icl3238e Intersil Corporation, icl3238e Datasheet - Page 10

• Manufacturer Part Number: icl3238e
• Description: ?15kv Esd Protected, +3v To +5.5v, 1?a, 250kbps, Rs-232 Transceivers With Enhanced Automatic Powerdown
• Manufacturer: Intersil Corporation

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
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.
Operation Down to 2.7V
ICL3238E transmitter outputs meet RS-562 levels (
full data rate, with V
typically ensure inter operability with RS-232 devices.
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 3kΩ in parallel with 2500pF. Note
that the transmitters enable only when the magnitude of the
supplies exceed approximately 3V.
High Data Rates
The ICL3238E maintains the RS-232
transmitter output voltages even at high data rates. Figure
11 details a transmitter loopback test circuit, and Figure 12
illustrates the loopback test result at 120kbps. For this test,
all transmitters were simultaneously driving RS-232 loads in
parallel with 1000pF, at 120kbps. Figure 13 shows the
loopback results for a single transmitter driving 1000pF and
5V/DIV
2V/DIV
FIGURE 10. TRANSMITTER OUTPUTS WHEN EXITING
V
C1 - C4 = 0.1µF
CC
= +3.3V
POWERDOWN
FORCEOFF
CC
as low as 2.7V. RS-562 levels
TIME (20µs/DIV.)
µ
10
F bypass capacitor is
CC
to ground with a
±
5V minimum
±
T2
T1
3.7V), at
ICL3238E
1
.
an RS-232 load at 250kbps. The static transmitters were
also loaded with an RS-232 receiver.
5V/DIV.
5V/DIV.
R1
R1
T1
T1
FIGURE 11. TRANSMITTER LOOPBACK TEST CIRCUIT
T1
T1
OUT
OUT
OUT
OUT
IN
IN
V
V
C
C
CC
CC
1
2
V
C1 - C4 = 0.1µF
V
C1 - C4 = 0.1µF
+
+
FIGURE 12. LOOPBACK TEST AT 120kbps
FIGURE 13. LOOPBACK TEST AT 250kbps
CC
CC
= +3.3V
= +3.3V
0.1µF
C1+
C1-
C2+
C2-
T
R
FORCEON
FORCEOFF
IN
OUT
+
ICL3238E
V
CC
2µs/DIV.
5µs/DIV.
T
OUT
R
V+
5k
V-
IN
+
+
C
C
1000pF
3
4