Datasheet

MAX253
Transformer Driver for
Isolated RS-485 Interface
Maxim Integrated | 9www.maximintegrated.com
C3
0.1μF
C2
22μF
ISO 5V
ISOLATION
BARRIER
5V
V
IN
1
8
5
C1
0.1μF
1N5817
MAX253
D1
D2
GND1 GND2
V
CC
6
27
N.C.
SD
4
ON / OFF
10 x PC417
*74HC04 OR EQUIVALENT
** SEE TABLE 2
MAX205
ENSD
C4
22μF
82
1N5817
MAX667
564
SHDNSET GND
IN OUT
390Ω
83
T1
IN
T1
OUT
390Ω
*74HC04
T1
IN
1
2
4
5
6
1
24
5
6
390Ω
74HC04
T2
IN
390Ω
74HC04
T3
IN
390Ω
74HC04
T4
IN
390Ω
74HC04
T5
IN
74HC04
R1
OUT
74HC04
74HC04
74HC04
74HC04
R2
OUT
R3
OUT
R4
OUT
R5
OUT
5 X 3.3kΩ
390Ω
390Ω
390Ω
390Ω
74
T2
IN
T2
OUT
15 2
T3
IN
T3
OUT
16 1
T4
IN
T4
OUT
22 19
T5
IN
T5
OUT
910
R1
OUT
R1
IN
65
R2
OUT
R2
IN
23 24
R3
OUT
R3
IN
17 18
R4
OUT
R4
IN
14 13
R5
OUT
R5
IN
V
CC
2021
GND
5 x 3.3kΩ
1N5711
6
5
4
1
2
390Ω
3.3kΩ
V
CC
ISO
R
OUT
R
OUT
1N5711
1
2
6
5
4
390Ω
3.3kΩ
V
CC
ISO
T
IN
T
IN
*74HC04
4N25 LOWER SPEED, LOWER COST ALTERNATE OPTOCOUPLER CONFIGURATIONS (FOR DATA RATES BELOW 9.6kbps)
FS
3
74HCO4
4N25
ISO
GND
4N25
ISO
GND
1CT:1.3CT**
Figure 5. Typical RS-232 Application Circuit