6

LT1780/LT1781

with a 0.1

µF ceramic capacitor close to the package pin.

Insufficient supply bypassing can result in low output

drive levels and erratic charge pump operation.

GND: Ground Pin.

ON/OFF: A TTL/CMOS Compatible Operating Mode Con-

trol. A logic low puts the LT1780 in SHUTDOWN mode.

Supply current drops to zero and both driver and receiver

outputs assume a high impedance state. A logic high fully

enables the device.

storage capacitor C

value capacitors may be used to reduce supply ripple. With

into common capacitors.

storage capacitor C

≥ 0.1µF. Larger value capacitors may

be used to reduce supply ripple. With multiple transceiv-

capacitors.

TR1 IN, TR2 IN: RS232 Driver Input Pins. These inputs are

TTL/CMOS compatible. Inputs should not be allowed to

TR1 OUT, TR2 OUT: Driver Outputs at RS232 Voltage

Levels. Driver output swing meets RS232 levels for loads

up to 3k. Slew rates are controlled for lightly loaded lines.

Output current capability is sufficient for load conditions

up to 2500pF. Outputs are in a high impedance state when

higher voltages will not damage the device if the overdrive

is moderately current limited. Short circuits on one

output can load the power supply generator and may

disrupt the signal levels of the other outputs. The driver

outputs are protected against ESD to IEC-1000-4-2

Level 4 discharges.

REC1 IN, REC2 IN: Receiver Inputs. These pins accept

RS232 level signals (

±30V) into a protected 5k terminat-

ing resistor. The receiver inputs are protected against ESD

to IEC-1000-4-2 Level 4 discharges. Each receiver pro-

vides 0.4V of hysteresis for noise immunity. Open receiver

inputs result in a logic high receiver output state.

REC1 OUT, REC2 OUT: Receiver outputs with TTL/CMOS

Voltage Levels. Outputs are in a high impedance state

when in SHUTDOWN mode to allow data line sharing.

with the power ON, OFF or in the SHUTDOWN mode.

These pins require two external capacitors C

≥ 0.1µF: one

be deleted if a separate 12V supply is available and

PI FU CTIO S