MAX3212CWI Maxim Integrated, MAX3212CWI Datasheet - Page 7

• Manufacturer Part Number: MAX3212CWI
• Description: RS-232 Interface IC
• Manufacturer: Maxim Integrated
• Series: MAX3212r

Specifications of MAX3212CWI

• Data Rate: 235 Kbps
• Operating Supply Voltage: 2.7 V to 3.6 V
• Supply Current: 3 mA
• Operating Temperature Range: 0 C to + 70 C
• Function: Transceiver
• Number Of Drivers: 3
• Number Of I/os: 17
• Number Of Receivers: 5
• Propagation Delay Time Ns: 2 us
• Shutdown: Yes

A 1µA supply current is achieved with Maxim’s new
AutoShutdown feature, which operates when
FORCEON is low and FORCEOFF is high. When the
MAX3212 senses no valid signal level on any receiver
input for typically 30µs, the on-board power supply and
drivers shut down. Internal 5kΩ resistors pull the receiv-
er inputs to ground, disabling the transmitters and
reducing supply current to 1 µA when the device is in
AutoShutdown mode. 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 level is applied to any RS-232 receiver input. As a
result, the system saves power without changes to the
existing BIOS or operating system. When using the
AutoShutdown feature, INVALID is high when the
device is on and low when the device is shut down. The
INVALID output indicates the condition of the receiver
inputs; INVALID can be used in any mode.
Figure 1. Interface Under Control of PMU
MANAGEMENT
CONTROLLER
KEYBOARD
UNIT OR
POWER
CPU
+2.7V to +3.6V-Powered, 1µA Supply Current,
3-Driver/5-Receiver, True RS-232 Transceiver
_______________________________________________________________________________________
FORCEOFF
WITH
UART
CHIP
FORCEON
INVALID
I/O
MAX3212
AutoShutdown
RS-232
Figure 2. Detection of RS-232 Activity when the UART and
Interface Are Shut Down: MAX3212 (b) vs. Previous
Transceivers (a)
b) NEW MAX3212: EN SHUTS DOWN RECEIVER OUTPUTS (EXCEPT FOR R5OUTB)
a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM
SO NO CURRENT FLOWS TO UART IN SHUTDOWN. R5OUTB INDICATES RECEIVER
ACTIVITY DURING SHUTDOWN WITH EN HIGH.
ACTIVE RECEIVER OUTPUT IN SHUTDOWN.
V
V
CC
CC
UART
GND
GND
UART
ESD
PROTECTION
DIODE
TO
ESD
PROTECTION
DIODE
P
TRANSITION
DETECTOR
LOGIC
Rx
Rx
Tx
Tx
V
SHDN = LOW
SHDN = LOW
CC
EN = LOW
V
R5OUTB
CC
R5OUT
T1IN
PREVIOUS
MAX3212
RS-232
5k
5k
T1OUT
R5IN
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