TYPICAL APPLICATIONS
INTRODUCTION
TYPICAL APPLICATIONS
INTRODUCTION
Figure 20 shows a typical application for the 33981. A brush DC motor is connected to the output. A low-side gate driver is
used for the freewheeling phase. Typical values for external capacitors and resistors are given.
.
VPWR
VPWR
VDD
VDD
330 µF
33981
100 nF
VPWR
SR
Voltage regulator
1.0 k
Ω
2.2 nF
10 k
CBOOT
Ω
100 nF
CONF
FS
OUT
DLS
I/O
10 kΩ
INLS
EN
I/O
I/O
10 k
10 k
Ω
Ω
MCU
I/O
INHS
TEMP
CSNS
OCLS
A/D
A/D
M
GLS
GND
1.0 kΩ
33 kΩ
Figure 20. 33981 Typical Application Diagram
EMC AND EMI RECOMMENDATIONS
the output and, therefore, reduce electromagnetic
perturbations.
INTRODUCTION
This section relates the EMC capability for 33981, High
Frequency High-Current High-Side Switch. This device is a
self-protected silicon switch used to replace
electromechanical relays, fuses, and discrete circuits in
power management applications.
In standard configuration, the motor current recirculation is
handled by an external freewheeling diode. To reduce global
power dissipation, the freewheeling diode can be replaced by
an external discrete MOSFET in low-side configuration. The
IC integrates a gate driver that controls and protects this
external MOSFET in the event of short circuit to battery. The
product manages the cross conduction between the internal
high side and the external low side when used in a half bridge
configuration. The two MOSFETs can be controlled
This section presents the key features of the device and its
targeted applications. The automotive standard to measure
conducted and radiated emissions is provided. Concrete
measurements on the 33981 and improvements to reduce
electromagnetic emission are described.
independently when the CONF pin is at 0 V. To eliminates
fuses, the device is self-protected from severe short-circuits
(100 A typical) with an innovative overcurrent strategy.
DEVICE FEATURES
This 33981 is a 4.0 mΩ self-protected, high-side switch
digitally controlled from a microcontroller (MCU) with
extended diagnostics, able to drive DC motors up to 60 kHz.
The 33981 has a current feedback for real-time monitoring
of the load current through an MCU analog/digital converter
to facilitate closed-loop operation for motor speed control.
A bootstrap architecture has been used to provide fast
transient gate voltage in order to reach 4.0 mΩ RDS(ON)
maximum at room temperature. In parallel, a charge pump is
implemented to offer continuous on-state capability. This
dual current supply of the high-side MOSFET allows a duty
cycle from 5% to 100%. An external capacitor connected
between pins SR and GND is used to control the slew rate at
The 33981 has an analog thermal feedback that can be
used by the MCU to monitor PC board temperature to
optimize the motor control and to protect the entire electronic
system. Therefore, an over temperature shutdown feature
protects the IC against high overload condition.
33981
Analog Integrated Circuit Device Data
Freescale Semiconductor
22
FREESCALE [ Freescale ]
