RC4190M datasheet(21/25 Pages) RAYTHEON

21 / 25 page

RC4190

PRODUCT SPECIFICATION

Note the approximate air gap at IMAX for the selected

core, and order the core with the gap. (If the gapping is

done by the user, remember that a washer spacer results

in an air gap of twice the washer thickness, because two

gaps will be created, one at the center post and one at the

rim, like taking two bites from a doughnut.)

If the required inductance is equal to the indicated value

on the graph, then wind the core with the number of

turns shown in table of sizes. The turns given are the

maximum number for that gauge of wire that can be

easily wound in the cores winding area.

If the required inductance is less than the value indicated

on the graph, a simple calculation must be done to ﬁnd

the adjusted number of turns. Find AL (inductance

index) for a speciﬁc air gap.

in Henrys/turn2

Then divide the required inductance value by AL to give

the actual turns squared, and take the square root to ﬁnd

the actual turns needed.

If the actual number of turns is signiﬁcantly less than the

number from the table then the wire size can be

increased to use up the left-over winding area and

reduce resistive losses.

Wind and gap the core as per calculations, and measure

the value with an inductance meter. Some adjustment of

the number of turns may be

necessary.

The saturation characteristics may be checked with the

inductor wired into the switching regulator application

circuit. To do so, build and power up the circuit. Then

(recommend Tektronix P6042 or equivalent) around the

inductor lead and monitor the current in the inductor.

Draw the maximum load current from the application

circuit so that the regulator is running at close to full

duty cycle.

Compare the waveform you see to those pictured in

Figure 28.

Check for saturation at the highest expected ambient

temperature.

After the operation in circuit has been checked,

reassemble and pot the core using a potting compound

recommended by the manufacturer.

If the core material differs greatly in magnetic character-

istics from the standard power material shown in Figure

22, then the following general equation can be used to

help in winding and gapping. This equation can be used

for any core geometry, such as an E-E core.

Where: N = number of turns

Ae = core area from data sheet (in cm2)

le = magnetic path length from data sheet (in cm)

ue = permeability of core from manufacturer's graph

g = center post air gap (in cm)

Manufacturers

Below is a list of several pot core manufacturers:

Ferroxcube Company

5083 Kings Highway

Saugerties, NY 12477

Indiana General Electronics

Keasley, NJ 08832

Siemens Company

186 Wood Avenue South

Iselin, NJ 08830

Stackpole Company

201 Stackpole Street

St. Mary, PA 15857

TDK Electronics

13-1-Chome

Nihonbaski, Chuo-ku, Tokyo

L indicated

(

)

Turns

---------------------------------

ActualTurns

L required

(

)

-------------------------------

1.26

(

) N

( ) Ae

(

) 10

(

)

( ) ue

( )

⁄

-----------------------------------------------------

Figure 28. Inductor Current Waveforms

IMAX

65-3464-08

Proper Operation

(Waveform is Fairly Linear)

Improper Operation

(Waveform is Nonlinear, Inductor

Is Saturating)

IMAX

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