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DESCRIPTION/ORDERING INFORMATION (CONTINUED)

FUNCTION TABLES

TRSF3243

3-V TO 5.5-V MULTICHANNEL RS-232 COMPATIBLE LINE DRIVER/RECEIVER

SLLS862 – AUGUST 2007

Flexible control options for power management are available when the serial port is inactive. The

auto-powerdown feature functions when FORCEON is low and FORCEOFF is high. During this mode of

operation, if the device does not sense a valid RS-232 signal, the driver outputs are disabled. If FORCEOFF is

set low, both drivers and receivers (except ROUT2B) are shut off, and the supply current is reduced to 1

μA.

Disconnecting the serial port or turning off the peripheral drivers causes the auto-powerdown condition to occur.

Auto-powerdown can be disabled when FORCEON and FORCEOFF are high and should be done when driving

a serial mouse. With auto-powerdown enabled, the device is activated automatically when a valid signal is

applied to any receiver input. The INVALID output is used to notify the user if an RS-232 signal is present at any

receiver input. INVALID is high (valid data) if any receiver input voltage is greater than 2.7 V or less than –2.7 V

or has been between –0.3 V and 0.3 V for less than 30

μs. INVALID is low (invalid data) if all receiver input

voltages are between –0.3 V and 0.3 V for more than 30

μs. Refer to Figure 5 for receiver input levels.

INPUTS

OUTPUT

VALID RIN

DRIVER STATUS

DOUT

DIN

FORCEON

FORCEOFF

RS-232

LEVEL

X

X

L

X

Z

Powered off

L

H

H

X

H

Normal operation with

auto-powerdown disabled

H

H

H

X

L

L

L

H

Yes

H

Normal operation with

auto-powerdown enabled

H

L

H

Yes

L

L

L

H

No

Z

Powered off by auto-powerdown

feature

H

L

H

No

Z

(1)

H = high level, L = low level, X = irrelevant, Z = high impedance

INPUTS

OUTPUTS

VALID RIN

RECEIVER STATUS

RIN1,

RIN2

FORCEOFF

RS-232

ROUT2B

ROUT

RIN3–RIN5

LEVEL

L

X

L

X

L

Z

Powered off while

ROUT2B is active

H

X

L

X

H

Z

L

L

H

Yes

L

H

L

H

H

Yes

L

L

Normal operation with

H

L

H

Yes

H

H

auto-powerdown

disabled/enabled

H

H

H

Yes

H

L

Open

Open

H

No

L

H

(1)

H = high level, L = low level, X = irrelevant, Z = high impedance (off), Open = input disconnected or

connected driver off

2

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