MAX3535E Maxim, MAX3535E Datasheet - Page 20

• Manufacturer Part Number: MAX3535E
• Description: +3V to +5V / 2500VRMS Isolated RS-485/RS-422 Transceivers with 15kV ESD Protection
• Manufacturer: Maxim

+3V to +5V, 2500V
Transceivers with ±15kV ESD Protection
Figure 12. Using the MAX3535E/MXL1535E as an RS-422 Line Repeater
Figure 13. Transformer Driver Output Stage
20
______________________________________________________________________________________
D
R
120Ω
TRANSFORMER DRIVER OUTPUT STAGE
R
R
ST1
OH
OL
TRANSFORMER
PRIMARY
120Ω
GND1
V
RO2
SLO
CC1
A
B
Y
Z
V
CC2
DRIVER
RECEIVER
ST2
R
R
OH
OL
0.1µF
REGULATOR
V
R
VOLTAGE
CC2
D
GND2
TRANSCEIVER
BAT54C
BAT54C
BARRIER
10µF
RMS
1/2
1/2
ISOLATION BARRIER
TGM-250
TRANSFORMER
TRANSCEIVER
Isolated RS-485/RS-422
BARRIER
DRIVER
The MXL1535E is a pin-for-pin compatible upgrade of
the LTC1535, making any transformer designed for that
device suitable for the MXL1535E (see Table 4). These
transformers all have a turns ratio of about 1:1.3CT.
The MAX3535E can operate with any of the transformers
listed in Table 4, in addition to smaller, thinner transform-
ers designed for the MAX845 and MAX253. The 420kHz
transformer driver operates with single primary and cen-
ter-tapped secondary transformers. When selecting a
transformer, do not exceed its ET product, the product of
the maximum primary voltage and half the highest period
of oscillation (lowest oscillating frequency). This ensures
that the transformer does not enter saturation. Calculate
the minimum ET product for the transformer primary as:
where, V
and f
Using +5.5V and 290kHz gives a required minimum ET
ST2
MXL1535E
MAX3535E
MIN
ST1
MAX
is the minimum frequency at that supply voltage.
V
RO1
RE
DE
DI
GND1
CC1
is the worst-case maximum supply voltage,
CONTROL GROUND
RS-422 GROUND
ET = V
10µF
MAX
0.1µF
RO
DI
+5V
Transformer Selection
/ (2 x f
D
MIN
R
MAX488
)
A
Y
Z
B