5
LTC1348
PI FU CTIO S
U
UU
V
CC
: 3V to 5.5V Input Supply Pin. This pin should be
decoupled with a 0.1µF ceramic capacitor.
GND: Ground Pin.
RXEN: TTL/CMOS Compatible Enable Pin. Refer to Table
1 for its functional description.
DREN: TTL/CMOS Compatible Enable Pin. Refer to Table
1 for its functional description.
V
+
: Positive Supply Output (RS232 Drivers). This pin
requires an external capacitor C = 0.1µF for charge stor-
age. The capacitor may be tied to ground or V
CC
. With
multiple devices, the V
+
and V
–
pins may be paralleled into
common capacitors. For large numbers of devices, in-
creasing the size of the shared common storage capaci-
tors is recommended to reduce ripple.
V
–
: Negative Supply Output (RS232 Drivers). This pin
requires an external capacitor C = 0.1µF for charge
storage.
C1
+
, C1
–
, C2
+
, C2
–
, C3
+
, C3
–
: Commutating Capacitor
Inputs. These pins require three external capacitors C =
0.1µF: one from C1
+
to C1
–
, another from C2
+
to C2
–
and
another from C3
+
to C3
–
. To maintain charge pump
efficiency, the capacitor’s effective series resistance should
be less than 1Ω. Ceramic capacitors are recommended.
DR IN: RS232 Driver Input Pins. Inputs are TTL/CMOS
compatible. The inputs of unused drivers can be left
unconnected since 300k input pull-up resistors to V
CC
are
included on chip. To minimize power consumption, the
internal driver pull-up resistors are disconnected from V
CC
in the Shutdown or Receiver Alive mode.
DR OUT: Driver Outputs at RS232 Voltage Levels. Outputs
are in a high impedance state when in the Shutdown,
Receiver Alive mode or V
CC
= 0V. The driver outputs are
protected against ESD to ±10kV for human body model
discharges.
RX IN: Receiver Inputs. These pins can be forced to ±25V
without damage. The receiver inputs are protected against
ESD to ±10kV for human body model discharges. Each
receiver provides 0.4V of hysteresis for noise immunity. In
Receiver Alive mode all receivers have no hysteresis.
RX OUT: Receiver Outputs with TTL/CMOS Voltage Lev-
els. Outputs are in a high impedance state when in the
Shutdown or Receiver Disable mode to allow data line
sharing.
Table 1. Functional Description
MODE RX ENABLE DR ENABLE DRIVERS RECEIVERS I
CC
TYP
Shutdown 0 0 All Drivers Shutdown. All Receivers Shutdown. 0.2µA
All Driver Outputs Assume High Impedance. All Receiver Outputs Assume High Impedance.
All Driver Pull-Up Resistors Disconnect
From V
CC
.
Receiver 0 1 All Drivers Alive. All Receiver Outputs in Three-State. 600µA at
Disable 3.3V,
800µA at
5V
Receiver 1 0 All Drivers Shutdown. All Receivers Alive. 15µA
Alive All Driver Outputs in Three-State.
All Driver Pull-Up Resistors Disconnect
From V
CC
.
Normal 1 1 All Drivers Alive. All Receivers Alive. 600µA at
3.3V,
800µA at
5V
