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
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.
and
show the schematics for the line coupling interface tuned
respectively to the 110 and 132.5 kHz channels.
3
1
2
D 1 0
BA T54S /SOT
PA_ OU T
R 17
47 0
VC C
VD C
L 6
220 u H
R x _I N
R 2 1
2 k7
C 26
22 n F
L 5
4 7 uH
C 23
10 0nF
P
N
VC C
C 2 2
1 0uF
L7
1 m H
3
1
2
D 8
BAT54S/ SOT
D 9
S M6T12 C A
C 27
10 nF