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3932
THREE-PHASE POWER MOSFET CONTROLLER
Pin Descriptions
RESET. A logic input that enables the device, internally
pulled up to LCAP. Logic HIGH will disable the device and
turn off MOSFETs, coasting the motor. Logic LOW will
enable gate drive to follow commutation logic. This input
will override BRAKE.
FAULT. Open drain output to indicate fault condition. Will
go active high for any of the following fault conditions:
1) Invalid HALL input code.
2) High side gate-source undervoltage.
3) Bootstrap capacitor not sufficiently charged.
4) Undervoltage condition detected at VREG.
5) Thermal Shutdown.
GLC/GLB/GLA. Low side gate drive outputs for external
MOSFET drivers. External series gate resistors can be used
to control slew rate seen at the power driver gate, thereby
controlling the di/dt and dv/dt of S outputs. The outputs will
source 1.25A for turn-on and sink 2.5A for gate discharge.
6) Motor lead (SA/SB/SC) connected to ground.
Any fault will force a COAST condition, which turns all
power MOSFETs off. The fault state for gate-source and
bootstrap monitors is cleared at each commutation. If the
motor has stalled, the fault must be cleared by toggling the
RESET pin or repeating a power up sequence.
SC/SB/SA. Directly connected to the motor terminals,
these pins sense the voltages switched across the load. The
pin is also connected to the negative side of the bootstrap
capacitor and negative supply connection for the floating
high side drive.
BRAKE. Logic input for braking function. Logic LOW will
turn on sink side MOSFETs, turn off the source side
MOSFETs. This will effectively short the BEMF in the
windings and brake the motor. Internally pulled up to logic
LCAP.
GHC/GHB/GHA. High side gate drive outputs for n-
channel MOSFET drivers. External series gate resistors can
be used to control slew rate seen at the power driver gate,
thereby controlling the di/dt and dv/dt of S outputs. The
outputs will source 1.25A for turn-on and sink 2.5A for gate
discharge.
SR. Synchronous rectification input. Logic LOW disables
the feature forcing current decay through flyback diodes.
Logic HIGH will result in the opposite pair of drivers to
switch in response to a PWM “off” command. Internally
pulled up to LCAP.
CC/CB/CA. High side connection for bootstrap capacitor,
positive supply for high side gate drive. The bootstrap
capacitor is charged to approximately VREG when the
output Sx terminal is low. When the output swings high, the
voltage on this pin rises with the output to provide the
boosted gate voltage needed for N-channel power
MOSFETs.
TACH. Digital output to indicate speed of rotation. A 3µs
pulse appears at every Hall transition.
PWM. Speed control input. Logic HIGH will turn on
MOSFETs selected by Hall input logic. Logic LOW turns
off the selected MOSFETs. The PWM input held high to
utilize internal current control circuitry. Internally pulled up
to logic LCAP.
MODE. Logic input to set current decay method. Slow
decay mode (logic HIGH) switches off the high side FET in
response to PWM Off command. Fast decay mode (logic
LOW) switches off the source and sink MOSFET’s. Mode
pin is internally pulled up to LCAP.
RC. Analog input. Connection for RT and CT to set the fixed
off time. The CT will also set the BLANK time. (see
applications information). It is recommended that the fixed
off time should not be less than 10ms. The resistor should be
in the range 10k to 500k.
H1/H2/H3. Hall sensor inputs, internally pulled up to
LCAP. Configured for 120-degree electrical spacing.
SENSE. Analog input to the current limit comparator.
Voltage representing load current appears on this pin.
Voltage transients seen at this pin when the drivers turn on
DIR. Logic input to reverse rotation, see commutation logic
table. Internally pulled up to LCAP.
are ignored for time Tblank
.
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
