SA303 Datasheet, PDF (7/14 Pages) Cirrus Logic – 3 Phase Switching Amplifier

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SA303
At, Bt, Ct: These Schmitt triggered logic level inputs are responsible for turning the associated top side, or upper
P-channel FET outputs on and off. Logic high turns the top P-channel FET on, and a logic low turns the top
P-channel FET off.
Ia, Ib, Ic: Current sense pins. The SA303 supplies a positive current to these pins which is proportional to the cur-
rent flowing through the top side P-channel FET for that phase. Commutating currents flowing through the
backbody diode of the P-channel FET or through external Schottky diodes are not registered on the current
sense pins. Nor do currents flowing through the low side N-channel FET, in either direction, register at the cur-
rent sense pins. A resistor connected from a current sense pin to SGND creates a voltage signal representa-
tion of the phase current that can be monitored with ADC inputs of a processor or external circuitry.
The current sense pins are also internally compared with the current limit threshold voltage reference, Vth. If
the voltage on any current sense pin exceeds Vth, the cycle by cycle current limit circuit engages. Details of
this functionality are described in the applications section of this datasheet.
I_LIM/DIS1: This pin is directly connected to the disable circuitry of the SA303. Pulling this pin to logic high places
OUT A, OUT B, and OUT C in a high impedance state. This pin is also connected internally to the output of the
current limit latch through a 12kΩ resistor and can be monitored to observe the function of the cycle-by-cycle
current limit feature. Pulling this pin to a logic low effectively disables the cycle-by-cycle current limit feature.
SGND: This is the ground return connection for the V_DD logic power supply pin. All internal analog and logic circuitry
is referenced to this pin. PGND is internally connected to GND through a resistance of a few ohms,. However, it
is highly recommended to connect the GND pin to the PGND pins externally as close to the device as possible.
Failure do to this may result in oscillations on the output pins during rising or falling edges.
VDD: This is the connection for the 5V power supply, and provides power for the logic and analog circuitry in the
SA303. This pin requires decoupling (at least 0.1μF capacitor with good high frequency characteristics is rec-
ommended) to the SGND pin.
DIS2: The DIS2 pin is a Schmitt triggered logic level input that places OUT A, OUT B, and OUT C in a high imped-
ance state when pulled high. DIS2 has an internal 12kΩ pull-down resistor and may therefore be left uncon-
nected.
TEMP: This logic level output goes high when the die temperature of the SA303 reaches approximately 135ºC. This
pin WILL NOT automatically disable the device. The TEMP pin includes a 12kΩ series resistor.
HS: These pins are internally connected to the thermal slug on the reverse of the package. They should be con-
nected to GND. Neither the heat slug nor these pins should be used to carry high current.
NC: These “no-connect” pins should be left unconnected.
2. SA303 OPERATION
The SA303 is designed primarily to drive three phase motors. However, it can be used for any application requir-
ing three high current outputs. The signal set of the SA303 is designed specifically to interface with a DSP or
microcontroller. A typical system block diagram is shown in the figure below. Over-temperature, Short-Circuit and
Current Limit fault signals provide important feedback to the system controller which can safely disable the output
drivers in the presence of a fault condition. High side current monitors for all three phases provide performance
information which can be used to regulate or limit torque.
SA303U