MAX3243ECWI Maxim, MAX3243ECWI Datasheet - Page 7

• Manufacturer Part Number: MAX3243ECWI
• Description: 15kV ESD-Protected / 1A / 3.0V to 5.5V / 250kbps / RS-232 Transceivers with AutoShutdown
• Manufacturer: Maxim

The MAX3221E/MAX3223E/MAX3243E’s receivers con-
vert RS-232 signals to CMOS-logic output levels. All
receivers have inverting three-state outputs and can be
active or inactive. In shutdown (FORCEOFF = low) or in
AutoShutdown, the MAX3221E/MAX3223E’s receivers
are active (Table 1). Drive EN high to place the receiv-
er(s) in a high-impedance state. The MAX3243E’s
receivers are high-impedance when the part is in shut-
down (FORCEOFF = low).
The MAX3243E features an extra, always-active com-
plementary output (R2OUTB). R2OUTB monitors
receiver activity while the other receivers are high-
impedance. This allows Ring Indicator to be monitored
without forward biasing other devices connected to the
receiver outputs. This is ideal for systems where V
drops to 0 in shutdown to accommodate peripherals
such as UARTs (Figure 2).
Figure 1. Interface Under Control of PMU
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
MANAGEMENT
CONTROLLER
CPU
KEYBOARD
POWER-
UNIT OR
RS-232 Transceivers with AutoShutdown
WITH
UART
CHIP
INVALID
FORCEOFF
FORCEON
I/O
_______________________________________________________________________________________
MAX3243E
RS-232 Receivers
RS-232
CC
Figure 2. The MAX3243E detects RS-232 activity when the
UART and interface are shut down.
a)
b)
OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
NEW MAX3243E: IN SHUTDOWN, R2OUTB IS USED TO MONITOR EXTERNAL
V
V
DEVICES AND R2OUT IS THREE STATED, ELIMINATING A CURRENT PATH
THROUGH THE UART'S PROTECTION DIODE.
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
CC
R2OUTB
R2OUT
T1IN
I
PREVIOUS
MAX3243E
RS-232
5k
5k
R2IN
T1OUT
7