ISL3232E Datasheet, PDF (10/14 Pages) Intersil Corporation – QFN Packaged, ±15kV ESD Protected, +2.7V to +5.5V, 150nA, 250kbps, RS-232 +2.7V to +5.5V, 150nA, 250kbps, RS-232

ISL3232E, ISL4221E, ISL4223E
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_CC to ground with a
capacitor of the same value as the charge-pump capacitor C₁.
Connect the bypass capacitor as close as possible to the IC.
Transmitter Outputs when Exiting
Power-down
Figure 8 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
ISL4221E, ISL4223E and ISL3232E 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 inter
operability with RS-232 devices.
High Data Rates
The ISL4221E, ISL4223E and ISL3232E maintain the RS-
232 ±5V minimum transmitter output voltages even at high
data rates. Figure 9 details a transmitter loopback test
circuit, and Figure 10 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 11 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.
V_CC
+
0.1µF
C₁ ⁺
C₂ ⁺
C1+
V_CC
V+
C1-
ISL4221E, ISL4223E
C2+
V-
C2-
T_IN
T_OUT
R_OUT
R_IN
+
C₃
+ ^C4
1000pF
V_CC
FORCEON
5k
FORCEOFF
FIGURE 9. TRANSMITTER LOOPBACK TEST CIRCUIT
5V/DIV
T1_IN
T1_OUT
R1_OUT
V_CC = +3.3V
C1 - C4 = 0.1µF
TIME (5µs/DIV)
FIGURE 10. LOOPBACK TEST AT 120kbps
5V/DIV
FORCEOFF
5V/DIV
T1
T1_IN
2V/DIV
T1_OUT
T2
V_CC = +3.3V
C1 - C4 = 0.1µF
TIME (20µs/DIV)
FIGURE 8. TRANSMITTER OUTPUTS WHEN EXITING
POWER-DOWN
R1_OUT
V_CC = +3.3V
C1 - C4 = 0.1µF
TIME (2µs/DIV)
FIGURE 11. LOOPBACK TEST AT 250kbps
10
FN6045.6
May 13, 2010