Transformer Driver for
Isolated RS-485 Interface
MAX253
V
IN
5V
C1
0.1µF
4
ON / OFF
6
V
CC
SD
D1
1
ICT:1.3CT*1N5817
C3
0.1µF
TP1
C2
22µF
5V @ 200mA
ISO OUTPUT
MAX253
3
FREQUENCY
SWITCH
FS
GND1
2
GND2
7
OUTPUT
D2
8
1N5817
OPTIONAL 21kHz LOWPASS OUTPUT FILTER
L2
25µH
FILTER
OUTPUT
C7
2.2µF
*SEE TABLE 2
Figure 6. 5V to Isolated 5V Application Circuit
V
IN
3.3V
C1
0.1µF
4
ON / OFF
1
ICT:2.1CT* 1N5817
C3
0.1µF
5V @ 100mA
TP1 ISO OUTPUT
C2
22µF
SD
D1
MAX253
3
FREQUENCY
SWITCH
FS
GND1
2
GND2
7
D2
V
CC
6
1N5817
1N5817
OUTPUT
8
1N5817
OPTIONAL 21kHz LOWPASS OUTPUT FILTER
L2
25µH
FILTER
OUTPUT
C7
2.2µF
*SEE TABLE 2
C4
0.1µF
Figure 7. 3.3V to Isolated 5V Application Circuit
10
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
