MAX3160E/MAX3161E/MAX3162E
±15kV ESD-Protected, +3.0V to +5.5V, 10nA,
RS-232/RS-485/RS-422 Multiprotocol Transceivers
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Detailed Description
The MAX3160E/MAX3161E/MAX3162E +3V to +5.5V,
multiprotocol transceivers can be pin-configured in a
number of RS-232 and RS-485/RE-422 interface combi-
nations. 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 selectable, allowing reduced EMI data
rates, or up to 10Mbps RS-485 communications. Power
consumption can be reduced to 10nA by using the
shutdown function, but the RS-232 receivers remain
active allowing other devices to query the interface con-
troller. A flow-through pinout and the space-saving
SSOP packages (available in commercial and extended
temperature ranges) facilitate board layout.
Device Selection
The MAX3160E/MAX3161E/MAX3162E contain RS-232
transceivers and an RS-485/RS-422 transceiver. The
primary difference between the devices is the multi-
plexing of the I/O ports.
The MAX3160E has common transmitter outputs and
receiver inputs for its RS-232 and RS-485/RS-422 trans-
ceivers, and common digital I/O ports. The MAX3160E
is optimized for multiprotocol operation on a single
interface bus and comes in a 20-pin SSOP package.
The MAX3161E has separate transmitter outputs and
receiver inputs for its RS-232 and RS-485/RS-422 trans-
ceivers, and common digital I/O ports. The MAX3161E is
optimized for multiplexing a single UART across two inter-
face buses and is available in a 24-pin SSOP package.
The MAX3162E has separate transmitter outputs and
receiver inputs for its RS-232 and RS-485/RS-422 trans-
ceivers, and separate digital I/O ports. The MAX3162E
is optimized for protocol translation between two inter-
face buses and comes in a 28-pin SSOP package.
See Tables 1–12, the Functional Diagrams, and the fol-
lowing descriptions for details on each device.
MAX3160E
The MAX3160E is a 2T
X
/2R
X
RS-232 transceiver in
RS-232 mode, capable of RS-232-compliant communi-
cation. Assertion of RS-485/RS-232 converts the device
to a single RS-485 transceiver by multiplexing the RS-
232 I/O ports 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 out-
put, and the other is tri-stated. The receiver input imped-
ance is dependent on the device mode and is 1/4-unit
load for RS-485 operation and 5kΩ for RS-232 operation.
MAX3161E
The MAX3161E is a 2T
X
/2R
X
RS-232 transceiver in
RS-232 mode or a single RS-485/RS-422 transceiver in
RS-485 mode. When in RS-485 mode, the unused RS-
232 transmitter and receiver outputs are disabled. When
in RS-232 mode, the RS-485 transmitter outputs are dis-
abled 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.
MAX3162E
The MAX3162E is a 2Tx/2Rx RS-232 transceiver and a
single RS-485/RS-422 transceiver simultaneously. All
drivers, receivers, and transmitters can be enabled or
disabled by pin selection. All outputs are high-imped-
ance 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 input is used to select the slew-rate
limiting of the RS-232 transmitters and the RS-485/
RS-422 drivers. With FAST unasserted, the RS-232
transmitters and the RS-485/RS-422 driver are slew-rate
limited to reduce EMI. RS-232 data rates up to 1Mbps
and RS-485/RS-422 data rates up to 10Mbps are possi-
ble when FAST is asserted. FAST can be changed dur-
ing operation without interrupting data communications.
Half-Duplex RS-485/RS-422 Operation
Asserting HDPLX places the MAX3160E/MAX3161E in
half-duplex mode. The RS-485 receiver inputs are inter-
nally connected to the driver outputs. To receive
RS-485 data, disable the RS-485 outputs by driving
DE485 low. HDPLX has no affect on RS-232 operation.
Low-Power Shutdown
The MAX3160E/MAX3161E/MAX3162E have an active-
low shutdown control input, SHDN. When SHDN is dri-
ven low, the charge pump and transmitters are shut
down and supply current is reduced to 10nA. The
RS-232 receiver outputs remain active if in RS-232
mode. The charge-pump capacitors must be
recharged when coming out of shutdown before resum-
ing operation in either RS-232 or RS-485/RS-422 mode
(Figure 12).
Dual Charge-Pump Voltage Converter
The MAX3160E/MAX3161E/MAX3162E’s 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 (V
CC
) over the +3.0V to +5.5V range. The
charge pumps operate in a discontinuous mode. If the
