LT1330CSW datasheet(6/8 Pages) LINER

6 / 8 page

LT1330

PI FU CTIO S

to reduce supply ripple. The ratio of the capacitors on V+

and V – should be greater than 5 to 1.

V–: Negative Supply Output. V –

≈ –(2VCC–2.5V).Thispin

requires an external charge storage capacitor, C

≥ 0.1µF.

See the Applications Information section for guidance in

choosing filter capacitors for V+ and V –.

C1+, C1–, C2+, C2–: Commutating Capacitor Inputs re-

quire two external capacitors, C

≥ 0.2µF: one from C1+ to

C1–, and another from C2+ to C2–. The capacitor’s effec-

tive series resistance should be less than 2

Ω. For C ≥ 1µF,

low ESR tantalum capacitors work well, although ceramic

capacitors may be used with a minimal reduction in charge

pump compliance.

DRIVER IN: RS232 Driver Input Pins. These inputs are

TTL/CMOS compatible. Unused inputs should be con-

nected to VCC.

DRIVER 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.

RX IN: Receiver Inputs. These pins accept RS232 level

signals (

±30V) into a protected 5k terminating 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.

RX OUT: Receiver Outputs with TTL/CMOS Voltage Lev-

els. Outputs are in a high impedance state when in shut-

down mode to allow data line sharing. Outputs, including

LOW-Q RX OUT, are fully short-circuit protected to ground

or VCC with the power on, off, or in shutdown mode.

LOW Q-CURRENT RX IN: Low Power Receiver Input. This

special receiver remains active when the part is in shut-

down mode, consuming typically 60

µA. This receiver has

the same 5k input impedance and

±10kV ESD protection

characteristics as the other receivers.

LOW Q-CURRENT RX OUT: Low Power Receiver Output.

This pin produces the same TTL/CMOS output voltage

levels as receivers RX1, RX2, RX3, and RX4 with slightly

decreased speed and short-circuit current. Data rates to

120kbaud are supported by this receiver.

The RS232 line inputs of the LT1330 have on-chip protec-

tion 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

LT1330 must be connected to ground through low imped-

ances. The power supply decoupling capacitors and charge

pump storage capacitors provide this low impedance in

normal application of the circuit. The only constraint 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.

ESD PROTECTIO

1330 TC01

5V VCC

µF

0.2

µF

0.1

µF

RS232

LINE PINS

PROTECTED

±10kV

LT1330

DRIVER 1 OUT

RX1 IN

DRIVER 2 OUT

RX2 IN

RX3 IN

RX4 IN

DRIVER 3 OUT

RX5 IN (LOW-Q)

ON/OFF

3V VL

0.2

µF

DRIVER 1 IN

RX1 OUT

DRIVER 2 IN

RX2 OUT

RX3 OUT

RX4 OUT

DRIVER 3 IN

RX5 OUT (LOW-Q)

V–

V+

0.1

µF

GND

DRIVER DISABLE

0.1

µF

ESD Test Circuit

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