7.3 Feature Description

7.3.1 Auto-Power-Down

Auto-Power-Down can be used to automatically save power when the receivers are unconnected or connected

to a powered down remote RS232 port. FORCEON being high will override Auto power down and the drivers will

be active. FORCEOFF being low will override FORCEON and will power down all outputs except for ROUT2B

and INVALID.

7.3.2 Charge Pump

The charge pump increases, inverts, and regulates voltage at V+ and V– pins and requires four external

capacitors.

7.3.3 RS232 Driver

Three drivers interface standard logic level to RS232 levels. All DIN inputs must be valid high or low.

7.3.4 RS232 Receiver

Five receivers interface RS232 levels to standard logic levels. An open input will result in a high output on ROUT.

Each RIN input includes an internal standard RS232 load.

7.3.5 ROUT2B Receiver

ROUT2B is an always-active noninverting output of RIN2 input, which allows applications using the ring indicator

to transmit data while the device is powered down.

7.3.6 Invalid Input Detection

The INVALID output goes active low when all RIN inputs are unpowered. The INVALID output goes inactive high

when any RIN input is connected to an active RS232 voltage level.

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MAX3243

SLLS350Q – APRIL 1999 – REVISED AUGUST 2024

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