ISL4260E Intersil Corporation, ISL4260E Datasheet - Page 7

• Manufacturer Part Number: ISL4260E
• Description: QFN Packaged, 15kV Esd Protected, +3V to +5.5V, 150nA, 250kbps, RS-232 Transmitters/receivers With Separate Logic Supply
• 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 0.1µF 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 3 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 ISL4260E maintains the RS-232
transmitter output voltages even at high data rates. Figure 4
details a transmitter loopback test circuit, and Figure 5
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 6 shows the
loopback results for a single transmitter driving 1000pF and
an RS-232 load at 250kbps. The static transmitters were
also loaded with an RS-232 receiver.
5V/DIV
2V/DIV
FIGURE 3. TRANSMITTER OUTPUTS WHEN EXITING
V
C1 - C4 = 0.1µF
CC
= +3.3V
POWERDOWN
SHDN
TIME (20µs/DIV.)
7
CC
to ground with a
±
5V minimum
T2
T1
ISL4260E
1
.
5V/DIV.
5V/DIV.
R1
R1
T1
T1
T1
T1
OUT
OUT
OUT
OUT
FIGURE 4. TRANSMITTER LOOPBACK TEST CIRCUIT
IN
IN
V
V
C
C
CC
CC
1
2
V
C1 - C4 = 0.1µF
V
C1 - C4 = 0.1µF
+
+
CC
FIGURE 5. LOOPBACK TEST AT 120kbps
FIGURE 6. LOOPBACK TEST AT 250kbps
CC
= +3.3V
= +3.3V
0.1µF
C1+
C1-
C2+
C2-
T
R
SHDN
IN
OUT
+
V
ISL4260E
CC
2µs/DIV.
5µs/DIV.
V
T
L
OUT
R
V+
5k
V-
IN
+
+
C
C
1000pF
3
4