MC33981BHFK Freescale Semiconductor, MC33981BHFK Datasheet - Page 26

• Manufacturer Part Number: MC33981BHFK
• Description: HF 4.0MOHM RDSON SWITCH
• Manufacturer: Freescale Semiconductor

APPLICATION
targeted automotive applications for the 33981. Conventional
solutions are designed with discrete components that are not
optimized in terms of component board size, protection, and
diagnostics. The 33981 is the right candidate to develop
lighter and more compact units.
consumption by reducing supply voltage, hence the mean
voltage applied to the motor. The commonly used control
technique is pulse wide modulation (PWM) where the
average voltage is proportional to the duty cycle. Most
applications require a PWM frequency of at least 20 kHz to
avoid audible noise.
when switching the 33981 at 20 kHz with a duty cycle of 80%.
The output voltage (OUT) and current in the motor (I
waveforms are represented.
26
33981
TYPICAL APPLICATIONS
EMC AND EMI RECOMMENDATIONS
Engine cooling, air conditioning, and fuel pump are the
DC motor speed adjustment allows optimization of energy
Figure 22. Current and Voltage waveforms
Figure 21. Typical Application Diagram
Figure 22
MC33981 ON
Imotor (10A/div)
illustrates typical waveforms
MC33981 OFF
OUT
MOTOR
)
HOW TO MEASURE ELECTROMAGNETIC
EMISSION ACCORDING TO THE CISPR25
level) is the CISPR25, edited by the International
Electrotechnical Commission. This standard describes the
measurement method to measure both conducted and
radiated emission.
CONDUCTED EMISSION MEASUREMENT
device on the battery cable. The test bench is described by
CISPR25 (see
called artificial network (AN), in a given frequency range
(150 kHz to 108 MHz), provides a specified load impedance
for the measurement of disturbance voltages and isolates the
equipment under test (EUT) from the supply in that frequency
range.
conditions just as it must in the vehicle so maximum emission
state occurs. These operating conditions must be clearly
defined in the test plan to ensure that both supplier and
customer are performing identical tests.
pin of the 33981 was connected to an inductive load (0.47 
+ 1.0 H) switching at 20 kHz with a duty cycle of 80%. The
output current was 17 A continuous.
short as possible. The power supply is 13.5 V.
RADIATED EMISSION MEASUREMENT
measuring the electromagnetic radiation produced by the
equipment under test. CISPR 25 gives the schematic test
bench described in
Electrical to Optical
12V Power Supply
One EMC standard in the automotive world (at system
Conducted emission is the emission produced by the
The Line Impedance Stabilization Network (LISN), also
The EUT must operate under typical loading and other
For the testing described in this application note, the out
The ground return of the EUT to the chassis must be as
The radiated emission measurement consists of
Power Supply
BF Generator
Converter
Figure 23. Test Bench for Conducted Emission
+
-
Figure
Coaxial Cable
Ground Plane
Contact to
Figure
23).
Load
Analog Integrated Circuit Device Data
LISN
Spectrum Analyzer
.
200
High Side Driver Signal
+
0
Freescale Semiconductor
200
Non-Conductive
mm
Material
Out
Ground Plane in Copper
EUT
Ground