Transformer Driver for
Isolated RS-485 Interface
MAX253
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 6, V
IN
= 5V ±10%, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(FS = HIGH)
plot09
OUTPUT VOLTAGE vs. LOAD CURRENT
(FS = LOW)
plot10
OUTPUT VOLTAGE vs. LOAD CURRENT
(FS = HIGH)
9
8
OUTPUT VOLTAGE (V)
7
6
5
4
3
2
1
0
CIRCUIT OF FIGURE 6
V
IN
= 5.0V
TURNS RATIO = 1:1
CIRCUIT OF FIGURE 7
V
IN
= 3.3V
TURNS RATIO = 1:2.1
CIRCUIT OF FIGURE 6
V
IN
= 5.0V
TURNS RATIO = 1:1.3
plot11
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
200
20 40 60 80 100120 140 160 180
LOAD CURRENT (mA)
V
IN
= 4.5V
V
IN
= 5.5V
10
9
8
OUTPUT VOLTAGE (V)
7
6
5
4
3
2
1
0
CIRCUIT OF FIGURE 6
V
IN
= 5.0V
TURNS RATIO = 1:1
CIRCUIT OF FIGURE 7
V
IN
= 3.3V
TURNS RATIO = 1:2.1
CIRCUIT OF FIGURE 6
V
IN
= 5.0V
TURNS RATIO = 1:1.3
10
MEASURED AT TP1
0 20 40 60 80 100 120 140 160 180 200 220
LOAD CURRENT (mA)
MEASURED AT TP1
0 20 40 60 80 100 120 140 160 180 200 220
LOAD CURRENT (mA)
SWITCHING WAVEFORMS
(TWO CYCLES)
SWITCHING WAVEFORMS
(BREAK BEFORE MAKE)
D1
D1
D2
D2
CIRCUIT OF FIGURE 1
CIRCUIT OF FIGURE 1
TIME FROM SHUTDOWN TO POWER-UP
SD
TP1 (OUTPUT VOLTAGE)
CIRCUIT OF FIGURE 6
4
_______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
