MAX3224E Maxim, MAX3224E Datasheet - Page 8

• Manufacturer Part Number: MAX3224E
• Description: 15kV ESD-Protected / 1A / 1Mbps / 3.0V to 5.5V / RS-232 Transceivers with AutoShutdown Plus
• Manufacturer: Maxim

±15kV ESD-Protected, 1µA, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
Figure 1. Interface Under Control of PMU
munication software (such as LapLink™). Transmitters
can be paralleled to drive multiple receivers. Figure 1
shows a complete system connection.
When FORCEOFF is driven to ground or when the Auto-
Shutdown Plus circuitry senses that all receiver and
transmitter inputs are inactive for more than 30sec, the
transmitters are disabled and the outputs go into a high-
impedance state. When powered off or shut down, the
outputs can be driven to ±12V. The transmitter inputs
do not have pull-up resistors. Connect unused inputs to
GND or V
The receivers convert RS-232 signals to CMOS-logic
output levels. The MAX3224E–MAX3227E feature
inverting outputs that always remain active (Table 1).
The MAX3244E/MAX3245E have inverting three-state
8
POWER-
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
_______________________________________________________________________________________
CPU
CC
.
WITH
UART
CHIP
INVALID
FORCEOFF
FORCEON
I/O
MAX3244E
MAX3245E
RS-232 Receivers
RS-232
Figure 2. The MAX3244E/MAX3245E detect RS-232 activity
when the UART and interface are shut down.
b)
a)
OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
EXTERNAL DEVICES AND R2OUT IS THREE STATED, ELIMINATING A CURRENT
PATH THROUGH THE UART'S PROTECTION DIODE.
V
NEW MAX3244E/MAX3245E: IN SHUTDOWN, R2OUTB IS USED TO MONITOR
V
CC
CC
GND
UART
GND
UART
TO
P
PROTECTION
DIODE
PROTECTION
DIODE
Rx
Rx
Tx
Tx
TRANSITION
DETECTOR
LOGIC
SHDN = GND
FORCEOFF = GND
THREE-STATED
V
CC
I
V
R2OUTB
CC
R2OUT
T1IN
I
PREVIOUS
MAX3244E
MAX3245E
RS-232
5k
5k
R2IN
T1OUT