MAX14780EEPA+ Maxim Integrated, MAX14780EEPA+ Datasheet - Page 12

• Manufacturer Part Number: MAX14780EEPA+
• Description: RS-422/RS-485 Interface IC PROFIBUS RS-485 Transceiver
• Manufacturer: Maxim Integrated

Specifications of MAX14780EEPA+

• Rohs: yes
• Data Rate: 500 Kbps
• Operating Supply Voltage: 5 V
• Supply Current: 1.8 mA
• Operating Temperature Range: - 40 C to + 85 C
• Number Of Drivers: 1
• Number Of Receivers: 1
• Product: RS-422/RS-485 Combination

Figure 10c. IEC 61000-4-2 ESD Test Model
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
The standard RS-485 receiver input impedance is 12kΩ
(1-unit load), and the standard driver can drive up
to 32-unit loads. The MAX14780E has a 1/8-unit load
receiver input impedance (96kΩ), allowing up to 256
transceivers to be connected in parallel on one commu-
nication line. Any combination of the MAX14780E, as well
as other RS-485 transceivers with a total of 32-unit loads
or fewer, can be connected to the line.
The MAX14780E features reduced slew-rate drivers that
minimize EMI and reduce reflections caused by improp-
erly terminated cables, allowing error-free data transmis-
sion up to 500kbps.
Low-power shutdown mode is initiated by bringing both
RE high and DE low. In shutdown, the devices typically
draw only 2.8μA of supply current.
RE and DE can be driven simultaneously; the devices
are guaranteed not to enter shutdown if RE is high and
DE is low for less than 50ns. If the inputs are in this state
for at least 700ns, the devices are guaranteed to enter
shutdown.
12
VOLTAGE
SOURCE
_____________________________________________________________________________________
HIGH-
DC
CHARGE-CURRENT-
LIMIT RESISTOR
50MΩ TO 100MΩ
Applications Information
R
C
150pF
Reduced EMI and Reflections
C
s
Low-Power Shutdown Mode
RESISTANCE
STORAGE
CAPACITOR
DISCHARGE
330Ω
R
D
DEVICE
UNDER
TEST
Enable times t
Characteristics section) assume the devices were not in
a low-power shutdown state. Enable times t
t
It takes drivers and receivers longer to become enabled
from low-power shutdown mode (t
than from driver/receiver-disable mode (t
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus conten-
tion. The first, a foldback current limit on the output
stage, provides immediate protection against short cir-
cuits over the whole common-mode voltage range (see
the Typical Operating Characteristics). The second, a
thermal-shutdown circuit, forces the driver outputs into
a high-impedance state if the die temperature exceeds
+175°C (typ).
The RS-485/RS-422 standard covers line lengths up to
4000ft. For line lengths greater than 4000ft, it may be
necessary to implement a line repeater.
Figure 10d. IEC 61000-4-2 ESD Generator Current Waveform
ZL(SHDN)
t
r
= 0.7ns TO 1ns
assume the devices were in shutdown state.
100%
90%
10%
I
ZH
30ns
and t
Driver Output Protection
60ns
ZL
(see the Switching
ZH(SHDN)
ZH
Line Length
ZH(SHDN)
, t
, t
ZL
ZL(SHDN)
).
t
and
)