ICL3243EIA Datasheet, PDF (16/33 Pages) Intersil Corporation – ±15kV ESD Protected, +3V to +5.5V, 1μA, 250kbps, RS-232 Transmitters/Receivers

ICL3221E, ICL3222E, ICL3223E, ICL3232E, ICL3241E, ICL3243E
TABLE 2. POWER-DOWN AND ENABLE LOGIC TRUTH TABLE (Continued)
RS-232
SIGNAL
PRESENT
AT
RECEIVER
INPUT?
FORCEOFF
OR SHDN
INPUT
FORCEON
INPUT
EN
INPUT
TRANSMITTER
OUTPUTS
RECEIVER
OUTPUTS
R_OUTB
OUTPUTS
(NOTE 7)
INVALID
OUTPUT
MODE OF
OPERATION
ICL3221E, ICL3223E
No
H
H
L
Active
Active
N/A
L
Normal Operation
No
H
H
H
Active
High-Z
N/A
L
(Auto Power-Down Disabled)
Yes
H
Yes
H
L
L
Active
Active
N/A
H
Normal Operation
L
H
Active
High-Z
N/A
H
(Auto Power-Down Enabled)
No
H
No
H
L
L
High-Z
Active
N/A
L
Power-Down Due to Auto
L
H
High-Z
High-Z
N/A
L
Power-Down Logic
Yes
L
X
L
High-Z
Active
N/A
H
Manual Power-Down
Yes
L
X
H
High-Z
High-Z
N/A
H
Manual Power-Down
with Receiver Disabled
No
L
X
L
High-Z
Active
N/A
L
Manual Power-Down
No
L
X
H
High-Z
High-Z
N/A
L
Manual Power-Down
with Receiver Disabled
ICL3243E
No
H
H
N/A
Active
Active
Active
L
Normal Operation
(Auto Power-Down Disabled)
Yes
H
L
N/A
Active
Active
Active
H
Normal Operation
(Auto Power-Down Enabled)
No
H
L
N/A
High-Z
Active
Active
L
Power-Down Due to Auto
Power-Down Logic
Yes
L
X
N/A
High-Z
High-Z
Active
H
Manual Power-Down
No
L
X
N/A
High-Z
High-Z
Active
L
Manual Power-Down
NOTE:
7. Applies only to the ICL3241E and ICL3243E.
The INVALID output always indicates whether or not a
valid RS-232 signal is present at any of the receiver
inputs (see Table 2), giving the user an easy way to
determine when the interface block should power
down. In the case of a disconnected interface cable
where all the receiver inputs are floating (but pulled to
GND by the internal receiver pull down resistors), the
INVALID logic detects the invalid levels and drives the
output low. The power management logic then uses
this indicator to power down the interface block.
Reconnecting the cable restores valid levels at the
receiver inputs, INVALID switches high, and the power
management logic wakes up the interface block.
INVALID can also be used to indicate the DTR or RING
INDICATOR signal, as long as the other receiver inputs
are floating, or driven to GND (as in the case of a
powered down driver). Connecting FORCEOFF and
FORCEON together disables the automatic power-down
feature, enabling them to function as a manual
SHUTDOWN input (see Figure 4).
V_CC
V_CC
V_CC
CURRENT
FLOW
POWERED
DOWN
UART
GND
V_OUT = V_CC
Rx
Tx
SHDN = GND
OLD
RS-232 CHIP
FIGURE 2. POWER DRAIN THROUGH POWERED
DOWN PERIPHERAL
16
FN4910.21
February 22, 2010