the Hall inputs (e.g., H1 = H2 = 1 (HIGH), H3 = 0 (LOW)).
Leave the appropriate phase driver outputs fl oating (in this case
CC, GHC, SC, and GLC because, from the Commutation Truth
Table, SC = Z). The DIR input controls the motor rotation while
the PWM, MODE, and SR inputs control the motor current
behavior as described in the Input Logic table.
Layout. Careful consideration must be given to PCB layout
when designing high-frequency, fast-switching, high-current
circuits.
1) The analog ground (AGND), the power ground (PGND),
and the high-current return of the external MOSFETs (the
negative side of the sense resistor) should return separately to the
negative side of the motor supply fi ltering capacitor. This will
minimize the effect of switching noise on the device logic and
analog reference.
2) Minimize stray inductances by using short, wide copper
runs at the drain and source terminals of all power MOSFETs.
This includes motor lead connections, the input power buss,
and the common source of the low-side power MOSFETs. This
will minimize voltages induced by fast switching of large load
currents.
3) Kelvin connect the SENSE terminal PC trace to the positive
side of the sense resistor.
Because the load current does not fl ow through the sense
RESET = 1 overrides BRAKE and turns all motor bridge
BB
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
is less than 12 V.
BB
less than 18 V, the V
REG
maximum rating of 15 V
REG
output
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