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
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.
POWER UP WITH SD ACTIVE (Charge pump in shutdown mode)
t
0 (POWERUP)
+5V
R
OUT
DATA VALID
0V
t
WAIT
ENABLE
SD
DISABLE
POWER UP WITH SD DISABLED (Charge pump in active mode)
t
0 (POWERUP)
+5V
R
OUT
DATA VALID
0V
t
ENABLE
ENABLE
SD
DISABLE
EXERCISING WAKE–UP FEATURE
t
0 (POWERUP)
+5V
R
OUT
DATA VALID
0V
t
ENABLE
SD
DISABLE
t
WAIT
V
CC
= +5V ±10%; T
A
= 25°C
t
WAIT
= 2ms typical, 3ms maximum
t
ENABLE
= 1ms typical, 2ms maximum
Figure 6. Wake–Up Timing
DATA VALID
t
ENABLE
ENABLE
DATA VALID
t
ENABLE
DISABLE
Date:05/26/2005
+5V High-Speed RS232 Transceivers
© Copyright 2005 Sipex Corporation
9
SIPEX [ SIPEX CORPORATION ]
