SI9979 Datasheet, PDF (5/7 Pages) Vishay Siliconix – 3-Phase Brushless DC Motor Controller

Si9979
Vishay Siliconix
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 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 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 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 18: R_T
One side of the current limit one shot timing resistor is
connected to this pin.
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
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 34: GT_A
This is the gate drive output for the top MOSFET in Phase A.
Pin 35: S_A
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 A output.
Pin 36: CAP_A
This pin is the positive supply of the high-side circuitry. The
bootstrap capacitor for Phase A is connected between this pin
and SA.
Pin 42: V+
The supply voltage for the Si9979 is connected between this
pin and ground. The internal logic and high-side supply
voltages are derived from V+.
Pin 43: V_DD
V_DD is the internal logic and gate drive voltage. It is necessary
to connect a capacitor between this pin and ground to insure
that the current surges seen at the turn on of the bottom
MOSFETs does not trip the undervoltage lockout circuitry.
FaxBack 408-970-5600, request 70012
www.siliconix.com
S-60752-Rev. D, 05-Apr-99
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