MAX13413EESA Datasheet, PDF (19/24 Pages) Maxim Integrated Products – RS-485 Transceiver with Integrated Low-Dropout Regulator and AutoDirection Control

RS-485 Transceiver with Integrated Low-Dropout
Regulator and AutoDirection Control
R_C
1MΩ
R_D
1500Ω
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
HIGH-
VOLTAGE
DC
SOURCE
Cs
100pF
STORAGE
CAPACITOR
Figure 8a. Human Body ESD Test Model
DEVICE
UNDER
TEST
I_P 100%
90%
Ir
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
AMPS
36.8%
10%
0
0 _tRL
TIME
t_DL
CURRENT WAVEFORM
Figure 8b. Human Body Current Waveform
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents
test setup, test methodology, and test results.
Human Body Model
Figure 8a shows the Human Body Model, and Figure
8b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter-
est, which is then discharged into the test device
through a 1.5kΩ resistor.
Applications Information
Typical Applications
The MAX13410E–MAX13415E transceivers are designed
for half-duplex, bidirectional data communications on
multipoint bus transmission lines. To minimize reflections,
terminate the line at both ends in its characteristic
impedance, and keep stub lengths off the main line as
short as possible. The slew-rate-limited MAX13410E/
MAX13412E/MAX13414E are more tolerant of imperfect
termination.
Typical Application Circuit for the
MAX13410E and MAX13411E
This application circuit shows the MAX13410E/
MAX13411E being used in an isolated application (see
Figure 9). The MAX13410E/MAX13411E use the industry-
standard pin out but do not have a V_REG output for
biasing external circuitry. The positive temperature coef-
ficient (PTC) and transient voltage suppressor (TVS)
clamp circuit on the RS-485 outputs are intended to pro-
vide overvoltage fault protection and are optional based
on the requirements of the design.
Typical Application Circuit for the
MAX13412E and MAX13413E
This application circuit shows the MAX13412E and
MAX13413E being used in an isolated application
where the AutoDirection feature is implemented to
reduce the number of optical isolators to two (see
Figure 10). The MAX13412E/MAX13413E provide a
V_REG output that can be used to power external circuit-
ry up to 20mA.
Typical Application Circuit for the
MAX13414E and MAX13415E
This application circuit shows the MAX13414E/
MAX13415E being used in an isolated application using
an unregulated power supply with three optical isolators
(see Figure 11). The MAX13414E/MAX13415E provide a
V_REG output that can be used to power external circuitry
up to 20mA.
256 Transceivers on the Bus
The RS-485 standard specifies the load each receiver
places on the bus in terms of unit loads. An RS-485-
compliant transmitter can drive 32 one-unit load
receivers when used with a 120Ω cable that is terminat-
ed on both ends over a -7V to +12V common-mode
range. The MAX13410E–MAX13415E are specified as
1/8 unit loads. This means a compliant transmitter can
drive up to 256 devices of the MAX13410E–MAX13415E.
Reducing the common mode, and/or changing the char-
acteristic impedance of the cable, changes the maxi-
mum number of receivers that can be used. Refer to the
TIA/EIA-485 specification for further details.
Proper Termination and Cabling/
Wiring Configurations
When the data rates for RS-485 are high relative to the
cable length it is driving, the system is subject to proper
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