MAX13444EASA/V+ Maxim Integrated, MAX13444EASA/V+ Datasheet - Page 13

• Manufacturer Part Number: MAX13444EASA/V+
• Description: RS-485 Interface IC +/-80V Fault Protected RS-485 Half-Duplex Transceiver with Foldback Current Limit
• Manufacturer: Maxim Integrated

Specifications of MAX13444EASA/V+

• Data Rate: 10 Mbps
• Operating Supply Voltage: 5 V
• Supply Current: 30 mA
• Operating Temperature Range: - 40 C to + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SO-8
• Function: Transceiver
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Number Of Drivers: 1
• Number Of Receivers: 1
• Propagation Delay Time Ns: 50 ns
• Shutdown: Yes

The MAX13442E/MAX13443E/MAX13444E fault-protect-
ed transceivers for RS-485/RS-422 and J1708 communi-
cation contain one driver and one receiver. These
devices feature fail-safe circuitry, which guarantees a
logic-high receiver output when the receiver inputs are
open or shorted, or when they are connected to a termi-
nated transmission line with all drivers disabled (see the
True Fail-Safe section). All devices have a hot-swap input
structure that prevents disturbances on the differential
signal lines when a circuit board is plugged into a hot
backplane (see the Hot-Swap Capability section). The
MAX13442E/MAX13444E feature a reduced slew-rate dri-
ver that minimizes EMI and reduces reflections caused
by improperly terminated cables, allowing error-free data
transmission up to 250kbps (see the Reduced EMI and
Reflections section). The MAX13443E driver is not slew-
rate limited, allowing transmit speeds up to 10Mbps.
The driver accepts a single-ended, logic-level input
(DI) and transfers it to a differential, RS-485/RS-422
level output (A and B). Deasserting the driver enable
places the driver outputs (A and B) into a high-imped-
ance state.
The receiver accepts a differential, RS-485/RS-422
level input (A and B), and transfers it to a single-ended,
logic-level output (RO). Deasserting the receiver enable
places the receiver inputs (A and B) into a high-imped-
ance state (see Tables 1–4).
The MAX13442E/MAX13443E/MAX13444E offer a low-
power shutdown mode. Force DE low and RE high to
shut down the MAX13442E/MAX13443E. Force DE and
RE high to shut down the MAX13444E. A time delay of
50ns prevents the device from accidentally entering
shutdown due to logic skews when switching between
transmit and receive modes. Holding DE low and RE
high for at least 800ns guarantees that the
MAX13442E/MAX13443E enter shutdown. In shutdown,
the devices consume a maximum 20µA supply current.
The driver outputs/receiver inputs of RS-485 devices in
industrial network applications often experience voltage
faults resulting from shorts to the power grid that exceed
the -7V to +12V range specified in the EIA/TIA-485 stan-
dard. In these applications, ordinary RS-485 devices
(typical absolute maximum -8V to +12.5V) require costly
external protection devices. To reduce system complexi-
ty and eliminate this need for external protection, the dri-
±15kV ESD-Protected, ±80V Fault-Protected,
______________________________________________________________________________________
Detailed Description
Low-Power Shutdown
± 80V Fault Protection
Fail-Safe RS-485/J1708 Transceivers
Receiver
Driver
ver outputs/receiver inputs of the MAX13442E/
MAX13444E withstand voltage faults up to ±80V (±60V
for the MAX13443E) with respect to ground without dam-
age. Protection is guaranteed regardless whether the
device is active, shut down, or without power.
The MAX13442E/MAX13443E/MAX13444E use a
-50mV to -200mV differential input threshold to ensure
true fail-safe receiver inputs. This threshold guarantees
the receiver outputs a logic-high for shorted, open, or
idle data lines. The -50mV to -200mV threshold com-
plies with the ±200mV threshold EIA/TIA-485 standard.
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against ESD
encountered during handling and assembly. The
MAX13442E/MAX13443E/MAX13444E receiver inputs/
driver outputs (A, B) have extra protection against stat-
ic electricity found in normal operation. Maxim’s engi-
neers have developed state-of-the-art structures to
protect these pins against ±15kV ESD without damage.
After an ESD event, the MAX13442E/MAX13443E/
MAX13444E continue working without latchup.
ESD protection can be tested in several ways. The
receiver inputs are characterized for protection to
±15kV using the Human Body Model.
ESD performance depends on a number of conditions.
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
Figure 9a shows the Human Body Model, and Figure
9b 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 device through a
1.5kΩ resistor.
Two mechanisms prevent excessive output current and
power dissipation caused by faults or bus contention.
The first, a foldback current limit on the driver output
stage, provides immediate protection against short cir-
cuits over the whole common-mode voltage range. The
second, a thermal shutdown circuit, forces the driver out-
puts into a high-impedance state if the die temperature
exceeds +160°C. Normal operation resumes when the
die temperature cools to +140°C, resulting in a pulsed
output during continuous short-circuit conditions.
Driver Output Protection
±15kV ESD Protection
ESD Test Conditions
Human Body Model
True Fail-Safe
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