參數(shù)資料
型號: MAX3243E
廠商: Maxim Integrated Products, Inc.
英文描述: Replaced by TMS320F2808 : 16-bit , 5V fixed point DSP w/ Flash 64-QFP
中文描述: ±15kV ESD保護、1µA、3.0V至5.5V、250kbps RS-232收發(fā)器,帶有AutoShutdown
文件頁數(shù): 9/16頁
文件大小: 153K
代理商: MAX3243E
M
_______________________________________________________________________________________
9
1μA S upply-Current, True +3V to +5.5V
RS -232 Transc eivers with AutoS hutdown
Table 2 and Figure 3c summarize the MAX3221E/
MAX3223E/MAX3243E operating modes. FORCEON
and
FORCEOFF
override AutoShutdown. When neither
control is asserted, the IC selects between these states
automatically, based on receiver input levels. Figures
3a, 3b, and 5a depict valid and invalid RS-232 receiver
levels. Figure 5 shows the input levels and timing dia-
gram for AutoShutdown operation.
A mouse or other system with AutoShutdown may need
time to wake up. Figure 4 shows a circuit that forces the
transmitters on for 100ms, allowing enough time for the
other system to realize that the MAX3221E/MAX3223E/
MAX3243E are awake. If the other system transmits
valid RS-232 signals within that time, the RS-232 ports
on both systems remain enabled.
When shut down, the device’s charge pumps are off, V+
is pulled to V
CC
, V- is pulled to ground, and the trans-
mitter outputs are high impedance. The time required to
exit shutdown is typically 100μs (Figure 5b).
Software-Controlled Shutdown
If direct software control is desired,
INVALID
can be
used to indicate DTR or Ring Indicator signal. Connect
FORCEOFF
and FORCEON together to disable Auto-
Shutdown so the line acts like a
SHDN
input.
V-
V
CC
0
V+
0
V
CC
t
INVL
t
WU
INVALID
REGION
RECEIVER
INPUT
VOLTAGE
(V)
INVALID
OUTPUT
(V)
t
INVH
TRANSMITTERS ENABLED, INVALID HIGH
R
AUTOSHUTDOWN, TRANSMITTERS DISABLED,
1
μ
A SUPPLY CURRENT, INVALID LOW
TRANSMITTERS ENABLED, INVALID HIGH
-2.7V
-0.3V
+2.7V
+0.3V
0
INDETERMINATE
INDETERMINATE
b)
a)
Figure 5. AutoShutdown Trip Levels
FORCEON
MASTER SHDN LINE
0.1μF
1M
FORCEOFF
MAX3221E
MAX3223E
MAX3243E
POWER-
MANAGEMENT
UNIT
Figure 4. AutoShutdown with Initial Turn-On to Wake Up a
Mouse or Another System
FORCEOFF
POWER DOWN
INVALID
FORCEON
INVALID IS AN INTERNALLY GENERATED SIGNAL
THAT IS USED BY THE AUTOSHUTDOWN LOGIC
AND APPEARS AS AN OUTPUT OF THE DEVICE.
POWER DOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 3c. MAX32_ _E AutoShutdown Logic
Table 2.
INVALID
Truth Table
Low
No
High
Yes
INVALID
OUTPUT
RS-232 SIGNAL PRESENT
AT ANY RECEIVER INPUT
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