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LT1237CSW

5V RS232 Transceiver with Advanced Power Management and One Receiver Active in Shutdown

Linear Technology 

TYPICAL PERFOR A CE CHARACTERISTICS

LT1237

Driver Short-Circuit Current

30

25

ISC+

20

15

ISC–

10

5

0

–55 –25

0 25 50 75

TEMPERATURE (°C)

100 125

1237 G10

Receiver Output Waveforms

Receiver Short-Circuit Current

50

40

RX1 TO RX4

ISC–

30

RX1 TO RX4

ISC+

20

RX5 ISC–

10

RX5 ISC+

0

–55 –25

0 25 50 75

TEMPERATURE (°C)

100 125

1237 G11

Driver Output Waveforms

RX5 OUTPUT

CL = 50pF

RX1 TO RX4

OUTPUT

CL = 50pF

INPUT

1237 G12

DRIVER OUTPUT

RL = 3k

CL = 2500pF

DRIVER OUTPUT

RL = 3k

INPUT

1237 G13

PI FU CTIO S

VCC: 5V Input Supply Pin. This pin should be decoupled

with a 0.1µF 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: TTL/CMOS Compatible Operating Mode Control.

A logic low puts the device in the low power shutdown

mode. All three drivers and four receivers (RX1, RX2, RX3,

and RX4) assume a high impedance output state in shut-

down. Only receiver RX5 remains active while the trans-

ceiver is in shutdown. The transceiver consumes only

60µA of supply current while in shutdown. A logic high

fully enables the transceiver.

DRIVER DISABLE: This pin provides an alternate control

for the charge pump and RS232 drivers. A logic high on

this pin shuts down the charge pump and places all driver

outputs in a high impedance state. All five receivers remain

active under these conditions. Floating the driver disable

pin or driving it to a logic low level fully enables the

transceiver. A logic low on the ON/OFF pin supersedes the

state of the DRIVER DISABLE pin. Supply current drops to

3mA when in driver disable mode.

V+: Positive Supply Output (RS232 Drivers). V+ ≈ 2VCC –

1.5V. This pin requires an external charge storage capaci-

tor C ≥ 1.0µF, tied to ground or VCC. Larger value capaci-

tors may be used to reduce supply ripple. The ratio of the

capacitors on V+ and V – should be greater than 5 to 1.

V–: Negative Supply Output (RS232 Drivers). V – ≈

–(2VCC – 2.5V). This pin requires an external charge

storage capacitor C ≥ 0.1µF. See the Applications Infor-

mation section for guidance in choosing filter capacitors

for V+ and V –.

5

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