MAX3224 Maxim, MAX3224 Datasheet - Page 9

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

The MAX3244/MAX3245 feature an extra, always
active, noninverting output, R2OUTB. R2OUTB output
monitors receiver activity while the other receivers are
high impedance, allowing Ring Indicator applications to
be monitored without forward biasing other devices
connected to the receiver outputs. This is ideal for sys-
tems where V
accommodate peripherals such as UARTs (Figure 2).
The MAX3224–MAX3227/MAX3244/MAX3245 feature
an INVALID output that is enabled low when no valid
RS-232 voltage levels have been detected on all
receiver inputs. Because INVALID indicates the receiv-
er input’s condition, it is independent of FORCEON and
FORCEOFF states (Figures 3 and 4).
Table 1. Output Control Truth Table
X = Don’t care
* INVALID connected to FORCEON
** INVALID connected to FORCEON and FORCEOFF
(AutoShutdown)
Shutdown
(Forced Off)
Normal
Operation
(Forced On)
Normal
Operation
(AutoShutdown
Plus)
Shutdown (Auto-
Shutdown Plus)
Normal
Operation
Normal
Operation
Shutdown
Normal
Operation
(AutoShutdown)
Shutdown
OPERATION
STATUS
RS-232 Transceivers with AutoShutdown Plus
CC
FORCEON
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
INVALID*
INVALID*
INVALID*
INVALID*
INVALID*
_______________________________________________________________________________________
is set to ground in shutdown to
X
1
0
0
FORCEOFF
INVALID**
INVALID**
0
1
1
1
1
1
1
RECEIVER
LEVEL
VALID
Yes
Yes
No
No
X
X
X
X
X
TRANSMITTER
RECEIVER OR
EDGE WITHIN
30sec
Yes
Yes
No
No
X
X
X
X
X
The MAX3224–MAX3227/MAX3244/MAX3245 achieve a
1µA supply current with Maxim’s AutoShutdown
Plusfeature, which operates when FORCEOFF is high
and a FORCEON is low. When these devices do not
sense a valid signal transition on any receiver and trans-
mitter input for 30sec, the on-board charge pumps are
shut down, reducing supply current to 1µA. This occurs
if the RS-232 cable is disconnected or if the connected
peripheral transmitters are turned off, and the UART dri-
ving the transmitter inputs is inactive. The system turns
on again when a valid transition is applied to any
RS-232 receiver or transmitter input. As a result, the sys-
tem saves power without changes to the existing BIOS
or operating system.
T_OUT
High-Z
High-Z
High-Z
High-Z
Active
Active
Active
Active
Active
(MAX3224/
MAX3225/
MAX3226/
MAX3227)
R_OUT
Active
Active
Active
Active
Active
Active
Active
Active
Active
AutoShutdown Plus Mode
(MAX3244/
MAX3245)
R_OUT
High-Z
High-Z
Active
Active
Active
Active
Active
Active
Active
(MAX3244/
MAX3245)
R2OUTB
Active
Active
Active
Active
Active
Active
Active
Active
Active
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