MAX13410E Datasheet, PDF (20/24 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_t
ISO_V_CC
V_SYS
UNREGULATED ISOLATED
POWER SUPPLY
ISO_V_CC
V_SYS
MCU AND
RELATED
CIRCUITRY
V_SYS
ISO_V_CC
+
RO
1
R
RE ₂
DE
3
DI
4
D
LDO
V_CC ^ISO_VCC
8
0.1μF
B
7
A
6
GND
5
MAX13410E
MAX13411E
R_t
Figure 9. Typical Application Circuit for the MAX13410E/MAX13411E
er transmission line design. In most cases, a single,
controlled-impedance cable or trace should be used
and should be properly terminated on both ends with
the characteristic impedance of the cable/trace. RS-
485 transceivers should be connected to the cable/
traces with minimum-length wires to prevent stubs. Star
configurations and improperly terminated cables can
cause data loss. Refer to the Applications section of the
Maxim website or to TIA/EIA publication TSB89 for fur-
ther information. While proper termination is always
desirable, in some cases, such as when data rates are
very low, it may be desirable and advantageous to not
properly terminate the cables. In such cases, it is up to
the designer to ensure that the improper termination
and resultant reflections (etc.) will not corrupt the data.
Reduced EMI and Reflections
The MAX13410E/MAX13412E/MAX13414E feature
reduced slew-rate drivers that minimize EMI and reduce
reflections caused by improperly terminated cables,
allowing error-free data transmission up to 500kbps.
Low-Power Shutdown Mode
Low-power shutdown mode is initiated in the
MAX13410E/MAX13411E by driving DE low and driving
RE high. In shutdown, the devices draw 65µA (typ) of
supply current.
The devices are guaranteed not to enter shutdown if
DE is low (while RE is high) for less than 50ns. If the
inputs are in this state for at least 700ns, the devices
are guaranteed to enter shutdown.
Enable times t_ZH and t_ZL (see the Switching Character-
istics table) assume the devices were not in a low-power
shutdown state. Enable times t_ZH(SHDN) and t_ZL(SHDN)
assume the devices were in shutdown state. It takes dri-
vers and receivers longer to become enabled from low-
power shutdown mode (t_ZH(SHDN), t_ZL(SHDN)) than from
driver/receiver disable mode (t_ZH, t_ZL).
Line Length
The Telecommunications Industry Association (TIA) pub-
lished the document TSB-89: Application Guidelines for
TIA/EIA-485-A, which is a good reference for determin-
ing maximum data rate vs. line length.
Isolated RS-485 Interface
An isolated RS-485 interface electrically isolates different
nodes on the bus to protect the bus from problems due
to high common-mode voltages that exceed the RS-485
common-mode voltage range, conductive noise, and
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