Datasheet

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.