SI9979 Vishay Siliconix, SI9979 Datasheet - Page 5

• Manufacturer Part Number: SI9979
• Description: 3-Phase Brushless DC Motor Controller
• Manufacturer: 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 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
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
Pin 18: R
One side of the current limit one shot timing resistor is
connected to this pin.
Pin 19: I
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
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
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
This is the gate drive output for the bottom MOSFET in
Phase C.
Pin 26: GT
This is the gate drive output for the top MOSFET in Phase C.
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S
S
T
T
+
-
/C
C
C
T
T
and C
T
, thus stopping the flow of current.
T
and C
T
, thus stopping the flow of
Pin 27: S
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
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
This is the gate drive output for the bottom MOSFET in
Phase B.
Pin 30: GT
This is the gate drive output for the top MOSFET in Phase B.
Pin 31: S
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 34: GT
This is the gate drive output for the top MOSFET in Phase A.
Pin 35: S
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
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
V
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.
DD
is the internal logic and gate drive voltage. It is necessary
C
B
A
DD
A
B
B
A
C
Vishay Siliconix
S-60752-Rev. D, 05-Apr-99
Si9979
5