AN2451 datasheet(46/55 Pages) STMICROELECTRONICS

46 / 55 page

Application ideas

AN2451

46/55

Doc ID 12791 Rev 3

topologies mainly include cost optimization, eliminating the need for isolation components,

and circuit simplicity.

Figure 46.

Example schematic for non-isolated solution

7.5

DC powerline applications

The ST7540 reference design can be adapted to communicate over a DC power line. In this

case, the schematic of Figure 46 has to be referred to as line coupling, with two

modifications: L7 can be removed and the C23 capacitor can be substituted with a lower

voltage ceramic component.

A DC-DC converter will substitute the ac-dc SMPS. For example, the L5970 DC-DC step-

down switching regulator can be used in case of 24 V bus to obtain the 12 V supply for the

ST7540 device.

7.6

110 and 132.5 kHz coupling circuit

In this paragraph application circuits for CENELEC band B and C are provided. The 110 and

132.5 kHz channels of the ST7540 transceiver are suitable for home automation

applications and in general for applications not subject to the European AMR regulations.

Figure 47 and Figure 48 show the schematics for the line coupling interface tuned

respectively to the 110 and 132.5 kHz channels.

D1 0

BA T54S /SOT

PA_ OU T

R17

47 0

VC C

VD C

220 uH

Rx _I N

R2 1

2k7

C26

22 n F

47 uH

C23

10 0nF

VC C

C2 2

10uF

1 m H

BAT54S/ SOT

S M6T12 C A

C27

10 nF

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