SI9979_04 Datasheet, PDF (5/9 Pages) Vishay Siliconix – 3-Phase Brushless DC Motor Controller

Si9979
Vishay Siliconix
PIN DESCRIPTION (CONT’D)
Pin 9: BRK
With this input at logic “1”, the top MOSFETs are turned off and
the bottom MOSFETs are turned on, shorting the motor
windings together. This provides a braking torque which is
dependent on the motor speed. This is the default condition as
this pin is pulled up internally. When this pin is pulled to ground,
the MOSFETs are allowed to follow the commutation
sequence.
Pin 10: TACH
This output provides a minimum 300-nanosecond output
pulse for every commutation sensor transition, yielding a 6
pulse per electrical revolution tachometer signal. This output
is open drain.
Pin 11: FAULT
The FAULT output switches low to indicate that at least one of
the following conditions exists, controller disable (EN),
undervoltage lockout, invalid commutation sensor code
shutdown, or overcurrent shutdown. This output is open drain.
Pin 17: R_T/C_T
The junction of the current limit one shot timing resistor and
capacitor is connected to this pin. This one-shot is triggered by
the current limit comparator when an overcurrent condition
exists. This action turns off all the gate drives for the period
defined by R_T and C_T, thus stopping the flow of current.
Pin 18: R_T
One side of the current limit one shot timing resistor is
connected to this pin.
Pin 19: I_S+
This is the sensing input of the current limit comparator and
should be connected to the positive side of the current sense
resistor. When the voltage across the current sense resistor
exceeds 100 mV, the comparator switches and triggers the
current limit one-shot. The one-shot turns off all the gate drives
for the period defined by R_T and C_T, thus stopping the flow of
current. If the overcurrent condition remains after the
shutdown period, the gate drives will be held off until the
overcurrent condition no longer exists.
Pin 20: I_S−
This pin is the ground reference for the current limit
comparator. It should be connected directly to the ground side
of the current sense resistor to enhance noise immunity.
Pins 12−16: 21−24, 37−41, 44−48, GND
These pins are the return path for both the logic and gate drive
circuits. Also, they serve to conduct heat out of the package,
into the circuit board.
Pin 25: GB_C
This is the gate drive output for the bottom MOSFET in
Phase C.
Pin 26: GT_C
This is the gate drive output for the top MOSFET in Phase C.
Pin 27: S_C
This pin is negative supply of the high-side drive circuitry. As
such, it is the connection for the negative side of the bootstrap
capacitor, the top MOSFET Source, the bottom MOSFET
Drain, and the Phase C output.
Pin 28: CAP_C
This pin is the positive supply of the high-side circuitry. The
bootstrap capacitor for Phase C is connected between this pin
and SC.
Pin 29: GB_B
This is the gate drive output for the bottom MOSFET in Phase
B.
Pin 30: GT_B
This is the gate drive output for the top MOSFET in Phase B.
Pin 31: S_B
This pin is negative supply of the high-side drive circuitry. As
such, it is the connection for the negative side of the bootstrap
capacitor, the top MOSFET Source, the bottom MOSFET
Drain, and the Phase B output.
Pin 32: CAP_B
This pin is the positive supply of the high-side circuitry. The
bootstrap capacitor for Phase B is connected between this pin
and SB.
Pin 33: GB_A
This is the gate drive output for the bottom MOSFET in
Phase A.
Document Number: 70012
S-41209—Rev. E, 21-Jun-04
www.vishay.com
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