A3932SEQ-TTR Allegro MicroSystems, Inc., A3932SEQ-TTR Datasheet - Page 9

• Manufacturer Part Number: A3932SEQ-TTR
• Description: IC MOSFET DRVR 5V DUAL HI/LO SIDE 3-PHASE BRDG 32PLCC T/R
• Manufacturer: Allegro MicroSystems, Inc.

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 fixed
off time. The current path during recirculation is determined by
the configuration of the MODE and SR inputs.
parallel from the RC terminal to AGND, are used to set the
fixed off-time period (t
of 10 k to 500 k . The t
50 s. Larger values for t
problems.
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.
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
external power MOSFETs. To prevent false tripping of the
current-sense comparator, the blank function disables the
comparator for a time
current-spike duration.
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:
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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
The A3932 will dynamically brake by forcing all
The capacitor (C
t
blank
Internal fixed off-time PWM circuitry is
= 1.9 x C
I
off
BRAKE
rr
I
TRIP
) of the intrinsic body diodes of the
= R
off
off
T
) and capacitor (C
can result in audible noise
T
should be in the range of 10 s to
= V
T
x C
V
/(0.001 - [2/R
T
T
REF
) also serves as the means to
BEMF
is large enough to cover the
T
). R
/R
/R
S
.
T
L
should be in the range
T
T
])
), connected in
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.
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 specification may not be met. Note that in this
mode the VREG undervoltage threshold may leave the system
with little headroom if V
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 floating (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.
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 filtering 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 flow through the sense
RESET = 1 overrides BRAKE and turns all motor bridge
Careful consideration must be given to PCB layout
MOSFET CONTROLLER
THREE-PHASE POWER
BB
The A3932 may be used to drive an H
is less than 12 V.
BB
Although VREG can be connected
less than 18 V, the V
REG
maximum rating of 15 V
3932
REG
output