ISL83387EIV-T Intersil, ISL83387EIV-T Datasheet - Page 9

• Manufacturer Part Number: ISL83387EIV-T
• Description: IC 3DRVR/3RCVR RS232 3V 24-TSSOP
• Manufacturer: Intersil
• Type: Transceiverr

Specifications of ISL83387EIV-T

• Number Of Drivers/receivers: 3/3
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 24-TSSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

RS-232 level, forcing the ISL83387E to power on. See the
“INVALID DRIVING FORCEON AND FORCEOFF” section
of Table 2 for an operational summary. This operational
mode is perfect for handheld devices that communicate with
another computer via a detachable cable. Detaching the
cable allows the internal receiver pull-down resistors to pull
the inputs to GND (an invalid RS-232 level), causing the
30µs timer to time-out and drive the IC into powerdown.
Reconnecting the cable restores valid levels, causing the IC
to power back up.
Hybrid Automatic Powerdown Options
For devices which communicate only through a detachable
cable, connecting INVALID to FORCEOFF (with
FORCEON = 0) may be a desirable configuration. While the
cable is attached INVALID and FORCEOFF remain high, so
the enhanced automatic powerdown logic powers down the
RS-232 device whenever there is 30 seconds of inactivity on
the receiver and transmitter inputs. Detaching the cable
allows the receiver inputs to drop to an invalid level (GND),
so INVALID switches low and forces the RS-232 device to
power down. The ISL83387E remains powered down until
the cable is reconnected (INVALID = FORCEOFF = 1) and a
transition occurs on a receiver or transmitter input (see
Figure 5). For immediate power up when the cable is
reattached, connect FORCEON to FORCEOFF through a
network similar to that shown in Figure 3.
Capacitor Selection
The ISL83387E charge pumps require only 0.1µF capacitors
for the full operational voltage range. Table 3 lists other
acceptable capacitor values for various supply voltage
ranges. Do not use values smaller than those listed in
Table 3. Increasing the capacitor values (by a factor of 2)
TRANSMITTER
TRANSMITTER
RECEIVER
OUTPUTS
OUTPUT
INVALID
INPUTS
INPUTS
V
CC
V+
V-
0
t
INVL
FIGURE 7. ENHANCED AUTOMATIC POWERDOWN AND INVALID TIMING DIAGRAMS
9
t
INVH
t
AUTOPWDN
ISL83387E
reduces ripple on the transmitter outputs and slightly
reduces power consumption.
When using minimum required capacitor values, make sure
that capacitor values do not degrade excessively with
temperature. If in doubt, use capacitors with a larger nominal
value. The capacitor’s equivalent series resistance (ESR)
usually rises at low temperatures and it influences the
amount of ripple on V+ and V-.
Power Supply Decoupling
In most circumstances a 0.1µF bypass capacitor is
adequate. In applications that are particularly sensitive to
power supply noise, decouple V
capacitor of the same value as the charge-pump capacitor C
Connect the bypass capacitor as close as possible to the IC.
Transmitter Outputs when Exiting
Powerdown
Figure 8 shows the response of two transmitter outputs
when exiting powerdown mode. As they activate, the two
transmitter outputs properly go to opposite RS-232 levels,
with no glitching, ringing, nor undesirable transients. Each
transmitter is loaded with 3kΩ in parallel with 2500pF. Note
that the transmitters enable only when the magnitude of the
supplies exceed approximately 3V.
t
WU
3.0 to 3.6
4.5 to 5.5
3.0 to 5.5
V
TABLE 3. REQUIRED CAPACITOR VALUES
(V)
CC
t
AUTOPWDN
0.047
(µF)
0.22
0.1
C
1
CC
to ground with a
t
WU
C
2
, C
0.33
(µF)
0.1
1
}
3
, C
INVALID
REGION
July 8, 2005
4
FN6040.1
1
.