12
High Data Rates
The ICL32XX maintain the RS-232
±
5V minimum transmitter
output voltages even at high data rates. Figure 12 details a
transmitter loopback test circuit, and Figure 13 illustrates the
loopback test result at 250kbps. For this test, all transmitters
were simultaneously driving RS-232 loads in parallel with
1000pF, at 250kbps. Figure 14 shows the loopback results
for a single transmitter driving 250pF and an RS-232 load at
1Mbps. The static transmitters were also loaded with an
RS-232 receiver.
Interconnection with 3V and 5V Logic
The ICL32XXE directly interfaces with 5V CMOS and TTL
logic families. Nevertheless, with the ICL32XX at 3.3V, and
the logic supply at 5V, AC, HC, and CD4000 outputs can
drive ICL32XX inputs, but ICL32XX outputs do not reach the
minimum V
IH
for these logic families. See Table 4 for more
information.
FIGURE 12. TRANSMITTER LOOPBACK TEST CIRCUIT
FIGURE 13. LOOPBACK TEST AT 250kbps (C
L
= 1000pF)
ICL32XX
V
CC
C
1
C
2
C
4
+
C
3
+
+
+
C
L
V+
V-
5K
T
IN
R
OUT
C1+
C1-
C2+
C2-
R
IN
T
OUT
+
V
CC
0.1
μ
F
V
CC
FORCEOFF
FORCEON
T1
IN
T1
OUT
R1
OUT
2
μ
s/DIV.
V
CC
= +3.3V
C1 - C4 = 0.1
μ
F
5V/DIV.
FIGURE 14. LOOPBACK TEST AT 1Mbps (C
L
= 250pF)
TABLE 4. LOGIC FAMILY COMPATIBILITY WITH VARIOUS
SUPPLY VOLTAGES
SYSTEM
POWER-SUPPLY
VOLTAGE
(V)
V
CC
SUPPLY
VOLTAGE
(V)
COMPATIBILITY
3.3
3.3
Compatible with all CMOS
families.
5
5
Compatible with all TTL and
CMOS logic families.
5
3.3
Compatible with ACT and HCT
CMOS, and with TTL. ICL32XX
outputs are incompatible with AC,
HC, and CD4000 CMOS inputs.
T1
IN
T1
OUT
R1
OUT
0.5
μ
s/DIV.
5V/DIV.
V
CC
= +3.3V
C1 - C4 = 0.1
μ
F
ICL3225, ICL3245