ICL3224 Intersil, ICL3224 Datasheet - Page 8

• Manufacturer Part Number: ICL3224
• Description: 1 Microamp/ +3V to +5.5V/ 250kbps/ RS-232 Transceivers with Enhanced Automatic Powerdown
• Manufacturer: Intersil

NOTES:
(not in powerdown mode). This is considerably less than the
5mA to 11mA current required of 5V RS-232 devices. The
already low current requirement drops significantly when the
device enters powerdown mode. In powerdown, supply
current drops to 1µA, because the on-chip charge pump
turns off (V+ collapses to V
the transmitter outputs tristate. Inverting receiver outputs
may or may not disable in powerdown; refer to Table 2 for
details. This micro-power mode makes these devices ideal
for battery powered and portable applications.
Software Controlled (Manual) Powerdown
These devices allow the user to force the IC into the low
power, standby state, and utilize a two pin approach where
the FORCEON and FORCEOFF inputs determine the IC’s
mode. For always enabled operation, FORCEON and
FORCEOFF are both strapped high. To switch between
ICL3224, ICL3226
ICL322X - INVALID DRIVING FORCEON AND FORCEOFF (EMULATES AUTOMATIC POWERDOWN)
ICL3238, ICL3244
ICL3238, ICL3244 - INVALID DRIVING FORCEON AND FORCEOFF (EMULATES AUTOMATIC POWERDOWN)
6. Applies only to the ICL3238 and ICL3244.
7. Input is connected to INVALID Output.
WITHIN 30
RCVR OR
XMTR
EDGE
SEC?
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
X
X
X
X
X
X
X
X
FORCEOFF
NOTE 7
NOTE 7
NOTE 7
NOTE 7
INPUT
H
H
H
H
H
H
H
H
H
H
H
H
L
L
L
L
FORCEON
CC
NOTE 7
NOTE 7
NOTE 7
NOTE 7
INPUT
, V- collapses to GND), and
8
H
H
H
H
L
L
L
L
X
X
L
L
L
L
X
X
TRANSMITTER
ICL3224, ICL3226, ICL3238, ICL3244
OUTPUTS
TABLE 2. POWERDOWN LOGIC TRUTH TABLE
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
Active
Active
RECEIVER
OUTPUTS
High-Z
High-Z
High-Z
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
OUTPUTS
(NOTE 6)
R
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
OUTB
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
N.A.
active and powerdown modes, under logic or software
control, only the FORCEOFF input need be driven. 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 enhanced automatic powerdown circuitry.
ICL3238 and ICL3244 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).
Connecting FORCEOFF and FORCEON together disables
the enhanced automatic powerdown feature, enabling them
to function as a manual SHUTDOWN input (see Figure 4).
With any of the above control schemes, the time required to
exit powerdown, and resume transmission is only 100µs.
RECEIVER
PRESENT
INPUT?
RS-232
LEVEL
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
AT
INVALID
OUTPUT
H
H
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
L
L
Normal Operation (Enhanced
Auto Powerdown Disabled)
Normal Operation (Enhanced
Auto Powerdown Enabled)
Powerdown Due to Enhanced
Auto Powerdown Logic
Manual Powerdown
Normal Operation
Forced Auto Powerdown
Normal Operation (Enhanced
Auto Powerdown Disabled)
Normal Operation (Enhanced
Auto Powerdown Enabled)
Powerdown Due to Enhanced
Auto Powerdown Logic
Manual Powerdown
Normal Operation
Forced Auto Powerdown
MODE OF OPERATION