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MAX3323EEUE+

P1-P3P4-P6P7-P9P10-P12P13-P13
MAX3322E/MAX3323E
±15kV ESD-Protected, RS-232 Transceivers for
Multidrop Applications
4 _______________________________________________________________________________________
Typical Operating Characteristics
(V
CC
= 3.3V, V
L
= 3.3V, C1–C4 = 0.1µF, T
A
= +25°C.)
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3322E toc01
LOAD CAPACITANCE (pF)
OUTPUT VOLTAGE (V)
4000300020001000
-5.0
-2.5
0
2.5
5.0
7.5
-7.5
0 5000
DATA RATE = 250kbps
LOAD = 3kΩ IN PARALLEL WITH C
L
SLEW RATE
vs. LOAD CAPACITANCE
MAX3322E toc02
LOAD CAPACITANCE (pF)
SLEW RATE (V/µs)
4000300020001000
3
6
9
12
15
18
0
0 5000
SLEW RATE-
SLEW RATE+
TRANSMITTER OUTPUT VOLTAGE
vs. DATA RATE
MAX3322E toc03
DATA RATE (kbps)
OUTPUT VOLTAGE (V)
20015010050
-5.0
-2.5
0
2.5
5.0
7.5
-7.5
0 250
LOAD = 3kΩ, 1000pF
ONE TRANSMITTER
SWITCHING AT DATA
RATE, OTHER
TRANSMITTER
AT 1/8 DATA RATE
SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3322E toc04
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
4000300020001000
10
20
30
40
0
0 5000
250kbps
125kbps
40kbps
LOAD = 3kΩ
ONE TRANSMITTER
SWITCHING AT DATA
RATE, OTHER
TRANSMITTER
AT 1/8 DATA RATE
RECEIVER INPUT RESISTANCE
vs. INPUT VOLTAGE RANGE
MAX3322E toc05
V
RIN
(V)
RECEIVER INPUT RESISTANCE (kΩ)
155-5-15
4.75
5.00
5.25
5.50
4.50
-25 25
RENABLE = 1
RECEIVER INPUT RESISTANCE
vs. INPUT VOLTAGE RANGE
MAX3322E toc06
V
RIN
(V)
RECEIVER INPUT RESISTANCE (MΩ)
155-5-15
1
2
3
4
5
0
-25 25
RENABLE = 0
V
L
= 5V
Detailed Description
The MAX3322E/MAX3323E are RS-232 transceivers for
multidrop applications (i.e., multiple-receiver operation).
The devices are pin selectable between standard RS-232
operation with 5kΩ input resistance receivers or high-
input-impedance receivers. Receivers of the MAX3322E/
MAX3323E remain active in both modes of operation. In
multidrop applications, a selected receiver is set at a 5kΩ
input resistance, while the others are high-input imped-
ance, maintaining RS-232 standards. Logic control per-
mits selection of the functional mode: high impedance or
normal load. The transmitters are enabled by logic control
to allow transmission-line sharing.
The logic supply input (V
L
) controls the levels of the
system’s I/O and works from 1.65V to 5.5V, providing
compatibility with lower microprocessor I/O voltages.
The transmitters are inverting level translators that con-
vert CMOS logic levels into RS-232-compatible levels.
They guarantee 250kbps with loads of R
L
= 3kΩ and C
L
= 1000pF. The transmitters are enabled or disabled
(three-stated) by the logic control TXENABLE, which
manages transmission-line sharing in multidrop applica-
tions. When TXENABLE is high, the transmitter is
enabled. When TXENABLE is low, the transmitter is put
in high-impedance state. The receivers can be used in
two conditions, selectable by the logic control RENABLE.
When RENABLE is high, the internal 5kΩ resistor is con-
nected across receiver input and ground. When
RENABLE is low, the receiver input is high impedance,
while maintaining receiving capability.
In shutdown mode, all transmitter and receiver outputs
are three-stated, receiver inputs are in high impedance,
the charge pump is turned off, V+ decays to V
CC
, and
V- decays to ground. ESD protection structures are
incorporated in all pins to protect against ESD events
encountered during handling and assembly. The
receiver inputs and the transmitter outputs have ±15kV
ESD structure implementation.
MAX3322E/MAX3323E
±15kV ESD-Protected, RS-232 Transceivers for
Multidrop Applications
_______________________________________________________________________________________ 5
Pin Description
PIN
MAX3322E
MAX3323E
NAME FUNCTION
1 1 C1+ Positive Terminal of the Voltage-Doubler Charge-Pump Capacitor
2 2 V+ +5.5V Generated by the Charge Pump
3 3 C1- Negative Terminal of the Voltage-Doubler Charge-Pump Capacitor
4 4 C2+ Positive Terminal of the Inverting Charge-Pump Capacitor
5 5 C2- Negative Terminal of the Inverting Charge-Pump Capacitor
6 6 V- -5.5V Generated by the Charge Pump
7, 9 7 TOUT_ Transmitter Output
8, 10 8 RIN_ Receiver Input
11, 13 9 ROUT_ Receiver Output
12, 14 10 TIN_ Transmitter Input
15 11
TXENABLE
Transmitter Enable. Drive TXENABLE high to enable transmitter. Drive TXENABLE low
to put transmitter into high impedance.
16 12
RENABLE
Receiver Termination Enable. Drive RENABLE high for normal RS-232 5kΩ termination.
Drive RENABLE low to make receiver inputs high impedance. In either case, the
receiver and its output are enabled.
17 13 V
L
Logic-Level Supply. All CMOS inputs and outputs are referred to V
L
, which is from
1.65V to 5.5V.
18 14 SHDN
Shutdown Input. Drive SHDN low to put device into shutdown mode. Drive SHDN high
for normal operation. In shutdown, all transmitter and receiver outputs are in three-state;
receiver inputs are high impedance.
19 15 GND Ground
20 16 V
CC
+3V to +5.5V Input Voltage. Bypass V
CC
to GND with a 0.1µF capacitor.
MAX3322E/MAX3323E
Dual Charge-Pump Voltage Converter
The MAX3322E/MAX3323Es’ internal power supply con-
sists of a regulated dual charge pump that provides out-
put voltages of +5.5V (doubling charge pump) and
-5.5V (inverting charge pump), regardless of the input
voltage (V
CC
), over a +3.0V to +5.5V range. The charge
pumps operate in a discontinuous mode: if the output
voltages are less than 5.5V, the charge pumps are
enabled; if the output voltages exceed 5.5V, the charge
pumps are disabled. Each charge pump requires a fly-
ing capacitor (C1, C2) and reservoir capacitor (C3, C4)
to generate the V+ and V- supplies. Because supply
voltages can vary from +3V up to +5.5V, the selection
of the capacitor values depends on the V
CC
value.
Table 2 shows minimum capacitor values.
RS-232 Transmitters
The transmitters are inverting level translators that con-
vert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The
transmitters are enabled or disabled (three-stated) by
the logic control TXENABLE, which manages transmis-
sion-line sharing in multidrop applications. When
TXENABLE is high, the transmitter is enabled. When
TXENABLE is low, the transmitter is put in a high-
impedance state (see Table 1).
The MAX3322E/MAX3323Es’ transmitters guarantee a
250kbps data rate with worst-case loads of 3kΩ in par-
allel with 1000pF, providing compatibility with PC-to-PC
communication software (such as LapLink™).
Transmitters can be paralleled to drive multiple
receivers or mice. Figure 3 shows a complete system
connection.
RS-232 Receivers
MAX3322E/MAX3323E receivers convert RS-232 sig-
nals to CMOS-logic output levels. The unique feature of
the receivers is the switchable input resistance. The
receiver input resistance can be 5kΩ or high imped-
ance. These two conditions are selectable by the logic
control RENABLE. When RENABLE is high, the 5kΩ
resistor is connected across the receiver input and
ground. When RENABLE is low, the receiver input is
high impedance, maintaining receiving capability. This
feature permits the design of multidrop applications,
which observe RS-232 interface standards.
±15kV ESD-Protected, RS-232 Transceivers for
Multidrop Applications
6 _______________________________________________________________________________________
LapLink is a trademark of Traveling Software.
INPUT
OUTPUT
+3V
V+
0V
V-
0V
t
PLH
t
PHL
Figure 1. Transmitter Propagation-Delay Timing
t
PHL
t
PLH
50%
V
CC
50%
+3V
50%
INPUT
OUTPUT
0V
50%
GND
Figure 2. Receiver Propagation-Delay Timing
MAX3322E
I/O
CHIP
WITH
UART
I/O
CHIP
POWER SUPPLY
V
L
V
L
CPU
RS-232
POWER-
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
SHDN
SHDN
Figure 3. Interface Under Control of PMU
P1-P3P4-P6P7-P9P10-P12P13-P13

MAX3323EEUE+

Mfr. #:
Buy MAX3323EEUE+
Manufacturer:
Maxim Integrated
Description:
RS-232 Interface IC Transceiver For Multidrop Aps
Lifecycle:
New from this manufacturer.
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