ICL3221 INTERSIL [Intersil Corporation], ICL3221 Datasheet - Page 12

• Manufacturer Part Number: ICL3221
• Description: 1 Microamp Supply-Current, +3V to +5.5V, 250kbps, RS-232 Transmitters/Receivers
• Manufacturer: INTERSIL [Intersil Corporation]

The FORCEON state isn’t critical, as FORCEOFF
dominates over FORCEON. Nevertheless, if strictly manual
control over powerdown is desired, the user must strap
FORCEON high to disable the automatic powerdown
circuitry. Inverting (standard) receiver outputs also disable
when the device is in powerdown, thereby eliminating the
possible current path through a shutdown peripheral’s input
protection diode (see Figures 2 and 3).
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
NOTE:
ICL3222, ICL3241
ICL3221, ICL3223
ICL3243
4. Applies only to the ICL3241 and ICL3243.
RECEIVER
PRESENT
SIGNAL
INPUT?
RS-232
YES
YES
YES
YES
YES
YES
N.A.
N.A.
N.A.
N.A.
NO
NO
NO
NO
NO
NO
NO
NO
NO
AT
FORCEOFF
OR SHDN
INPUT
H
H
H
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
FORCEON
3-12
INPUT
N.A.
N.A.
N.A.
N.A.
H
H
X
X
X
X
H
X
X
L
L
L
L
L
L
TABLE 2. POWERDOWN AND ENABLE LOGIC TRUTH TABLE
INPUT
N.A.
N.A.
N.A.
N.A.
N.A.
EN
H
H
H
H
H
H
H
L
L
L
L
L
L
L
TRANSMITTER
OUTPUTS
ICL3221 thru ICL3243
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
Active
Active
Active
Active
Active
Active
Active
Active
RECEIVER
OUTPUTS
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
High-Z
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
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 powerdown feature, enabling them to function as
a manual SHUTDOWN input (see Figure 4).
OUTPUTS
(NOTE 4)
R
Active
Active
Active
Active
Active
Active
Active
Active
Active
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
OUTB
OUTPUT
INVALID
N.A.
N.A.
N.A.
N.A.
H
H
H
H
H
H
L
L
L
L
L
L
L
L
L
Manual Powerdown
Manual Powerdown w/Rcvr. Disabled
Normal Operation
Normal Operation w/Rcvr. Disabled
Normal Operation
(Auto Powerdown Disabled)
Normal Operation
(Auto Powerdown Enabled)
Powerdown Due to Auto Powerdown
Logic
Manual Powerdown
Manual Powerdown w/Rcvr. Disabled
Manual Powerdown
Manual Powerdown w/Rcvr. Disabled
Normal Operation
(Auto Powerdown Disabled)
Normal Operation
(Auto Powerdown Enabled)
Powerdown Due to Auto Powerdown
Logic
Manual Powerdown
Manual Powerdown
MODE OF OPERATION