MAX3224 Maxim, MAX3224 Datasheet - Page 8

• Manufacturer Part Number: MAX3224
• Description: 1A Supply Current / 1Mbps / 3.0V to 5.5V / RS-232 Transceivers with AutoShutdown Plus
• Manufacturer: Maxim

1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
Figure 1. Interface Under Control of PMU
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 MAX3224–MAX3227 feature inverting
outputs that always remain active (Table 1). The
MAX3244/MAX3245 have inverting three-state outputs
that are high impedance when shut down (FORCEOFF
= GND) (Table 1).
8
POWER-
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
_______________________________________________________________________________________
CPU
CC
.
WITH
UART
CHIP
INVALID
FORCEOFF
FORCEON
I/O
RS-232 Receivers
MAX3244
MAX3245
RS-232
Figure 2. The MAX3244/MAX3245 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.
V
NEW MAX3244/MAX3245: IN SHUTDOWN, R2OUTB IS USED TO MONITOR
EXTERNAL DEVICES AND R2OUT IS THREE STATED, ELIMINATING A CURRENT
PATH THROUGH THE UART’S PROTECTION DIODE.
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
MAX3244
MAX3245
RS-232
5k
5k
R2IN
T1OUT