MAX3162 MAXIM [Maxim Integrated Products], MAX3162 Datasheet - Page 14

• Manufacturer Part Number: MAX3162
• Description: +3.0V to +5.5V, 1uA, RS-232/RS-485/422 Multiprotocol Transceivers
• Manufacturer: MAXIM [Maxim Integrated Products]

The MAX3160/MAX3161/MAX3162 3V/5V, multiprotocol
transceivers can be pin configured in a number of RS-
232 and RS-485/422 interface combinations. These cir-
cuit configurations are ideal for the design of RS-232 to
RS-485 converters, multiprotocol buses, or any applica-
tion that requires both RS-232 and RS-485 transceivers.
The slew rate of these devices is on-the-fly pin pro-
grammable, 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 (avail-
able in the commercial and extended temperature
ranges) facilitate board layout.
The MAX3160/MAX3161/MAX3162 contain RS-232
transceivers and an RS-485/422 transceiver. The pri-
mary 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 trans-
ceivers, and common digital I/O pins. The MAX3160 is
optimized for multiprotocol operation on a single inter-
face 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 trans-
ceivers, 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 trans-
ceivers, 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.
The MAX3160 is a 2Tx/2Rx RS-232 transceiver in RS-
232 mode, capable of RS-232-compliant communica-
tion. Assertion of RS-485/RS-232 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.
+3.0V to+5.5V, 1µA, RS-232/RS-485/422
Multiprotocol Transceivers
14
______________________________________________________________________________________
Detailed Description
Device Selection
MAX3160
The MAX3161 is a 2Tx/2Rx RS-232 transceiver in RS-
232 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.
The MAX3162 is a 2Tx/2Rx RS-232 transceiver and a
single RS-485/422 transceiver simultaneously. All dri-
vers, receivers, and transmitters can be enabled or dis-
abled 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.
The FAST control pin is used to select the slew-rate lim-
iting of the RS-232 transmitters and the RS-485/422 dri-
vers. 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 RS-
485/422 data rates up to 10Mbps are possible when
FAST is asserted. FAST can be changed during opera-
tion without interrupting data communications.
Asserting HDPLX places the MAX3160/MAX3161 in
half-duplex mode. The RS-485 receiver inputs are inter-
nally connected to the driver outputs. The RS-485 dri-
ver outputs can be disabled by pulling DE485 low.
HDPLX has no affect on RS-232 operation.
The MAX3160/MAX3161/MAX3162 have an active-low
shutdown control input, SHDN. When driven low, the
charge pump and transmitters are shut down and sup-
ply current is reduced to 1µA. The RS-232 receiver out-
puts remain active if in RS-232 mode. The charge-
pump capacitors must be recharged when coming out
of shutdown before resuming operation in either RS-232
or RS-485/422 mode (Figure 10).
The MAX3160/MAX3161/MAX3162s’ internal power sup-
ply consists of a regulated dual charge pump that pro-
vides output voltages of +5.5V (doubling charge pump)
and -5.5V (inverting charge pump) for input voltages
(V
operate in a discontinuous mode: if the magnitude of
either output voltage is less than 5.5V, the charge pumps
CC
) over the 3.0V to 5.5V range. The charge pumps
Dual Charge-Pump Voltage Converter
Half-Duplex RS-485/422 Operation
Low-Power Shutdown
FAST Mode operation
MAX3161
MAX3162