MAX3160EEAP/GH9-T Maxim Integrated, MAX3160EEAP/GH9-T Datasheet - Page 18

• Manufacturer Part Number: MAX3160EEAP/GH9-T
• Description: RS-422/RS-485 Interface IC
• Manufacturer: Maxim Integrated

Specifications of MAX3160EEAP/GH9-T

• Data Rate: 250 Kbps
• Operating Supply Voltage: 3 V to 5.5 V
• Supply Current: 2.5 mA
• Operating Temperature Range: 0 C to + 70 C
• Propagation Delay Time Ns: 0.15 us

±15kV ESD-Protected, +3.0V to +5.5V, 10nA,
RS-232/RS-485/RS-422 Multiprotocol Transceivers
Figure 12 shows two transmitter outputs when exiting
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. Figure 14 shows a transmitter
loopback test circuit. Figure 15 shows a loopback test
result at 250kbps, and Figure 16 shows the same test at
1Mbps. Figure 15 demonstrates a single slew-rate limit-
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
______________________________________________________________________________________
Protection Against Wiring Faults
256 Transceivers on the Bus
RS-232 Transmitter Outputs
Driver Output Protection
when Exiting Shutdown
High Data Rates
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 17.
Figure 18 shows the MAX3162E configured as an
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
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
is transmitted as an RS-
T_ OUT
5k
R_ IN
V+
V-
C3
C4
Length
1000pF
OUT
.