9

Date:05/26/2005

+5V High-Speed RS232 Transceivers

© Copyright 2005 Sipex Corporation

computer to power up the microprocessor and

the SP2XXB/SP213 drivers. After the supply

voltage to the SP2XXB/SP213 reaches +5.0V,

the SHUTDOWN pin can be disabled, taking

the SP2XXB/SP213 out of the shutdown mode.

All receivers that are active during shutdown

maintain 500mV (typ.) of hysteresis.

A typical application of this function would be

where a modem is interfaced to a computer in a

power–down mode. The ring indicator signal

from the modem could be passed through an

active receiver in the SP2XXB/SP213 that is

itself in the shutdown mode. The ring indicator

signal would propagate through the SP2XXB/

SP213 to the power management circuitry of the

Figure 6. Wake–Up Timing

+5V

0V

ENABLE

DISABLE

SD

DATA VALID

+5V

0V

+5V

0V

ENABLE

DISABLE

SD

POWER UP WITH SD ACTIVE (Charge pump in shutdown mode)

POWER UP WITH SD DISABLED (Charge pump in active mode)

DATA VALID

SD

DATA VALID

DATA VALID

DATA VALID

EXERCISING WAKE–UP FEATURE

DISABLE

DISABLE

ENABLE