ICL3221EM, ICL3221EF

4. Application Information

FN7552 Rev.2.00

Page 16 of 22

May.29.19

4.11 High Data Rates

The ICL3221EM and ICL3221EF maintain the RS-232 ±5V minimum transmitter output voltages even at high data

rates. Figure 13 shows a transmitter loopback test circuit, and Figure 14 shows the loopback test result at

120kbps. For this test, all transmitters were simultaneously driving RS-232 loads in parallel with 1000pF at

120kbps. Figure 15 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.

4.12 Interconnection with 3V and 5V Logic

The ICL3221EM and ICL3221EF directly interface with 5V CMOS and TTL logic families. With the ICL3221EM

and ICL3221EF at 3.3V, and the logic supply at 5V, AC, HC, and CD4000 outputs can drive ICL3221EM and

ICL3221EF inputs, but ICL3221EM and ICL3221EF outputs do not reach the minimum VIH for these logic families.

See Table 7 for more information.

Figure 13. Transmitter Loopback Test Circuit

Figure 14. Loopback Test at 120kbps

Figure 15. Loopback Test at 250kbps

Table 7.

Logic Family Compatibility with Various Supply Voltages

System Power-Supply Voltage (V)

VCC Supply Voltage (V)

Compatibility

3.3

3.3

Compatible with all CMOS families.

ICL3221EM

VCC

FORCEOFF

C1

C2

C4

C3

+

+

+

+

1000pF

V+

V-

5k

TIN

ROUT

C1+

C1-

C2+

C2-

RIN

TOUT

+

VCC

0.1µF

VCC

EN

ICL3221EF

T1IN

T1OUT

R1OUT

5µs/Div

VCC = +3.3V

5V/Div

C1 - C4 = 0.1µF

T1IN

T1OUT

R1OUT

2µs/Div

5V/Div

VCC = +3.3V

C1 - C4 = 0.1µF