MAX3248EEAI-T Maxim Integrated, MAX3248EEAI-T Datasheet - Page 7

• Manufacturer Part Number: MAX3248EEAI-T
• Description: RS-232 Interface IC
• Manufacturer: Maxim Integrated
• Series: MAX3238E, MAX3248Er

Figure 1. Interface Under Control of PMU
A 10nA supply current is achieved with Maxim’s
AutoShutdown Plus feature, which operates when
FORCEOFF is low and FORCEON is high. When the
MAX3238E/MAX3248E sense no valid signal transitions
on all receiver and transmitter inputs for 30s, the on-
board power supply and drivers are shut off, reducing
supply current to 1µA. If the receiver inputs are in the
invalid range (-0.3V < R_IN < +0.3V) and the transmit-
ter inputs are at GND or V
reduced to 10nA. This occurs if the RS-232 cable is
disconnected or if the connected peripheral transmit-
ters are turned off. The system turns on again when a
valid transition is applied to any RS-232 receiver or
transmitter input. As a result, the system saves power
without changes to the existing BIOS or operating sys-
tem. The INVALID output is high when the receivers are
active. Since INVALID indicates the receiver inputs’
condition, it can be used in any mode (Figure 3).
+3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers
MANAGEMENT
CONTROLLER
CPU
KEYBOARD
UNIT OR
POWER
with ±15kV ESD-Protected I/O and Logic Pins
WITH
UART
CHIP
INVALID
FORCEOFF
FORCEON
I/O
_______________________________________________________________________________________
AutoShutdown Plus Mode
CC
, supply current is further
MAX3238E/
MAX3248E
T1
T2
T3
T4
T5
R1
R2
R3
RS-232
Figure 2. MAX3238E/MAX3248E detect RS-232 activity when
the UART and interface are shut down.
b) NEW MAX3238E/MAX3248E: IN SHUTDOWN, R1OUTB IS USED TO MONITOR
a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
EXTERNAL DEVICES AND R1OUT IS THREE STATED, ELIMINATING A CURRENT
PATH THROUGH THE UART'S PROTECTION DIODE.
V
V
CC
CC
GND
UART
GND
UART
TO
µP
PROTECTION
DIODE
PROTECTION
DIODE
Rx
Rx
Tx
Tx
TRANSITION
DETECTOR
LOGIC
SHDN = GND
FORCEOFF = GND
THREE-STATED
V
CC
I
V
R1OUTB
CC
R1OUT
T1IN
I
PREVIOUS
MAX3238E
MAX3248E
RS-232
5kΩ
5kΩ
R1IN
T1OUT
7