MAX13223E Datasheet, PDF (8/11 Pages) Maxim Integrated Products – ±70V Fault-Protected, 3.0V to 5.5V, 2Tx/2Rx RS-232 Transceiver

±70V Fault-Protected, 3.0V to 5.5V,
2Tx/2Rx RS-232 Transceiver
POWER-
MANAGEMENT
UNIT OR CPU
FORCEOFF
FORCEON
INVALID
MAX13223E
UART
RS-232
Figure 5. Interface Under Control of PMU
Table 1. Receiver Control Truth Table
EN
R_OUT
0
Active
1
High Impedence
a)
+2.7V
+0.3V
0
-0.3V
-2.7V
b)
RECEIVER
INPUT
VOLTAGE
(V)
+2.7V
+0.3V
-0.3V
-2.7V
V_CC
INVALID
OUTPUT
(V)
0
V+
V_CC
0
V-
TRANSMITTER ENABLED, INVALID HIGH
INDETERMINATE
AutoShutdown, TRANSMITTER DISABLED,
1µA SUPPLY CURRENT
INDETERMINATE
TRANSMITTER ENABLED, INVALID HIGH
INVALID
REGION
t_INVL
t_INVH
t_WU
AutoShutdown
The MAX13223E achieves 1µA supply current with
Maxim’s AutoShutdown feature, which operates when
FORCEON is low and FORCEOFF is high. When the
device senses no valid signal levels on both receiver
inputs for > 30µs (typ), the onboard charge pump and
drivers are shut off, reducing supply current to 1µA.
This occurs if the RS-232 cable is disconnected or the
connected peripheral transmitters are turned off. The
device turns on again when a valid level is applied to
either RS-232 receiver input. As a result, the system
saves power. Table 2 summarizes the MAX13223E’s
operating modes. FORCEON and FORCEOFF override
Figures 6a and 6b. Trip Levels for Entering and Exiting
AutoShutdown
AutoShutdown. When neither control is asserted, the IC
selects between these states automatically, based on
receiver input levels. Figure 6a shows the input levels
and Figure 6b shows the timing diagram for
AutoShutdown operation.
Software-Controlled Shutdown
If direct software control is desired, INVALID can be
used to indicate a DTR or Ring indicator signal.
Connect FORCEOFF and FORCEON together to bypass
AutoShutdown; therefore, the line acts as a SHDN input.
8 _______________________________________________________________________________________