1 µA S u p p ly Cu rre n t , 1 Mb p s , 3 .0 V t o 5 .5 V,
RS -2 3 2 Tra n s c e ive rs w it h Au t o S h u t d o w n P lu s
–7/MAX3245
Table 1. Output Control Truth Table
R_OUT
RECEIVER OR
VALID
RECEIVER
LEVEL
(MAX3224/
MAX3225/
MAX3226/
MAX3227)
R_OUT
(MAX3244/
MAX3245)
R2OUTB
(MAX3244/
MAX3245)
OPERATION
STATUS
TRANSMITTER
EDGE WITHIN
30sec
FORCEON
T_OUT
FORCEOFF
Shutdown
(Forced Off)
X
1
0
1
X
X
X
X
High-Z
Active
Active
Active
High-Z
Active
Active
Active
Normal
Operation
(Forced On)
Normal
Operation
(AutoShutdown
Plus)
0
1
X
Yes
Active
Active
Active
Active
Shutdown (Auto-
Shutdown Plus)
0
1
1
X
No
X
High-Z
Active
Active
Active
Active
Active
Active
Active
Normal
Operation
Yes
INVALID*
Normal
Operation
1
1
X
Yes
No
Active
Active
Active
Active
Active
Active
Active
INVALID*
INVALID*
Shutdown
No
High-Z
Normal
Operation
(AutoShutdown)
Yes
No
X
X
Active
Active
Active
Active
Active
Active
INVALID*
INVALID*
INVALID**
INVALID**
Shutdown
(AutoShutdown)
High-Z
High-Z
X = Don’t care
* INVALID connected to FORCEON
** INVALID connected to FORCEON and FORCEOFF
The MAX3244/MAX3245 fe a ture a n e xtra , a lwa ys
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-
Au t o S h u t d o w n P lu s Mo d e
The MAX3224–MAX3227/MAX3244/MAX3245 achieve a
1µA s up p ly c urre nt with Ma xim’s AutoShutd own
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 a g a in whe n a va lid tra ns ition is a p p lie d to a ny
RS-232 receiver or transmitter input. As a result, the sys-
tem saves power without changes to the existing BIOS
or operating system.
te ms whe re V
is s e t to g round in s hutd own to
CC
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 volta g e le ve ls ha ve b e e n d e te c te d on a ll
receiver inputs. Because INVALID indicates the receiv-
er input’s condition, it is independent of FORCEON and
FORCEOFF states (Figures 3 and 4).
_______________________________________________________________________________________
9
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
