13
FN4876.10
March 1, 2006
1000pF, at 120kbps. Figure 14 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.
Interconnection with 3V and 5V Logic
The ICL32XX directly interface 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 120kbps
ICL32XX
V
CC
FORCEOFF
C
1
C
2
C
4
C
3
+
+
+
+
1000pF
V+
V-
5K
T
IN
R
OUT
C1+
C1-
C2+
C2-
R
IN
T
OUT
+
V
CC
0.1µF
V
CC
FORCEON
T1
IN
T1
OUT
R1
OUT
5µs/DIV.
V
CC
= +3.3V
5V/DIV.
C1 - C4 = 0.1µF
FIGURE 14. LOOPBACK TEST AT 250kbps
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
2µs/DIV.
5V/DIV.
V
CC
= +3.3V
C1 - C4 = 0.1µF
ICL3224, ICL3226, ICL3238, ICL3244
