8

The ICL3244E inverting receivers disable during forced

(manual) powerdown, but not during automatic powerdown

(see Table 2). Conversely, the monitor receiver remains

active even during manual powerdown making it extremely

useful for Ring Indicator monitoring. Standard receivers

driving powered down peripherals must be disabled to

prevent current flow through the peripheral’s protection

diodes (see Figures 2 and 3). This renders them useless for

wake up functions, but the corresponding monitor receiver

can be dedicated to this task as shown in Figure 3.

TABLE 2. POWERDOWN LOGIC TRUTH TABLE

RCVR OR

XMTR

EDGE

WITHIN 30

SEC?

FORCEOFF

INPUT

FORCEON

INPUT

TRANSMITTER

OUTPUTS

RECEIVER

OUTPUTS

(NOTE 3)

OUTPUTS

RS-232

LEVEL

PRESENT

AT

RECEIVER

INPUT?

INVALID

OUTPUT

MODE OF OPERATION

ICL3224E, ICL3226E

NO

H

H

Active

Active

N.A.

NO

L

Normal Operation (Enhanced

Auto Powerdown Disabled)

NO

H

H

Active

Active

N.A.

YES

H

YES

H

L

Active

Active

N.A.

NO

L

Normal Operation (Enhanced

Auto Powerdown Enabled)

YES

H

L

Active

Active

N.A.

YES

H

NO

H

L

High-Z

Active

N.A.

NO

L

Powerdown Due to Enhanced

Auto Powerdown Logic

NO

H

L

High-Z

Active

N.A.

YES

H

X

L

X

High-Z

Active

N.A.

NO

L

Manual Powerdown

X

L

X

High-Z

Active

N.A.

YES

H

ICL322XE - INVALID DRIVING FORCEON AND FORCEOFF (EMULATES AUTOMATIC POWERDOWN)

X

NOTE 4

NOTE 4

Active

Active

N.A.

YES

H

Normal Operation

X

NOTE 4

NOTE 4

High-Z

Active

N.A.

NO

L

Forced Auto Powerdown

ICL3244E

NO

H

H

Active

Active

Active

NO

L

Normal Operation (Enhanced

Auto Powerdown Disabled)

NO

H

H

Active

Active

Active

YES

H

YES

H

L

Active

Active

Active

NO

L

Normal Operation (Enhanced

Auto Powerdown Enabled)

YES

H

L

Active

Active

Active

YES

H

NO

H

L

High-Z

Active

Active

NO

L

Powerdown Due to Enhanced

Auto Powerdown Logic

NO

H

L

High-Z

Active

Active

YES

H

X

L

X

High-Z

High-Z

Active

NO

L

Manual Powerdown

X

L

X

High-Z

High-Z

Active

YES

H

ICL3244E - INVALID DRIVING FORCEON AND FORCEOFF (EMULATES AUTOMATIC POWERDOWN)

X

NOTE 4

NOTE 4

Active

Active

Active

YES

H

Normal Operation

X

NOTE 4

NOTE 4

High-Z

High-Z

Active

NO

L

Forced Auto Powerdown

NOTES:

3. Applies only to the ICL3244E.

4. Input is connected to INVALID Output.

ICL3224E, ICL3226E, ICL3244E