The MAX3160/MAX3161/MAX3162 are programmable
RS-232/RS-485/422 multiprotocol transceivers. The
MAX3160/MAX3161 are pin programmable as a 2TX/2RX
RS-232 interface or a single RS-485/422 transceiver. The
MAX3162 is configured as a 2TX/2RX RS-232 interface
and a single RS-485/422 transceiver simultaneously.
All devices incorporate a proprietary low-dropout transmitter output stage and an on-board dual charge pump
to allow RS-232 and RS-485/422 compliant performance from a +3V to +5.5V supply. The receivers
feature true fail-safe circuitry that guarantees a logichigh receiver output when the receiver inputs are open
or shorted. These devices also feature pin-selectable
transmitter slew rates for both RS-232 and RS-485/422
modes. Slew-rate limiting minimizes EMI and reduces
reflections caused by improperly terminated cables,
allowing error-free data transmission up to 250kbps.
Disabling slew-rate limiting allows these devices to
transmit at data rates up to 10Mbps in RS-485/422
mode and up to 1Mbps in RS-232 mode. The
MAX3160/MAX3161/MAX3162 feature a 1µA shutdown
mode, and short-circuit limiting and thermal shutdown
circuitry to protect against excessive power dissipation.
The MAX3160/MAX3162 offer a flow-through pinout that
facilitates board layout. The MAX3160/MAX3161/
MAX3162 are available in tiny SSOP packages and
operate over the commercial and extended temperature ranges.
________________________Applications
Point-of-Sales EquipmentPeripherals
Industrial ControlsNetworking
RS-232 to RS-485
Interface Converters
Features
♦ Single-Supply Operation from +3V to +5.5V
♦ Pin-Programmable as 2TX/2RX RS-232 or Single
RS-485/422 (MAX3160/MAX3161)
♦ 2TX/2RX RS-232 and Single RS-485/422
(MAX3162)
♦ Pin-Programmable RS-232/RS-485 Transmitter
Slew Rates Reduce EMI
♦ 10Mbps RS-485 and 1Mbps RS-232 Data Rates
♦ Pin-Programmable Half-Duplex or Full-Duplex
RS-485/422 Operation (MAX3160/MAX3161)
♦ RS-485/422 True Fail-Safe Receivers
♦ Transmitters and Receivers Protected Against
Wiring Faults
♦ 1µA Shutdown Supply Current
♦ 1/8-Unit Load Allows up to 256 Transceivers on
Pin Configurations appear at end of data sheet.
Selector Guide appears at end of data sheet.
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
PARTTEMP RANGEPIN-PACKAGE
MAX3160CAP+0°C to +70°C20 SSOPMAX3160EAP+-40°C to +85°C20 SSOPMAX3161CAG+0°C to +70°C24 SSOPMAX3161EAG+-40°C to +85°C24 SSOPMAX3162CAI+0°C to +70°C28 SSOP
(VCC= +3V to +5.5V, C1–C4 = 0.1µF when tested at +3.3V ±10%; C1 = 0.047µF and C2, C3, C4 = 0.33µF when tested at +5V
±10%; T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Note 1: V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V.
VCCto GND..............................................................-0.3V to +6V
V+ to GND ................................................................-0.3V to +7V
V- to GND....................................................................0.3V to -7V
Figure 4. RS-485/422 Driver Enable/Disable Timing Test Load
Figure 5. RS-485/422 Driver Propagation Delays
Figure 6. RS-485/422 Driver Enable and Disable Times
Figure 7. RS-485/422 Receiver Propagation Delays
Figure 9. RS-485/422 Receiver Propagation Delays Test Circuit
Figure 8. MAX3162 RS-485/422 Receiver Enable and Disable
Times
V
CC
OUTPUT
UNDER TEST
500Ω
C
L
S1
S2
3V
DE485
Y, Z
V
Y, Z
1.5V1.5V
0
t
DZL
2.3V
OL
0
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
2.3V
t
DZH
t
DLZ
V
+0.5V
OL
V
-0.5V
OH
t
DHZ
3V
DI
V
DIFF
RO
1V
-1V
1.5V
0
Z
V
O
Y
1/2 V
V
O
0
-V
O
V
OH
V
OL
A
B
O
10%
T
DR
t
DPLH
V
90%
t
DSKEW = | tDPLH
/2VCC/2
V
CC
t
RPHL
DIFF
INPUT
= Vy - V
OUTPUT
t
DPHL
z
90%
T
DF
- t
DPHL
|
t
RPLH
1.5V
10%
1/2 V
O
3V
RE485
V
RO
RO
CC
1.5V1.5V
0
t
RZL
1.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
0
1.5V
t
RZH
t
RLZ
VOL + 0.5V
V
- 0.5V
OH
t
RHZ
B
V
ID
R
A
RO
C
L
MAX3160/MAX3161/MAX3162
Detailed Description
The MAX3160/MAX3161/MAX3162 3V/5V, multiprotocol
transceivers can be pin configured in a number of RS232 and RS-485/422 interface combinations. These circuit configurations are ideal for the design of RS-232 to
RS-485 converters, multiprotocol buses, or any application that requires both RS-232 and RS-485 transceivers.
The slew rate of these devices is on-the-fly pin programmable, allowing reduced EMI data rates, or up to
10Mbps RS-485 communications. Power consumption
can be reduced to 1µA by using the shutdown function,
but the RS-232 receivers remain active allowing other
devices to query the interface controller. A flow-through
pinout and the space-saving SSOP packages (available in the commercial and extended temperature
ranges) facilitate board layout.
Device Selection
The MAX3160/MAX3161/MAX3162 contain RS-232
transceivers and an RS-485/422 transceiver. The primary difference between the devices is the multiplexing
of the I/O pins.
The MAX3160 has common transmitter outputs and
receiver inputs for its RS-232 and RS-485/422 transceivers, and common digital I/O pins. The MAX3160 is
optimized for multiprotocol operation on a single interface bus and comes in a 20-pin SSOP.
The MAX3161 has separate transmitter outputs and
receiver inputs for its RS-232 and RS-485/422 transceivers, and common digital I/O pins. The MAX3161 is
optimized for multiplexing a single UART across two
interface buses and comes in a 24-pin SSOP.
The MAX3162 has separate transmitter outputs and
receiver inputs for its RS-232 and RS-485/422 transceivers, and separate digital I/O pins. The MAX3162 is
optimized for protocol translation between two interface
buses and comes in a 28-pin SSOP.
See Tables 1–12,
Functional Diagrams
, and the follow-
ing descriptions for details on each device.
MAX3160
The MAX3160 is a 2TX/2RX RS-232 transceiver in RS232 mode, capable of RS-232-compliant communication. Assertion of RS-485/RS232 converts the device to
a single RS-485 transceiver by multiplexing the RS-232
I/O pins to an RS-485 driver and receiver pair. The
logic inputs now control the driver input and the driver
enable. One logic output carries the RS-485 receiver
output, and the other is three-stated. The receiver input
impedance is dependent on the device mode and is
1/4-unit load for RS-485 operation and 5kΩ for RS-232
operation.
MAX3161
The MAX3161 is a 2TX/2RX RS-232 transceiver in RS232 mode or a single RS-485/422 transceiver in RS-485
mode. When in RS-485 mode, the unused RS-232
transmitter and receiver output pins are disabled. When
in RS-232 mode, the RS-485 transmitter outputs are
disabled and the RS-232 receiver inputs are 5kΩ to
GND. The RS-485 receiver inputs are always 1/8-unit
load. Logic lines are shared between the two protocols
and are used for signal inputs and as an RS-485 driver
enable.
MAX3162
The MAX3162 is a 2TX/2RX RS-232 transceiver and a
single RS-485/422 transceiver simultaneously. All drivers, receivers, and transmitters can be enabled or disabled by pin configuration. All outputs are high-Z when
not activated. RS-232 receiver inputs are 5kΩ when
enabled, and RS-485 receiver inputs are 1/8-unit load.
FAST Mode operation
The FAST control pin is used to select the slew-rate limiting of the RS-232 transmitters and the RS-485/422 drivers. With FAST unasserted, the RS-232 transmitters
and the RS-485/422 driver are slew-rate limited to
reduce EMI. RS-232 data rates up to 1Mbps and RS485/422 data rates up to 10Mbps are possible when
FAST is asserted. FAST can be changed during operation without interrupting data communications.
Half-Duplex RS-485/422 Operation
Asserting HDPLX places the MAX3160/MAX3161 in
half-duplex mode. The RS-485 receiver inputs are internally connected to the driver outputs. The RS-485 driver outputs can be disabled by pulling DE485 low.
HDPLX has no affect on RS-232 operation.
Low-Power Shutdown
The MAX3160/MAX3161/MAX3162 have an active-low
shutdown control input, SHDN. When driven low, the
charge pump and transmitters are shut down and supply current is reduced to 1µA. The RS-232 receiver outputs remain active if in RS-232 mode. The chargepump capacitors must be recharged when coming out
of shutdown before resuming operation in either RS-232
or RS-485/422 mode (Figure 10).
Dual Charge-Pump Voltage Converter
The MAX3160/MAX3161/MAX3162s’ internal power
supply consists of a regulated dual charge pump that
provides output voltages of +5.5V (doubling charge
pump) and -5.5V (inverting charge pump) for input voltages (VCC) over the 3.0V to 5.5V range. The charge
pumps operate in a discontinuous mode: if the magnitude of either output voltage is less than 5.5V, the
charge pumps are enabled; if the magnitude of both
output voltages exceeds 5.5V, the charge pumps are
disabled. Each charge pump requires a flying capacitor (C1, C2) and a reservoir capacitor (C3, C4) to generate the V+ and V- supplies (see
Functional
Diagrams).
RS-485/422 Transceivers
The MAX3160/MAX3161/MAX3162 RS-485/422 transceivers feature fail-safe circuitry that guarantees a
logic-high receiver output when the receiver inputs are
open or shorted, or when they are connected to a terminated transmission line with all drivers disabled (see
Fail-Safe
). The MAX3160/MAX3161/MAX3162 also feature pin-selectable reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly
terminated cables, allowing error-free data transmission
up to 250kbps (see
RS-485/422 Reduced EMI and
Reflection
s). The transmitters may operate at speeds
up to 10Mbps with the slew-rate limiting disabled.
Drivers are short-circuit current limited and thermally
limited to protect them against excessive power dissipation. Half-duplex communication is enabled by driving HDPLX high.
Fail-Safe
The MAX3160/MAX3161/MAX3162 guarantee a logichigh RS-485 receiver output when the receiver inputs
are shorted or open, or when they are connected to a
terminated transmission line with all drivers disabled.
This is done by having the receiver threshold between
-50mV and -200mV. If the differential receiver input voltage (A-B) is greater than or equal to -50mV, RO is logic
high. If A-B is less than or equal to -200mV, RO is logic
low. In the case of a terminated bus with all transmitters
disabled, the receiver’s differential input voltage is
pulled to GND by the termination. This results in a logic
high with a 50mV minimum noise margin. Unlike other
fail-safe devices, the -50mV to -200mV threshold complies with the ±200mV EIA/TIA-485 standard.
RS-232 Transceivers
The MAX3160/MAX3161/MAX3162 RS-232 transmitters
are inverting-level translators that convert CMOS-logic
levels to ±5.0V EIA/TIA-232-compliant levels. The transmitters are guaranteed at a 250kbps data rate in slewrate limited mode (FAST = GND) with worst-case loads
of 3kΩ in parallel with 1000pF. Data rates up to
1Mbps can be achieved by asserting FAST.
When powered down or in shutdown, the MAX3160/
MAX3161/MAX3162 outputs are high impedance and
can be driven to ±12V. The transmitter inputs do not
have pullup resistors. Connect unused inputs to ground
or VCC.
The receivers convert RS-232 signals to CMOS-logic output levels. All receivers have inverting outputs that
remain active in shutdown. The MAX3160/MAX3161/
MAX3162 permit their receiver inputs to be driven to Dia
±25V. Floating receiver input signals are pulled to
ground through internal 5kΩ resistors, forcing the outputs to a logic high. The MAX3162 has transmitter and
receiver enable pins that allow its outputs to be threestated.
Applications Information
Capacitor Selection
The capacitor type used for C1–C4 is not critical for
proper operation; polarized or nonpolarized capacitors
can be used. Ceramic chip capacitors with an X7R
dielectric provide the best combination of performance,
cost, and size. The charge pump requires 0.1µF
capacitors for 3.3V operation. For other supply voltages, see Table 13 for required capacitor values. Do
not use values smaller than those listed in Table 13.
Increasing the capacitor values reduces ripple on the
transmitter outputs and slightly reduces power consumption. C2, C3, and C4 can be changed without
changing C1’s value. However, do not increase C1
without also increasing the values of C2, C3, C4,
and C
BYPASS
to maintain the proper ratios to the
other capacitors.
When using the minimum required capacitor values,
make sure the capacitance value does not degrade
excessively with temperature or voltage. This is typical
of Y5V and Z5U dielectric ceramic capacitors. If in
doubt, use capacitors with a larger nominal value. The
capacitor’s equivalent series resistance (ESR), which
usually rises at low temperatures, influences the
amount of ripple on V+ and V-.
Power-Supply Decoupling
In applications that are sensitive to power-supply noise,
decouple VCCto ground with a capacitor of the same
value as reservoir capacitors C2, C3, and C4. Connect
the bypass capacitor as close to the IC as possible.
RS-232 Transmitter Outputs
when Exiting Shutdown
Figure 10 shows two transmitter outputs when exiting
shutdown mode. As they become active, the two transmitter outputs are shown going to opposite RS-232 levels (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 undesirable transients as they come out of shutdown. Note that
the transmitters are enabled only when V- exceeds
approximately -3V.
The MAX3160/MAX3161/MAX3162 maintain the RS-232
±5.0V required minimum transmitter output voltage even
at high data rates. Figure 11 shows a transmitter loopback test circuit. Figure 12 shows a loopback test result
at 250kbps, and Figure 13 shows the same test at
1000kbps. Figure 12 demonstrates a single slew-rate
limited transmitter driven at 250kbps (FAST = GND) into
an RS-232 load in parallel with 1000pF. Figure 13 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 ±5.0V minimum
transmitter output voltage at data rates up to 1Mbps.
256 Transceivers on the Bus
The standard RS-485 receiver input impedance is 12kΩ
(one-unit load), and the standard driver can drive up to
32-unit loads. The MAX3160 has a 1/4-unit load receiver input impedance (48kΩ), allowing up to 128 trans-
ceivers to be connected in parallel on one communication line. The MAX3161/MAX3162 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.
The MAX3160/MAX3161/MAX3162 RS-485 driver outputs are 1/8-unit load when disabled This impedance
may be reduced if the D1 pin is toggled at a high frequency. With no power applied (VCC= GND), the RS485 transmitter output impedances typically go to 1/2unit load on the MAX3161/MAX3162, and to one-unit
load on the MAX3160.
Driver Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus contention. The first, a foldback current limit on the output
stage, provides immediate protection against short circuits over the whole common-mode voltage range (see
Typical Operating Characteristics
). The second, a thermal shutdown circuit, forces the driver outputs into a
high-impedance state if the die temperature becomes
excessive.
Protection Against Wiring Faults
EIA/TIA-485 standards require a common input voltage
range of -7V to +12V to prevent damage to the device.
The MAX3160/MAX3161/MAX3162 inputs are protected
to RS-232 levels of ±25V for the receiver inputs and
±13.2V for the transmitter/driver outputs. This provides
additional protection for the RS-485 transceivers
against ground differential or faults due to miswiring.
RS-485/422 Reduced EMI and Reflections
The MAX3160/MAX3161/MAX3162 can be configured
for slew-rate limiting by pulling FAST low. This minimizes
EMI and reduces reflections caused by improperly terminated cables. Operation in slew-rate limited mode
reduces the amplitudes of high-frequency harmonics.
The RS-485/422 standard covers line lengths up to
4000 feet. For line lengths greater than 4000 feet, use
the repeater application shown in Figure 14.
RS-232/RS-485 Protocol Translator
Figure 15 shows the MAX3162 configured as an RS232/RS-485 protocol translator. The direction of translation is controlled through the RTS signal (R1IN). The
single-ended RS-232 receiver input signal is translated
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 R2IN is transmitted as an RS-485 signal on
Z and Y. RS-485 signals received on A and B are transmitted as an RS-232 signal on T1OUT.
Multiprotocol Bus
The
Typical Operating Circuit
shows a standard application for the MAX3160. The MAX3160’s output pins
are multiplexed between RS-232 and RS-485 protocols
by a microprocessor (µP). The µP also directs the shutdown functions, enable lines, and the duplex of the
MAX3160. Data is transmitted to the MAX3100 UART
through an SPI™ port. The UART asynchronously
Figure 10. MAX3160 RS-232 Transmitter Outputs When Exiting
Shutdown
Figure 12. RS-232 Loopback Test Result at 250kbps, FAST =
Low
Figure 13. RS-232 Loopback Test Result at 1000kbps, FAST =
High
transfers data through the MAX3160 to the pin-selected
RS-232 or RS-485 protocol; see Table 14 for commonly
used cable connections.
Multiprotocol Bus Multiplexer
The
Typical Application Circuit
shows the MAX3161 configured as a multiprotocol bus multiplexer. The MAX3161
separates the RS-232 and RS-485 lines, but shares the
logic pins between modes. This application allows the
µP to monitor a point-to-point RS-232 bus, and a multidrop RS-485 interface. The MAX3100 UART asynchronously transfers data through the MAX3161 to the
pin-selected RS-232 or RS-485 protocol.
For the latest package outline information and land patterns,
go to www.maxim-ic.com/packages
. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package
drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
TOP VIEW
C1+
V
C1-
Z(B)/T1OUT
Y(A)/T2OUT
R1OUT
SHDN
FAST
1
2
CC
3
4
5
6
7
8
9
10
+
MAX3160
20-PIN SSOP
20
V+
19
C2+
18
C2-
17
V-GND
16
DI/T1IN
15
DE485/T2IN
14
B/R1IN
A/R2INRO/R2OUT
13
12
HDPLX
11
RS-485/RS-232
T1OUT
R1OUT
RO/R2OUT
SHDN
C1+
V
C1-
Z(B)
Y(A)
+
1
2
CC
3
4
MAX3161
5
6
7
8
9
10
11
12
24-PIN SSOP
FLOW-
PARTDUAL-MODE
THROUGH
PIN-OUT
MAX3160NoYes1/4MAX3161NoNo1/8MAX3162YesYes1/8
RS-485
INPUT UNIT
LOADS
24
23
22
21
20
19
18
17
16
15
14
13
V+
C2+
C2-
V-GND
DI/T1IN
DE485/T2IN
R1IN
R2INT2OUT
B
A
HDPLX
RS-485/RS-232FAST
+
C1+
V
C1-
GND
T1OUT
T2OUT
R1OUT
R2OUT
RE485
SHDN
FAST
1
2
CC
3
4
5
Z
Y
RO
MAX3162
6
7
8
9
10
11
12
13
14
V+
28
C2+
27
C2-
26
V-
25
T1IN
24
DI
23
DE485
22
T2IN
21
R1IN
20
R2IN
19
B
18
A
17
TE232
16
RE232
15
28-PIN SSOP
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________