13
FN4900.9
February 27, 2006
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 VIH for these logic families. See Table 4 for more
information.
±15kV ESD Protection
All pins on ICL32XX devices include ESD protection
structures, but the ICL32XXE family incorporates advanced
structures which allow the RS-232 pins (transmitter outputs
and receiver inputs) to survive ESD events up to
±15kV. The
RS-232 pins are particularly vulnerable to ESD damage
because they typically connect to an exposed port on the
exterior of the finished product. Simply touching the port
pins, or connecting a cable, can cause an ESD event that
might destroy unprotected ICs. These new ESD structures
protect the device whether or not it is powered up, protect
without allowing any latchup mechanism to activate, and
don’t interfere with RS-232 signals as large as
±25V.
FIGURE 12. TRANSMITTER LOOPBACK TEST CIRCUIT
FIGURE 13. LOOPBACK TEST AT 250kbps (CL = 1000pF)
ICL32XXE
VCC
C1
C2
C4
C3
+
CL
V+
V-
5k
TIN
ROUT
C1+
C1-
C2+
C2-
RIN
TOUT
+
VCC
0.1
F
VCC
FORCEOFF
FORCEON
T1IN
T1OUT
R1OUT
2
s/DIV.
VCC = +3.3V
5V/DIV.
C1 - C4 = 0.1
F
FIGURE 14. LOOPBACK TEST AT 1Mbps (CL = 250pF)
TABLE 4. LOGIC FAMILY COMPATIBILITY WITH VARIOUS
SUPPLY VOLTAGES
SYSTEM
POWER-SUPPLY
VOLTAGE
(V)
VCC
SUPPLY
VOLTAGE
(V)
COMPATIBILITY
3.3
Compatible with all CMOS
families.
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.
T1IN
T1OUT
R1OUT
0.5
s/DIV.
5V/DIV.
VCC = +3.3V
C1 - C4 = 0.1
F
ICL3225E, ICL3227E, ICL3245E