33981 datasheet(23/37 Pages) FREESCALE

23 / 37 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

33981

TYPICAL APPLICATIONS

EMC AND EMI RECOMMENDATIONS

Figure 21 illustrates the typical application diagram.

Figure 21. Typical Application Diagram

APPLICATION

Engine cooling, air conditioning, and fuel pump are the

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.

DC motor speed adjustment allows optimization of energy

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. Figure 22 illustrates typical waveforms

when switching the 33981 at 20 kHz with a duty cycle of 80%.

The output voltage (OUT) and current in the motor (IMOTOR)

waveforms are represented.

Figure 22. Current and Voltage waveforms

HOW TO MEASURE ELECTROMAGNETIC

EMISSION ACCORDING TO THE CISPR25

One EMC standard in the automotive world (at system

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

Conducted emission is the emission produced by the

device on the battery cable. The test bench is described by

CISPR25 (see Figure 23, Test Bench for Conducted

Emission, on page 23).

The Line Impedance Stabilization Network (LISN), also

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.

Figure 23. Test Bench for Conducted Emission

The EUT must operate under typical loading and other

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.

For the testing described in this application note, the out

pin of the 33981 was connected to an inductive load (0.47

+ 1.0

μH) switching at 20 kHz with a duty cycle of 80%. The

output current was 17 A continuous.

The ground return of the EUT to the chassis must be as

short as possible. The power supply is 13.5 V.

RADIATED EMISSION MEASUREMENT

The radiated emission measurement consists of

measuring the electromagnetic radiation produced by the

equipment under test. CISPR 25 gives the schematic test

bench described in Figure 24, Test Bench for Radiated

Emission, on page 24.

To measure radiated emission over all frequency ranges,

several antenna types must be used:

•0.15 MHz to 30 MHz: 1.0 m vertical monopole in

vertical polarization.

•30 MHz to 200 MHz: a biconical antenna used in

vertical and horizontal polarization.

•200 MHz to 1,000 MHz: a log-periodic antenna used in

vertical and horizontal polarization.

Imotor (10A/di

OU T

M C 33981 ON

MC 33981 OFF

Load

BF Generator

LISN

Spectrum Analyzer

EU T

Out

Ground

Contactto

Ground Plan

Ground Pl

ane in Copper

200

Coaxial Cable

Electricalto Optic

Converter

High Si

de Dr

iver Si

gnal

12V Pow erSupply

Power Supply

Non-Conductive

Material

33981 датащи(PDF) 23 Page - Freescale Semiconductor, Inc

33981 датащи(HTML) 23 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

датащи скачать

ссылки URL