LT1180ACSW datasheet(6/12 Pages) LINER

6 / 12 page

LT1180A/LT1181A

PI FU CTIO S

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

TTL/CMOS compatible. Inputs should not be allowed to

float. Tie unused inputs to VCC.

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

in shutdown mode, VCC = 0V, or when the driver disable

pin is active. Outputs are fully short-circuit protected from

V – + 30V to V + – 30V. Applying 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

±10kV for human body model discharges.

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

RS232 level signals (

±30V)intoaprotected5kterminating

resistor. The receiver inputs are protected against ESD to

±10kV for human body model discharges. Each receiver

provides 0.4V of hysteresis for noise immunity. Open

receiver inputs assume a logic low 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. Outputs

are fully short-circuit protected to ground or VCC with the

power on, off or in the shutdown mode.

C1+, C1–, C2 +, C2 –: Commutating Capacitor Inputs.

These pins require two external capacitors C

≥ 0.1µF: one

from C1+ to C1– and another from C2+ to C2 –. C1 should

be deleted if a separate 12V supply is available and con-

nected to pin C1+. Similarly, C2 should be deleted if a

separate – 12V supply is connected to pin V –.

ESD Test Circuit

ESD PROTECTIO

The RS232 line inputs of the LT1180A/LT1181A have on-

chip protection from ESD transients up to

±10kV. The

protection structures act to divert the static discharge

safely to system ground. In order for the ESD protection to

function effectively, the power supply and ground pins of

the circuit must be connected to ground through low

impedances. The power supply decoupling capacitors and

charge pump storage capacitors provide this low imped-

ance in normal application of the circuit. The only con-

straint is that low ESR capacitors must be used for

bypassing and charge storage. ESD testing must be done

with pins VCC, VL, V+, V –, and GND shorted to ground or

connected with low ESR capacitors.

LT1180A • ESD TC

RS232

LINE PINS

PROTECTED

±10kV

0.1

µF

0.1

µF

C1+

V+

C1–

C2+

C2–

V–

DR2 OUT

LT1180A

ON/OFF

5V VCC

GND

DR1 OUT

RX1 IN

RX1 OUT

DR1 IN

DR2 IN

RS232

LINE PINS

PROTECTED

±10kV

RX2 IN

RX2 OUT

0.1

µF

0.1

µF

0.1

µF

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