AN2844 datasheet(31/37 Pages) STMICROELECTRONICS

31 / 37 page

AN2844

Transformer specification

31/37

For enhanced magnetic coupling, a sandwich topology has been used for the windings. The

secondary winding is placed beside the split of the primary winding. The primary winding

parts have half the total number of turns and are connected in series. The order of the

windings, starting from the winding nearest the core, is: PRIMARY - A, SECONDARY,

PRIMARY - B, and then the top AUXILIARY winding for the SMPS’ self-supply.

Figure 30.

Winding position

9.2

Mechanical aspects

●

Maximum height from PCB: 40 mm

●

Occupied area on PCB: 35 mm x 25 mm

●

Coil former: 14 pins

●

Diameter of pins: 1.3 mm + 0.1 mm

●

Raster of pins: 5 mm

Figure 31 shows the mechanical arrangement of the transformer. The figure should be

viewed from a mounting angle.

Table 9.

Winding characteristics

Pins

Winding

Number of turns

Wire type

1-2

PRIMARY - A

1 x AVG34

10-12

SECONDARY

3 x AVG24

3-4

PRIMARY - B

1 x AVG34

6-7

AUXILIARY

1 x AVG32

3 mm

AUXILIARY

PRIMARY - B

SECONDARY

PRIMARY - A

Coil former

Insulation tape

AM003548

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