33937_09 Datasheet, PDF (25/48 Pages) Freescale Semiconductor, Inc – Three Phase Field Effect Transistor Pre-driver

FUNCTIONAL DESCRIPTIONS
INTRODUCTION
and off the Low Side FET.. A low-impedance drive ensures
transient currents do not overcome an off-state driver and
allow pulses of current to flow in the external FET. This output
has also been designed to resist the influence of negative
currents.
PHASE C HIGH SIDE SOURCE (PC_HS_S)
The source connection for the phase C High Side output
FET is the reference voltage for the gate drive on the High
Side FET and also the low voltage end of the bootstrap
capacitor.
PHASE C HIGH SIDE GATE (PC_HS_G)
This is the gate drive for the phase C High Side output
FET. This pin provides the gate bias to turn the external FET
on or off. The gate voltage is limited to about 15 V above the
FET source voltage. A low-impedance drive is used, ensuring
transient currents do not overcome an off-state driver and
allow pulses of current to flow in the external FETs. This
output has also been designed to resist the influence of
negative currents.
PHASE C BOOTSTRAP (PC_BOOT)
This is the bootstrap capacitor connection for phase C. A
capacitor connected between PC_HS_S and this pin
provides the gate voltage and current to drive the external
FET gate. Typically, the boostrap capacitor selection is 10 to
20 times the gate capacitance. The voltage across this
capacitor is limited to about 15 V. Use the 33937A to avoid
the CAUTION on page 28 for bootstrap capacitances greater
than 100 nF.
PHASE B LOW SIDE SOURCE (PB_LS_S)
The phase B Low Side source is the pin used to return the
gate currents from the Low Side FET. Best performance is
realized by connecting this node directly to the source of the
Low Side FET for phase B.
PHASE B LOW SIDE GATE (PC_LS_G)
This is the gate drive for the phase B Low Side output FET.
It provides high current through a low impedance to turn on
and off the Low Side FET. A low-impedance drive ensures
transient currents do not overcome an off-state driver and
allow pulses of current to flow in the external FET. This output
has also been designed to resist the influence of negative
currents.
PHASE B HIGH SIDE SOURCE (PB_HS_S)
The source connection for the phase B High Side output
FET is the reference voltage for the gate drive on the High
Side FET and also the low voltage end of the bootstrap
capacitor.
PHASE B HIGH SIDE GATE (PB_HS_G)
This is the gate drive for the phase B High Side output
FET. This pin provides the gate bias to turn the external FET
Analog Integrated Circuit Device Data
Freescale Semiconductor
on or off. The gate voltage is limited to about 15 V above the
FET source voltage. A low-impedance drive is used, ensuring
transient currents do not overcome an off-state driver and
allow pulses of current to flow in the external FETs. This
output has also been designed to resist the influence of
negative currents.
PHASE B BOOTSTRAP (PB_BOOT)
This is the bootstrap capacitor connection for phase B. A
capacitor connected between PC_HS_S and this pin
provides the gate voltage and current to drive the external
FET gate. Typically, the boostrap capacitor selection is 10 to
20 times the gate capacitance. The voltage across this
capacitor is limited to about 15 V. Use the 33937A to avoid
the CAUTION on page 28 for bootstrap capacitances greater
than 100 nF.
PHASE A LOW SIDE SOURCE (PA_LS_S)
The phase A Low Side source is the pin used to return the
gate currents from the Low Side FET. Best performance is
realized by connecting this node directly to the source of the
Low Side FET for phase A.
PHASE A LOW SIDE GATE (PA_LS_G)
This is the gate drive for the phase A Low Side output FET.
It provides high current through a low impedance to turn on
and off the Low Side FET. A low-impedance drive ensures
transient currents do not overcome an off-state driver and
allow pulses of current to flow in the external FET. This output
has also been designed to resist the influence of negative
currents.
PHASE A HIGH SIDE SOURCE (PA_HS_S)
The source connection for the phase A High Side output
FET is the reference voltage for the gate drive on the High
Side FET and also the low voltage end of the bootstrap
capacitor.
PHASE A HIGH SIDE GATE (PA_HS_G)
This is the gate drive for the phase A High Side output
FET. This pin provides the gate bias to turn the external FET
on or off. The gate voltage is limited to about 15 V above the
FET source voltage. A low-impedance drive is used, ensuring
transient currents do not overcome an off-state driver and
allow pulses of current to flow in the external FETs. This
output has also been designed to resist the influence of
negative currents.
PHASE A BOOTSTRAP (PA_BOOT)
This is the bootstrap capacitor connection for phase A. A
capacitor connected between PC_HS_S and this pin
provides the gate voltage and current to drive the external
FET gate. Typically, the boostrap capacitor selection is 10 to
20 times the gate capacitance. The voltage across this
capacitor is limited to about 15 V. Use the 33937A to avoid
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