ISL83387E Intersil Corporation, ISL83387E Datasheet - Page 7

• Manufacturer Part Number: ISL83387E
• Description: +/-15kV ESD Protected/+3#V to +5.5V/ 1Microamp/ 250kbps/ RS-232 Transceivers with Enhanced Automatic Powerdown and a Separate Logic Supply
• Manufacturer: Intersil Corporation

NOTES:
mode an RC time constant after this rising edge. The time
constant isn’t critical, because the ISL83387E remains
powered up for 30 seconds after the FORCEON falling
edge, even if there are no signal transitions. This gives slow-
to-wake systems (e.g., a mouse) plenty of time to start
transmitting, and as long as it starts transmitting within 30
seconds both systems remain enabled.
INVALID DRIVING FORCEON AND FORCEOFF (EMULATES AUTOMATIC POWERDOWN)
EDGE WITHIN 30
3. Input is connected to INVALID Output.
RCVR OR XMTR
FIGURE 2. CONNECTIONS FOR MANUAL POWERDOWN
SEC?
YES
YES
NO
NO
NO
NO
CPU
X
X
X
X
LOGIC
PWR
MGT
FORCEOFF
NOTE 3
NOTE 3
INVALID
INPUT
UART
I/O
V
H
H
H
H
H
H
L
L
CC
I/O CHIP
POWER SUPPLY
FORCEOFF, FORCEON
7
FORCEON
NOTE 3
NOTE 3
INPUT
H
H
X
X
L
L
L
L
V
L
ISL83387E
TABLE 2. POWERDOWN LOGIC TRUTH TABLE
TRANSMITTER
OUTPUTS
High-Z
High-Z
High-Z
High-Z
High-Z
Active
Active
Active
Active
Active
ISL83387E
RECEIVER
OUTPUTS
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
V
Unlike other RS-232 interface devices where the CMOS
outputs swing between 0 and V
a separate logic supply input (V
V
Connecting V
prevents the ISL83387E outputs from forward biasing the
input diodes of a logic device powered by that lower supply.
Connecting V
that the receiver and INVALID output levels are compatible
even with the CMOS input V
devices. Note that the V
with V
powers the transmitter and logic inputs, thereby setting their
switching thresholds to levels compatible with the logic
supply. This separate logic supply pin allows a great deal of
flexibility in interfacing to systems with different logic
supplies. If logic translation isn’t required, connect V
ISL83387E V
INVALID Output
The INVALID output always indicates (see Table 2) whether
or not 30 s have elapsed with invalid RS-232 signals (see
RECEIVER INPUT?
CC
L
FIGURE 3. CIRCUIT TO ENSURE IMMEDIATE POWER UP
RS-232 LEVEL
PRESENT AT
MANAGEMENT
Logic Supply Input
) that sets V
L
POWER
= 5V and V
YES
YES
YES
YES
YES
UNIT
NO
NO
NO
NO
NO
CC
WHEN EXITING FORCED POWERDOWN
L
L
to a host logic supply lower than V
to a logic supply greater than V
.
OH
CC
for the receiver and INVALID outputs.
OUTPUT
INVALID
MASTER POWERDOWN LINE
= 3.3V (see Figure 16). V
L
H
H
H
H
H
L
L
L
L
L
supply current increases to 100 A
FORCEOFF
IH
of AC, HC, and CD4000
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
CC
L
; 1.8V to 5V, regardless of
, the ISL83387E features
MODE OF OPERATION
ISL83387E
0.1 F
FORCEON
CC
1M
L
CC
also
ensures
L
,
to the