MAX13413EESA Datasheet, PDF (16/24 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
Detailed Description
The MAX13410E–MAX13415E are half-duplex RS-485/
RS-422-compatible transceivers optimized for isolated
applications. These devices feature an internal LDO reg-
ulator, one driver, and one receiver. The internal LDO
allows the part to operate from an unregulated +6V to
+28V power supply. The AutoDirection feature reduces
the number of optical isolators needed in isolated appli-
cations. Other features include ±15kV ESD protection
(MAX13412E/MAX13413E only), ±14kV (MAX13410E/
MAX13411E only) fail-safe circuitry, slew-rate limiting, and
full-speed operation.
The MAX13410E–MAX13415E internal LDO generates a
5V ±10% power supply that is used to power its internal
circuitry. The MAX13412E–MAX13415E bring the 5V to an
output V_REG that allows the user to power additional exter-
nal circuitry with up to 20mA to further reduce external
components. The MAX13410E/MAX13411E do not have a
5V output and come in industry-compatible pinouts. This
allows easy replacement in existing designs.
The MAX13412E/MAX13413E feature Maxim’s propri-
etary AutoDirection control. This architecture eliminates
the need for the DE and RE control signals. In isolated
applications, this reduces the cost and size of the sys-
tem by reducing the number of optical isolators required.
The MAX13410E/MAX13412E/MAX13414E feature
reduced slew-rate drivers that minimize EMI and reduce
reflections caused by improperly terminated cables,
allowing error-free transmission up to 500kbps. The
MAX13411E/MAX13413E/MAX13415E are not slew-rate
limited, allowing transmit speeds up to 16Mbps.
The MAX13410E–MAX13415E feature a 1/8-unit load
receiver input impedance, allowing up to 256 trans-
ceivers on the bus. All driver outputs are protected to
±15kV ESD using the Human Body Model. These
devices also include fail-safe circuitry, MAX13410E/
MAX13411E/MAX13414E/MAX13415E, guaranteeing a
logic-high receiver output when the receiver inputs are
open or shorted. The receiver outputs a logic-high
when the transmitter on the terminated bus is disabled
(high impedance).
Internal Low-Dropout Regulator
The MAX13410E–MAX13415E include an internal low-
dropout regulator that allows it to operate from input volt-
ages of up to +28V. The internal LDO has a set output
voltage of 5V ±10% that is used to power the internal cir-
cuitry of the device. The MAX13412E–MAX13415E offer
the LDO output at the V_REG output. This allows additional
external circuitry to be powered without the need for
additional external regulators. The V_REG output can
source up to 20mA.
When using these devices with high input voltages and
heavily loaded networks, special care must be taken
that the power dissipation rating of the package and
the maximum die temperature of the device is not
exceeded. Die temperature of the part can be calculat-
ed using the equation:
T_DIE = [(θ_JC + θ_CA) x P_DISS] + T_AMBIENT, where
T_DIE = Temperature of the Die
θ_JC = 6.0°C/W = Junction-to-Case Thermal Resist-
ance
θ_CA = Case-to-Ambient Thermal Resistance
θ_JA = θ_JC + θ_CA = 52.0°C/W = Junction-to-Ambient
Thermal Resistance
P_DISS = (I_CC - V_CC) + [(V_CC - V_REG) x I_REG)] + [(V_CC -
V_OD) x I_DRIVER] = Power Dissipation of the Part
T_AMBIENT = Ambient Temperature
V_CC = Voltage on the V_CC Input
I_CC = Current in to V_CC
V_REG = Voltage on the V_REG Output
I_REG = Current Drawn from the V_REG Output
V_OD = Voltage at the Driver Output (|V_A - V_B|)
I_DRIVER = Current Driven Out of the Driver. Typically,
this is the current through the termination resistor.
The absolute maximum rating of the die temperature of
the MAX13410E–MAX13415E is +150°C. To protect the
part from overheating, there is an internal thermal shut-
down that shuts down the part when the die tempera-
ture reaches +150°C. To prevent damage to the part,
and to prevent the part from entering thermal shutdown,
keep the die temperature below +150°C, plus some
margin. The circuit designer can minimize the die tem-
perature by controlling the following parameters:
• V_CC
• I_REG
• θ_CA
Measuring the V_CC Current
Measured current at the V_CC pin is a function of the
quiescent current of the part, the amount of current that
the drivers must supply to the load, and in the case of
the MAX13412E–MAX13415E, the load on the V_REG
output. In most cases, the load that the drivers must
supply will be the termination resistor(s). Ideally, the ter-
mination resistance should match the characteristic
impedance of the cable and is usually not a parameter
the circuit designer can easily change. In some low-
speed, short-cable applications, proper termination
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