33937_09 Datasheet, PDF (23/48 Pages) Freescale Semiconductor, Inc – Three Phase Field Effect Transistor Pre-driver

FUNCTIONAL DESCRIPTIONS
INTRODUCTION
FUNCTIONAL DESCRIPTIONS
INTRODUCTION
The 33937 provides an interface between an MCU and the
large FETs used to drive three phase loads. A typical load
FET may have an on resistance of 4.0 mΩ or less and could
require a gate charge of over 400 nC to fully turn on. The IC
can operate in automotive 12 to 42 V environments.
Because there are so many methods of controlling three
phase systems, the IC enforces few constraints on driving the
FETs. It does provide deadtime (cross-over) blanking and
logic, both of which can be overridden, ensuring both FETs in
a phase are not simultaneously enabled.
An SPI port is used to configure the IC modes.
FUNCTIONAL PIN DESCRIPTION
PHASE A (PHASEA)
This pin is the totem pole output of the Phase A
comparator. This output is low when the voltage on Phase A
High Side source (source of the High Side load FET) is less
than 50 percent of VSUP.
POWER GROUND (PGND)
This pin is power ground for the charge pump. It should be
connected to VSS, however routing to a single point ground
on the PCB may help to isolate charge pump noise.
ENABLE 1 AND ENABLE 2 (EN1, EN2)
Both of these logic signal inputs must be high to enable
any gate drive output. When either or both are low, the
internal logic (SPI port, etc.) still functions normally, but all
gate drives are forced off (external power FET gates pulled
low). The signal is asynchronous.
When EN1 and EN2 return high to enable the outputs,
each LS driver must be pulsed on before the corresponding
HS driver can be commanded on. This ensures that the
bootstrap capacitors are charged.
RESET (RST)
When the reset pin is low the integrated circuit (IC) is in a
low power state. In this mode all outputs are disabled, internal
bias circuits are turned off, and a small pull-down current is
applied to the output gate drives. The internal logic will be
reset within 77 ns of RESET going low. When RST is low, the
IC will consume minimal current.
CHARGE PUMP OUT (PUMP)
This pin is the switching node of the charge pump circuit.
The output of the internal charge pump support circuit. When
the charge pump is used, it is connected to the external
pumping capacitor. This pin may be left floating if the charge
pump is not required.
CHARGE PUMP INPUT (VPUMP)
This pin is the input supply for the charge pump circuit.
When the charge pump is required, this pin should be
connected to a polarity protected supply. This input should
never be connected to a supply greater than 40 V.
If the charge pump is not required this pin may be left
floating.
VSUP INPUT (VSUP)
The supply voltage pin should be connected to the
common connection of the High Side FETs. It is the reference
bias for the Phase Comparators and Desaturation
Comparator. It is also used to provide power to the internal
steady state trickle charge pump and to energize the hold off
circuit.
PHASE B (PHASEB)
This pin is the totem pole output of the Phase B
comparator. This output is low when the voltage on Phase B
High Side source (source of the High Side load FET) is less
than 50 percent of V_SUP.
PHASE C (PHASEC)
This pin is the totem pole output of the Phase C
comparator. This output is low when the voltage on Phase C
High Side source (source of the High Side load FET) is less
than 50 percent of V_SUP.
PHASE A HIGH SIDE INPUT (PA_HS)
This input logic signal pin enables the High Side Driver for
Phase A. The signal is active low, and is pulled up by an
internal current source.
PHASE A LOW SIDE INPUT (PA_LS)
This input logic signal pin enables the Low Side Driver for
Phase A. The signal is active high, and is pulled down by an
internal current sink.
VDD VOLTAGE REGULATOR (VDD)
VDD is an internally generated 5.0 V supply. The internal
regulator provides continuous power to the IC and is a supply
reference for the SPI port. A 0.47 µF (min) decoupling
capacitor must be connected to this pin.
This regulator is intended for internal IC use and can
supply only a small (1.0 mA) external load current.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33937
23