參數(shù)資料
型號: ISL4244E
廠商: Intersil Corporation
英文描述: QFN Packaged, ±15kV ESD Protected, +2.7V to +5.5V, 10Nanoamp, 250kbps/1Mbps, RS-232 Transceivers with Enhanced Automatic Powerdown(QFN封裝, ±15kV ESD 防護(hù), +2.7V至+5.5V, 10Nanoamp, 250kbps/1Mbps, 具有自動斷電功能的RS-232收發(fā)器)
中文描述: QFN封裝,具有± 15kV ESD保護(hù),2.7V至5.5V,10Nanoamp,250kbps/1Mbps,RS - 232接口的增強(qiáng)型自動掉電封裝(QFN封裝,具有± 15kV ESD防護(hù),收發(fā)器為2.7V至5.5V之間,10Nanoamp,250kbps/1Mbps,具有自動斷電功能的RS - 232接口收發(fā)器)
文件頁數(shù): 12/17頁
文件大小: 457K
代理商: ISL4244E
12
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 ISL4238E/4XE 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 0.1
μ
F, 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
μ
F capacitors
for proper operation. Increasing the capacitor values (by a
factor of 2) reduces ripple on the transmitter outputs and
slightly reduces power consumption. C
2
, C
3
, and C
4
can be
increased without increasing C
1
’s value, however, do not
increase C
1
without also increasing C
2
, C
3
, and C
4
to
maintain the proper ratios (C
1
to the other capacitors).
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 0.1
μ
F bypass capacitor is
adequate. In applications that are particularly sensitive to
power supply noise, decouple V
CC
to ground with a
capacitor of the same value as the charge-pump capacitor C
1
.
Connect the bypass capacitor as close as possible to the IC.
Transmitter Outputs when Exiting
Powerdown
Figure 10 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 3k
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/4XE transmitter outputs meet RS-562 levels
(
±
3.7V), at the full data rate, with V
CC
as low as 2.7V.
RS-562 levels typically ensure interoperability with RS-232
devices.
RECEIVER
INPUTS
TRANSMITTER
OUTPUTS
INVALID
OUTPUT
V+
V
CC
0
V-
t
INVL
t
INVH
FIGURE 9. ENHANCED AUTOMATIC POWERDOWN AND INVALID TIMING DIAGRAMS
OUTPUT
TRANSMITTER
INPUTS
t
WU
t
AUTOPWDN
t
AUTOPWDN
t
WU
INVALID
REGION
}
TABLE 3. REQUIRED CAPACITOR VALUES (ISL4238E)
V
CC
(V)
C
1
(
μ
F)
C
2
, C
3
, C
4
(
μ
F)
3.0 to 3.6 (3.3V
±
10%)
0.22
0.22
3.15 to 3.6 (3.3V
±
5%)
0.1
0.1
4.5 to 5.5
0.047
0.33
3.0 to 5.5
0.22
1
ISL4238E, ISL4244E, ISL4245E
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