ISL4244EIR-T Intersil, ISL4244EIR-T Datasheet - Page 12

• Manufacturer Part Number: ISL4244EIR-T
• Description: IC 3DRVR/5RCVR RS232 3V 32-QFN
• Manufacturer: Intersil
• Type: Transceiverr

Specifications of ISL4244EIR-T

• Number Of Drivers/receivers: 3/5
• Protocol: RS232
• Voltage - Supply: 2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 32-VQFN Exposed Pad, 32-HVQFN, 32-SQFN, 32-DHVQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Hybrid Automatic Power-down 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 power-down 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
ISL4238E, ISL4244E, ISL4245 remains powered down until the
cable is reconnected (INVALID = FORCEOFF = 1) and a
transition occurs on a receiver or transmitter input (see Figure
7). For immediate power up when the cable is reattached,
connect FORCEON to FORCEOFF through a network similar
to that shown in Figure 5.
Capacitor Selection
The ISL4238E charge pumps require 0.1μF, or greater,
capacitors for 3.3V (5% tolerance) operation. For other
supply voltages refer to Table 3 for capacitor values. Do not
use values smaller than those listed in Table 3.
The ISL4244E/45E charge pumps require 0.1
for proper operation. Increasing the capacitor values (by a
factor of 2) reduces ripple on the transmitter outputs and
3.0 to 3.6 (3.3V ±10%)
3.15 to 3.6 (3.3V ±5%)
TRANSMITTER
TRANSMITTER
TABLE 3. REQUIRED CAPACITOR VALUES (ISL4238E)
RECEIVER
OUTPUTS
4.5 to 5.5
3.0 to 5.5
OUTPUT
OUTPUT
V
INVALID
INPUTS
INPUTS
CC
V
(V)
CC
V+
V-
0
t
INVL
FIGURE 9. ENHANCED AUTOMATIC POWER-DOWN AND INVALID TIMING DIAGRAMS
C
0.047
1
0.22
0.22
12
0.1
(µF)
t
INVH
C
ISL4238E, ISL4244E, ISL4245E
2
, C
µ
t
AUTOPWDN
F capacitors
3
0.22
0.33
0.1
, C
1
4
(µF)
slightly reduces power consumption. C
increased without increasing C
increase C
maintain the proper ratios (C
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
Power-down
Figure 10 shows the response of two transmitter outputs
when exiting power-down 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.
Operation Down to 2.7V
ISL4238E, ISL4244E, ISL4245 transmitter outputs meet
RS-562 levels (±3.7V), at the full data rate, with V
as 2.7V. RS-562 levels typically ensure interoperability with
RS-232 devices.
t
WU
1
t
AUTOPWDN
without also increasing C
1
to the other capacitors).
1
’s value, however, do not
CC
t
to ground with a
WU
2
2
, C
, C
3
3
, and C
, and C
}
CC
INVALID
REGION
4
May 13, 2010
4
to
can be
as low
FN8038.5
1
.