MAX3160E MAXIM [Maxim Integrated Products], MAX3160E Datasheet - Page 18

• Manufacturer Part Number: MAX3160E
• Description: +5kV ESD-Protected, +3.0V to +5.5V, 10nA, RS-232/RS-485/RS-422 Multiprotocol Transceivers
• Manufacturer: MAXIM [Maxim Integrated Products]

±15kV ESD-Protected, +3.0V to +5.5V, 10nA,
RS-232/RS-485/RS-422 Multiprotocol Transceivers
Figure 12
shutdown mode. As they become active, the two trans-
mitter outputs are shown going to opposite RS-232 lev-
els (one transmitter input is high, the other is low). Each
transmitter is loaded with 3kΩ in parallel with 1000pF.
The transmitter outputs display no ringing or undesir-
able transients as they come out of shutdown. Note that
the transmitters are enabled only when V- exceeds
approximately -3V.
The MAX3160E/MAX3161E/MAX3162E maintain the
RS-232 ±5V required minimum transmitter output voltage
even at high data rates.
loopback test circuit. Figure 15 shows a loopback test
result at 250kbps, and
1Mbps.
ed transmitter driven at 250kbps (FAST = GND) into an
RS-232 load in parallel with 1000pF. Figure 17 shows a
single transmitter driven at 1Mbps (FAST asserted),
loaded with an RS-232 receiver in parallel with 1000pF.
These transceivers maintain the RS-232 ±5V minimum
transmitter output voltage at data rates up to 1Mbps.
The standard RS-485 receiver input impedance is 12kΩ
(one-unit load), and the standard driver can drive up to
32-unit loads. The MAX3160E has a 1/4-unit load
receiver input impedance (48kΩ), allowing up to 128
transceivers to be connected in parallel on one com-
munication line. The MAX3161E/MAX3162E have a 1/8-
unit load receiver input impedance (96kΩ), allowing up
to 256 transceivers to be connected in parallel on one
communication line. Any combination of these devices
and/or other RS-485 transceivers with a total of 32-unit
loads or fewer can be connected to the line.
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus con-
tention. 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 becomes
excessive, typically over +150°C.
EIA/TIA-485 standards require a common input voltage
range of -7V to +12V to prevent damage to the device.
18
______________________________________________________________________________________
Figure 15
shows two transmitter outputs when exiting
Protection Against Wiring Faults
demonstrates a single slew-rate limit-
256 Transceivers on the Bus
RS-232 Transmitter Outputs
Figure 16
Driver Output Protection
when Exiting Shutdown
Figure 14
shows the same test at
High Data Rates
shows a transmitter
RS-485/RS-422
The MAX3160E/MAX3161E/MAX3162E inputs are pro-
tected to RS-232 levels of ±25V for the receiver inputs
and ±13V for the transmitter/driver outputs. This pro-
vides additional protection for the RS-485 transceivers
against ground differential or faults due to miswiring.
The MAX3160E/MAX3161E/MAX3162E can be config-
ured for slew-rate limiting by pulling FAST low. This mini-
mizes EMI and reduces reflections caused by improperly
terminated cables. Operation in slew-rate limited mode
reduces the amplitudes of high-frequency harmonics.
The RS-485/RS-422 standard covers line lengths up to
4000ft. For line lengths greater than 4000ft, use the
repeater application shown in
Figure 18
RS-232/RS-485 protocol translator. The direction of
translation is controlled through the RTS signal (R1IN).
The single-ended RS-232 receiver input signal is trans-
lated to a differential RS-485 transmitter output.
Similarly, a differential RS-485 receiver input signal is
translated to a single-ended RS-232 transmitter output.
RS-232 data received on R
485 signal on Z and Y. RS-485 signals received on A
and B are transmitted as an RS-232 signal on T1
Figure 14. Loopback Test Circuit
V
V
C1
C2
CC
CC
RS-485/RS-422 Line Length vs. Data
RS-232/RS-485 Protocol Translator
C
shows the MAX3162E configured as an
BYPASS
C1+
C1-
C2+
C2-
T_ IN
R_ OUT
SHDN
MAX3160E
MAX3161E
MAX3162E
RS-485/RS-422 Reduced
GND
V
CC
2IN
EMI and Reflections
Figure 17.
is transmitted as an RS-
T_ OUT
5k
R_ IN
V+
V-
C3
C4
Length
1000pF
OUT
.