1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
MAX3224–MAX3227/MAX3244/MAX3245
†
RECEIVER
INPUTS
}
REGION
INVALID
TRANSMITTER
INPUTS
TRANSMITTER
OUTPUTS
V
CC
0
*V
CC
OUTPUT
0
V+
V
CC
0
V-
*MAX3224–MAX3227
INVALID
OUTPUT
t
INVL
t
INVH
t
AUTOSHDN
t
WU
t
AUTOSHDN
t
WU
Figure 4b. AutoShutdown Plus,
INVALID,
and READY Timing Diagram
By connecting FORCEON to
INVALID,
the MAX3224–
MAX3227/MAX3244/MAX3245 shut down when no valid
receiver level and no receiver or transmitter edge is
detected for 30sec, and wake up when a valid receiver
level or receiver or transmitter edge is detected.
By connecting FORCEON and
FORCEOFF
to
INVALID,
the MAX3224–MAX3227/MAX3244/MAX3245 shutdown
when no valid receiver level is detected and wake up
when a valid receiver level is detected (same function-
ality as AutoShutdown feature on MAX3221/MAX3223/
MAX3243).
A mouse or other system with AutoShutdown Plus may
need time to wake up. Figure 5 shows a circuit that
forces the transmitters on for 100ms, allowing enough
time for the other system to realize that the MAX3244/
MAX3245 is awake. If the other system outputs valid
RS-232 signal transitions within that time, the RS-232
ports on both systems remain enabled.
POWER-
MANAGEMENT
UNIT
MASTER SHDN LINE
0.1μF
1MΩ
FORCEOFF FORCEON
MAX3224
MAX3225
MAX3226
MAX3227
MAX3244
MAX3245
Figure 5. AutoShutdown Plus Initial Turn-On to Wake Up a
Mouse or Another System
______________________________________________________________________________________
11
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
